CN1811931A - Optical disk device - Google Patents

Abstract

The optical disc device of the present invention records/regenerates an information carrier having at least two stacked information surfaces, comprising: a light beam irradiation mechanism; a focusing mechanism; a focusing device for moving the focusing mechanism; a light receiving mechanism for receiving reflected light; The focusing state detection mechanism detects the signal corresponding to the focusing state of the light beam on the information surface; the focus adjustment mechanism drives the focusing device to control the beam to focus on the desired position on the information surface; the spherical aberration detection mechanism The mechanism signal detects the spherical aberration signal corresponding to the beam focusing position on the information surface; the spherical aberration variable mechanism is driven by an elastic body to change the spherical aberration of the beam at the focusing position; the spherical image The difference control mechanism controls the spherical aberration variable mechanism so that the spherical aberration becomes approximately 0; the offset application mechanism applies offset to the spherical aberration variable mechanism; the offset replacement mechanism replaces the offset application according to the information surface The offset of the body.

Description

CD device

This application is a divisional application with the application number 02805745.7 and the title of the invention "optical disk device".

technical field

The present invention relates to an optical disc device for recording and reproducing optical information. In particular, the present invention relates to an optical disc device capable of correcting spherical aberration with high precision even by using a lens with a large numerical aperture in order to condense light beams, and capable of recording and reproducing with high precision.

Background technique

Conventionally, there are various optical recording media such as so-called playback-only optical discs, phase-change optical discs, magneto-optical discs, and optical cards as recording media for storing data such as image information, audio information, or computer programs.

An optical disc device is used to write data on such an optical recording medium (hereinafter referred to as "optical disc") or to read data recorded on the optical disc. In addition, the optical disc device in this specification is not only an optical disc drive (optical drive), but also includes various devices capable of writing data into or reading data from an optical disc. That is, the "optical disk device" in this specification includes a game machine; an audio-visual device; and a home computer. In addition, a portable terminal (PDA) capable of recording/reproducing data on a compact disc is also included.

First, the structure of an optical disc will be described with reference to FIG. 1 . The optical disc 20 shown in Fig. 1 starts from the side where the optical head irradiates light beams, and has: a base member 21 made of a transparent material for transmitting light beams; The base member 21, like the protective layer 25, has the anti-damage and anti-pollution functions of protecting the data on the optical disc. In addition, the terms "base member" and "protective layer" in this specification refer to the terms of the transparent member that exists between the information surface of the optical disc and the atmosphere, and do not strictly distinguish "base member" by material, thickness, or manufacturing method. " and "protection layer". Therefore, the optical head can be arranged on one side of the protective layer. In this specification, the members expressed by the term "base member" and the members expressed by the term "protective layer" can be replaced with each other.

FIG. 2 is a schematic enlarged perspective view showing the information surface 29 of the optical disc 20 . The optical disc 20 is irradiated with a light beam from above in the figure. As shown in FIG. 2 , on the information surface 29 of the optical disc 20 there are convex tracks 28 . The tracks 28 are formed concentrically or spirally to the center of the optical disk. Track 28 may be wobbled. Information such as address information is pre-recorded on the upper surface of the optical disc 20 using the wobble shape or wobble frequency of the track 28 .

FIG. 3 is a block diagram showing the structure of a conventional optical disc device. The optical disk 20 is rotated at a predetermined rotational speed by the optical disk motor 10 . The light beam emitted by the light source 3 such as a semiconductor laser as the beam irradiation mechanism is focused on the information surface 29 of the optical disc 20 by the objective lens 1 as the focusing mechanism to form a beam spot at a desired position on the information surface 29.

The design of the optical system including the objective lens 1 is based on the premise that the focus control on the information plane 29 of the optical disc 20 works stably, and performs fixed spherical aberration correction. That is, according to the thickness of the base member 21 of the optical disc 20, an optical design is performed to minimize spherical aberration. This is because dynamic (dynamic) correction of spherical aberration is not necessary in conventional optical disc devices.

The reflected light of the optical disc 20 is received by the light receiving unit 4, and a photocurrent is generated according to the received light amount.

The optical disc device has a focus device 2 and a tracking regulator 27 . In order to change the focusing position of the light beam, the focusing device 2 moves the objective lens 1 at a position approximately perpendicular to the information surface 29 of the optical disc 20 . The tracking regulator 27 moves the objective lens 1 in the radial direction of the optical disc 20 so that the focusing position of the beam correctly tracks the track 28 on the information surface 29 of the optical disc 20 .

The above-mentioned objective lens 1; focusing device 2; light source 3; The optical head 5 can be moved in the radial direction of the optical disc 20 by the transport table 60 functioning as a retrieval mechanism, and the transport table 60 is driven by an output signal (drive signal) of the transport table driving circuit 62 .

Next, the focus adjustment of the above-mentioned optical disc device will be described.

A light beam generated by a light source 3 such as a semiconductor laser is focused by the objective lens 1 on the information surface 29 of the optical disc 20 to form a beam spot. The light reflected from the optical disc 20 at this beam spot enters the light receiving unit 4 through the objective lens 1 again.

The light receiving unit 4 is divided into four areas, generates a photocurrent based on the amount of light detected in each area, and outputs it to the preamplifier 11 . The preamplifier 11 has an I/V converter, and the photocurrent input to the preamplifier 11 from the light receiving unit 4 is converted into a voltage by the I/V converter. The transformed individual signals are sent to the focus error signal generator 7 and the tracking error signal generator 18 . The focus error signal generator 7 generates, using the preamplifier 11 , an error signal related to the vertical direction between the beam spot of the combined light output from the optical head 5 and the optical disc 20 .

This optical system includes a focus error detection system generally called an astigmatism method and a tracking error detection system called a push-pull method.

The focus error signal generator 7 generates a focus error signal (hereinafter referred to as FE signal) based on the input signal by using an astigmatism method. The FE signal, which is an output signal of the focus error signal generator 7 , is output to the focus device drive circuit 9 after performing filter operations such as phase compensation and gain compensation by the focus adjustment unit 17 .

The focusing device 2 drives the objective lens 1 according to a driving signal from the focusing device driving circuit 9 . As a result, the beam spot becomes a predetermined convergent state on the information surface 29 of the optical disc 20, and focus adjustment can be realized.

Next, tracking control of the above-mentioned optical disc device will be described.

The tracking error signal generator 18 uses the preamplifier 11 to generate an error signal in the radial direction of the optical disc 20 between the beam spot of the combined light output from the optical head 5 and the track 28 . The tracking error signal generator 18 generates a tracking error signal (hereinafter referred to as a TE signal) by a push-pull method based on an input signal. The tracking control unit 19 performs phase compensation of the TE signal, which is the output signal of the tracking error signal generator 18 , filter calculations such as gain compensation, and then outputs to the tracking regulator drive circuit 26 .

The objective lens 1 is driven by the tracking regulator 27 according to the driving signal output by the tracking regulator driving circuit 26 . As a result, the beam spot follows the track 28 of the information surface 29 of the optical disc 20, and tracking control can be realized.

Next, the generation of the focus error signal and the tracking error signal will be described in detail with reference to FIG. 4 .

As shown in FIG. 4 , the light receiving unit 4 is divided into regions A; B; C; D. Each area A to D of the light receiving part 4 generates a photocurrent according to the amount of light detected in each area, and outputs it to the corresponding I/V converter 6a installed inside the preamplifier 11; I/V converter 6b; I/V converter 6c; I/V converter 6d.

I/V converter 6a; I/V converter 6b; I/V converter 6c; I/V converter 6d The respective signals converted from current to voltage are sent to focus error signal generator 7 and tracking error signal generator 18.

"Information track length direction" shown in FIG. Therefore, in the focus error signal generator 7, the sum of the output of the I/V converter 6a and the output of the I/V converter 6c is subtracted from the sum of the output of the I/V converter 6b and the output of the I/V converter 6d, The FE signal of the astigmatism method can be obtained.

In the tracking error signal generator 18, the sum of the output of the I/V converter 6a and the output of the I/V converter 6d is subtracted from the sum of the outputs of the I/V converter 6b and the I/V converter 6c. Obtain the TE signal of the astigmatism method.

In this way, in the conventional optical disc device, when writing information to/from the optical disc or reading information from the optical disc, focus adjustment and tracking control are performed.

However, in conventional optical disc devices, it is difficult to write and/or read information from a high-density optical disc. Hereinafter, this point will be described in detail.

In recent years, it has been proposed to make the numerical aperture (NA) of the objective lens larger than 0.6 and to make the wavelength of the light source shorter than 650 nm in order to increase the recording density and increase the capacity of the optical disc. For example, a numerical aperture is 0.85; a wavelength of a light source is 405 nm; a thickness of a base member (thickness of a protective layer) is 0.1 mm; and an optical disk has a capacity of 20 to 25 GB. This is because the laser beam diameter (spot diameter) on the optical disk is proportional to λ/NA, and it is advantageous to reduce λ and increase NA from the viewpoint of increasing recording density. Here, λ is the wavelength of laser light.

If the NA is 0.85; the wavelength of the light source is 405nm, then the light spot can be made small, but the aberration of the beam cannot be ignored; especially the spherical aberration caused by the objective lens and the base part (or protective layer) that constitutes the optical disc .

As shown in FIG. 1 , the information surface 29 of the optical disc 20 is protected by a base member 21 , and the light beam output by the optical head 5 passes through the thickness of the base member 21 to form a beam spot on the information surface 29 .

In the conventional DVD used in the optical system having an NA of 0.6, the fluctuation of spherical aberration due to the non-uniform thickness of the base member 21 is within the allowable range and can be ignored. However, when the base member 21 is constant, spherical aberration proportional to the fourth power of the NA occurs in the beam spot, and therefore, when the NA becomes 0.85, the fluctuation of the spherical aberration cannot be ignored.

In the DVD standard, in order to increase the recording capacity per disc, a two-layer disc (dual-layer disc) having two information recording surfaces is used. FIG. 5 is a diagram showing an example of a dual-layer disc structure. As shown in Figure 5, the dual-layer disk has from the optical head side in order: base member 21; LO layer (first information recording surface) 22; intermediate layer 24; L1 (second information recording surface) 23 and the protection inside Layer 25. The base member 21 and the intermediate layer 24 are made of a transparent medium such as resin.

According to the stacked structure shown in FIG. 5, in an optical disc 20 having a plurality of information recording surfaces, the beam spot needs to be moved from the current information recording surface to the adjacent information recording surface. Such shifting of the focal position of the light beam to a different information recording surface is called "interlayer shifting" below. Next, this interlayer moving method will be described with reference to FIG. 3 and FIG. 6 .

First, consider the case where the focus of the light beam is moved from the information recording surface of the objective lens 1 close to the optical head 5 to the information recording surface farther away. Once the microcomputer 8 stops the focus adjustment, it outputs an acceleration pulse for moving the objective lens 1 to the focus device drive circuit 9 . This acceleration pulse has a waveform shown in FIG. 6(a) and is a signal for moving the objective lens 1 to the back side (that is, the side of the information recording surface farther from the objective lens 1).

Next, the microcomputer 8 compares the FE signal from the focus error signal generator 7 with the deceleration start level, and outputs a deceleration pulse if the FE signal exceeds the deceleration start level. Finally, at the end of the acceleration pulse, the focus adjustment is restarted.

Next, consider the case where the focus of the light beam is moved from the information recording surface of the objective lens 1 of the difference optical head 5 to the near information recording surface. At this time, by applying the acceleration pulse/deceleration pulse with the waveform shown in FIG. 6(b) by the method described above, the focus of the beam can be shifted between layers.

Even in a two-layer optical disc, it is necessary to increase the recording density and increase the capacity. For this purpose, the numerical aperture of the objective lens should be greater than 0.6, and the wavelength of the light source should be less than 650 nm.

In the case of a two-layer disc, because there is an intermediate layer 24 between the LO layer 22 and the L1 layer 23, the thickness of the L1 layer 23 from the surface of the optical disc 20 on the optical head side to the information recording surface is greater than the thickness of the LO layer 22 by the amount equal to the thickness of the middle layer 24 . This difference in thickness is the main cause of spherical aberration. In the DVD optical system whose NA of the objective lens is 0.6, the size of this spherical aberration is within the allowable range, and it is not necessary to perform aberration correction and the recording and reproduction of information can be performed, but the use of a larger NA (such as 0.8 or more) When the objective lens is used, the spherical aberration occurring on the other information recording surface due to the thickness of the intermediate layer 24 cannot be ignored.

That is, when the NA of the objective lens becomes larger than 0.6, it is impossible to record information on the two information recording surfaces or to reproduce already recorded information in the conventional optical disc device.

When the NA is greater than 0.6 (for example, 0.8), it may be considered to install the spherical aberration correction lens 15 shown in FIG. 7 . A typical spherical aberration correcting lens 15 is composed of two lens groups, and the relative distance between the two lens groups is changed by moving one of the two lens groups. With such a spherical aberration correcting lens 15, when recording/reproducing on a two-layer optical disk, appropriate spherical aberration correction can be performed for each information recording surface, thereby eliminating spherical aberration caused by the intermediate layer.

The spherical aberration correcting lens 15 is driven with a leaf spring. In this case, the responsiveness is fast; high-precision control can be performed, but since the movement range of the spherical aberration correcting lens 15 is narrow, there is a problem that the spherical aberration correction possible range is narrow. Especially in the above-mentioned two-layer optical disk, if including uneven thickness of the base member; unevenness of the characteristics of the objective lens; unevenness of the characteristics of the spherical aberration correction lens 15, etc., the correction range is insufficient, and recording and reproduction cannot be performed well. The problem.

Contents of the invention

The present invention has been made in view of the above problems, and its object is to provide an optical disc device that can stably record or reproduce information even if the thickness of the base member (or protective layer) that is the main cause of the spherical aberration of the optical disc is uneven.

Another object of the present invention is to provide: even if the NA of the objective lens is larger than the conventional NA (for example, 0.8 or more), the spherical aberration correction range is wide; An optical disc device capable of recording/reproducing a high-capacity optical disc.

The optical disk device of the present invention is a device for recording and reproducing an information carrier, and it includes a beam irradiation mechanism for irradiating a beam; a focusing mechanism for focusing a beam on the information carrier; The first adjuster for relative movement in the approximately vertical direction of the carrier information surface; the spherical aberration variable mechanism for changing the spherical aberration of the beams converged by the above-mentioned converging mechanism at the converging position; moving the above-mentioned spherical aberration can be The second adjuster of the variable mechanism; the third adjuster of the above-mentioned spherical aberration variable mechanism; the light-receiving mechanism for receiving the reflected light of the above-mentioned light beam carrier; according to the signal of the above-mentioned light-receiving mechanism, it is detected that the above-mentioned light beam is on the information surface of the information carrier The focus adjustment mechanism corresponding to the focus state signal on the above-mentioned focus state detection mechanism; according to the signal of the above-mentioned focus state detection mechanism, controls and drives the above-mentioned first regulator to make the beam focus on the desired position of the information surface of the above-mentioned information carrier ; According to the signal of the above-mentioned light-receiving mechanism, detect the spherical aberration detection mechanism corresponding to the signal of the beam spherical aberration amount occurring on the focusing position on the information surface of the above-mentioned information carrier; according to the above-mentioned spherical aberration detection mechanism signal respectively control A spherical aberration control mechanism that drives the third adjuster and the second adjuster to make the spherical aberration approximately zero; wherein: the third adjuster is at least based on the DC component contained in the signal of the spherical aberration detection mechanism, The spherical aberration variable mechanism is moved, and the second adjuster moves the spherical aberration variable mechanism based on an AC component included in the signal of the spherical aberration detection mechanism. In this way, even if the NA of the objective lens used as the focusing mechanism is larger than that of the past (such as NA greater than 0.8; .085 or greater), good responsiveness can be achieved; spherical aberration correction control range is wide, and higher density recording can be provided • A reproducible optical disc device.

As an ideal embodiment, the above-mentioned spherical aberration control mechanism separates the control frequency bands, so that the spherical aberration variation lower than the information carrier rotation frequency is driven by the third regulator, and the spherical aberration variation higher than the information carrier rotation frequency is driven. drive of the second regulator. As a result, the slow tracking speed of the third adjuster is not overly sensitive to the uneven thickness of the base member constituting the information carrier, and can follow the change in the thickness of the base member in the radial direction, further improving the spherical aberration. The accuracy of correction control, therefore, the response to spherical aberration correction becomes better, and an optical disc device capable of recording and reproducing with higher density can be provided.

The optical disc device of the present invention is an optical disc device for recording and reproducing an information carrier having at least two information planes in a laminated structure; it includes a beam irradiation mechanism for irradiating a light beam; a focusing mechanism for converging a light beam to the above-mentioned information carrier; A first adjuster that changes the focusing position of the above-mentioned light beam to make the above-mentioned focusing mechanism relatively move in the approximate vertical direction of the information surface of the information carrier; change the spherical aberration of the beam focused by the above-mentioned focusing mechanism at the focusing position The spherical aberration variable mechanism; the third adjuster that moves the spherical aberration variable mechanism; the second adjuster that moves the spherical aberration variable mechanism; the light receiving mechanism that receives the carrier reflected light of the above light beam; according to the above Receiving the light mechanism signal, detecting the focusing state detection mechanism corresponding to the focusing state signal of the light beam on the information surface of the information carrier; controlling and driving the above-mentioned first regulator according to the signal of the above-mentioned focusing state detection mechanism, so that the above-mentioned A focusing adjustment mechanism that focuses the light beam at the desired position on the information surface of the information carrier; drives the first adjuster to move the beam focusing position to another interlayer moving mechanism on the information surface; detects the A spherical aberration detection mechanism on the information surface of the information carrier corresponding to the signal of the amount of spherical aberration occurring at the beam focusing position; according to the signal of the spherical aberration detection mechanism, respectively control and drive the third regulator and the second regulator The device is a spherical aberration control mechanism that makes the spherical aberration approximately zero; wherein, the third adjuster moves the spherical aberration variable mechanism at least according to the DC component included in the signal of the spherical aberration detection mechanism; the above-mentioned The second actuator moves the spherical aberration variable mechanism according to the AC component included in the signal of the spherical aberration detection mechanism, and at the same time, drives the spherical aberration variable mechanism with the third actuator or the like so that the layer When the inter-movement mechanism is working and the focusing position of the light beam is moved to the other information plane, the spherical aberration caused by the movement is the smallest. As a result, for an information carrier having at least two information planes, it is possible to control spherical aberration in a wide range during interlayer movement, and it is possible to provide an optical disc device capable of recording and reproducing higher densities.

