JP2000076678A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate a tilt between an optical axis and a recording and reproducing medium with accuracy. SOLUTION: A transparent substrate 9 side of an optical disk 11 is irradiated with a light beam emitted from semiconductor laser 2 through a beam splitter 3, a collimator lens 4, and an object lens 5. The front face of the object lens 5 is formed of 1st and 2nd regions AR1, AR2 of mutually different curvatures. A recording and reproducing plane 10 of the optical disk 11 is irradiated with a spot light beam from the 1st region AR1, and the surface of the transparent substrate 9 is irradiated with pattern light from the 2nd region AR2, and the return light reflected and diffracted by each of the planes 10, 9a is condensed by the object lens 5 again passing through the return light path and is emitted on the 1st and 2nd light-receiving regions 12, 13 of a photo-detector 7 via a hologram element 12. Since the return light contains the tilt information of the optical disk 11, it is possible to detect a tilt omni-directionally. It is possible to compensate a tilt between the optical axis and the recording and reproducing medium with accuracy by performing tilt support, etc., based on the detection result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device for recording information on a recording / reproducing medium or reproducing information from the recording / reproducing medium, and more particularly, to an optical pickup device capable of detecting an inclination of a recording / reproducing surface of the recording / reproducing medium. It relates to a pickup device.

[0002]

2. Description of the Related Art Conventionally, CDs (Compact Discs) and D
2. Description of the Related Art In a recording / reproducing apparatus that records or reproduces information on an optical disk represented by a VD (digital versatile disk) or the like, tilt servo is performed so that the optical axis of the optical pickup device is perpendicular to a transparent substrate of the optical disk. This prevents the spot light focused on the recording / reproducing surface through the transparent substrate from causing aberration.

For example, if a warp occurs in a transparent substrate covering a recording / reproducing surface in a manufacturing process of an optical disc and the warping causes the recording / reproducing surface to be inclined with respect to the optical axis of an optical pickup device, When the spot light is obliquely incident on the transparent substrate, aberration occurs, and the transfer function (OTF) of the optical pickup device is deteriorated. In order to avoid such a situation, a tilt servo is performed.

In this conventional tilt servo, a light emitting diode (LED) for irradiating a detection light to an optical disk and a light receiving element for receiving a reflection light from the optical disk are provided on a mount of an optical pickup device, and a balance of the reflection light is adjusted. The amount of tilt of the recording / reproducing surface in the radial direction (radial direction) is detected, and based on the detection result, the angle of the entire optical pickup device is adjusted in the radial direction, so that the optical axis of the optical pickup device is adjusted to the recording / reproducing surface of the optical disk. To keep it vertical.

[0005]

By the way, as the amount of information increases, the recording density of an optical disk is required to be improved. To realize this, the numerical aperture of an objective lens provided in an optical pickup device is required. It is considered that spot light having a smaller diameter is focused on the recording / reproducing surface of the optical disk.

When the numerical aperture of the objective lens is increased in this way, the tolerance for the tilt (skew) between the optical axis of the optical pickup device and the optical disk is reduced, so that an extremely high-precision tilt servo is required.

However, in the above-described conventional tilt servo, only the radial tilt of the optical disk is detected, and the time axis (circumferential) tilt of the optical disk is not taken into consideration. Was difficult.

Further, in the conventional tilt servo, separately from an optical system for condensing a spot light on a recording / reproducing surface,
The light emitting diode and the light receiving element described above are provided, and the detection light is applied to a position distant from the condensing position of the spot light on the recording / reproducing surface, thereby detecting a radial inclination. Therefore, since the inclination in the radial direction and the time axis direction at the position where recording and reproduction are to be actually performed are not detected at the same time, it is difficult to reliably compensate for the skew, realizing high-density recording and achieving high-density recording. In order to reproduce information with high accuracy, there is a problem that the tolerance for skew cannot be sufficiently secured.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-mentioned conventional problems, and irradiates a recording / reproducing medium having a transparent substrate and a recording / reproducing surface with light for recording or reproduction. An optical pickup device, comprising: a light source that emits the light; a condensing unit that irradiates the light emitted from the light source to the recording / reproducing surface and the transparent substrate; and a return light from a surface of the transparent substrate. A light detecting means and a signal processing means for extracting inclination information of the recording / reproducing medium based on a light receiving output outputted from the light detector by return light from the surface of the transparent substrate.

According to this configuration, when the recording / reproducing medium is tilted with respect to the optical axis of the optical pickup device, the light emitted from the light condensing means to the surface of the transparent substrate responds to the inclination of the surface of the transparent substrate. Is reflected and becomes return light. By detecting the return light by the light detecting means, a light receiving output having information on the inclination of the surface of the transparent substrate is generated. Then, the signal processing means performs signal processing on the received light output to extract tilt information of the recording / reproducing medium.