As an ideal embodiment, when the beam focusing position is moved to another information surface by using the interlayer moving mechanism, the signal based on the amount of spherical aberration occurring on the other information surface is applied as an offset to the third adjustment device. As a result, the spherical aberration variable mechanism moves so that the spherical aberration that occurs due to this movement is minimized as the beam converging position of the converging mechanism approaches the other information surface and approaches the other center. The spherical aberration correction amount that becomes the reference, therefore, can reduce the focus error caused by the movement to the other information plane or the influence of the total reflection light amount of the information carrier, and will not hinder the stability of the movement of the other information plane, so that it can be An optical disc device capable of recording and reproducing at a higher density is provided.

As an ideal embodiment, due to the interlayer moving mechanism, the focusing position of the light beam is moved to another information plane and during the period until the focusing state detection mechanism signal converges within a given range, the spherical aberration detection mechanism signal according to the spherical surface The aberration control mechanism does not work. As a result, when the spherical aberration variable mechanism moves between layers, it is possible to control the fluctuation of the signal of the spherical aberration detection mechanism. Therefore, it is possible to realize stable control and conversion of the spherical aberration of each information surface, and to provide higher density recording. • A reproducible optical disc device.

The optical disc device of the present invention is a device for recording and reproducing an information carrier, and it includes an optical head; a light beam irradiation mechanism for irradiating a light beam in the optical head, a focusing mechanism for converging a light beam to the above-mentioned information carrier, and in order to change the focusing position of the above-mentioned light beam, a first adjuster for relatively moving the above-mentioned focusing mechanism in a direction approximately perpendicular to the information surface of the information carrier; a spherical aberration variable mechanism for changing the spherical aberration occurring at the converging position of the beam converged by the above-mentioned converging mechanism; The third adjuster for moving the above-mentioned variable spherical aberration mechanism, the second adjuster for moving the above-mentioned spherical aberration variable mechanism, and the mechanism for receiving the reflected light from the light beam carrier are integrated; A focusing state detection mechanism corresponding to the focusing state signal of the above-mentioned light beam on the information surface of the information carrier; according to the signal of the above-mentioned focusing state detection mechanism, control and drive the above-mentioned first regulator to make the light beam focus on the above-mentioned information carrier information The focus adjustment mechanism at the desired position on the surface; the spherical aberration detection mechanism that detects the spherical aberration signal on the information surface of the above-mentioned information carrier corresponding to the beam focusing position according to the signal of the above-mentioned receiving light mechanism; according to the above-mentioned spherical image The difference detection mechanism signal controls and drives the above-mentioned third adjuster and the second adjuster respectively, so that the spherical aberration control mechanism that makes the spherical aberration become approximately 0; the retrieval mechanism that makes the above-mentioned optical head move to the radial direction of the above-mentioned information carrier; Wherein, the third adjuster moves the spherical aberration variable mechanism at least according to the DC component included in the signal of the spherical aberration detection mechanism; and the second adjuster moves the spherical aberration variable mechanism according to the signal included in the spherical aberration detection mechanism. AC component, moving the above-mentioned spherical aberration variable mechanism; at the same time, driving the above-mentioned third adjuster so that when the beam focusing position is moved from the above-mentioned focusing mechanism to the different radius positions of the above-mentioned information carrier, the above-mentioned movement occurs Spherical aberration is minimal. Like this, utilize the 3rd adjuster to correct, the direct current component signal of the spherical aberration detection mechanism that occurs when the optical head moves to the radial direction by the above-mentioned retrieval mechanism; Thus, the unevenness of the thickness of the absorption information carrier or the sticking unevenness; Can carry out range With wide spherical aberration correction control, it is possible to provide an optical disc device capable of higher density recording and reproduction.

As an ideal embodiment, due to the operation of the above-mentioned search mechanism, during the movement of the light beam focusing position to the radial position of another information surface, the signal based on the amount of spherical aberration occurring on the radial position of the other information surface is used as the deviation. shift applied to the third regulator. As a result, when the spherical aberration variable mechanism makes the optical head approach from the inner circumference to the outer circumference, the spherical aberration caused by this movement is minimized; Reduce the impact on the tracking error signal or focus error signal caused by the large change of spherical aberration when the optical head moves in the radial direction, and will not hinder the stability of the pullback work of the tracking control after moving in the radial direction, and can provide more An optical disc device with high recording and reproducing capabilities.

In an ideal embodiment, through the operation of the retrieval mechanism, the beam focusing position moves to another information surface, and at the radial position of the other information surface, the signal of the focusing state detection mechanism is focused before the above-mentioned specified range, The spherical aberration control mechanism based on the signal of the spherical aberration detection mechanism does not operate. As a result, more stable spherical aberration control switching can be realized when moving in the radial direction by the search mechanism, and an optical disc device capable of recording and reproducing with higher density can be provided.

The optical disc device of the present invention is an optical disc device for recording and reproducing an information carrier having at least two information planes in a laminated structure, and includes: a beam irradiation mechanism for irradiating a beam; a converging mechanism for converging a beam to the information carrier; In order to change the focusing position of the above-mentioned light beam, the focusing device that makes the above-mentioned focusing mechanism relatively move in the approximate vertical direction of the information surface of the information carrier; the receiving light mechanism that receives the carrier reflected light of the above-mentioned light beam; according to the signal of the above-mentioned light receiving mechanism, detect The focusing state detection mechanism corresponding to the focusing state signal of the above-mentioned light beam on the information surface of the information carrier; according to the signal of the above-mentioned focusing state detection mechanism, control and drive the above-mentioned focusing device, so that the light beam is focused on the desired position on the information surface of the information carrier A focus adjustment mechanism; a spherical aberration detection mechanism that detects a signal on the information surface of the above-mentioned information carrier corresponding to the spherical aberration amount that occurs at the beam focusing position according to the signal of the above-mentioned light-receiving mechanism; using a method of driving an elastic body , the spherical aberration variable mechanism that changes the spherical aberration of the beam converged by the above-mentioned converging mechanism at the converging position; according to the signal of the above-mentioned spherical aberration detection mechanism, control and drive the above-mentioned spherical aberration variable mechanism to make the spherical aberration A spherical aberration control mechanism whose aberration becomes approximately 0; an offset applying mechanism that applies an offset to the above-mentioned spherical aberration variable mechanism; an offset corresponding to an information surface of the above-mentioned information carrier replacing the offset of the above-mentioned offset applying mechanism Offset replacement mechanism. In this way, stable and highly accurate spherical aberration correction control can be performed, and an optical disc device capable of recording and reproducing with higher density can be provided.

As an ideal embodiment, when the above-mentioned spherical aberration control mechanism is not working, the offset applying mechanism applies a given offset to the spherical aberration variable mechanism; when the spherical aberration control mechanism is working, according to the information carrier The offset is determined by the average drive output of the spherical aberration variable mechanism per cycle, and the offset applied to the offset mechanism is replaced. As a result, the follow-up speed to fluctuations in spherical aberration can be further improved, and an optical disc device capable of recording and reproducing with higher density can be provided. The optical disc device of the present invention is an optical disc device for recording and reproducing an information carrier, and includes: a beam irradiation mechanism for irradiating a beam; a converging mechanism for converging a beam to the above-mentioned information carrier; A focusing device that moves relatively in the approximate vertical direction of the information surface of the information carrier; a spherical aberration variable mechanism that changes the spherical aberration that occurs at the focusing position of the beam focused by the above-mentioned focusing mechanism; accepts information from the above-mentioned beam The receiving light mechanism of the carrier reflected light; according to the signal of the above-mentioned receiving light mechanism, the focusing state detection mechanism corresponding to the focusing state signal of the above-mentioned light beam on the information surface of the information carrier is detected; according to the signal of the above-mentioned focusing state detection mechanism, control A focus adjustment mechanism that drives the above-mentioned focusing device to make the above-mentioned light beam converge at the desired position on the information surface of the information carrier; according to the signal of the above-mentioned receiving light mechanism, detect the spherical surface corresponding to the beam converging position on the information surface of the above-mentioned information carrier A spherical aberration detection mechanism for a signal of an aberration amount; a spherical aberration control mechanism for controlling and moving a spherical aberration variable mechanism based on the signal of the above-mentioned spherical aberration detection mechanism so that the spherical aberration becomes approximately zero; the above-mentioned spherical aberration control When the signal value of the mechanism is within a predetermined range, the signal from the spherical aberration control mechanism is not transmitted to the dead zone generating mechanism of the spherical aberration variable mechanism. In this way, it is possible to reduce the excessive movement error caused by the excessive sensitivity (response) of the spherical aberration variable mechanism, and the excessive movement error when the signal of the spherical aberration detection mechanism changes slightly, especially in the spiral parity check operation due to the thickness change of the optical disc. When the spherical aberration changes at a low frequency, smooth tracking control can be performed, and an optical disc device capable of recording and reproducing with higher density can be provided.

The optical disc device of the present invention is an optical disc device for recording and reproducing an information carrier, and it includes: a beam centering mechanism for converging a light beam to an information carrier; ; the spherical aberration variable mechanism that changes the spherical aberration of the beam converged by the above-mentioned beam-converging mechanism at the converging position; the driving mechanism that makes the above-mentioned spherical aberration variable mechanism work; receiving the information carrier from the above-mentioned beam A light-receiving mechanism for reflected light; according to the signal of the above-mentioned light-receiving mechanism, detect the focusing state detection mechanism corresponding to the focusing state signal of the above-mentioned light beam on the information surface of the information carrier; according to the signal of the above-mentioned focusing state detection mechanism, control the drive The above-mentioned focusing device is a focus adjustment mechanism for converging the light beam at a desired position on the information surface of the above-mentioned information carrier; according to the signal of the above-mentioned light-receiving mechanism, it detects the spherical aberration corresponding to the converging position of the light beam on the information surface of the above-mentioned information carrier The spherical aberration detection mechanism of the quantity signal; according to the above-mentioned spherical aberration detection mechanism signal, the spherical aberration control mechanism that drives the above-mentioned drive mechanism to make the spherical aberration approximately become 0; after amplifying the above-mentioned focusing state signal according to the specified gain A spherical aberration correction mechanism that corrects the interference or interference that occurs between the spherical aberration control mechanism and the focus adjustment mechanism in the working state by adding to the detection signal of the spherical aberration detection mechanism. In this way, even if the NA of the objective lens used as a focusing mechanism is larger than conventional ones (for example, NA is 0.8 or more or 0.85 or more), the responsiveness is high, spherical aberration control can be realized in a wide range, and higher density recording can be provided. • A reproducible optical disc device.

As an ideal embodiment, it also includes: a first test signal generating mechanism for adding a test signal to the above-mentioned focusing device; a first amplitude detection mechanism for detecting the amplitude of the detection signal of the spherical aberration detection mechanism, and a spherical aberration correction learning mechanism The spherical aberration correction learning mechanism is a state where the test signal is added to the above-mentioned focusing device by the first test signal generating mechanism, and the addition operation gain of the spherical aberration signal correction mechanism is obtained by the above-mentioned first amplitude detection mechanism, so that The above-mentioned spherical aberration correction learning mechanism with the minimum amplitude of the spherical aberration detection signal. As a result, it is possible to provide an optical disc device for each recording and reproduction; particularly, an optical disc device which can perform optimal focus adjustment for each optical disc and eliminate disturbance of spherical aberration control.

As an ideal embodiment, the spherical aberration correction learning mechanism performs the calculation of the addition gain when the focus adjustment mechanism is in operation and the spherical aberration control mechanism is not in operation. As a result, it is possible to provide an optical disc device in which interference due to focus adjustment and spherical aberration control can be eliminated before the operation of the two control systems becomes unstable.

As an ideal embodiment, the above-mentioned spherical aberration signal correction mechanism includes: an additive operation gain storage mechanism to save a mechanism for each layer of the information carrier with a laminated structure information surface; an additive operation gain replacement mechanism, A mechanism for adding the addition gain corresponding to the light beam to the above-mentioned addition gain storage means. As a result, it is not necessary to re-learn the focus adjustment and spherical aberration interference elimination amount adapted to the information plane every time when moving between different information planes, and it becomes possible to provide an optical disc device for high-speed recording and reproduction.

As an ideal embodiment, it also includes: a first test signal generator that applies the test signal to the above-mentioned focusing device; a focus adjustment gain adjustment mechanism that adjusts the gain of the focus adjustment mechanism; a second test signal generator that adds the test signal to the drive mechanism Mechanism; a spherical aberration control gain adjustment mechanism for adjusting the gain of the spherical aberration control mechanism; wherein, after the focus adjustment mechanism and the spherical aberration control mechanism work, according to the first test signal generated by the first test signal generation mechanism and the focus Adjust the above-mentioned first test signal after one round, and adjust the above-mentioned focus adjustment gain adjustment mechanism; control the above-mentioned spherical aberration test after one round according to the spherical aberration test signal and spherical aberration generated by the second test signal generating mechanism signal, the above adjustment spherical aberration control mechanism is adjusted. As a result, it becomes possible to provide an optical disc device that includes and adjusts the gain portion that is shifted by the interference of focus adjustment and spherical aberration control.

The optical disk device of the present invention comprises: a converging mechanism for converging light beams to the information carrier; a focusing device for relatively moving the above-mentioned converging mechanism in an approximately vertical direction on the information surface of the information carrier; A spherical aberration variable mechanism for spherical aberration occurring at the beam position; a drive mechanism for making the above-mentioned variable spherical aberration mechanism work; a light receiving mechanism for receiving reflected light from an information carrier of the above light beam; A focusing state detection mechanism corresponding to the focusing state signal that emits the above-mentioned light beam on the information surface of the information carrier; according to the signal of the above-mentioned focusing state detection mechanism, control and drive the above-mentioned focusing device, so that the above-mentioned light beam is focused on the information surface of the information carrier The focus adjustment mechanism at the desired position; the spherical aberration detection mechanism that detects the spherical aberration signal on the information surface of the above-mentioned information carrier corresponding to the spherical aberration signal that occurs at the beam focusing position according to the signal of the above-mentioned receiving light mechanism; according to the above-mentioned spherical aberration The detection mechanism signal controls and drives the above-mentioned driving mechanism to make the spherical aberration approximately become 0 spherical aberration control mechanism; after the signal of the above-mentioned spherical aberration detection mechanism is amplified according to a given gain, it is added to the detection signal of the above-mentioned focusing state detection mechanism The method is to correct the external disturbance or interference of the focusing state detection signal correction mechanism that occurs during the work of the aforementioned spherical aberration control mechanism and focus adjustment mechanism. In this way, even if the NA of the objective lens used as the focusing mechanism is larger than the conventional one (NA is 0.8 or more or 0.85 or more), good responsiveness can be achieved; a wide range of spherical aberration control can provide higher density recording. Reproducible optical disc device.

As an ideal embodiment, it includes a focus adjustment mechanism; this mechanism is that when the above-mentioned spherical aberration control mechanism is not working, the detection signal of the above-mentioned spherical aberration detection mechanism with a specified multiple by the focus state detection signal correction mechanism is not added to the focus. Only based on the detection signal of the beam state detection mechanism, the above-mentioned focusing device is driven to control the focus adjustment mechanism that makes the beam converge at the desired position on the information surface of the information carrier. As a result, when the spherical aberration control mechanism is not in operation, it is possible to provide an optical disc device in which focus adjustment can be prevented from being unstable by the detection signal of the spherical aberration detection mechanism.

As an ideal embodiment, it includes: a second test signal generating device that applies a test signal to the above-mentioned driving mechanism; a second amplitude detection mechanism that detects the amplitude of the detection signal of the focusing state detection mechanism; and a focusing state detection correction learning mechanism , this mechanism adds the test signal state on the above-mentioned driving mechanism by the above-mentioned second test signal generating mechanism, and obtains the addition operation gain of the focusing state detection signal correction mechanism, so that the focusing state detected by the above-mentioned second amplitude detecting mechanism The actual value of the detection signal is the smallest. As a result, it is possible to provide an optical disk device capable of performing optimum focus adjustment for each optical disk for recording and reproducing and eliminating interference with spherical aberration control.

As an ideal embodiment, the focusing state detection and correction learning mechanism is to learn the addition gain when the focus adjustment mechanism is working and the spherical aberration control mechanism is not working. As a result, it is possible to provide an optical disc device capable of eliminating interference before both control systems become unstable due to interference of focus adjustment and spherical aberration control.

As an ideal embodiment, it includes: the first test signal generating mechanism that applies the test signal to the above-mentioned focusing device; the focus adjustment gain adjustment mechanism that adjusts the gain of the focus adjustment mechanism; the second test signal generator that adds the test signal to the above-mentioned driving mechanism mechanism; a spherical aberration control gain adjustment mechanism for adjusting the gain of the spherical aberration control mechanism; wherein after the focus adjustment mechanism and the spherical aberration control mechanism are made to work, the focus adjustment gain adjustment mechanism is based on the first test signal generated by the first test signal generation mechanism. 1. Test signal and focus adjustment-the above-mentioned first test signal after the tour is adjusted; and the above-mentioned spherical aberration control gain adjustment mechanism is based on the test signal and spherical aberration control-after the tour produced by the second test signal generating mechanism The above-mentioned spherical aberration test signal is adjusted. As a result, it is possible to provide an optical disc device that can be adjusted with higher precision.

The optical disk device of the present invention comprises: a converging mechanism for converging light beams to the information carrier; a focusing device for relatively moving the above-mentioned converging mechanism in an approximately vertical direction on the information surface of the information carrier; The spherical aberration variable mechanism for the spherical aberration that occurs at the beam position; the driving mechanism for making the above-mentioned spherical aberration variable mechanism work; the receiving light mechanism for receiving the reflected light of the above-mentioned beam information carrier; The focusing state detection mechanism corresponding to the focusing state signal of the above-mentioned light beam on the information surface of the information carrier; according to the signal of the above-mentioned focusing state detection mechanism, the above-mentioned focusing device is driven to control the focusing of the above-mentioned light beam on the information surface of the information carrier The focus adjustment mechanism at the desired position; the spherical aberration detection mechanism that detects the corresponding signal on the information surface of the above-mentioned information carrier corresponding to the amount of spherical aberration that occurs at the beam focusing position according to the signal of the above-mentioned receiving light mechanism; from the above-mentioned spherical image A low-pass filter mechanism that extracts frequency components lower than a predetermined frequency from the output signal of the difference detection mechanism; and a spherical aberration control mechanism that controls and drives the above-mentioned driving mechanism based on the signal of the low-pass filter mechanism so that the spherical aberration becomes approximately zero. ; A high-pass filter mechanism that takes out higher than a predetermined frequency component from the output signal of the above-mentioned spherical aberration detection mechanism; a spherical aberration signal addition mechanism that adds the signal of the above-mentioned high-pass filter mechanism to the signal of the above-mentioned focusing state detection mechanism . In this way, it is possible to improve the reduction of the RF signal reading performance of the information carrier due to the fluctuation of the spherical aberration AC that occurs at the beam converging position by using the focus adjustment mechanism.