An optical pickup device for irradiating a recording / reproducing medium having a transparent substrate and a recording / reproducing surface with light for recording or reproduction, comprising: a light source for emitting the light; and a light emitted from the light source. Focusing means for irradiating the recording / reproducing surface and the transparent substrate; light detecting means for receiving return light from the recording / reproducing surface and the surface of the transparent substrate; and detecting the light by returning light from the recording / reproducing surface. First signal generation means for generating a first signal based on a light reception output output from the detector, and a second signal generation means based on a light reception output output from the photodetector by return light from the surface of the transparent substrate. And a signal processing means for extracting the inclination information of the recording / reproducing medium by comparing the first and second signals.

According to this configuration, when the recording / reproducing medium is tilted with respect to the optical axis of the optical pickup device, the light emitted from the light condensing means to the surface of the transparent substrate responds to the inclination of the surface of the transparent substrate. Is reflected and becomes return light. Further, the light emitted from the light condensing means to the recording / reproducing surface is reflected or diffracted by the recording / reproducing surface to become return light. Further, these return lights are light from substantially the same area. By detecting the return light having the information of the inclination of the recording / reproducing medium by the light detecting means, the first signal is generated based on the light receiving output corresponding to the return light from the recording / reproducing surface, The second based on the light receiving output corresponding to the returning light from the surface
Is generated. Then, the signal processing means compares the first and second signals to extract the inclination information of the recording / reproducing medium.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) An optical pickup device according to a first embodiment will be described with reference to FIGS. FIG. 1 is a configuration diagram showing a configuration of an optical system provided in the present optical pickup device 1. In the figure, an optical pickup device 1 is
A semiconductor laser 2 as a light source, a beam splitter 3,
A collimator lens 4 disposed in front of the beam splitter 3 and an objective lens 5 as a condensing means, and a hologram element 6 and a photodetector 7 disposed behind the beam splitter 3 are provided. Optical elements 2 to 7
Are aligned with the optical axis. An optical disk 11 having a structure in which a recording / reproducing surface 10 is sandwiched between a hard protective layer 8 and a transparent substrate 9 is arranged with the transparent substrate 9 facing the front surface of the objective lens 5.

In this configuration, when light of a predetermined wavelength is emitted from the semiconductor laser 2, the light is reflected by the beam splitter 3 toward the collimator lens 4. The reflected light is converted into parallel light by the collimator lens 4 and the objective lens 5
Then, the objective lens 5 converges the parallel light and irradiates it to the optical disk 11 side. Further, light (hereinafter, referred to as first return light) generated by the light irradiated by the objective lens 5 being reflected or diffracted by the recording / reproducing surface 10 and the surface of the transparent substrate 9 of the optical disk 11 (hereinafter, referred to as substrate surface). That)
The light reflected by 9 a (hereinafter, referred to as second return light) is condensed by the objective lens 5, and emitted to the beam splitter 3 side via the collimator lens 4. The beam splitter 3 transmits these return lights to the hologram element 6 side.
The hologram element 6 diffracts the return light from the beam splitter 3 to split it into a zero-order light h ₀ and a high-order light h ₁ ,
The zero-order light h ₀ is radiated to the first light receiving region 12 provided in the photodetector 7, and the high-order light h ₁ is radiated to the second light receiving region 13 provided in the photodetector 7.

Here, the objective lens 5 has a longitudinal sectional structure as shown in FIG. In other words, the front surface of the objective lens 5 has a ring-shaped peripheral portion (hereinafter, referred to as a first region) AR1 having a small curvature and a central portion (hereinafter, referred to as a second region) having a larger curvature than the first region. Molded with two regions with AR2. Thereby, the first area A
The focal length of the second area AR2 is shorter than the focal length of R1.

Further, when the recording / reproducing surface 10 of the optical disk 11 is made to coincide with the focal position of the first area AR1, the focal position of the second area AR2 is outside the substrate surface 9a, and the focal position is placed on the substrate surface 9a. The first and second regions AR1 and AR2 are set in advance so that diffusion pattern light deviating from
Are set.

According to the objective lens 5 having such a structure, of the parallel light from the collimator lens 4, the first area AR1
The light condensed by the orifice opening of the optical disk 11 passes through the transparent substrate 9 of the optical disk 11 to form a minute spot on the recording / reproducing surface 10, and is further reflected or diffracted by the recording / reproducing surface 10 (first return). (Light) is again condensed in the first area AR1 and emitted to the photodetector 7 side.

On the other hand, of the parallel light, the second area AR
The light condensed at 2 is applied to the substrate surface 9a of the optical disk 11 as a relatively large pattern as shown by a dotted line in the figure, and further reflected at the substrate surface 9a (second return light). Is condensed again in the second area AR2 and emitted to the photodetector 7 side.

The substrate surface 9a passes through the second area AR2.
A part of the light applied to the recording / reproducing surface 10 is transmitted through the transparent substrate 9 and reaches the recording / reproducing surface 10.
There is no adverse effect on the information recording or information reproduction in the computer.

Further, since the second area AR2 does not contribute to the light condensed in the first area AR1, the minute spot-shaped light condensed only at the above-mentioned orifice opening is recorded and reproduced. Incident on. Therefore, the first light generated when the light having the spot shape is reflected or diffracted by the recording / reproducing surface 10 is used.
It is possible to perform tracking servo by analyzing the return light of the so-called push-pull method or the like, or perform focus servo by analyzing the return light by the so-called Foucault method or astigmatism method. Further, the information recorded on the recording / reproducing surface 10 can be reproduced by detecting the first return light with a photoelectric conversion element (not shown).

Next, the structure of the hologram element 6 will be described with reference to FIG. The hologram element 6 has an annular diffraction pattern as shown in FIG. This allows
The first coming through the beam splitter 3, of the second returning light, as it is irradiated with 0 order light h ₀ by the first light receiving region 12 provided on the optical detector 7, whereas, the higher-order beam h
Regarding ₁ , the second light receiving area 1 provided in the photodetector 7 is provided by giving a diffraction effect equivalent to refracting a peripheral ray on a peripheral surface shifted from the optical axis of the convex lens.
Irradiate 3

The photodetector 7 includes the first and second light receiving areas 1
2 and 13 are configured by an integrated OEIC or the like.
As shown in FIG. 4, the first light receiving region 12 includes four light receiving elements a to d each having light receiving surfaces having the same shape.
And the recording / reproducing surface 10 shown in FIG.
When the focusing state, the zero-order light component h ₀ of the first return beam is positioned to be incident at a predetermined size with respect.

Similarly, the second light receiving area 13 has four light receiving elements e to h each having light receiving surfaces of the same shape.
In which is formed, when the focusing state, high-order light component h ₁ of the second return beam is positioned to be incident at a predetermined size.

A signal processing circuit composed of differential amplifiers 18 to 23 and amplifiers 24 and 25 is connected to these light receiving elements a to h. The differential amplifiers 18 to 21
For signals Sa to Sh photoelectrically converted by the light receiving elements a to h (hereinafter referred to as photoelectric conversion signals), the following equations (1) to (1) are used.
By performing the calculation process represented by (4), the respective calculation signals Rdc, Tba, Rhg, and Tfe shown in the figure are generated.

Rdc = Sd-Sc (1) Tba = Sb-Sa (2) Rhg = Sh-Sg (3) Tfe = Sf-Se (4) The amplifiers 24 and 25 are each a predetermined amplifier. Rate α, β
The calculation signals αRdc and βTba are generated by performing calculation processing represented by the following equations (5) and (6). αRdc = α × Rdc (5) βTba = β × Tba (6) The differential amplifiers 22, 23 calculate the operation signals αRdc, βTba, R
The first signal indicating the amount of tilt of the optical disk 11 in the radial direction (hereinafter, referred to as a first error detection signal) is obtained by performing arithmetic processing represented by the following equations (7) and (8) on hg and Tfe. RE and a second signal indicating the amount of tilt of the optical disk 11 in the time axis direction (hereinafter, referred to as a second error detection signal)
Generate TE. RE = Rhg−αRdc (7) TE = Tfe−βTba (8) Next, the first error detection signal RE and the second error detection signal T
The principle of obtaining the amount of tilt of the optical disc 11 in the radial direction and the time axis direction by E will be described with reference to FIGS.

FIG. 5 shows the recording / reproducing surface 10 of the optical disk 11.
When the optical pickup device 1 is moved in the radial direction by driving the tracking actuator in a state where the optical axis of the optical pickup device 1 is not tilted in both the radial direction and the time axis direction,
Shows a pattern change in the zero-order light component h ₀ irradiated to the light receiving regions 12 and 13 high-order light component h _1.

In this state, the spot light generated in the first area AR1 of the objective lens 5 irradiates the track on the recording / reproducing surface 10 and the pattern light generated in the second area AR2 is applied to the substrate surface 9a. Fig. 5
As shown in (b), the first pattern P1 due to the first return light is incident on the center of the first light receiving area 12, and the second pattern P2 due to the second return light is the second pattern. The light enters the center of the light receiving area 13.

Also, from the state of FIG.
Is moved to the center axis side (lead-in side) of the optical disk, as shown in FIG.
1 and P2 are both displaced to the left of the first and second light receiving regions 12 and 13.

Also, from the state of FIG.
Is moved radially outward (lead-out side) of the optical disk, as shown in FIG. 5C, the first and second patterns P1 and P2 are both the first and second light receiving regions 12,
13 to the right.

The first and second patterns P1, P
When the changes in the output levels of the operation signals Rdc and Rhg output from the differential amplifiers 18 and 20 in FIG. 4 are plotted with the displacement of FIG. 2, the state shown in FIG. An almost symmetrical characteristic curve is obtained as "0".

Here, the amplification factor α of the amplifier 24 is set in advance to be equal to the ratio (Rhg / Rdc) of the output levels of the operation signals Rdc and Rhg. The output level of the 1 error detection signal RE is almost always 0.

As described above, the first error detection signal RE obtained when the optical axis of the optical pickup device 1 is not inclined with respect to the recording / reproducing surface 10 of the optical disk 11 is almost zero.
The amplification factor α of the amplifier 24 is set in advance so that the output level of the first error detection signal RE is compared with a predetermined threshold value (a value that allows skew) Vth. It is possible to detect the case where no error has occurred.