The optical disc device of the present invention comprises: a converging mechanism for converging light beams to an information carrier; a focusing device for relatively moving the above-mentioned converging mechanism in an approximate vertical direction of the information surface of the information carrier; a spherical aberration variable mechanism for spherical aberration occurring at the focusing position; a drive mechanism for operating the spherical aberration variable mechanism; a light receiving mechanism for receiving reflected light from the beam carrier; based on a signal from the light receiving mechanism, Detect the focusing state detection mechanism corresponding to the focusing state signal of the above-mentioned light beam on the information surface of the information carrier; drive the above-mentioned focusing device according to the signal of the above-mentioned focusing state detection mechanism, and make the above-mentioned light beam focus on the above-mentioned information carrier The focus adjustment mechanism of the desired position on the information surface; the spherical aberration detection mechanism that detects the signal corresponding to the amount of spherical aberration that occurs on the beam focusing position on the information surface of the above-mentioned information carrier according to the signal of the above-mentioned receiving light mechanism; according to the above-mentioned The detection signal of the spherical aberration detection mechanism controls the spherical aberration control mechanism that drives the above-mentioned driving mechanism to make the spherical aberration approximately become zero; the frequency band of the above-mentioned focus adjustment mechanism is more than ten times larger than the frequency band of the above-mentioned spherical aberration control mechanism. In this way, the interference of focus adjustment and spherical aberration control can be out of the control frequency band, and an optical disc device in which focus adjustment and spherical aberration control are stable can be provided.

The optical disk device of the present invention comprises: the focusing mechanism that light beam is focused on the information carrier with helical or concentric circular track; Make above-mentioned focusing mechanism relatively move on the approximate vertical direction of information carrier information surface; Change The spherical aberration variable mechanism of the spherical aberration that occurs in the focused beam of the above-mentioned converging mechanism at the converging position; the driving mechanism that makes the above-mentioned spherical aberration variable mechanism work; A tracking regulator that moves in the direction; a light receiving mechanism that receives reflected light from the above-mentioned light beam carrier; according to the signal of the above-mentioned light receiving mechanism, detect the focusing state detection corresponding to the focusing state signal of the above-mentioned light beam on the information surface of the information carrier mechanism; according to the signal of the above-mentioned focusing state detection mechanism, drive the above-mentioned focusing device, and control the focus adjustment mechanism that makes the above-mentioned light beam focus on the desired position of the information surface of the above-mentioned information carrier; according to the signal of the above-mentioned receiving light mechanism, detect the above-mentioned information carrier information A spherical aberration detection mechanism corresponding to the signal of the amount of spherical aberration generated at the beam focusing position on the surface; according to the detection signal of the spherical aberration detection mechanism, the above-mentioned drive mechanism is controlled and driven to make the spherical aberration approximately zero The spherical aberration control mechanism; according to the signal of the above-mentioned light-receiving mechanism, the track deviation detection mechanism that detects the corresponding signal of the position deviation of the above-mentioned light beam relative to the track of the information carrier; according to the signal of the above-mentioned track deviation detection mechanism, control the above-mentioned tracking regulator , control the tracking control mechanism that makes the above-mentioned light beam scan on the magnetic track; make the above-mentioned tracking regulator move along the radial direction of the information carrier. When the moving mechanism is activated while the control mechanism is not in operation, the variable spherical aberration mechanism is moved to a position shifted by a predetermined amount. In this manner, it is possible to provide an optical disc device capable of performing stable focus adjustment while reducing the influence of the groove bottom crossing that occurs on the FE signal during retrieval with movement in the radial direction.

Description of drawings

Fig. 1 is a schematic diagram of an optical disc.

Fig. 2 is an enlarged schematic view of the information surface of the optical disc.

FIG. 3 is a block diagram showing the structure of a conventional optical disc device.

FIG. 4 is a block diagram showing the structure of a light receiving unit and a preamplifier of a conventional optical disc device.

Fig. 5 is a schematic diagram of an optical disc having a plurality of information planes.

6(a) and (b) are waveform diagrams of focus drive signals during layer-to-layer movement of a conventional optical disc device.

Fig. 7 is a cross-sectional view of a spherical aberration correcting lens.

Fig. 8 is a block diagram showing the structure of an optical disc device according to Embodiment 1 of the present invention.

FIG. 9 is a beam cross-sectional view for explaining a spherical aberration detection method.

Fig. 10 is a cross-sectional view showing the structure of the light receiving part in detail.

Fig. 11 is a block diagram showing the details of the light receiving unit and the preamplifier.

12(a) to (c) are diagrams showing waveforms of driving signals for spherical aberration correction in Embodiment 1. FIG.

Fig. 13 is a block diagram showing the structure of an optical disc device according to Embodiment 2 of the present invention.

14(a) to (d) are waveform diagrams showing spherical aberration correction drive signals during interlayer movement of the optical disc device according to the second embodiment.

FIG. 15 is a flow chart of the procedure for correcting spherical aberration at the time of interlayer movement in Example 2. FIG.

Fig. 16 is a waveform diagram of the focusing lens and LO; the position of the L1 information plane and each signal during interlayer movement in the second embodiment.

Fig. 17 is a block diagram showing the structure of an optical disc device according to Embodiment 3 of the present invention.

18( a ) to ( d ) are diagrams showing spherical aberration correction drive signal waveforms during movement in the radial direction of the third embodiment.

Fig. 19 is a flow chart showing the spherical aberration correction procedure when moving in the radial direction according to the third embodiment.

Fig. 20 is a waveform diagram of the focusing lens when moving in the radial direction in the third embodiment; the pressure change of the disk base member and various signals.

Fig. 21 is a block diagram showing the structure of an optical disc device according to Embodiment 4 of the present invention.

22(a) to (d) are diagrams showing spherical aberration correction drive signal waveforms during interlayer movement of the optical disc device according to the fourth embodiment.

Fig. 23 is a flow chart showing the spherical aberration correction procedure when moving in the radial direction according to the fourth embodiment.

Fig. 24 is a block diagram showing the structure of an optical disc device according to Embodiment 5 of the present invention.

25(a) to (d) are diagrams showing spherical aberration correction drive signal waveforms during interlayer movement of the optical disc device according to the fifth embodiment.

Fig. 26 is a block diagram showing the configuration of an optical disc device according to Embodiment 6 of the present invention.

27( a ) and ( b ) are beam cross-sectional views for explaining the spherical aberration detection method.

28(a) and (e) are waveform diagrams for explaining the spherical aberration correction method of the sixth embodiment.

Fig. 29 is a block diagram showing the structure of an optical disc device for explaining the method of learning the magnification of the spherical aberration correcting unit according to the sixth embodiment.

30( a ) to ( g ) are waveform diagrams for explaining the learning of the spherical aberration correcting unit in the sixth embodiment.

Fig. 31 is a flowchart of the learning procedure of the spherical aberration signal correcting unit in the sixth embodiment.

32( a ) to ( f ) are waveform diagrams showing the replacement of the magnification of the spherical aberration signal correcting unit during interlayer movement in Example 6. FIG.

Fig. 33 is a block diagram showing the structure of an optical disc device according to Embodiment 7 of the present invention.

34(a) and (g) are waveform diagrams for explaining FE signal correction in the seventh embodiment.

FIG. 35 is a block diagram showing the FE signal correction unit 30 of the seventh embodiment.

36(a) to (g) are waveform diagrams for explaining the learning method of the FE signal correcting unit of the seventh embodiment.

Fig. 37 is a flowchart showing the learning procedure of the FE signal correcting unit in the seventh embodiment.

Fig. 38 is a block diagram showing the structure of an optical disc device according to Embodiment 8 of the present invention.

Fig. 39 is a characteristic diagram for explaining jitter with respect to spherical aberration and focus eccentricity.

FIGS. 40( a ) to ( d ) are waveform diagrams for illustrating correction by using the influence of defocus residual spherical aberration in Embodiment 8. FIG.

Fig. 41 is a block diagram showing the structure of an optical disc device according to Embodiment 9 of the present invention.

42A to D are characteristic diagrams for explaining the control band and influence of interference of the ninth embodiment.

Fig. 43 is a block diagram for explaining the control frequency band and influence of interference in the ninth embodiment.

44A to D are characteristic diagrams for explaining the characteristics of the control section, the drive circuit and the regulator of the ninth embodiment.

Fig. 45 is a block diagram showing the structure of an optical disc device according to Embodiment 10 of the present invention.

46(a) to (e) are waveform diagrams for explaining spherical aberration correction during retrieval in the tenth embodiment.

Fig. 47 is a flowchart showing the spherical aberration correction procedure in the tenth embodiment when moving in the radial direction.

48(a) to (c) are waveform diagrams showing the effect of the groove bottom crossing in the focus error signal of the tenth embodiment.

49( a ) to ( e ) are waveform diagrams showing the influence of defocus on the spherical aberration detection signal.

50( a ) to ( e ) are waveform diagrams showing the influence of defocus on the spherical aberration detection signal.

51( a ) to ( e ) are waveform diagrams showing the influence of the difference in the information plane on the spherical aberration detection signal.

52( a ) to ( e ) are waveform diagrams showing the influence of the difference in the information plane on the spherical aberration detection signal.

53( a ) to ( c ) are schematic diagrams showing the influence of the position of the spherical aberration correction lens on the focusing distance from the objective lens.

54( a ) to ( c ) are schematic diagrams showing the influence of the position of the spherical aberration correction lens on the focusing distance from the objective lens.

Detailed ways

Next, examples of the present invention will be described.

"Example 1"

Fig. 8 is a block diagram showing the structure of an optical disc device according to Embodiment 1 of the present invention. FIG. 9 is a cross-sectional view of a light beam for illustrating a spherical aberration detection method in the embodiment of FIG. 8 . FIG. 10 is a cross-sectional view illustrating in detail the light receiving portion 37 in the optical disc device shown in FIG. 8 . FIG. 11 is a block diagram showing details of the light receiving unit 37 and the preamplifier 12 in the optical disc device shown in FIG. 8 . In these figures, components corresponding to those of the conventional optical disc device are given the same reference numerals.

The focus adjustment in this embodiment is performed by driving the objective lens 1 toward the focus device 2 as the first adjuster, similarly to the focus adjustment of the optical disc device in FIG. 3 .

However, the spherical aberration correction in this embodiment is performed by using two types of actuators (first and second actuators) 34; 35 to drive the spherical aberration correction lens 15 which functions as the spherical aberration variable mechanism. Hereinafter, this point will be described in detail.

In this embodiment, there is a spherical aberration correcting lens 15 shown in FIG. 7, and a spherical aberration correcting adjuster (the second adjuster) 34 and a stepping motor 35 (third adjuster) that roughly moves the spherical aberration correcting lens 15 and the spherical aberration correcting adjuster 34.

The spherical aberration correction actuator 34 functioning as the second actuator is for driving the spherical aberration correction lens 15 functioning as the spherical aberration variable mechanism. This spherical aberration correction adjuster 34 can adjust the spherical aberration by changing the distance between the spherical aberration correction lenses 15 . The range in which the spherical aberration correction actuator 34 can move one of the spherical aberration correction lenses 15 (possible movement distance) is smaller than that of the stepping motor 35 which functions as a third actuator to be described below. However, the spherical aberration correction adjuster 34 responds to the signal included in the alternating current component (AC component) of the spherical aberration correction signal calculated in response to the spherical aberration detection signal with high precision, and moves the spherical aberration correction lens 15 to correct the spherical aberration. correction.

A stepping motor 35 as a third actuator can move one lens of the spherical aberration correction lens 15 and the spherical aberration correction actuator 34 . The stepping motor 35 has low followability to high-frequency signals, but the range in which the spherical aberration correction lens 15 can be moved (movable distance) is larger than that of the spherical aberration correction adjuster 34 . Therefore, the stepping motor 35 can smoothly follow a DC signal or a low frequency signal.

In this embodiment, the stepping motor 35 moves the spherical aberration The correction lens 15 performs rough correction of spherical aberration. In addition, fine correction of spherical aberration is performed by the spherical aberration correction adjuster 34 of the second adjuster.

The spherical aberration correction adjuster 34 and the stepping motor 35 are driven by a beam expander fine drive circuit 33 and a beam expander rough drive circuit 32 , respectively. The beam expander fine drive circuit 33 and the beam expander rough drive circuit 32 amplify the AC component and the DC component of the control signal (spherical aberration correction signal) output from the microcomputer 8, respectively. Based on the spherical aberration detection signal, the microcomputer 8 outputs a spherical aberration correction signal.

The spherical aberration correction control of Embodiment 1 will be described in detail with reference to FIGS. 8 to 12 . FIG. 12 is a waveform diagram of a spherical aberration correction drive signal in the first embodiment.

First, refer to FIG. 8 .

Based on the signal from the light receiving unit 37 as the light receiving mechanism, the focusing error signal generator 36 functioning as the focusing state detection mechanism detects a signal corresponding to the focusing state of the light beam on the information surface of the optical disc 20 . Specifically, a vertical direction error signal between the collected beam spot output from the optical head 5 and the optical disc 20 is generated based on the signal output from the preamplifier 12 .

Next, a method of generating a focus error signal (hereinafter referred to as FE signal) will be described in detail. As shown in FIG. 10 , the light receiving unit 37 splits and detects the beam passing through the lens 46 by a polarizing beam splitter 47 , and extracts only the peripheral beam by using a first light shield 48 . On the other hand, only the inner peripheral light beam is taken out by the second light shielding plate 49;

As shown in FIG. 11 , the light receiving part 40 on the outer peripheral side and the light receiving part 41 on the inner peripheral side are respectively divided into four regions A; B; C; D. Each region generates a photocurrent corresponding to the amount of detected light, and outputs it to I/V converters 42 a to 42 d and I/V converters 43 a to 43 d mounted inside the preamplifier 12 .

The signals converted into voltage by I/V converters 42a-42d; I/V converters 43a-43d are respectively used by the focus error signal generator 44 on the outer circumference side; the focus error signal generator 45 on the inner circumference side. The signal generator 7 performs the same operation, and converts them into the focus error signal on the outer periphery side and the focus error signal on the inner periphery side respectively.

The focus error signal of Embodiment 1 actually used for focus adjustment is a signal obtained by adding the outer peripheral side focus error signal and the inner peripheral side focus error signal by the focus error signal generator 36 .

Thus, the method of generating the focus error signal of this embodiment is slightly different from the focus error signal of the conventional astigmatism method, but its characteristics are equivalent. Therefore, using the FE signal which is the output signal of the focus error signal generator 36, it is driven in the same way as the conventional device to realize focus adjustment so that the beam spot is focused on the information recording surface of the optical disc 20 into a predetermined focusing state.

Next, with reference to FIG. 9; FIG. 11; FIG. 12, the detection method of the spherical aberration detection signal and the control method thereof will be described.

When the focus adjustment is in working state, as shown in FIG. 2 , the light beam emitted by the optical head 5 is refracted by the base part 21 of the optical disc 20, and the light beam on the outer peripheral side is at focus B, while the light beam on the inner peripheral side is collected at focus C.

When spherical aberration does not occur on the information recording surface of the optical disc 20, the focus B of the light beam on the outer peripheral side; When the focal point C and the focal point C are separated from each other, the information recording surface corresponding to the convergence of the two focal points at the same time becomes a defocused state.

As shown in FIG. 11 , the spherical aberration detection mechanism 31 functioning as the spherical aberration detection mechanism detects the amount by which the light beam on the outer peripheral side is affected by spherical aberration (the amount of defocus of the focal point B) and the amount by which the light beam on the inner peripheral side is affected by the spherical aberration. Amount of aberration influence (defocus amount of focal point C); thus, a signal corresponding to the amount of spherical aberration occurring at the light beam converging position is detected. More specifically, a method of calculating an outer focus error signal as an output signal of the outer focus error signal generator 44 and an inner focus error signal as an output signal of the inner focus error signal generator 45 is used to generate The spherical aberration detection signal corresponds to the signal of the amount of spherical aberration occurring at the beam focusing position.

The spherical aberration detection signal, which is the output signal of the spherical aberration detector 31, is input to the microcomputer 8, and filter operations such as phase compensation and gain compensation are performed to generate a spherical aberration correction signal for spherical aberration correction. The microcomputer 8 having the function of the focus adjustment mechanism and the function of the spherical aberration control mechanism separates the frequency of the spherical aberration correction signal after the filter operation; and the beam expander coarse drive circuit 32 that responds to the DC component of the spherical aberration correction signal. A drive signal that moves the spherical aberration correction lens 15 to a position where the DC component of the spherical aberration correction signal becomes approximately 0 is sent to the stepping motor (see FIG. 12( b )). The stepping motor 35 receiving this drive signal moves the spherical aberration correcting lens 15 (time t1) to perform correction so that the DC component of the spherical aberration becomes almost zero.

Next, the microcomputer 8 outputs a drive signal (time t2) to move the spherical aberration correction lens 15 to the beam expander precision drive circuit 33, that is, as shown in FIG. The drive signal in which the AC component of the spherical aberration correction signal becomes approximately 0; the spherical aberration correction adjuster 34 receiving this signal moves the spherical aberration correction lens 15 to perform correction control so that the spherical aberration becomes approximately 0, That is, focus B; focus C are consistent (that is, focus B; focus C is close to focus A at the same time).

Specifically, the microcomputer 8 performs filter calculation on the spherical aberration detection signal of the output signal of the spherical aberration detector 31 . The DC component of the spherical aberration detection signal after the filtering operation is driven by the beam expander coarse drive circuit 32 and the stepping motor 35 to drive the spherical aberration correction lens 15 to perform correction control so that the focal points A; B; C coincide. In addition, for the AC component, the spherical aberration correction lens 15 is driven by the beam expander precision driving circuit 33 and the spherical aberration correction regulator 34, and the correction control is performed so that the focal points A; B; C are aligned.