FIG. 7 shows first and second optical disks 11 when the optical disk 11 is tilted in the radial direction from the state shown in FIG.
Shows how the patterns P1 and P2 change.
FIG. 7B shows the same state as FIG. 5B, that is, the case where no skew has occurred.

The recording / reproducing surface 10 of the optical disk 11 is
As shown in FIG. 7A, when the light is inclined toward the lead-in side in the radial direction, the spot light on the recording / reproducing surface 9 is focused as shown in FIG.
1 hardly displaces.

On the other hand, the second pattern P2 is
Since the pattern light irradiated on the light receiving element a is not at the focal position and the optical path of the second return light is largely shifted from the optical axis by the inclination of the substrate surface 9a, the light is displaced toward the light receiving element h. .

The recording / reproducing surface 10 of the optical disk 11
However, as shown in FIG. 8 (b), when tilting toward the readout side in the radial direction, the spot light on the recording / reproducing surface 9 is focused as shown in FIG. 7 (c).
Pattern P1 hardly displaces. On the other hand, in the second pattern P2, the optical path of the second return light is largely shifted from the optical axis due to the inclination of the substrate surface 9a.
It is displaced to the light receiving element g side.

As described above, the first and second patterns P1, P
2, the differential amplifiers 18, 20
The output levels of the operation signals Rdc and Rhg output from are changed in the same manner as in FIG.

Therefore, by measuring the actual output level of the first error detection signal RE, in addition to the amount of tilt of the recording / reproducing surface 10 in the radial direction, it can be tilted in either the lead-in side or the lead-out side. Information can be extracted.

Next, the principle of detection when the optical disk 11 is tilted in the time axis direction will be described. When the optical pickup device 1 is moved in the time axis direction in a state where the optical axis of the optical pickup device 1 is not inclined in both the radial direction and the time axis direction with respect to the recording / reproducing surface 10 of the optical disk 11, The output levels of the operation signals Tba and Tfe output from the differential amplifiers 19 and 21 change similarly to the operation signals Rdc and Rhg shown in FIG.

Therefore, by setting the gain β of the amplifier 25 to be equal to the ratio of the output levels of the operation signals Tba and Tfe (Tfe / Tba) in advance, the light from the recording / reproducing surface 10 of the optical disk 11 is The second error detection signal TE obtained in a state where the optical axis of the pickup device 1 is not tilted is always substantially zero.

FIG. 9 shows how the first and second patterns P1 and P2 change when the optical disk 11 is tilted in the time axis direction from the state shown in FIG. 5B. Note that FIG.
FIG. 5B shows the same state as FIG. 5B, that is, the case where no skew has occurred.

When the optical disk 11 is tilted counterclockwise in the time axis direction, the spot light on the recording / reproducing surface 9 is focused, and as shown in FIG. Almost no displacement. On the other hand, the second pattern P2 is displaced toward the light receiving element e because the optical path of the second return light is largely deviated from the optical axis due to the inclination of the substrate surface 9a.

When the optical disk 11 is tilted clockwise in the time axis direction, the spot light on the recording / reproducing surface 9 is focused, and as shown in FIG. Is hardly displaced. On the other hand, the second pattern P2 is displaced toward the light receiving element f because the optical path of the second return light is largely deviated from the optical axis due to the inclination of the substrate surface 9a.

As described above, the first and second patterns P1, P
2 is displaced, the differential amplifiers 19, 21
Respectively, the output levels of the operation signals Tba and Tfe output from the CPU change.

Therefore, by measuring the actual output level of the second error detection signal TE, in addition to the amount of tilt of the recording / reproducing surface 10 in the time axis direction, it can be set in either the counterclockwise direction or the clockwise direction. It is possible to extract information as to whether it is tilted.

As described above, according to the present embodiment, the first,
Based on the output levels of the second error detection signals RE and TE, the inclination of the optical disk 11 in the radial direction and the time axis direction can be detected.

Then, the disc tilt correcting means is driven by using the first error detection signal RE,
It is possible to control the power at the time of recording, the strategy, and the like to vary the crosstalk canceller characteristic when reproducing information from the writer. Further, it is possible to delay the recording signal by using the second error detection signal TE, or to drive the time axis tilt correction means. As a result, even when the objective lens 5 with a high numerical aperture is used, the tolerance for the inclination (skew) between the optical axis and the optical disk 11 is improved, and high-density recording and
It is possible to reproduce information recorded at high density with high accuracy.

Further, good recording and reproduction can be performed with one semiconductor laser 2 while suppressing the loss of light quantity.

The optical pickup device of the present embodiment employs various design modes in accordance with the irradiation power of spot light or pattern light irradiating the optical disk, the recording sensitivity, the thickness of the transmission substrate, the control range of the optical disk, and the like. Since it has a configuration and functions that can be used, it can be applied to optical discs of various standards.

In this embodiment, a case has been described in which the first and second light receiving regions 12 and 13 are each divided into four and constituted by four light receiving elements a to d and e to h.
However, in the case of a general optical pickup device, that is, when the actuator is not driven in the time axis direction, the operation signal T generated by the differential amplifier 21 in FIG.
fe can be used as it is as a tilt detection signal in the time axis direction. When the calculation signal Tfe is used as it is as the inclination detection signal in the time axis direction, the first light receiving region 12 is set in the radial direction, that is, the light receiving elements a and b.
It is only necessary to provide two light receiving elements by dividing into two in the arrangement direction.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
Will be described with reference to FIG. Note that the optical pickup device of the present embodiment has a configuration similar to that of the first embodiment described with reference to FIGS. However,
Instead of the objective lens 5 shown in FIGS. 1 and 2, an objective lens 5 'shown in a longitudinal sectional view of FIG. 10 is provided.

In FIG. 10, the front surface of the objective lens 5 'is formed in an annular peripheral portion (first region) AR having a small curvature.
1 ′ and a central portion (second portion) having a larger curvature than the first region.
Area) AR2 '.

Here, of the light incident on the optical disk 11 through the first area AR1, the light reflected on the substrate surface 9a (second return light) is collected by the second area AR2. The light is emitted to the photodetector 7 side. Further, of the light incident on the optical disk 11 through the first area AR1, the light transmitted through the transparent substrate 9 and reflected or diffracted by the recording / reproducing surface 10 (first return light) is again transmitted to the first area AR. AR1
And is emitted to the photodetector 7 side. Light incident on the optical disk 11 side through the second area AR2 'is condensed on an imaginary point, and return light generated by the reflection on the substrate surface 9a is not emitted to the photodetector 7 side. Is set.

According to the objective lens 5 'having such a structure, the light condensed in the first area AR1' is not reflected on the second area AR.
Since 2 ′ does not contribute, the light having a minute spot shape condensed only at the annular zone aperture enters the recording / reproducing surface 10. Therefore, this spot-shaped light is applied to the recording / reproducing surface 1
The first return light generated by being reflected or diffracted at 0 is
Tracking servo can be performed by performing analysis processing by a so-called push-pull method or the like, and focus servo can be performed by performing analysis processing by a so-called Foucault method or astigmatism method. Further, the information recorded on the recording / reproducing surface 10 can be reproduced by detecting the first return light with a photoelectric conversion element (not shown).

Further, similarly to the first embodiment, the photoelectric conversion signals Sa to Sh output from the first and second light receiving regions 12 and 13 shown in FIG. Thus, a first error detection signal RE indicating the amount of tilt of the optical disk 11 in the radial direction and a second error detection signal TE indicating the amount of tilt of the optical disk 11 in the time axis direction are obtained.

The optical pickup device of the present embodiment employs various design modes according to the irradiation power of spot light or pattern light to be irradiated on the optical disk, the recording sensitivity, the thickness of the transmission substrate, the control range of the optical disk, and the like. Since it has a configuration and functions that can be used, it can be applied to optical discs of various standards.

In the first and second embodiments, the first and second regions AR1, AR2, AR2 on the front surface of the objective lenses 5, 5 '.
The case where AR1 'and AR2' are spherical is described.
It may have an aspherical shape. With such a structure, aberration can be reduced. Also, the second areas AR2 and AR
By making 2 ′ a toric surface, aspherical aberration can be given to light passing through this region, and it can be used for generating a phase detection signal. Further, the second regions AR2 and AR2 'need not be formed at the center of the objective lenses 5 and 5', and may have an asymmetric shape. In the case where the second area AR2 of the objective lens 5 has an asymmetric shape in the first embodiment, a portion where parallel light from the collimator lens 4 is incident and a portion where return light from the optical disk 11 is incident. There is no need to match.

In the objective lenses 5 and 5 ′ of the first and second embodiments, the first and second objective lenses 5 and 5 ′
Although the case where the second areas AR1, AR2, AR1 ', AR2' are formed has been described, instead of this, the first and second areas AR1, AR1, AR2 are formed on the rear surface facing the collimator lens 4 side.
2, AR1 'and AR2' may be formed. The first and second regions AR1, AR2, AR1 ', AR2 are not limited to the single-lens objective lenses 5 and 5', but may be made to have a double-ball structure or use one surface of a plurality of objective lenses. The same function as' may be exhibited.

In the first and second embodiments, the first and second embodiments
Although the case where the objective lenses 5 and 5 ′ having different curvatures are applied in the second region has been described, a hologram element having a lens effect similar to these may be applied. In this case, since the non-diffracted light passes through the hologram element as it is, it is possible to configure so that the central part (portion on the paraxial side) of the hologram element is not completely shielded. Therefore, by adjusting the diffraction efficiency, the shape of the spot light focused on the recording / reproducing surface 10 of the optical disk 11 can be variously adjusted, and thus the degree of freedom in design can be increased.

(Third Embodiment) Next, a third embodiment will be described with reference to FIG. FIG. 11 is a configuration diagram showing a configuration of an optical system of the optical pickup device 26 of the present embodiment. In FIG. 11, the same or corresponding components as those in FIG. 1 are indicated by the same reference numerals.

In FIG. 11, the optical pickup device 26
A first and a second semiconductor lasers 27 and 28 for emitting lights having different wavelengths from each other; and a dichroic prism 30
And a collimator lens 4 and an objective lens 31 disposed in front of the beam splitter 3, and a dichroic prism 32 and first and second photodetectors 33 and 34 disposed behind the beam splitter 3. The optical axes of these optical elements 3, 4, 27 to 34 are aligned.