In this embodiment, as for the DC component of the spherical aberration correction signal, the beam expander coarse drive circuit 32 transmits the drive signal which becomes approximately 0 to the stepping motor 35, and the stepping motor 35 moves the spherical aberration correction The lens 15 corrects the spherical aberration of the DC component; as for the AC component of the spherical aberration correction signal, the beam expander precision drive circuit 33 transmits the driving signal that becomes approximately 0 to the spherical aberration correction regulator 34, and the spherical aberration correction regulator 34 The aberration correction adjuster 34 moves the spherical aberration correction lens 15 to correct the spherical aberration of the AC component; therefore, in order to achieve higher-density recording on the optical disc 20, even if an optical disc with a larger NA ( For example, NA is 0.8 or more; further, 0.85 or more), the responsiveness is good, and a wide range of spherical aberration correction control can be realized.

In addition, in the control of the stepping motor 35 using the rough drive signal of the beam expander in FIG. to the beam expander coarse drive circuit 32, and the AC component spherical aberration correction signal and the DC component spherical aberration correction signal higher than the optical disc 20 rotation frequency are sent to the beam expander fine drive circuit 33, then follow The slow-speed stepping motor 35 does not exhibit excessive responsiveness due to the influence of the thickness unevenness of the base member 21 per revolution, but can follow the change in the thickness of the base member in the radial direction, and the spherical aberration correction control can be further improved. Accuracy, responsiveness to spherical aberration correction becomes better.

"Example 2"

Fig. 13 is a block diagram showing the structure of the optical disc device of the second embodiment. FIG. 14 is a waveform diagram of spherical aberration correction signals during interlayer movement in this embodiment. FIG. 15 is a flow chart of the procedure for correcting spherical aberration during interlayer movement in this embodiment. Components and parts in these figures that are the same as those of the prior art and Embodiment 1 are assigned the same symbols, and description thereof will be omitted.

The interlayer movement mechanism for driving the focus device is constituted by the microcomputer 8 and the focus device drive circuit 9 . In FIG. 13 , the drive position selection unit 13 fetches the target drive position from the drive position storage unit 14 and outputs it to the beam expander rough drive circuit 32 .

In addition, as in the first embodiment, the focus error signal which is the sum of the focus error signal on the outer circumference side and the focus error signal on the inner circumference side; the spherical aberration detection signal which is the difference between the focus error signal on the outer circumference side and the focus error signal on the inner circumference side is used. for focus adjustment and spherical aberration control.

The spherical aberration correction control at the time of the layer-to-layer movement in Example 2 having the above-mentioned structure will be described with reference to FIGS. 13 to 15 .

14 (c); (d), when moving between layers, at first at time t1, the microcomputer 8 stops the output to the beam expander precision drive circuit 33 according to the output signal from the spherical aberration detector 31, On the other hand, the output from the focus error signal generator 36 is stopped corresponding to the focus device drive circuit 9 . Thus, the correction control and focus adjustment of spherical aberration do not work, that is, stop working (steps S1; S2 of FIG. 15).

Next, as shown in FIG. 14( d ), as in the conventional procedure, a drive command for interlayer movement is output to the focuser drive circuit 9 until time t2 (step S3 in FIG. 15 ). If at time t2 the drive instruction for interlayer movement is finished, at the same time, the microcomputer 8 releases the stop of the focus device drive circuit 9 output, that is, according to the stop of the focus error signal generator 36 output, as shown in Figure 14 (d), The focus adjustment is restarted (step S4 of Fig. 15).

Then, until time t3, after waiting for the stabilization of the focus adjustment (step S5 of FIG. 15 ), the microcomputer 8 utilizes the drive position selection part 13 to save the spherical image suitable for the moving target information recording surface from the drive position storage part 14. The driving position storage unit 14 shown in FIG. 13 of the information on the driving position of the aberration correcting lens 15 takes out the relevant information, and the spherical aberration correcting lens 15 is set as shown in FIG. A drive signal (offset signal) for moving to the drive position is output to the stepping motor 35 . As a result, the stepping motor 35 is driven, and as shown in FIG. 14( a ), the DC component of the spherical aberration signal becomes approximately 0 (steps S6 and S7 in FIG. 15 ).

Finally, the microcomputer 8 releases the stop of the output of the beam expander precision drive circuit 33 at time t4, and outputs a correction signal that cannot be corrected by the stepping motor 35 as shown in FIG. AC component of the spherical aberration signal) (step S8 in FIG. 15 ), the spherical aberration correction controller 34 restarts the correction control of the spherical aberration.

In addition, by configuring the focus adjustment time, the spherical aberration control stop time, and the drive signal output time of the beam expander coarse drive circuit as follows, higher-speed interlayer access becomes possible.

FIG. 16 is a waveform diagram of the positions of the focusing lens and the information plane L0 and L1 and each signal when moving between layers of a two-layer optical disc. The following description will be made in conjunction with FIG.

Initially, the light beam is set to scan an arbitrary track on the information surface L0. In this state, when the data on the information plane L1 is reproduced, the focus adjustment and the spherical aberration correction control do not operate, that is, stop (time a). Next, after the driving instruction is given to the focusing device driving circuit 9, the driving position selection unit 13 is used to save the relevant information suitable as the target layer (the information plane L1 in this embodiment) from the driving position storage unit 14 shown in FIG. 13 . ) The driving position storage unit 14 of the driving position information of the spherical aberration correcting lens 15 on the other information surface takes out the relevant information, and outputs to the beam expander rough driving circuit 32 to move the spherical aberration correcting lens 15 to the driven position taken out. The driving signal (time b).

Thus, as the focus of the objective lens 1 moves closer to the information surface L1 from the information surface L0, the stepping motor 35 moves and the spherical aberration generated by the movement becomes the minimum, that is, it is closer to the reference spherical surface in the information surface L1. Therefore, it is possible to reduce the influence of the FE signal or the amount of light totally reflected by the optical disk 20 due to large fluctuations in spherical aberration during focus transition, without hindering the stability of focus transition. Immediately after the inactive focus adjustment becomes ON (time c) after moving to the information plane L1, even if the spherical aberration control is ON, if the focus adjustment is unstable, the spherical aberration control Therefore, for example, while observing the FE signal, if the FE signal is focused within a specified range, the focus adjustment is considered to be stable, and the inactive spherical aberration control is turned on (time d).

As a result, the stepping motor 35 (especially the spherical aberration correcting lens 15) is moved to suppress the fluctuation of the spherical aberration that occurs when moving between the layers, so that stable control switching of the spherical aberration of each layer can be realized, Its effect is great.

As described above, by using the coarse drive system (stepping motor 35) to correct the spherical aberration DC component variation that occurs when moving between layers, a wide range of spherical aberration correction control corresponding to two or more layers of optical discs can be realized.

"Example 3"

Fig. 17 is a block diagram showing the structure of an optical disc device according to Embodiment 3 of the present invention. 18 is a diagram showing a spherical aberration correction drive signal waveform during movement in the radial direction of the third embodiment. FIG. 19 is a flowchart showing the spherical aberration correction procedure during movement in the radial direction according to the third embodiment. In these figures, the same members and parts as those in the prior art and the first embodiment are given the same reference numerals and their descriptions are omitted.

In the present embodiment, the optical head 5 is housed as a whole: the light source 3 as the light beam irradiation mechanism function of illuminating the light beam; Position, the focusing device 2 that moves the objective lens 1 on the information plane perpendicular to the optical disc 20 as a first adjuster; in order to change the spherical aberration that occurs at the focusing position of the beam focused by the objective lens 1, as the spherical aberration The spherical aberration correcting lens 15 of variable mechanism function; the stepping motor 35 which moves the spherical aberration correcting lens 15; the spherical aberration correcting adjuster 34 which moves the spherical aberration correcting lens 15; and the reflected light of the optical disc 20 which receives the light beam The receiving light part 37.

The optical head 5 can move in the radial direction of the optical disk 20 by the transport table 60 functioning as a search mechanism, and the transport table 60 is driven by the output signal (drive signal) of the transport table drive circuit 62 .

In addition, like Embodiment 1, the focus error signal (signal output by the focus error signal generator 36) based on the sum of the focus error signal on the outer periphery side and the focus error signal on the inner periphery side; the focus error signal on the outer periphery side and the focus error signal on the inner periphery The spherical aberration detection signal (signal output from the spherical aberration detector 31 ) of the difference between the side focus error signals is used to perform focus adjustment and spherical aberration control.

17; FIG. 18; FIG. 19 illustrates the spherical aberration correction control when moving in the radial direction in Embodiment 3 with the above structure. As shown in Figure 18 (c), in the movement in the radial direction during the search, at first, at the time t1 when the tracking control state is not performed, the microcomputer 8 stops the output to the beam expander precision drive circuit 33, that is, the output of the circuit 33 according to the spherical surface The output of the aberration detector 31 outputs the method of making the spherical aberration correction regulator 34 inactive, and the correction control of the spherical aberration is stopped (step S1 of FIG. 19 ), as shown in FIG. 18( d), until time t2 , outputting a driving signal for moving the conveying stage to the conveying stage drive circuit 62 (step S2 in FIG. 19 ).

The transport table driving circuit 62 moves the transport table 60 on which the optical head 5 is mounted in the radial direction of the optical disc 20 according to the transport table driving signal transmitted from the microcomputer 8 . Next, at time t3, the microcomputer 8 outputs a drive signal to the beam expander coarse drive circuit 32 so that the DC component of the spherical aberration detection signal becomes approximately 0 as shown in FIG. 18(b). The stepping motor 35 is driven according to the drive signal transmitted from the beam expander coarse drive circuit 32, and the microcomputer 8 waits for the stepping motor 35 to move to a predetermined position (steps S3 and S4 in FIG. 19).

At the next time t4, the microcomputer 8 cancels the output corresponding to the spherical aberration detector 31, stops the output to the beam expander precision driving circuit 33, and outputs what cannot be corrected by the stepping motor 35 as shown in FIG. 18(c ) (that is, the AC component of the spherical aberration signal in this embodiment) (step S5 in FIG. 19 ), the spherical aberration correction controller 34 is used to restart the correction control of the spherical aberration.

In addition, by configuring the spherical aberration control stop time and the drive signal output time of the beam expander rough drive circuit as follows, higher-speed access in the radial direction becomes possible.

FIG. 20 is a waveform diagram of the change in pressure of the base member of the objective lens 1 and the optical disk 20 and each signal when moving in the radial direction, and will be described below with reference to FIG. 20 . Initially, it is assumed that the light beam scans an arbitrary track on the inner circumference of the optical disc 20 . In this state, when reproducing data on the peripheral side, first, the microcomputer 8 disables tracking control and spherical aberration correction control, that is, stops (time a). Next, after giving a drive command to the transport table drive circuit 62, the microcomputer 8 performs rough drive on the beam expander in order to move (beam) to the drive position of the spherical aberration correcting lens 15 adapted to the pressure of the base member at the target radius position. The circuit 32 transmits the spherical aberration correction signal, and the beam expander coarse drive circuit 32 outputs a drive signal (bias signal) corresponding to the transmitted spherical aberration correction signal (time b).

Thereby, as the conveying table 60 moves closer to the outer periphery from the inner periphery, the stepping motor 35 is moved so that the spherical aberration generated due to this movement is the smallest, that is, it is closer to the spherical aberration amount that is the reference as the target outer periphery position, and therefore , can reduce the influence of the tracking error signal or FE signal caused by the large fluctuation of spherical aberration during the movement in the radial direction, and will not hinder the stability of the pull-back operation of the tracking control shortly after the movement in the radial direction.

After moving to the outer periphery of the target, stop the tracking control (time C), and continue to release the stop of the spherical aberration control. Even if it is turned on, if the tracking control is unstable, the tracking control may be unstable. Therefore, for example, while observing the tracking The error signal, if the tracking error signal converges within a predetermined range, the microcomputer 8 judges that the tracking control is stable, cancels the stop of the spherical aberration control, and turns on (time d). As a result, when moving in the radial direction, more stable spherical aberration conversion for each radius can be realized, and the effect is large.

As described above, by using the rough drive system (stepping motor 35) to correct the spherical aberration DC component that occurs when moving in the radial direction, it is possible to correct the spherical aberration that absorbs the uneven thickness of the optical disc 20 or the sticking unevenness in a wide range. control.

"Example 4"

Fig. 21 is a block diagram showing the structure of an optical disc device according to Embodiment 4 of the present invention. Fig. 22 is a waveform diagram showing the spherical aberration correction drive signal during the interlayer movement of the optical disc device according to the fourth embodiment. Fig. 23 is a flow chart showing the spherical aberration correction procedure during interlayer movement in the fourth embodiment. In these figures, the same members and parts as those in the prior art and the first embodiment are given the same reference numerals and their descriptions are omitted.

The microcomputer 8 has an offset storage unit 68 for storing offsets corresponding to each information surface of the optical disc 20, and an offset selection unit 67 serving as an offset addition means and functioning as an offset replacement means. The microcomputer 8 fetches the value to be stored corresponding to each information plane of the optical disc 20 from the offset storage section 68 by the offset selection section 67 and replaces it with the fetched offset. After the addition of the offset amount and the spherical aberration correction signal is performed by the adder 69, it is used as a drive signal to the beam expander precision drive circuit 33 to be applied to the spherical aberration correction lens 15 as an offset. superior.

A beam expander precision drive circuit 33 that amplifies the control output current of the microcomputer 8 drives a spherical aberration correction adjuster 34 . An elastic body such as a leaf spring is attached to the spherical aberration correction lens 15 , and a force corresponding to a signal applied from the spherical aberration correction adjuster 34 acts on the leaf spring. As described above, the force corresponding to the offset amount of each information plane is applied to the leaf spring supporting the spherical aberration correcting lens 15, and therefore, this spherical aberration correcting lens 15 can be moved finely.

In addition, as in Embodiment 1, the sum of the focus error signal on the outer peripheral side and the focus error signal on the inner peripheral side is used to generate the focus error signal; the difference between the focus error signal on the outer peripheral side and the focus error signal on the inner peripheral side is used to generate spherical aberration detection Signal.

The spherical aberration correction control at the time of the layer-to-layer movement in Embodiment 4 with the above structure will be described with reference to FIGS. 21 to 23 .

In this embodiment, as in Embodiment 1, the focus adjustment is in operation, and the spherical aberration detection signal output from the spherical aberration detector 31 is input to the microcomputer 8, where filtering operations such as phase compensation and gain compensation are performed.

The microcomputer 8 uses the offset selection unit 67 to select and replace the offset corresponding to the moving destination information plane stored in the offset of the offset storage unit 68 . Then, the microcomputer 8 uses the adder 69 to add the replaced offset amount and the filtered spherical aberration correction signal, and outputs the added signal to the beam expander precision driving circuit 33 . The beam expander precision drive circuit 33 performs spherical aberration correction based on the offset-added spherical aberration correction signal.

When moving between layers, at first, as shown in FIG. 22(b); (d), at time t1, the microcomputer 8 stops the focus adjustment and the spherical aberration correction control without working (step S1 of FIG. 23; S2), In the same procedure as the conventional one, as shown in FIG. 22(d), a command is output to the focus device drive circuit 9 until time t2 (step S3 in FIG. 23). Next, when the same conventional interlayer shift processing is finished, the focus adjustment is restarted at the same time (step S4 in FIG. Beam expander precision driving circuit 33 is used for the offset of the target movement information recording surface as shown in Figure 22 (c), and is added to the beam expander precision drive signal as shown in Figure 22 (b). .

Thus, the beam expander precision drive circuit 33 drives the spherical aberration correction adjuster 34 based on the beam expander precision drive signal so that the DC component of the spherical aberration detection signal becomes approximately 0 (step S5 in FIG. 23 ). After the focus adjustment is stabilized (step S6 in FIG. 23), at time t3, the microcomputer 8 outputs to the beam expander precision drive circuit 33 a spherical image that cannot be corrected only with the offset as shown in FIG. 22(b). The difference correction signal is received, the stop of the spherical aberration correction regulator 34 is released, and the correction control of the spherical aberration is resumed (step S7 in FIG. 23 ).

In this way, the DC component of the spherical aberration that occurs when moving between layers is added to the offset of the precision drive system (spherical aberration correction adjuster 34), and stable spherical aberration correction control with high correction accuracy can be realized. .

In addition, the method of measuring the DC component of spherical aberration within a predetermined period of time and adding the average value to the offset of the offset storage unit 68 currently selected by the offset selection unit 67 makes the spherical aberration The correction control target position becomes the best, which can improve the tracking accuracy.

"Example 5"

Fig. 24 is a block diagram showing the configuration of an optical disc device according to Embodiment 5 of the present invention. 25(a) to (d) are waveform diagrams showing spherical aberration correction drive signals and the like during the interlayer movement of the optical disc device according to the fifth embodiment. In these figures, the same members and parts as those in the prior art and the first embodiment are given the same reference numerals and their descriptions are omitted.

The microcomputer 8 of this embodiment shown in FIG. 24 has a quiet zone generator 70 . The quiet zone generator 70 receives the signal output from the gain adjuster 66, and when the absolute value of the signal reaches a predetermined value, blocks the signal and operates so as not to transmit it to the beam expander rough driving circuit 32.

The stepping motor 35 is driven by the beam expander rough drive circuit 32 that amplifies the current of the control output of the microcomputer 8 .

The spherical aberration correcting lens 15 can be moved in a wider range by the stepping motor 35 . In addition, as in the first embodiment, the focus error signal is generated from the sum of the focus error signal on the outer periphery side and the focus error signal on the inner periphery side, and the spherical image is generated by the difference between the focus error signal on the outer periphery side and the focus error signal on the inner periphery side. Bad detection signal.

The spherical aberration correction control of Embodiment 5 with the above structure will be described with reference to FIGS. 24 and 25 .

In this embodiment, as in Embodiment 1, when the focus adjustment is in operation, the spherical aberration detection signal output by the spherical aberration detector 31 is input to the microcomputer 8, where phase compensation, gain compensation, etc. are performed. filter operation. The quiet zone generation unit 70 in the microcomputer 8 receives the spherical aberration correction signal after the filter calculation by the gain adjustment unit 66, and outputs the signal to the beam expander coarse driving circuit 32 when the absolute value of the signal exceeds a predetermined value. , when the absolute value of the signal becomes below the specified value, the output of the signal is blocked.