The first semiconductor laser 27 is
The light source is a light source for recording information on the recording / reproducing surface 10, and a blue laser or the like that emits light having a short wavelength λ1 is used. The second semiconductor laser 28 is a light source for detecting the inclination of the substrate surface 9a of the optical disk 11, and an infrared laser or the like that emits light having a long wavelength λ2 is used.
The objective lens 31, unlike the objective lenses 5 and 5 'of the first and second embodiments, has a structure in which the front surface is not divided into two regions. Further, the spot light of the short wavelength λ1 passes through the transparent substrate 9 of the optical disk 11 and passes through the recording / reproducing surface 10.
The pattern light of long wavelength λ2 is focused on the optical disk 1
The shape of the objective lens 31 is set so as to connect a relatively large pattern to one substrate surface 9a.

The optical axis distance L1 from the light emitting end of the first semiconductor laser 27 to the collimator lens 4 and the optical axis distance L2 from the light emitting end of the second semiconductor laser 28 to the collimator lens 4 are L1 <L2. It is set so that it may become. More specifically, the first and second semiconductor lasers 2
The relationship of L1 <L2 is set by adjusting the distance between the dichroic prism 30 and the dichroic prism 30. Thereby, the chromatic aberration of the objective lens 31 can be reduced, and the size of the pattern of the long wavelength λ2 irradiated on the substrate surface 9a can be adjusted.

The dichroic prism 30 has a wavelength-selective dielectric multilayer film deposited on the prism surface, transmits the short wavelength λ1 light emitted from the first semiconductor laser, and transmits the light from the second semiconductor laser. Emitted long wavelength λ
By reflecting the two lights, these lights are emitted to the beam splitter 3 side.

The first light detector 33 is provided with four divided light receiving elements a to d, like the first light receiving area 12 shown in FIG. Similarly to the second light receiving area 13 shown in FIG. 4, four light receiving elements e to h are provided. Further, similarly to FIG. 4, the first error detection signal RE indicating the amount of tilt of the optical disk 11 in the radial direction is calculated by calculating the photoelectric conversion signals Sa to Sh output from the light receiving elements a to h. And a signal processing circuit for generating a second error detection signal TE indicating the amount of tilt of the optical disk 11 in the time axis direction.

In the dichroic prism 32, a dielectric multilayer film having wavelength selectivity is deposited on the prism surface, and the light having the short wavelength λ1 and the light having the long wavelength λ2 are
When light is incident from the side, the light having the short wavelength λ1 is transmitted and emitted to the light receiving elements a to d of the first photodetector 33, and the light having the long wavelength λ2 is transmitted to the light receiving element e of the second photodetector 34. ~
Reflects to h.

Next, the operation of the optical pickup device 26 having the above configuration will be described. Light is emitted from the first and second semiconductor lasers 27 and 28 simultaneously. These lights are combined by the dichroic prism 30 and reflected by the beam splitter 3 toward the collimator lens 4. The multiplexed light is collimated by the collimator lens 4 and emitted to the objective lens 31 side, and the collimated light is further condensed by the objective lens 31 and irradiated to the optical disk 11 side.

As a result, the spot light having the short wavelength λ1 is condensed on the recording / reproducing surface 9 of the optical disk 11, and the light (first return light) generated by being reflected or diffracted on the recording / reproducing surface 9 is again emitted. The light is condensed by the objective lens 31 and emitted to the collimator lens 4 side. At the same time, the optical disk 1
The first conductor surface 9a is irradiated with the pattern light of the long wavelength λ2, and the light reflected on the conductor surface 9a (second return light) is again condensed by the objective lens 31 and emitted to the collimator lens 4 side. You.

The first and second return lights reach the dichroic prism 32 through the collimator lens 4 and the beam splitter 3, and further, due to the wavelength selectivity of the dichroic prism 32, the first light having the short wavelength λ1.
Returns to the photodetector 33, and the second return light having the long wavelength λ2 enters the photodetector.

The first and second photodetectors 33 and 34 output the photoelectric conversion signals Sa to Sh by photoelectrically converting these return lights, and further described in the first embodiment. The signal processing circuit generates these photoelectric conversion signals Sa to S
h to calculate the optical disk 11
Error detection signal RE indicating the amount of tilt in the radial direction of
And a second error detection signal TE indicating the amount of tilt of the optical disk 11 in the time axis direction.

As described above, according to the present embodiment, in addition to the short wavelength λ1 spot light for recording and reproduction, the long wavelength λ2 pattern light for tilt detection is irradiated onto the optical disc 11, and Since the first and second error detection signals RE and TE are generated based on the first and second return lights, it is possible to accurately detect the inclination of the optical disk 11 in the radial direction and the time axis direction.

Then, the disc tilt correcting means is driven by using the first error detection signal RE,
It is also possible to control the power at the time of recording, the strategy, etc., to vary the crosstalk canceller characteristics when information is reproduced from the device. Further, it is possible to delay the recording signal by using the second error detection signal TE, or to drive the time axis tilt correction means. As a result, even when the objective lens 31 with a high numerical aperture is used, the tolerance for the inclination (skew) between the optical axis and the optical disc 11 is improved, and high-density recording and
It is possible to reproduce information recorded at high density with high accuracy.

The optical pickup device of the present embodiment employs various design modes according to the irradiation power of spot light or pattern light to be irradiated on the optical disk, the recording sensitivity, the thickness of the transmission substrate, the control range of the optical disk, and the like. Since it has a configuration and functions that can be used, it can be applied to optical discs of various standards.

In this embodiment, the photoelectric conversion signals Sa to Sh output from the first and second photodetectors 33 and 34 are provided.
Has been described, the tilt in the radial direction and the tilt in the time axis direction have been described. However, the tilt in the radial direction and the tilt in the time axis direction is detected based on the photoelectric conversion signal output from the second photodetector 34. You can also.

In this embodiment, four light receiving elements a to d, four light receiving elements a to d,
The configuration including each of e to h has been described.
Similarly to the above embodiment, two light receiving elements may be used.

Further, in the present embodiment, the case where the recording / reproducing on the optical disk 11 and the inclination detection are performed at the same time using two lights having different wavelengths has been described, but two lights having the same wavelength and different light powers are used. Is also good. As an example of this case, the dichroic prisms 30 and 32 in FIG.
Is replaced with a half prism or the like, and the first and second semiconductor lasers 27 and 28 are semiconductor lasers having the same wavelength.
By making the emission intensity of the second semiconductor laser 28 lower than the emission intensity of the semiconductor laser 27, the radial intensity based on the detection outputs of the first and second photodetectors 33 and 34 can be obtained. The inclination in the direction and the time axis direction can be detected.

(Fourth Embodiment) Next, a fourth embodiment will be described with reference to FIG. FIG. 12 is a configuration diagram showing a configuration of an optical system of the optical pickup device 35 of the present embodiment. In FIG. 12, the same or corresponding components as those in FIG. 11 are denoted by the same reference numerals.

In FIG. 12, a first hologram element 37 is disposed between a semiconductor laser 36 serving as a light source and the beam splitter 3, and a second hologram element 38 and a photodetector 39 are provided behind the beam splitter 3. It is arranged.

The first hologram element 37 has a diffraction pattern that gives a diffraction effect equivalent to refracting a marginal ray on a peripheral surface shifted from the optical axis of the convex lens. The second hologram element 38 has a diffraction pattern that exhibits a diffraction effect equivalent to that of a concave lens. The light detector 39 includes first and second light receiving regions 40 and 41 having light receiving surfaces capable of detecting a two-dimensional image.

According to this configuration, the emitted light of the semiconductor laser 36 passes through the first holobram element 37, so that the real image light of the semiconductor laser 36 is transmitted to the recording / reproducing surface 10 of the optical disk 11 and the virtual image light of the semiconductor laser 36 is transmitted. Irradiates the substrate surface 9a of the optical disk 11. Further, the real image light is reflected or diffracted on the recording / reproducing surface 10 and the virtual image light is reflected on the substrate surface 9.
The return light generated by the reflection at a
The light is condensed by 1 and enters the second holobram element 38 via the collimator lens 4 and the beam splitter 3. In the second hologram element 38, the return light is enlarged and emitted to the first and second light receiving regions 40 and 41 of the photodetector 39.

In the first and second light receiving areas 40 and 41, the first light receiving area 40 photoelectrically converts the real image light of the return light into a first image signal, and the second light receiving area 41 receives the return light. Is converted into a second image signal by photoelectric conversion and output. Then, by comparing the first and second image signals, the inclination of the optical disk 11 in the radial direction and the time axis direction is detected.

As described above, according to the present embodiment, it is possible to detect the inclination of the optical disk in the radial direction and the time axis direction by applying a single light source, and to realize a simplified configuration and the like. Can be. Further, a general high numerical aperture objective lens 31 can be applied.

In the first and second embodiments described above, the light condensing means such as the objective lenses 5 and 5 'having two divided regions having different curvatures and the semiconductor laser 2 having a single wavelength are used. The light source means is provided to detect the inclination of the optical disk. In the third and fourth embodiments, a light condensing means such as a general objective lens 31 and a light source means such as semiconductor lasers 27 and 28 having a plurality of wavelengths or a single light source means are provided. The case where the light source means such as the one-wavelength semiconductor laser 36 is provided to detect the inclination of the optical disk has been described.
However, the present invention is not limited to these configurations, and a configuration in which the light collecting unit and the light source unit of each embodiment are individually combined may be employed.

In the first to fourth embodiments, the inclination of a recording / reproducing medium such as an optical disk represented by a CD (compact disk), a DVD (digital versatile disk), and an LD (laser disk) can be detected. is there. Also, a read-only recording / reproducing medium such as a CD-ROM,
The present invention can be applied to a writable recording / reproducing medium such as a CD-R.