As will be described later, at time t1, for driving the stepping motor, the spherical aberration correction signal after filtering operation has a waveform as shown in FIG. 25(a). During time t1 to t2, it can be seen that the spherical aberration detection signal becomes smaller due to the driving of the stepping motor.

FIG. 25( d ) shows the output of the quiet zone generator 70 (the spherical aberration detection signal after the quiet zone processing). This spherical aberration detection signal is output to the circuit 32 for coarse driving of the beam expander, and the circuit 32 for rough driving of the beam expander outputs a signal as shown in FIG. Correction control for aberrations.

As shown in FIG. 25(c), during time t1 to t2, the stepping motor 35 is driven by the beam expander rough drive circuit to correct spherical aberration. However, as shown in FIG. 25(d), the absolute value of the spherical aberration correction signal becomes below a predetermined value after time t2, and the output is blocked. Therefore, as shown in FIG. 25(c), the stepping motor 35 Cannot be corrected.

In this way, when the change of the spherical aberration correction signal (or spherical aberration detection signal) is small, the overrun error caused by the oversensitive response of the stepping motor 35 can be reduced. In particular, when the thickness of the optical disk changes gradually during spiral operation and the spherical aberration fluctuates at a low frequency, smooth follow-up control (whether or not to control) becomes possible, and the effect is large.

"Example 6"

Fig. 26 is a block diagram showing the configuration of an optical disc device according to Embodiment 6 of the present invention. FIG. 27 is a cross-sectional view of light beams for describing spherical aberration detection in this embodiment. In the optical disc device of the present embodiment, the light receiving unit 37 and the preamplifier 12 have the configurations shown in FIGS. 10 and 11 in the same manner as in the first embodiment.

In FIG. 26 , the reflected light from the optical disc 20 received by the light receiving unit 37 is detected as a photocurrent corresponding to the amount of received light, and sent to the preamplifier 12 . The preamplifier 12 performs current-voltage conversion, and sends an output voltage corresponding to the photocurrent to the focus error signal generator 36 and the spherical aberration detector 31 .

The focus error signal generator 36 functioning as the focusing state detection mechanism detects a signal corresponding to the focusing state on the information surface 29 of the optical disc 20 based on the signal of the light receiving unit 37 functioning as the light receiving unit. Specifically, based on the output signal of the preamplifier 12, a signal corresponding to the focusing state is detected, and an error signal related to the vertical direction between the focused beam spot output by the optical head 5 and the optical disc 20 is generated.

The spherical aberration correction adjuster 34 drives the spherical aberration correction lens 15 which functions as a spherical aberration variable mechanism. Specifically, the method of adjusting the two combined lenses constituting the spherical aberration correcting lens 15 can change the spherical aberration of the beam spot.

In this embodiment and the embodiments described later, the spherical aberration correcting lens 15 is used as the spherical aberration variable mechanism, but the present invention is not limited thereto. It is also possible to use a liquid crystal or the like to change the optical distance (optical path length); and thereby correct the spherical aberration element. The spherical aberration variable mechanism of this type is driven by applying a voltage suitable for the liquid crystal.

The spherical aberration detector 31, which functions as a spherical aberration detection mechanism, detects the state of spherical aberration generated by the beam spot generated on the information surface 29 of the optical disc 20 based on a signal from the light receiving unit 37, which functions as a light receiving mechanism. , and output a signal corresponding to the state of the spherical aberration (hereinafter referred to as the spherical aberration signal).

However, the focus adjustment system and the spherical aberration control system interfere with each other. Specifically, a detection error corresponding to defocus occurs on the spherical aberration signal, and a variation in the distance from the objective lens to the focal point corresponding to the spherical aberration correction amount occurs on the FE signal. Therefore, by amplifying the FE signal by a predetermined factor by the spherical aberration correcting unit 132 and adding it to the spherical aberration signal, the influence of defocus on the spherical aberration signal is eliminated. Thereby, it becomes possible to cut off the loop of interference between the focus adjustment system and the spherical aberration control system.

The spherical aberration signal corrected based on the FE signal is transmitted to the beam expander drive circuit 133 through the spherical aberration control unit 135 . Therefore, the spherical aberration correction adjuster 34 is controlled accordingly by the spherical aberration signal corrected according to the FE signal. In addition, the spherical aberration control unit 135 has filters for phase compensation, gain compensation, etc., and stabilizes the spherical aberration control system. In addition, the beam expander drive circuit 133 is a drive circuit for the spherical aberration correction adjuster 34 .

The method of generating the FE signal will be described with reference to FIG. 10 .

The detection lens 46 collects the reflected beam of the optical disc 20 . The polarizing beam splitter 47 splits the reflected beam into two. The first light shielding plate 48 blocks the light beam on the inner peripheral side according to a predetermined radius of the reflected light beam. The light receiving unit 40 on the outer peripheral side receives the light beam passing through the first light shielding plate 48 and converts it into a photocurrent. The second light shielding plate 49 blocks the light beam outside the predetermined beam radius, and the light receiving unit 41 on the inner peripheral side receives the light beam passing through the second light shielding plate 49 and converts it into photocurrent.

Specifically, as shown in FIG. 10 , its structure is that the light receiving part 37 utilizes a polarized light beam splitter 47 to separate the reflected light beam of the optical disc 20 passing through the detection lens 46, and one side uses the first light shielding plate 48 to only take out the light beam of the outer periphery, The other way is to use the second shading plate 49 to take out only the light beam on the inner periphery, and use the light receiving part 40 on the outer peripheral side and the light receiving part 41 on the inner peripheral side to detect.

The light receiving unit 37; the focus error signal generator 36; the spherical aberration detector 31 and the preamplifier 12 of this embodiment also have the configuration shown in FIG. 11 .

The light-receiving part 40 on the outer peripheral side shown in FIG. 11 ; the light-receiving part 41 on the inner peripheral side is divided into four regions: A; B; C; D, respectively, generate photocurrent corresponding to the amount of detected light, and output it to the preamplifier 12. Internal I/V converters 42a-42d; I/V converters 43a-43d. I/V converters 42a-42d; I/V converters 43a-43d are converted into current-voltage signals, and sent to the outer peripheral side focus error signal generator 44; the inner peripheral side focus error signal generator 45 respectively.

Here, the length direction of the information track refers to the tangential direction of the magnetic track 28 of the optical disc 20 , and the radial direction of the optical disc refers to the direction perpendicular to the magnetic track 28 of the optical disc 20 . Therefore, the sum of the I/V converter 42a and the I/V converter 42c minus the sum of the I/V converter 42b and the I/V converter 42d is obtained in the focus error signal generator 44 on the outer peripheral side, and is used The astigmatism method obtains the focus error signal on the outer peripheral side as the FE signal; the focus error signal generator 45 on the inner peripheral side obtains the sum of the I/V converter 43a and the I/V converter 43c minus the I/V The calculation of the sum of the converter 43b and the I/V converter 43d uses the astigmatism method to obtain an inner peripheral side focus error signal as an FE signal.

The focus error signal of this embodiment that is actually used for focus adjustment is this outer peripheral side focus error signal and a signal that is added in the inner peripheral side focus error signal generator 36 . That is, (I/V converter 42a+I/V converter 42c)-(I/V converter 42b+I/V converter 42d) and (I/V converter 43a+I/V converter 43c)- The sum of (I/V converter 43b+I/V converter 43d) can be written as ((I/V converter 42a+I/V converter 43a)+(I/V converter 42c+I/V converter 43c))-((I/V converter 42b+I/V converter 43b)+(I/V converter 42d+I/V converter 43d)).

Therefore, the focus error signal of this embodiment is slightly different from the focus error signal of the conventional astigmatism method, but its characteristics are equivalent.

Therefore, by using the FE signal as the output signal of the focus error signal generator 36, the beam spot can be controlled so as to be in a predetermined focused state with respect to the information surface 29 of the optical disc 20, as in conventional devices.

Next, a method of generating (a method of detecting) a spherical aberration signal will be described.

The spherical aberration signal is a signal obtained by subtracting the focus error signal on the outer peripheral side and the focus error signal on the inner peripheral side by the spherical aberration detector 31 .

The spherical aberration signal will be described with reference to FIG. 27 . Fig. 27(a) shows a state where the distance from the surface of the optical disc to the information plane is optimal and spherical aberration does not occur on the information plane. Fig. 27(b) shows a state where the distance is small and spherical aberration occurs on the information plane.

The above-mentioned focus adjustment is in the working state, as shown in Figure 27 (a), the light beam emitted from the optical head 5 is refracted on the base part 21 of the optical disc 20, the light beam on the outer peripheral side is at the focus B; the light beam on the inner peripheral side is at the focus C set light. The position A is located on the straight line connecting the focus B and the focus C, and is on the information surface 29 . Since spherical aberration does not occur on the information surface 29 of the optical disc 20, the focus B of the light beam on the outer circumference side and the focus C of the light beam on the inner circumference side coincide with the position A at the same time. That is, the equidistant plane from position A coincides with the wavefront of the beam.

As shown in FIG. 27(b), as the thickness of the base member 21 corresponding to the distance from the surface of the optical disk to the information surface becomes thinner, the influence of spherical aberration increases. That is, the focal point B and the focal point C are separated from each other, and corresponding to the position A of the information surface 29 to be converged, the two focal points are in a defocused state at the same time. However, the focus adjustment operates so that the focus error signal (the output signal of the focus error signal generator 36 ) obtained by adding the above-mentioned outer peripheral side focus error signal and the inner peripheral side focus error signal becomes approximately 0. Therefore, the position A coincides with the information plane 29 . At this time, the wavefront of the beam is inconsistent with the equidistant surface at position A. Here, the solid lines indicate the inner and outer light beams when spherical aberration occurs, and the broken lines indicate the inner and outer light beams when no spherical aberration occurs. In addition, as shown in Figure 27(a), when the thickness from the surface of the optical disc to the information surface becomes thicker, the focus B and the focus C are also separated from each other, and the two foci at position A on the information surface 29 where the light beam should be converged are in a defocused state at the same time .

As shown in FIG. 11 , the spherical aberration detector 31 functioning as a spherical aberration detection mechanism detects the amount of spherical aberration (the amount of defocus of the focal point B) received by the light beam on the outer peripheral side and the amount of spherical aberration received by the light beam on the inner peripheral side. Based on the amount of spherical aberration received (the amount of defocus of the focal point C), a signal corresponding to the amount of spherical aberration occurring at the beam focusing position is detected. More specifically, the difference between the outer focus error signal which is the output signal of the outer focus error signal generator 44 and the inner focus error signal which is the output signal of the inner focus error signal generator 45 is calculated. A method of generating a spherical aberration signal corresponding to a signal of a spherical aberration amount occurring at a beam focusing position.

In FIG. 26 , in the spherical aberration control unit 135 , the above-mentioned phase compensation of the spherical aberration signal; filter calculations such as gain compensation are performed. Thereafter, the spherical aberration control unit 135 outputs an output signal for moving the spherical aberration correcting lens 15 to the beam expander drive circuit 133 , and the spherical aberration correcting adjuster 34 receiving the drive signal moves the spherical aberration correcting lens 15 . That is, the correction control is performed so that the spherical aberration becomes zero, that is, the focus B; However, there is a problem that the above-mentioned focus adjustment system and spherical aberration control system interfere with each other and the control systems are mutually unstable.

Combined with Fig. 49; the waveform diagram of Fig. 50 illustrates the interference of the focus adjustment system and the spherical aberration control system. First, the influence of the focus adjustment system on the spherical aberration signal will be described. In addition, it is assumed that the spherical aberration control system is in operation. Fig. 49(a) shows how the first shading plate 48 and the second shading plate 49 are adjusted to divide the focused light beam at the 50% radial position of the received light beam radius. Figure 49(b) shows the focus error signal on the outer peripheral side, Figure 49(c) shows the focus error signal on the inner circumference side, Figure 49(d) shows the focus error signal, and Figure 49(e) shows the spherical aberration detection Signal. The signal obtained by subtracting the inner focus error signal of FIG. 49( c ) from the outer focus error signal of FIG. 49( b ) above is the spherical aberration detection signal of FIG. 49( e ). The vertical axis represents the voltage of each signal, and the horizontal axis represents defocus.

Fig. 50(a) shows how the first shading plate 48 and the second shading plate 49 are adjusted to divide the focused light beam at the 75% radial position of the received light beam radius. Figure 50(b) shows the focus error signal on the outer peripheral side, Figure 50(c) shows the focus error signal on the inner circumference side, Figure 50(d) shows the focus error signal, and Figure 50(e) shows the spherical aberration detection Signal. The vertical axis represents the voltage of each signal, and the horizontal axis represents defocus.

As shown in FIG. 49(a), when the received beam is divided at a radial position of 50% of the beam radius, the light quantity on the outer peripheral side is larger than that on the inner peripheral side. Therefore, the focus error signal on the outer peripheral side in FIG. 49(b) The amplitude is larger than that of the focus error signal on the inner peripheral side in FIG. 49(c). As a result, although the spherical aberration is constant, the spherical aberration detection signal changes due to defocusing. In addition, the polarity of the spherical aberration signal and the focus error signal of 49(d) become the same due to defocus (the phase of the FE signal has a lag of 0 degrees).

On the other hand, as shown in Fig. 50(a), when the beam receiving light is divided at a radial position of 75% of the beam radius, the amount of light on the outer peripheral side is less than that on the inner peripheral side. Therefore, the outer peripheral region in Fig. 50(b) The amplitude of the side focus error signal is smaller than the amplitude of the side focus error signal on the inner circumference of FIG. 50(c). As a result, although the spherical aberration is constant, the spherical aberration detection signal changes due to defocusing. In addition, the polarity of the spherical aberration signal is opposite to the focus error signal in FIG. 50( d ) due to defocus (the phase of the FE signal is retarded by 180 degrees).

The aforementioned shift of the spherical aberration signal due to defocus acts as an external disturbance to the spherical aberration control system.

Next, the external interference of the movement of the spherical aberration correcting lens 15 on the focus adjustment system will be described in detail with reference to FIG. 53 . Fig. 53 is a schematic diagram showing the influence of the position of the spherical aberration correction lens on the focusing distance from the objective lens. Fig. 53(a) shows that the thickness from the surface of the optical disc to the information plane is optimal; and no spherical aberration occurs on the information plane. Similarly, Fig. 53(b) shows a case where the thickness is thick. In addition, the focus adjustment system works normally; and the state of spherical aberration occurring on the information plane is corrected by the spherical aberration correcting lens 15 . Fig. 53(c) shows a case where the thickness is thin. Similar to FIG. 53( b ), the state of spherical aberration occurring on the information plane is corrected by the spherical aberration correcting lens 15 .

As shown in FIG. 53( b ), as the thickness of the base member becomes thicker, the interval W between the spherical aberration correcting lenses 15 becomes narrower. In addition, the distance Z from the objective lens 1 to the focal point becomes longer.

Also, as shown in FIG. 53(c), as the base member becomes thinner, the interval W becomes wider and the distance Z becomes shorter. As the interval W of the spherical aberration correcting lenses 15 changes, the distance Z changes. That is, the variation of this distance Z acts as an external disturbance of the focus adjustment system.

Next, a method for eliminating the influence of the spherical aberration signal by the focus adjustment system will be described. In addition, the spherical aberration correcting unit 132 is a subroutine that eliminates this influence. The operation of the spherical aberration correction unit 132 will be described with reference to FIG. 28 . FIG. 28( a ) shows the output of the focusing device drive circuit 9 . Fig. 28(b) shows the output of focus error signal generator 36, Fig. 28(c) shows the output of spherical aberration correction unit 132, Fig. 28(d) shows the output of spherical aberration detector 31, Fig. 28(e) Indicates the corrected spherical aberration signal.

In addition, it shows a state where external disturbance of a frequency higher than the frequency band of the focus adjustment system is applied to the focus adjustment system. As shown in FIG. 28(a), the output of the focusing device drive circuit 9 becomes a drive signal corresponding to the external disturbance applied. In addition, the amount of defocus becomes a waveform corresponding to FIG. 28( a ). As described above, the spherical aberration signal becomes the waveform shown in FIG. 28( d ) corresponding to the defocus amount change level. Fig. 28(d) shows the external disturbance given to the spherical aberration signal by the focus adjustment system. When the microcomputer 8 is working on focus adjustment, it utilizes the method of amplifying the FE signal by a given factor (K times) in the spherical aberration correcting part 132 and adding it to the spherical aberration signal, as shown in FIG. 28(e), to eliminate accompanying astigmatism Influence of spherical aberration signal of focus.

Next, a method of determining the magnification K of the spherical aberration correcting unit 132 will be described. FIG. 29 is a block diagram showing the configuration of an optical disc device for explaining the spherical aberration correcting unit magnification learning method of the present embodiment. The optical disc device shown in FIG. 29 is an optical disc device shown in FIG. 1 with a subroutine for magnification K learning added. Therefore, the sub-program with the same number in Fig. 29 represents the sub-program with the same number in Fig. 1 . The focus test signal generator 50 is a test signal added to the focus drive signal output by the focus adjustment unit 17 . The first amplitude detector 51 detects the amplitude of the spherical aberration signal. The spherical aberration correction learning unit 52 detects the amplification factor of the spherical aberration correction unit 132 at which the amplitude detection signal of the first amplitude detector 51 becomes the minimum.

Its operation will be described with reference to the waveforms in FIG. 30 . FIG. 30( a ) shows the output of the focusing device drive circuit 9 . Similarly, FIG. 30( b) shows the output of the focus error signal generator 36, FIG. 30( c) shows the magnification of the spherical aberration correcting unit 132, and FIG. 30( d) shows the output of the spherical aberration correcting unit 132. FIG. 30 30( e ) shows the output of the spherical aberration detector 31 , FIG. 30( f ) shows the corrected spherical aberration signal, and FIG. 30( g ) shows the output of the first amplitude detector 51 . In addition, as shown in FIG. 50( a ), it shows a case where the receiving light is divided at a radius of 75% of the beam radius. The vertical axis represents the voltage of each signal, and the horizontal axis represents time. The spherical aberration correction learning unit 52 sets the magnification of the spherical aberration correction unit 132 as a coefficient K, and sets Ka at the initial time t0.

When the focus adjustment is in operation but the spherical aberration control is not in operation, the focus test signal generator 50 adds the focus drive signal output from the focus adjustment unit 17 to the test signal shown in FIG. 30( a ). Because the polarity of the focus error signal generator 36 is opposite to that of the focus drive signal, the output of the focus error signal generator 36 becomes as shown in FIG. signal shown. In this state, the amplitude of the spherical aberration signal is proportional to the focus error signal, and therefore, the spherical aberration signal becomes the waveform shown in Fig. 30(e). However, as shown in FIG. 50( a ), the polarity of the spherical aberration signal is opposite to that of the FE signal.

The spherical aberration correction learning unit 52 uses the microcomputer 8 to measure the amplitude of the corrected spherical aberration signal while gradually changing the coefficient K of the spherical aberration correcting unit 132 . The coefficient at time t1 is Kb, and the coefficient at time t2 is Kc. In addition, the amplitude of the corrected spherical aberration signal is measured by the first amplitude detector 51 . In FIG. 30 , when the coefficient is Ka; Kc, the signal of the corrected spherical aberration signal does not become the minimum, and when the coefficient is Kb, the amplitude becomes the minimum. Therefore, as shown in FIG. 30( g ), in the state of the magnification Kb, the amplitude of the corrected spherical aberration signal becomes minimum, and is determined as the magnification K of the spherical aberration correcting unit 132 .

The operation for determining the magnification K of the spherical aberration correcting unit 132 will be described with reference to the flowchart of FIG. 31 . First, the spherical aberration correction learning unit 52 sets the initial value Ka as the magnification of the spherical aberration correction unit 132 through the microcomputer 8 in step S1. In step S2, the focus test signal generator 50 starts adding the focus drive signal of the focus adjustment unit 17 to the test signal when the focus adjustment is in operation and the spherical aberration control is not in operation. In step S3 , the amplitude of the spherical aberration signal corrected by the spherical aberration correcting unit 132 is obtained from the first amplitude detector 51 and stored as the minimum amplitude value. In step S4, the magnification of the spherical aberration correcting unit 132 is decreased by a predetermined value.

In step S5, the first amplitude detector 51 is used to compare whether the detected amplitude of the corrected spherical aberration signal is smaller than the stored amplitude minimum value. When the amplitude of the corrected spherical aberration signal is smaller than the stored minimum amplitude value, then in step S6, the corrected spherical aberration signal amplitude is re-stored as the minimum value as the minimum amplitude value, and the process proceeds to step S7. When the amplitude of the corrected spherical aberration signal is not less than the stored minimum amplitude value, go to step S7. In step S7, it is compared whether the magnification of the spherical aberration correcting unit 132 is larger than Kc. If it is larger, return to step S4. If not, proceed to step S8. In step S8, the amplification factor of the spherical aberration correcting unit 132 corresponding to the stored amplitude minimum value is set, and the process ends.

Next, when recording or reproducing the information surface of the optical disc 20 having a multi-layer structure having a plurality of information surfaces, the case where the magnification K of the spherical aberration correcting unit 132 is replaced for each layer will be described.

Recording/reproduction on the optical disc 20 shown in FIG. 5 will be described. In the two-layer disk, if the information planes are different, the effects of defocus on the spherical aberration signal explained in conjunction with Fig. 49 and Fig. 50 are also different. This point is illustrated in conjunction with Fig. 51; the waveform diagram of Fig. 52 .

Fig. 51(a) shows how the information surface L0 is divided by the first light shielding plate 48 and the second light shielding plate 49 when recording or reproducing is performed. Figure 51(b) shows the focus error signal on the outer peripheral side, Figure 51(c) shows the focus error signal on the inner circumference side, Figure 51(d) shows the focus error signal, and Figure 51(e) shows the spherical aberration signal . The vertical axis represents the voltage of each signal, and the horizontal axis represents defocus.

Fig. 52(a) shows a state divided by the first shading plate 48 and the second shading plate 49 when the focus is on the information plane L1. Figure 51(b) shows the focus error signal on the outer peripheral side, Figure 51(c) shows the focus error signal on the inner circumference side, Figure 51(d) shows the focus error signal, and Figure 51(e) shows the spherical aberration signal . The vertical axis represents the voltage of each signal, and the horizontal axis represents defocus.

As shown in FIG. 51( a ), it is assumed that when the focal point is designed to be located on the information surface L0, the beam of received light is split at 50% of the radius of the beam of received light. Therefore, the waveforms in Fig. 51(b); (c); (d); (e) are the same as those illustrated in Fig. 49 .

On the other hand, as shown in Figure 52 (b), when the focus is on the information surface L1, the distance W between the spherical aberration correcting lenses 15 is narrower than when the focus is on the information surface L0, and the light beam incident on the objective lens 1 becomes scattered. Light. Therefore, the radius of returning light reflected by the information surface and passing through the spherical aberration correcting lens 15 and entering the light receiving portion becomes smaller. For example, even if the adjustment amount of the first shading plate 48 and the second shading plate 49 are the same, the radius of the light beam still becomes smaller, so the actual division position is larger than the above-mentioned 50% radius. In the picture it is 75%. Therefore, the light quantity on the outer peripheral side is smaller than that on the inner peripheral side, so the amplitude of the focus error signal on the outer peripheral side in FIG. 52( b ) is smaller than the amplitude of the focus error signal on the inner peripheral side in FIG. 52( c ).

As a result, due to defocusing, the spherical aberration signal of FIG. 53(e), which is the difference between the focus error signal on the outer periphery side and the focus error signal on the inner periphery side, is relative to the sum of the focus error signal on the outer periphery side and the focus error signal on the inner periphery side. The polarity of the focus error signal of Fig. 53(d) is reversed (180 degrees phase retardation to the FE signal). As mentioned above, if the information plane of recording or reproduction is different, the influence on the spherical aberration signal of the spherical aberration detector 31 as the objective lens 1 moves is also different, therefore, it is necessary to change: the spherical aberration correction which excludes this influence The magnification of section 132.

The replacement of the magnification of the spherical aberration correcting portion at the time of interlayer movement in the laminated optical disc will be described with reference to FIG. 32 . Fig. 32(a) shows the movement of the beam spot during interlayer movement. Fig. 32(b) shows the magnification of the spherical aberration signal correction unit. The vertical axis represents the voltage of each signal, and the horizontal axis represents time. Fig. 32(c) shows on/off (ON/OFF) of spherical aberration control, and Fig. 32(d) shows on/off of focus adjustment. The vertical axis is the ON/OFF of the control, H indicates conduction, L indicates disconnection, and the horizontal axis indicates time. FIG. 32(e) shows the FE signal, and FIG. 32(f) shows the focus drive signal. The vertical axis represents the voltage of each signal, and the horizontal axis represents time.

The laminated optical disc of the present invention includes: an additive gain storage section for storing the amplification factor of the spherical aberration correction section 132 for each layer; the desired amplification factor of the spherical aberration correction section 132 is taken out from the gain storage section and reset. Addition gain replacement part and microcomputer 8. First, it is assumed that the light beam scans an arbitrary track at L0, and then, the operation of reproducing L1 data will be described. First, the microcomputer 8 stores the magnification of the spherical aberration correction unit 132 for L0 in the addition gain storage unit, and stops the focus adjustment and the spherical aberration control without operating (a).

Next, a predetermined acceleration/deceleration drive pulse command is given to the focus device drive circuit 9 . After moving to L1, the spherical aberration control is turned on immediately (time b) after the focus adjustment, which was originally inactive, is turned on. However, if focus adjustment is unstable, spherical aberration control is also unstable. Therefore, while observing the FE signal, if the FE signal is focused within a predetermined range, it is judged that the focus adjustment is stable, and the amplification factor of the spherical aberration correcting unit 132 is replaced by the addition gain replacement unit (time c). Then, the inactive spherical aberration control can be turned on (time d). In this way, there is no need to classify layers; according to each inter-layer movement, the influence of different movement amounts of the objective lens 1 on the spherical aberration signal of the spherical aberration detector 31 can be relearned, and the influence can be eliminated at high speed and high precision, and the effect is great.

In addition, after excluding the influence of the focus adjustment system on the spherical aberration signal, when the focus adjustment and spherical aberration control work, the focus adjustment part 17 or the gain adjustment of the spherical aberration control part 135 can be adjusted. Spherical aberration controls the gain characteristic of the offset of the disturbance, and higher precision adjustment is also possible. In addition, the adjustment of the gain compensation can be carried out by using, for example, the addition operation of the test signal on the control system; the quadrature phase homodyne detection method.

"Embodiment 7"

Fig. 33 is a block diagram showing the structure of the optical disc device of the seventh embodiment. Fig. 34 is a waveform diagram for explaining FE signal correction in the seventh embodiment. In these figures, components and parts that are the same as those of the prior art and Embodiment 6 are assigned the same symbols, and descriptions thereof are omitted.

In this embodiment, as in Embodiment 6, the focus adjustment is performed according to the focus error signal of the sum of the focus error signal on the outer peripheral side and the focus error signal on the inner peripheral side; the focus error signal on the outer peripheral side and the focus error signal on the inner peripheral side The difference to generate a spherical aberration signal.

The FE signal correcting unit 30 processes the output signal of the beam expander drive circuit 133 and then performs addition to the FE signal. The FE signal correcting unit 30 has a filter having the same characteristics as the spherical aberration correcting adjuster 34 (hereinafter referred to as “equivalent filter”) and a bandpass filter. These two filters are connected in series, and the output of the filter is doubled to a specified value and then output. The pass band of the band-pass filter is set higher than the focus adjustment system band and lower than the spherical aberration control system band. In addition, in Embodiment 7, the frequency band of the focus adjustment system is lower than that of the spherical aberration control system. Therefore, the addition operation to the FE signal is performed after amplifying the frequency components of the spherical aberration correcting lens pitch variation higher than the frequency band of the focus adjustment system and lower than the frequency band of the spherical aberration control system by a predetermined value. The influence of the spherical aberration control system on the focus adjustment system will be described.

The spherical aberration correction amount in the spherical aberration control system is added to the focus adjustment system corresponding to the external disturbance of the spherical aberration correction lens interval. This external disturbance is a disturbance that changes the distance from the objective lens to focusing.

The change in the distance from the objective lens to focusing due to the change in the distance between the spherical aberration correcting lenses 15 will be described in detail with reference to FIG. 53 . Fig. 53 is a schematic view showing the influence of the spherical aberration correcting lens interval on the distance from the objective lens to focus.

Fig. 53(a) shows that the thickness from the surface of the optical disc to the information surface is optimal; the spherical aberration does not occur on the information surface. Similarly, Fig. 53(b) shows a case where the thickness is thick. In addition, the focus adjustment system works normally and corrects the state of the spherical aberration occurring on the information plane with the spherical aberration correcting lens 15 . Fig. 53(c) shows a case where the thickness is thin. Similar to the case of FIG. 53( b ), a state in which spherical aberration occurring on the information plane is corrected by the spherical aberration correcting lens 15 is shown.

As shown in FIG. 53(b), since the thickness of the base member becomes thicker, the interval W between the spherical aberration correcting lenses 15 becomes narrower. In addition, the distance Z from the objective lens 1 to the focus becomes longer. In addition, as shown in FIG. 53(c), if the base member becomes thinner, the interval W becomes wider; the distance Z becomes shorter. The distance Z varies due to the variation of the interval W of the spherical aberration correcting lenses 15 . That is, the variation of this distance Z acts as an external disturbance of the focus adjustment system.

In this way, the distance from the objective lens to focusing varies according to the distance between the spherical aberration correcting lenses, so this external disturbance is of the same nature as the surface contact of the optical disc 20 . Therefore, the focus adjustment system follows this external disturbance. However, frequency components higher than the frequency band of the focus adjustment system of this external disturbance flow into the focus device 2, which can only increase the temperature of the focus device 2, but cannot follow.

Therefore, in the FE signal correcting section 30, a multiplication operation is performed by a coefficient L to a frequency component higher than the frequency band of the focus adjustment system and lower than the frequency band of the spherical aberration control system included in the variation in the distance between the spherical aberration correction lenses. By performing addition to the FE signal, the influence of the spherical aberration correction amount on the FE signal is eliminated. In this way, the effect of uneven thickness of the optical disk base member higher than the frequency band of the focus adjustment system can be eliminated from the focus adjustment system, and it is possible to reduce the heat generation of the focusing device.

The effective value detection unit 54 and the FE correction learning unit 55 are subroutines for determining the coefficient L described above. The effective value detection unit 54 detects and outputs an effective value of components higher than the frequency band of the focus adjustment system and lower than the frequency band of the spherical aberration control system, including frequency components of the corrected FE signal. The FE correction learning unit 55 learns the coefficient L at which the output of the effective value detection unit 54 becomes the minimum. Then, the microcomputer 8 sets the coefficient L in the FE signal correction unit 30 .

Next, the FE signal correction unit 30 will be described in detail with reference to FIG. 35 . FIG. 35 is a block diagram of the FE signal correction unit 30 . The input connector 900 is connected to the output of the beam expander driving circuit 133 . The second input connector 904 is connected to the output signal of the FE correction learning unit 55 via the microcomputer 8 . The signal output from the output terminal 905 is added to the FE signal which is the output of the focus error signal generator 36 .

The signal input at the input connector 900 is sent to the equivalent filter 901 . The equivalent filter 901 is a filter having the same characteristics as the spherical aberration correction adjuster 34 described above. The output of the equivalent filter 901 is sent to the bandpass filter 902 . Hereinafter, the bandpass filter is referred to as BPF. The pass frequency band of the BPF 902 is higher than the above frequency band of the focus adjustment system and lower than the frequency range of the spherical aberration control system frequency band. The output of BPF 902 is sent to multiplier 903 . The multiplier 903 multiplies the signals of the connector a and the connector b, and outputs the signal through the connector c. Connector c passes to output connector 905 . Connector b is connected to the second input connector 904 .

Since the output of the beam expander drive circuit 133 is connected to the input connector 900, the output of the equivalent filter 901 represents the spacing of the spherical aberration correcting lens. The BPF 902 extracts frequency components that are higher than the frequency band of the focus adjustment system and lower than the frequency band of the spherical aberration control system included in this spherical aberration correction lens interval variation. The multiplier 903 multiplies the extracted signal by the predetermined value L set by the FE correction learning unit 55 , and outputs it through the output connector 905 .

This operation will be described with reference to FIG. 34 . In addition, the unevenness of the thickness of the base member is set to fluctuate within a frequency range higher than the frequency band of the focus adjustment system and lower than the frequency band of the spherical aberration control system. Figure 34(a) shows that the thickness of the base member is not uniform. Fig. 34(b) shows the output of the beam expander driving circuit 133, Fig. 34(c) shows the output of the equivalent filter 901, Fig. 34(d) shows the output of the PF902, and Fig. 34(e) shows the FE signal correction part 30 34(f) shows the output of the focus error signal generator 36, and FIG. 34(g) shows the corrected FE signal. The vertical axis of FIG. 34(b) represents current, the vertical axis of other waveform diagrams represents the voltage of each signal, and the horizontal axis represents time.

The beam expander drive current shown in FIG. 34( a ) to follow the variation in the thickness of the base member has the waveform shown in FIG. 34( b ). In addition, the relationship between the driving current of the spherical aberration correction regulator 34 and the distance between the correction lenses has a characteristic of a secondary vibration element. Therefore, at a high frequency higher than each fixed frequency, the correction lens spacing with respect to the drive current has a relationship of a phase delay of 180 degrees. This is the reason why the phase difference between the waveform of FIG. 34( a ) and the waveform of FIG. 34( b ) is 180 degrees. If the beam expander driving current shown in FIG. 34(b) is input to the equivalent filter 901 of FIG. 35, its waveform becomes that of FIG. 34(c). Since the frequency component of the thickness variation of the base member is lower than the frequency band of the spherical aberration control system, the phases between the waveforms in FIG. 34(a) and the waveforms in FIG. 34(c) coincide for the above-mentioned reason.

Since the frequency component of the thickness variation of the base member is the pass band of the BPF 902, the output of the BPF 902 has the same waveform as shown in FIG. 34(d) as the output of the equivalent filter 901. The output of the FE signal correction unit 30 has the waveform of FIG. 34( e ) in which the output of the doubled BPF 902 is multiplied by a predetermined value.

Since the frequency component of the thickness variation of the base member is higher than the frequency band of the focus adjustment system, the focus adjustment system cannot follow the above-mentioned external disturbance caused by the variation of the spherical aberration correcting lens interval. Therefore, the FE signal becomes a waveform shown in 34(f). By using the FE correction learning part 55 to adjust the specified value L set at the second input connector, the output signal amplitude of the FE signal correction part 30 is adjusted, and the corrected FE signal becomes the excluded AC as shown in FIG. 34(g). The waveform of the composition. Therefore, the driving current for the variation in the thickness of the base member shown in FIG. 34( a ) does not flow into the focusing device driving circuit 9 .

In addition, the spherical aberration control is not in operation state, and the spherical aberration correcting lens 15 is stopped, and there is no influence on the FE signal. Therefore, the addition of the predetermined multiple spherical aberration signal to the FE signal by the signal correction unit 30 is stopped. Thereby, stable focus adjustment becomes possible.

Next, a method of determining the above-mentioned coefficient L will be described. In order to obtain the coefficient L, predetermined thickness unevenness is required. That is, thickness unevenness that fluctuates at frequencies higher than the frequency band of the focus adjustment system and lower than the frequency band of the spherical aberration control system is required. However, such thickness unevenness is not always expected to be present in an actual optical disc. Therefore, by changing the interval between the spherical aberration correcting lenses at a frequency higher than the frequency band of the focus adjustment system and lower than the frequency band of the spherical aberration control system, a state equivalent to a state in which predetermined thickness unevenness exists can be achieved.

Next, the state when the spherical aberration correcting lens interval is changed at a frequency higher than the frequency band of the focus adjustment system and lower than the frequency band of the spherical aberration control system will be described with reference to FIG. 54 . Fig. 54 is a schematic view showing the influence of the position of the spherical aberration correction lens on the distance from the objective lens to the focus. The thickness of the optical disk base member is uniformly removed from Fig. 54 (a) to (c), and the above-described diagrams 53 same situation.

Fig. 54(a) shows a state in which the thickness from the surface of the optical disc to the information surface is optimal and spherical aberration does not occur on the information surface. Similarly, Fig. 54(b) shows the best state when the thickness of the original base member is thick. In addition, the spherical aberration correction lens 15 operates with frequency components higher than the focus adjustment frequency band, and the focus adjustment system does not normally follow and correct the spherical aberration occurring on the information plane. Fig. 54(c) shows the best state when the thickness of the original base member is thin. Similar to Fig. 54(b), it shows a state where the spherical aberration occurring on the information plane has not been corrected. As in FIG. 53 , as shown in FIG. 54( b ), the distance W between the spherical aberration correcting lenses 15 becomes narrower and the distance Z from the objective lens 1 to the focus becomes longer. Also, as shown in FIG. 54(c), the distance Z becomes shorter as the interval W becomes wider.