[0085]

As described above, according to the present invention, at least the surface of the transparent substrate constituting the recording / reproducing medium is irradiated with light and returned light generated by reflection on the surface, that is, the recording light is recorded. Since the return light having the tilt information of the reproducing medium is detected, the tilt information of the recording / reproducing medium can be accurately extracted. Further, the tilt information inherent in the return light has omnidirectional tilt information according to the tilt mode of the recording medium. For this reason, it is possible to detect the inclination in the radial direction and the inclination in the time axis direction, which are the conventional problems.

Therefore, based on the extracted tilt information, tilt correction of the recording / reproducing medium and variably control of recording light irradiation power, strategy, reproduction equalizer characteristics, etc. can be performed. Even if the light condensing means is applied, it is possible to realize an optical pickup device which is strong against the inclination (skew) of the recording medium. Further, since an objective lens or the like having a high numerical aperture can be applied as described above, high-density recording can be performed, and information can be reproduced with high accuracy from a recording / reproducing medium on which high-density recording has been performed. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a configuration of an optical pickup device according to a first embodiment.

FIG. 2 is a longitudinal sectional view showing a structure of an objective lens.

FIG. 3 is an explanatory diagram schematically showing a diffraction pattern shape of a hologram element.

FIG. 4 is a block diagram showing shapes of first and second light receiving areas and a configuration of a signal processing circuit.

FIG. 5 is an explanatory diagram for explaining the operation principle of tilt detection.

FIG. 6 is a characteristic diagram for further explaining the operation principle of tilt detection.

FIG. 7 is an explanatory diagram for further explaining the operation principle of tilt detection.

FIG. 8 is a longitudinal sectional view showing a state in which the optical disc is inclined with respect to the objective lens in order to further explain the operation principle of the inclination detection.

FIG. 9 is an explanatory diagram for further explaining the operation principle of tilt detection.

FIG. 10 is a longitudinal sectional view illustrating a structure of an objective lens for describing a configuration of an optical pickup device according to a second embodiment.

FIG. 11 is a configuration diagram illustrating a configuration of an optical pickup device according to a third embodiment.

FIG. 12 is a configuration diagram illustrating a configuration of an optical pickup device according to a fourth embodiment.

[Explanation of symbols]

 2, 27, 28, 36 semiconductor laser 3 beam splitter 4 collimator lens 5, 5 ', 31 objective lens 6, 37, 38 hologram element 7, 33, 34, 39 photodetector 9 transparent substrate 9a: substrate surface 10: recording / reproducing surface 11: optical disk 12, 13: light receiving area 18 to 21, 22, 23: differential amplifier 24, 25: amplifier AR1: first area AR2: second area

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5D118 AA04 AA13 BA01 BF02 BF03 CA02 CC12 CD02 CD03 CD04 CD08 CF06 DA20 DC03 5D119 AA12 AA22 BA01 DA01 DA05 JA14 JA24 JA44 KA24

Claims (8)

[Claims] 1. An optical pickup device for irradiating a recording / reproducing medium having a transparent substrate and a recording / reproducing surface with light for recording or reproduction, comprising: a light source for emitting the light; and a light emitted from the light source. Light collecting means for irradiating the recording / reproducing surface and the transparent substrate; light detecting means for receiving return light from the surface of the transparent substrate; output from the photodetector by return light from the surface of the transparent substrate. A signal processing means for extracting tilt information of the recording / reproducing medium based on the received light output. 2. An optical pickup device for irradiating a recording / reproducing medium having a transparent substrate and a recording / reproducing surface with light for recording or reproduction, comprising: a light source for emitting the light; and a light emitted from the light source. Light collecting means for irradiating the recording / reproducing surface and the transparent substrate; light detecting means for receiving return light from the recording / reproducing surface and the surface of the transparent substrate; and detecting the light by returning light from the recording / reproducing surface. Generating a first signal based on a light receiving output output from the detector.
Signal generating means for generating a second signal based on a light receiving output output from the photodetector by return light from the surface of the transparent substrate; and a first signal generating means and a second signal generating means. And a signal processing unit for extracting the tilt information of the recording / reproducing medium by comparing the signals. 3. The light condensing means has a first region through which return light from the recording / reproducing surface is transmitted and a second region through which return light from the surface of the transparent substrate is transmitted. The optical pickup device according to claim 2, wherein 4. The light condensing means has a first area for transmitting light from the light source and a second area for transmitting light from the light source.
An optical pickup device according to item 1. 5. The optical pickup device according to claim 1, wherein the return light from the surface of the transparent substrate is in a defocused state on the surface of the transparent substrate. 6. The light collector irradiates the transparent substrate side with light emitted from the light source through the first region, and emits return light from the surface of the transparent substrate through the second region. The optical pickup device according to claim 2, wherein: 7. The optical pickup device irradiates the recording / reproducing medium with a plurality of light beams having different wavefronts from the focusing means, and irradiates one of the plurality of light beams to the recording / reproducing surface. 3. The method according to claim 2, further comprising irradiating another surface of the plurality of light beams to a surface of the transparent substrate.
The optical pickup device according to any one of claims 1 to 6. 8. The optical pickup device according to claim 1, further comprising a hologram element that converts the light emitted from the light source into a plurality of light beams having different wavefronts and outputs the light. An optical pickup device according to the item.