As the interval W of the spherical aberration correcting lenses 15 changes, the distance Z changes. That is, the variation of this distance Z acts as an external disturbance of the focus adjustment system. The ratio of Z to the change in the interval W of the spherical aberration correcting lenses 15 is almost the same as the ratio of Z to the change in the interval W of the spherical aberration correcting lenses 15 described with reference to FIG. 53 .

In addition, the spherical aberration correcting lens 15 operates with a frequency component higher than the focus adjustment frequency band; the state in which the focus adjustment system cannot normally follow and does not correct the spherical aberration occurring on the information plane is when the spherical aberration control system is stopped. In this state, it is realized by changing the distance between the spherical aberration correction lenses at a frequency higher than the frequency band of the focus adjustment system and lower than the frequency band of the spherical aberration control system.

Therefore, the method of varying the distance between the spherical aberration correcting lenses at a frequency higher than the frequency band of the focus adjustment system and lower than the frequency band of the spherical aberration control system can be changed to a state equivalent to a state where predetermined thickness unevenness exists. Its operation will be described with reference to the waveforms in FIG. 36 . FIG. 36( a ) shows the output of the beam expander driving circuit 133 . Similarly, FIG. 36(b) shows the output of the PF902 of the FE signal correction unit 30, FIG. 36(c) shows the coefficient L that the FE correction learning unit 55 outputs to the FE signal correction unit 30, and FIG. 36(d) shows the FE signal correction unit 30, FIG. 36(e) shows the FE signal as the output of the focus error signal generator 36, FIG. 36(f) shows the corrected FE signal, and FIG. 36(g) shows the output of the effective value detection unit 54. The vertical axis of FIG. 36(b) represents current, the vertical axis of other waveform diagrams represents the voltage of each signal, and the horizontal axis represents time.

In addition, when learning the predetermined value L, the spherical aberration control is stopped, and the beam expander drive signal is output along with the output of the spherical aberration test signal generator 53, and its frequency band is the same as the waveform shown in FIG. 34(a). That is, the output signal of the spherical aberration test signal generator 53 fluctuates at a frequency higher than the frequency band of the focus adjustment system and lower than the frequency band of the spherical aberration control system. The FE correction learning unit 55 sets La as the coefficient L of the FE signal correction unit 30 at the initial value time t0.

At this time, the spherical aberration control is stopped, and the beam expander drive circuit 133 follows the output signal of the spherical aberration test signal generator 53, so the beam expander drive current becomes the waveform shown in FIG. 34(a). Therefore, the output of the BPF 902 of the FE signal correction unit 30 becomes a waveform shown in FIG. 34( b ). The output of the FE signal correcting unit 30 becomes a waveform multiplied by the coefficient La in FIG. 34( b ). Because the phase of the FE signal in Figure 34(e) is 180 degrees different from that of the FE signal in Figure 34(d), as shown in Figure 34(f), the corrected FE signal becomes a signal with a large amplitude. In this state, the output of the effective value detection unit 54 becomes Ea shown in FIG. 34(g).

The FE correction learning unit 55 gradually changes the coefficient L of the FE signal correction unit 30 through the microcomputer 8 and measures the level of the effective value detection unit 54 . The coefficient at time t1 is Lb, and the coefficient at time t2 is Lc. In FIG. 36 , when the coefficient is La; Lc, the level of the measurement effective value detection unit 54 does not become the minimum, but when the coefficient is Lb, it becomes the minimum.

Therefore, as shown in FIG. 34( g ), at time t1 when the coefficient Lb is set, the output level of the effective value detection unit 54 becomes minimum. That is, the amplitude of the corrected FE signal becomes minimum at the coefficient Lb. Therefore, the FE correction learning unit 55 sets Lb as the optimum coefficient for the FE signal correction unit 30 . In addition, this coefficient Lb is as illustrated in FIG. 53 and FIG. 54. Due to spherical aberration control, when the spherical aberration correcting lens 15 actually moves relative to the thickness of the base member, it also plays the same role.

The operation of determining the coefficient L of the FE signal correction unit 30 will be described with reference to the flowchart of FIG. 37 . First, in step S1 , the FE correction learning unit 55 sets the coefficient as the FE signal correcting unit 30 to an initial value La through a microcomputer. In step S2 , when the focus adjustment is active and the spherical aberration is not active, the spherical aberration test signal generator 53 starts adding the test signal to the beam expander driving signal of the spherical aberration control unit 135 . In step S3 , the effective value of the FE signal corrected by the FE signal correcting unit 30 is obtained from the effective value detecting unit 54 and stored as the minimum value of the effective value. In step S4, the coefficient L of the FE signal correction unit 30 is decreased by a predetermined value.

In step S5 , it is compared by the effective value detection unit 54 whether the detected effective value of the corrected FE signal is smaller than the stored effective value minimum value. If the effective value of the FE signal after correction is also smaller than the minimum value of the preserved effective value, then in step S6, the effective value of the FE signal after correction is used as the minimum value to save the minimum value of the effective value again, and enter step S7. deal with. If the effective value of the corrected FE signal is not less than the saved minimum value of the effective value, then go to step S7. In step S7, it is compared whether the coefficient L of the FE signal correction unit 30 is larger than Lc, and if it is larger, it returns to step S4, and if not, it goes to step S8. In step S8, the coefficient L of the FE signal correcting unit 30 corresponding to the stored minimum value of the effective value is set, and the process ends.

In addition, when the focus adjustment and the spherical aberration control are not working, the method of performing the gain compensation adjustment of the focus adjustment part 17 or the spherical aberration control part 135 can adjust the part of the gain characteristic caused by the interference of the focus adjustment and the spherical aberration control, and more High-precision adjustment is possible.

"Embodiment 8"

Fig. 38 is a block diagram showing the structure of an optical disc device according to Embodiment 8 of the present invention. Fig. 39 is a characteristic diagram for explaining jitter with respect to spherical aberration and focus eccentricity. In these figures, components and parts that are the same as those of the prior art and Embodiment 6 are assigned the same symbols, and descriptions thereof are omitted. In addition, as in Embodiment 6, the focus adjustment is performed based on the focus error signal which is the sum of the focus error signal on the outer circumference side and the focus error signal on the inner circumference side, and the difference between the focus error signal on the outer circumference side and the focus error signal on the inner circumference side signal to generate a spherical aberration signal.

The high-pass filter unit 56 extracts an AC component higher than the rotation frequency of the disc motor 10 included in the spherical aberration signal.

Local thickness unevenness exists in the optical disc 20, and these cause high-frequency spherical aberration at the time of recording and reproduction. Therefore, when the frequency band of the spherical aberration control system is DC, spherical aberration remains due to local thickness unevenness. Deteriorated by this spherical aberration, such as distortion of the reproduced signal.

The present invention is a method of changing the target position of the focus adjustment system, in other words, reducing the influence of residual spherical aberration such as distortion deterioration of reproduced signals by intentional defocusing. The influence of spherical aberration, which has an effective value of about 20mλrms, can be reduced by using defocus of about 0.1μm. When the control frequency band of the focus adjustment system is higher than that of the spherical aberration control system, the influence of high-frequency spherical aberration that cannot be followed by the spherical aberration control system can be reduced.

First, correction of spherical aberration will be described with reference to FIG. 38 . The microcomputer 8 outputs a driving signal of a predetermined value to the beam expander driving circuit 133 . The beam expander drive circuit 133 corrects the DC component of the spherical aberration of the beam spot formed on the information surface of the optical disc 20 by driving the spherical aberration correction lens 15 by the spherical aberration correction adjuster 34 according to the drive signal.

The high-pass filter unit 56 extracts high-frequency components of the spherical aberration detection signal output from the spherical aberration detector 31 . After the extracted signal is multiplied by M times, addition is performed to the FE signal output from the focus error signal generator 36 . The extracted components are frequencies higher than the control band of the spherical aberration control system. In this embodiment, since the spherical aberration control system is DC, the high-pass filter unit 56 outputs the DC component after removing it.

In the AC band, the target position of the focus adjustment system is changed according to the spherical aberration detection signal. That is, defocus occurs in the focus adjustment system.

The residual spherical aberration; the general relationship between defocus and distortion will be described with reference to FIG. 39 . The y-axis of FIG. 39 represents defocus, the x-axis represents spherical aberration, and the contour lines represent distortion. The innermost contour represents distortion j1. Distortion j2; Distortion j3; Distortion j4; Distortion j5 are indicated in turn along the outward contour line. And the relationship of j1<j2<j3<j4<j5 is established.

Assuming a state where the defocus is 0 and the spherical aberration is 0, that is, the information reading performance of the optical disc 20 at point A is the best. That is, the distortion representing the read performance becomes the minimum value j0. However, during one revolution of the actual optical disc 20 , there is high-frequency thickness unevenness, and thus high-frequency spherical aberration occurs. Spherical aberrations that occur are assumed to be s1 and s2. Consequently, spherical aberration occurs between point α and point β to worsen distortion. In addition, the spherical aberration at the point α is s2, and the spherical aberration at the point β is s1. Distortion varies between j0 and j2. However, if the defocus is changed corresponding to the spherical aberration, the distortion varies in the range of j0 and j1. That is, if the defocus at the point α is f1 and the defocus at the point β is f2, the distortion becomes j1. Therefore, according to the method of generating defocus by spherical aberration, deterioration of distortion can be improved. Accordingly, the coefficient M of the above-described high-pass filter unit 56 becomes the following relational expression.

M=(f2-f1)/(s2-s1)

A correction method for correcting the influence of residual spherical aberration through defocusing will be described with reference to FIG. 40 . Fig. 40 shows a state in which spherical aberration of the DC component due to the non-uniform thickness of the base member is corrected. Figure 40(a) shows waveforms showing non-uniform thickness of the base member. FIG. 40( b ) shows the output of the optical spherical aberration detector 31 . FIG. 40( c ) shows the output of the high-pass filter 56 , and FIG. 40( d ) shows the output of the focus error signal generator 36 . The vertical axis represents the voltage of each signal, and the horizontal axis represents time.

As shown in FIG. 40( a ), the thickness unevenness of the base member includes local AC component unevenness and DC component thickness unevenness of the optical disc 20 . The microcomputer 8 controls the spherical aberration correction adjuster 34 to correct the spherical aberration of the DC component, so that the spherical aberration detection signal becomes the signal shown in FIG. 40(b) with only the AC component. In addition, s1 and s2 correspond to s1 and s2 of FIG. 39 . The high-pass filter unit 56 extracts the AC component shown in FIG. 40( b ) from this spherical aberration detection signal, and amplifies it M times. Accordingly, the output of the high-pass filter section 56 becomes as shown in FIG. 40(c). In addition, f1 and f2 correspond to f1 and f2 of FIG. 39 . The control system operates so that the output signal of the high-pass filter unit 56 becomes a signal subtracted from the FE signal, and the subtracted signal becomes zero. Therefore, the FE signal becomes the waveform shown in Fig. 40(d). Thus, defocusing corresponding to spherical aberration occurs, and deterioration of distortion can be reduced.

"Example 9"

Fig. 41 is a block diagram showing the structure of an optical disc device according to Embodiment 9 of the present invention. In these figures, components and parts that are the same as those of the prior art and Embodiment 6 are assigned the same symbols, and descriptions thereof are omitted. In addition, as in Embodiment 6, the focus adjustment is performed based on the focus error signal which is the sum of the focus error signal on the outer circumference side and the focus error signal on the inner circumference side, and the difference between the focus error signal on the outer circumference side and the focus error signal on the inner circumference side signal to generate a spherical aberration signal.

In this embodiment, the position of the objective lens 1 is controlled so that the FE signal which is the output signal of the focus error signal generator 36 becomes 0. In addition, the interval of the spherical aberration correcting lenses 15 is controlled so that the spherical aberration detection signal output as the spherical aberration detector 31 becomes 0. There is no correction subroutine of the spherical aberration detection signal based on the FE signal described in the sixth embodiment.

Interference between focus adjustment and spherical aberration control is illustrated in conjunction with block diagram 43 . Fig. 43 is a block diagram for explaining the control frequency band and influence of interference in the ninth embodiment. In these figures, components and parts that are the same as those of the prior art and Embodiment 6 are assigned the same symbols, and descriptions thereof are omitted. The α1 system represents the interference of the spherical aberration control system on the focus adjustment system. α1 is the ratio of the driving value of the beam expander to the distance from the objective lens to focus. The α2 system means that the focus adjustment interferes with the spherical aberration control system. α2 is the error ratio of the spherical aberration detection signal to defocus. K1 is the detection sensitivity of the focus error signal generator 36 . K2 is the detection sensitivity of the spherical aberration detector 31 .

As described in Embodiment 6, focus adjustment and spherical aberration control interfere with each other. Specifically, when the defocus amount is f3, the detection error corresponding to the defocus becomes K1×α2×f3. In addition, when the spherical aberration correction amount is b1, the distance variation from the objective lens to focusing is α1×b1, which becomes an external disturbance of the focus adjustment system. In Embodiment 6, the configuration for eliminating the detection error of the spherical aberration detection signal corresponding to the defocus was described, but in this embodiment, the control frequency band for focus adjustment is set to ten times the detection error of the spherical aberration detection signal. With the multiplier method, even if a detection error of a spherical aberration detection signal corresponding to defocus occurs, stable focus adjustment and spherical aberration control can be realized.

42A to 42D are characteristic diagrams for explaining the nine control frequency bands and interference effects of this embodiment. 44A to 44D are characteristic diagrams for explaining the characteristics of the control unit, drive circuit and regulator of the ninth embodiment. Hereinafter, the above-mentioned characteristics will be described with reference to these figures as an example.

First, the characteristics of the control unit, drive circuit, and regulator will be described with reference to FIGS. 44A to 44D. FIG. 44A shows the characteristics from the focus adjustment unit 17 to the focus device drive circuit 9 . FIG. 44B shows the characteristics of the focusing device 2 . FIG. 44C shows the characteristics from the spherical aberration control unit 135 to the beam expander drive circuit 133 . FIG. 44D shows the characteristics of the spherical aberration correction adjuster 34. As shown in FIG. The upper graph of each graph shows gain characteristics, the vertical axis represents gain, and the horizontal axis represents frequency. The following figure shows the phase characteristics, the vertical axis represents the phase, and the horizontal axis represents the frequency.

As shown in FIG. 44A, the phase compensation of the focus adjustment is performed in the focus adjustment section 17, and the phase of focus at 2 KHz is raised to 45 deg (degrees) as a focus gain. As shown in FIG. 44B, the focusing device 2 has a primary resonance frequency of about 46 Hz, and the frequency band above the primary resonance frequency is inclined at -40 dB/dec. Similarly, as shown in FIG. 44C, phase compensation for spherical aberration control is performed in the spherical aberration control section 135, and the phase of focusing at 300 Hz is increased to 45 deg as spherical aberration gain. As shown in FIG. 44D, the spherical aberration correction adjuster 34 has a primary resonance frequency of about 66 Hz, and the frequency band above the primary resonance frequency is inclined by -40 dB/dec.

Next, mutual interference between focus adjustment and spherical aberration control will be described with reference to FIG. 42 . Fig. 42A shows the open-loop characteristics of the focus affected by interference in the control frequency band of focus is 2 KHz; the frequency band of spherical aberration control is 300 Hz. Likewise, Fig. 42B shows the open-loop characteristic of spherical aberration control. Fig. 42C shows the open-loop characteristics of focus affected by interference in the control frequency band of focus is 5 KHz; the frequency band of spherical aberration control is 300 Hz. Likewise, Figure 42D shows the open-loop characteristics of spherical aberration control. The upper graph of each graph shows gain characteristics, the vertical axis represents gain, and the horizontal axis represents frequency. The figure below shows the phase characteristics, the vertical axis is the phase, and the horizontal axis is the frequency.

As shown in Figures 42A and 42C, the method of increasing the focus control frequency band from 2KHz (Figure 42A) to 5KHz (Figure 42C), and making the control frequency band of spherical aberration correction away from 300Hz can make the frequency band of interference effect much higher Control band for spherical aberration correction. Specifically, the increase in gain expressed in the frequency range of about 50 Hz to 4 KHz ( FIG. 42B ) is in the range of 1.3 KHz to 11 KHz. As shown in FIG. 42D , when the gain increase range is close to the control frequency band, the gain increase rises to around 0 dB, so slight gain fluctuations or external disturbances tend to cause oscillations. However, as shown in FIG. 42D, when the gain increase range is far from the control frequency band, the gain increase is much lower than 0 dB, so the control system is stable. Also, when the control band for spherical aberration correction is lowered from 300 Hz, the influence of noise can also be avoided from the control band for focusing. As described above, the method in which the control frequency band of the focus adjustment becomes more than 10 times the frequency band of the spherical aberration control can reduce the influence of interference between the focus adjustment system and the spherical aberration control system, and can realize stable focus adjustment and spherical aberration control .

"Example 10"

Fig. 45 is a block diagram showing the structure of an optical disc device according to Embodiment 10 of the present invention. Fig. 46 is a waveform diagram for explaining spherical aberration at the time of searching in the tenth embodiment. Fig. 47 is a flow chart of the procedure for correcting spherical aberration when moving in the radial direction according to the tenth embodiment. In these figures, components and parts that are the same as those of the prior art and Embodiment 6 are assigned the same symbols, and descriptions thereof are omitted. In addition, as in Embodiment 6, the focus adjustment is performed based on the focus error signal which is the sum of the focus error signal on the outer circumference side and the focus error signal on the inner circumference side, and the difference between the focus error signal on the outer circumference side and the focus error signal on the inner circumference side signal to generate a spherical aberration signal.

The spherical aberration detection signal as the output signal of the spherical aberration detector 31 of FIG. Spherical aberration correction signal for spherical aberration correction. The spherical aberration control unit 135 outputs to the beam expander drive circuit 133 a drive signal for moving the spherical aberration correction lens 15 ; the spherical aberration correction adjuster 34 receiving the drive signal moves the spherical aberration correction lens 15 . That is, the spherical aberration becomes approximately 0, that is, the focus B and the focus C of FIG.

The tracking error signal generator 18 utilizes the output signal of the preamplifier 11 to generate an error signal about the radial direction of the optical disc 20 between the collected light beam spot output from the optical head 5 and the magnetic track 28 . The tracking error signal generator 18 generates a tracking error signal (hereinafter referred to as a TE signal) based on an input signal by a tracking error detection method generally called a push-pull method. The TE signal, which is the output signal of the tracking error signal generator 18 , is output to the tracking regulator drive circuit 26 after phase compensation, gain compensation, and other filter calculations are performed in the tracking control unit 19 .

The objective lens 1 is driven by the tracking regulator 27 according to the driving signal of the tracking regulator driving circuit 26, so that the beam spot scans the track 28 on the information surface 29 of the optical disc 20 to realize tracking control.

The optical head 5 can be moved in the radial direction of the optical disk 20 by the transport table 60 functioning as a retrieval mechanism, and the transport table 60 is driven by the output signal (drive signal) of the transport table driving circuit 62 . However, there is a problem as follows: when the focus adjustment and the spherical aberration control are in operation and the tracking control is not in operation, when the beam spot crosses the track on the information surface 29, the external disturbance having the same frequency as the TE signal is superimposed on the FE signal, causing the focus regulation becomes unstable. The present invention has been made in view of the above problems.

Therefore, the tracking control does not work, the spherical aberration control is stopped and the spherical aberration adjuster is moved away from the optimum position, resulting in spherical aberration. Due to the occurrence of spherical aberration, the beam spot on the information surface becomes larger. Therefore, the size of the beam spot is larger than the pitch of the grooves, so the amplitude of the TE signal becomes smaller.

This operation will be described with reference to FIG. 48 . In addition, the thickness unevenness of the base member is set to fluctuate at a frequency higher than the frequency band of the focus adjustment system and lower than the frequency band of the spherical aberration control system. FIG. 48(a) shows the output of the tracking error signal generator 18. As shown in FIG. FIG. 48( b ) shows the output of the focus error signal generator 36 , and FIG. 48( c ) shows the output of the beam expander drive circuit 133 . The vertical axis of FIG. 48(c) represents current, the vertical axis of other waveform diagrams represents the voltage of each signal, and the horizontal axis represents time. In addition, the period from time t1 to time t2 is a state where the output of the beam expander driving circuit 133 is optimal and no spherical aberration of the beam spot occurs on the information plane of the optical disc 20 . In addition, the period from t2 to time t3 is a state in which the output of the beam expander drive circuit 133 deviates from the optimum value by a predetermined amount, and spherical aberration of the beam spot significantly occurs on the information plane of the optical disc 20 .

Since there is eccentricity in the track of the optical disc 20, when the tracking control is not in operation, the tracking error signal has the waveform of FIG. 48(a) across a plurality of tracks. Since the focus error signal is generated by the astigmatism method, when the beam spot crosses the track, the effect of crossing the groove occurs, and the waveform becomes as shown in FIG. 48(b).

In addition, in FIG. 48(b), the solid line indicates a focus error signal affected by crossing a groove, and the dotted line represents a focus error signal not affected by a groove crossing.

In addition, in Fig. 48 (c), the interval from time t1 to time t2 represents the optimum output without spherical aberration of the beam spot on the information plane of the optical disc 20, and the interval from time t2 to time t3 represents the optimal output on the information plane 29. An output by a prescribed amount away from the optimum value of the beam point spherical aberration apparently occurs.

In the interval from time t1 to time t2, since the spherical aberration of the beam spot does not occur on the information plane, as shown in FIG. 48(a), the amplitude of the tracking error signal is maximum. However, the period from time t2 to time t3 indicates that the spherical aberration of the beam spot has clearly occurred on the information surface 29, and the amplitude of the tracking error signal becomes smaller. Likewise, the influence of the groove crossing that occurs in the focus error signal becomes maximum in the period from time t1 to time t2 when spherical aberration of the beam spot does not occur, and becomes maximum in the period from time t2 to time t2 when spherical aberration of the beam spot significantly occurs. becomes smaller in the interval of time t3.

In this way, when the tracking control is disabled, the spherical aberration control is stopped and the spherical aberration correction amount is separated from the optimum position by a predetermined amount, thereby reducing the influence of crossing the groove expressed in the focus error signal and stabilizing the focus adjustment. In addition, because the external interference caused by crossing the trench can be reduced, the current flowing into the focusing device 2 can be reduced, and the damage caused by excessive current passing through the focusing device 2 can be avoided, so as to protect the focusing device 2 .

This operation is described in more detail in conjunction with FIG. 46 . Fig. 46(a) shows the radial position of the beam spot with respect to time. Similarly, FIG. 46( b ) shows the output of the spherical aberration detector 31 , and FIG. 46( c ) shows the output of the beam expander drive circuit 133 . FIG. 46( d ) shows the operation state of the tracking control unit 19 , and FIG. 46( e ) shows the output of the transport table drive circuit 62 . The vertical axis represents the voltage of each signal, and the horizontal axis represents time.

During the movement in the radial direction during the search, as shown in FIG. 46(c), first, at time a, the spherical aberration control unit 135 stops the detection by the spherical aberration to the beam expander driving circuit 133 according to the instruction of the microcomputer 8. The output of device 31 output. At the same time, the output value of the beam expander driving circuit 133 is changed so as to move the spherical aberration correcting lens 15 so that the spherical aberration is approximately shifted from the zero position by a predetermined value. Next, as shown in FIG. 46( d ), at time b, the tracking control unit 19 temporarily stops the tracking control in accordance with an instruction from the microcomputer 8 .

Next, as shown in FIG. 46( e ), until time c, a conveyance table drive signal is output to the conveyance table drive circuit 62 . During the period from time b to time c, the table driving circuit 62 moves the table 60 on which the optical head 5 is mounted in the radial direction of the optical disk 20 according to the table driving signal transmitted from the microcomputer 8 . Thereby, as shown in FIG. 46( a ), the beam spot moves from the inner peripheral side to the outer peripheral side of the optical disk. Then, as shown in FIG. 46( d ), the tracking control unit 19 resumes the tracking control at time c in accordance with an instruction from the microcomputer 8 . Finally, as shown in FIG. 46(c), at time d, the spherical aberration control unit 135 cancels the stop of the output to the beam expander drive circuit 133 corresponding to the output of the spherical aberration detector 31 according to the instruction of the microcomputer 8, and restarts Start spherical aberration control.

In this way, when the tracking control is disabled, the spherical aberration correcting lens 15 is shifted by a predetermined value to increase the spherical aberration occurring on the beam spot, and it becomes possible to reduce the influence on the FE signal when crossing the groove.

The operation for moving the beam spot in the radial direction will be described in more detail with reference to the flow chart of FIG. 47 . First, in step S1, the microcomputer 8 instructs the spherical aberration control unit 135 to shift the spherical aberration correcting lens 15 from the current position to a predetermined value while stopping the spherical aberration control. In step S2, the microcomputer 8 instructs the tracking control unit 19 to temporarily stop the tracking control. In step S3, the microcomputer 8 outputs a table driving signal to the table driving circuit 62 so that the beam spot moves to the target radial position. In step S4, the microcomputer 8 instructs the tracking control unit 19 to restart the tracking control. In step S5, the microcomputer 8 instructs the spherical aberration control unit 135 to restart the spherical aberration control while returning the spherical aberration correcting lens 15 shifted by a predetermined value from the control position to the control position of step S1, and to end the control. deal with.

In this way, the influence of crossing the groove which occurs in the FE signal can be reduced during the search accompanying the movement in the radial direction, and stable focus adjustment can be realized.

In the above-mentioned embodiments, an optical disc device for writing data or reading data in an optical disc whose information recording surface is one layer or two layers has been described, but if the number of information recording surfaces is three or more layers, it is also fine.

In addition, in the optical disk devices of the sixth to tenth embodiments described above, the spherical aberration correction lens may be driven by the stepping motor 35 and the spherical aberration correction actuator used in the optical disk of the first embodiment. In particular, when the information recording surface of the optical disc has three or more layers, it is more effective to add the stepping motor 35 .

Industrial Utilization Possibility

According to the optical disc device of the present invention, even if the NA of the objective lens that irradiates a light beam on the optical disc is larger than the conventional NA (for example, NA is 0.85 or more), spherical aberration can be corrected appropriately, and higher-density data recording and reproduction can be realized. .

Claims (13)

1, a kind of optical disc apparatus carries out record/or regeneration to the information carrier of two information faces having lamination at least, comprising:

The light beam irradiates mechanism of illumination beam;

Pack mechanism to the above-mentioned light beam of above-mentioned information carrier pack;

Focalizer in order to change the pack position of above-mentioned light beam, moves above-mentioned pack mechanism on the almost vertical direction of information carrier information faces;

Accept optical mechanism, accept the reflected light from information carrier of above-mentioned light beam;

The pack state detection mechanism according to the above-mentioned signal of accepting optical mechanism, detects the signal corresponding to pack state of above-mentioned light beam on the information carrier information faces;

Focus adjustment mechanism according to the signal of above-mentioned pack state detection mechanism, drives above-mentioned focalizer, and control makes the want position of light beam pack in above-mentioned information carrier information faces;

Spherical aberration testing agency according to the above-mentioned optical mechanism signal of accepting, detects the signal corresponding to the amount of spherical aberration that takes place on the light beam pack position on the above-mentioned information carrier information faces;

The spherical aberration changeable mechanism by being driven by elastic body, changes the spherical aberration that the light beam of institute of above-mentioned pack mechanism pack is taken place on the pack position;

The spherical aberration control gear according to the described spherical aberration changeable mechanism of signal controlling of above-mentioned spherical aberration testing agency, makes that spherical aberration is approximate to become 0;

The skew applying mechanism applies skew to above-mentioned spherical aberration changeable mechanism;

Mechanism is replaced in skew, the side-play amount of replacing above-mentioned skew applying mechanism according to above-mentioned information carrier information faces.

2, optical disc apparatus according to claim 1 is characterized in that,

When the spherical aberration control gear is not worked, given skew is applied to the spherical aberration changeable mechanism by the skew applying mechanism; When the spherical aberration control gear is worked, on average decide skew and the skew of replacing the skew applying mechanism according to what the above-mentioned spherical aberration changeable mechanism in each week of information carrier drove output.

3, a kind of optical disc apparatus comprises:

The pack mechanism of light beam pack on information carrier;

Focalizer moves above-mentioned pack mechanism on the approximately perpendicular direction of information carrier information faces;

The spherical aberration changeable mechanism changes the spherical aberration that the light beam of institute of above-mentioned pack mechanism pack takes place on the pack position;

Make the driving mechanism of above-mentioned spherical aberration changeable mechanism work;

Accept optical mechanism, accept the reflected light from information carrier of above-mentioned light beam;

The pack state detection mechanism according to the above-mentioned optical mechanism signal of accepting, detects the signal corresponding to pack state of above-mentioned light beam on the information carrier information faces;

Focus adjustment mechanism according to the signal of above-mentioned pack state detection mechanism, drives above-mentioned focalizer, and control makes the want position of light beam pack in above-mentioned information carrier information faces;

Spherical aberration testing agency according to the above-mentioned signal of accepting optical mechanism, detects the signal corresponding to the amount of spherical aberration that takes place on the light beam pack position on the above-mentioned information carrier information faces;

The spherical aberration control gear, the signal according to above-mentioned spherical aberration testing agency drives above-mentioned driving mechanism, and control makes that spherical aberration is approximate to become 0; And

The spherical aberration straightening mechanism, gain is in accordance with regulations amplified after the signal of above-mentioned pack state detection mechanism, is added on the detection signal of above-mentioned spherical aberration testing agency.

4, optical disc apparatus according to claim 3 is characterized in that, comprising:

The first test signal generating mechanism applies test signal to above-mentioned focalizer;

The first amplitude detecting mechanism detects the detection signal amplitude of above-mentioned spherical aberration testing agency;

Spherical aberration is corrected learning organization, test signal is added in the state of above-mentioned focalizer by the above-mentioned first test signal generating mechanism, the additive operation of being obtained the spherical aberration signal straightening mechanism by the above-mentioned first amplitude detecting mechanism gains, so that spherical aberration detection signal amplitude minimum.

5, optical disc apparatus according to claim 4 is characterized in that, above-mentioned spherical aberration is corrected learning organization in the work of focus adjustment mechanism and above-mentioned spherical aberration control gear when not working carries out the study of additive operation gain.

6, optical disc apparatus according to claim 3 is characterized in that, above-mentioned spherical aberration signal straightening mechanism comprises:

Mechanism is preserved in additive operation gain, has the additive operation gain in the information monomer of rhythmo structure information carrier information faces by each layer preservation;

Mechanism is replaced in additive operation gain, preserves from above-mentioned additive operation gain and takes out corresponding to the additive operation gain of light-beam position the mechanism and replace.

7, optical disc apparatus according to claim 3 is characterized in that, comprising:

The first test signal generating mechanism applies test signal to above-mentioned focalizer;

Focus adjustment gain adjusting mechanism is adjusted the gain of focus adjustment mechanism;

The second test signal generating mechanism applies test signal to above-mentioned driving mechanism;

Spherical aberration ride gain adjusting mechanism is adjusted the gain of spherical aberration control gear;

When focus adjustment mechanism and the work of spherical aberration control gear, above-mentioned first test signal after first test signal that above-mentioned focus adjustment gain adjusting mechanism is taken place according to the above-mentioned first test signal generating mechanism and focus adjustment one are touring, adjust, and the above-mentioned spherical aberration test signal of above-mentioned spherical aberration ride gain adjusting mechanism after to be the spherical aberration test signal that taken place according to the above-mentioned second test signal generating mechanism and spherical aberration control one touring adjusted.

8, a kind of optical disc apparatus comprises:

Pack mechanism to information carrier pack light beam;

Focalizer moves above-mentioned pack mechanism on the almost vertical direction of information carrier information faces;

The spherical aberration changeable mechanism changes the spherical aberration that institute of above-mentioned pack mechanism pack light beam is taken place on the pack position;

Driving mechanism makes the work of above-mentioned spherical aberration changeable mechanism;

Accept optical mechanism, accept the reflected light from carrier of above-mentioned light beam;

The pack state detection mechanism according to the above-mentioned signal of accepting optical mechanism, detects the signal corresponding to pack state of above-mentioned light beam on the information carrier information faces;

Focus adjustment mechanism according to the signal of above-mentioned pack state detection mechanism, drives above-mentioned focalizer, and control makes the want position of above-mentioned light beam pack in above-mentioned information carrier information faces;

Spherical aberration testing agency according to the above-mentioned optical mechanism signal of accepting, detects the signal of the amount of spherical aberration that takes place corresponding to light beam pack position on the above-mentioned information carrier information faces;

The spherical aberration control gear, the signal according to above-mentioned spherical aberration testing agency drives above-mentioned driving mechanism, and control makes that spherical aberration is approximate to become 0; And

Pack state detection signal straightening mechanism amplifies by given gain after the signal of above-mentioned spherical aberration testing agency, is added on the detection signal of above-mentioned pack state detection mechanism.

9, optical disc apparatus according to claim 8 is characterized in that,

Comprise focus adjustment mechanism, when above-mentioned spherical aberration control gear is not worked, the detection signal that pack state detection signal straightening mechanism defined multiple is amplified above-mentioned spherical aberration testing agency is not added on the detection signal of pack state detection mechanism, and only according to the detection signal of above-mentioned pack state detection mechanism, drive above-mentioned focalizer, control makes the want position of light beam pack in above-mentioned information carrier information faces.

10, optical disc apparatus according to claim 8 is characterized in that, also comprises:

The second test signal generating mechanism applies test signal to above-mentioned driving mechanism;

The second amplitude detecting mechanism, the detection signal amplitude of detection pack state detection mechanism;

The pack state-detection is corrected learning organization, by the above-mentioned second test signal generating mechanism test signal is added in the state of above-mentioned driving mechanism, the virtual value of obtaining the pack state detection signal by the above-mentioned second amplitude detecting mechanism becomes the additive operation gain of minimum pack status detection signal straightening mechanism.

11, optical disc apparatus according to claim 10 is characterized in that, above-mentioned pack state-detection is corrected learning organization and under the idle state of above-mentioned spherical aberration control gear, carried out the study of additive operation gain in the work of focus adjustment mechanism.

12, optical disc apparatus according to claim 8, comprising:

The first test signal generating mechanism applies test signal to above-mentioned focalizer;

Focus adjustment gain adjusting mechanism is adjusted the gain of focus adjustment mechanism;

The second test signal generating mechanism applies test signal to above-mentioned driving mechanism;

Spherical aberration ride gain adjusting mechanism is adjusted the gain of spherical aberration control gear;

When making the work of focus adjustment mechanism and spherical aberration control gear, above-mentioned first test signal after first test signal that above-mentioned focus adjustment gain adjusting mechanism is taken place according to the above-mentioned first test signal generating mechanism and focus adjustment one are touring, and adjust, above-mentioned spherical aberration test signal after the spherical aberration test signal that above-mentioned spherical aberration ride gain adjusting mechanism is taken place according to the above-mentioned second test signal generating mechanism and spherical aberration control one are touring, and adjust.

13, a kind of optical disc apparatus comprises:

Pack mechanism to information carrier pack light beam;

Focalizer moves above-mentioned pack mechanism on the almost vertical direction of information carrier information faces;

The spherical aberration changeable mechanism changes the spherical aberration that institute of above-mentioned pack mechanism pack light beam takes place on the pack position;

Driving mechanism makes the work of above-mentioned spherical aberration changeable mechanism;

Accept optical mechanism, accept the reflected light of above-mentioned light beam heating from information carrier;

The pack state detection mechanism according to the above-mentioned optical mechanism signal of accepting, detects the signal corresponding to pack state of above-mentioned light beam on the information carrier information faces;

Focus adjustment mechanism according to the signal of above-mentioned pack state detection mechanism, drives above-mentioned focalizer, and control makes the want position of light beam pack in above-mentioned information carrier information faces;

Spherical aberration testing agency according to the above-mentioned signal of accepting optical mechanism, detects the signal corresponding to the amount of spherical aberration that takes place on the light beam pack position on the above-mentioned information carrier information faces; With

The spherical aberration control gear, the detection signal according to above-mentioned spherical aberration testing agency makes above-mentioned driving mechanism work, and control makes that spherical aberration is approximate to become 0;

Make frequency band ten times or more of the frequency band of above-mentioned focus adjustment mechanism at above-mentioned spherical aberration control gear.

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