JPH01256045A - Optical disk check device - Google Patents

Abstract

PURPOSE:To select number of revolutions at check and the check mode by switching the control in response to the deflection of an optical disk. CONSTITUTION:A servo switching circuit 7 uses a tracking servo circuit 5 to control the optical pickup 4 and the tracking servo in response to the fact that the deflection of the optical disk 2 is decided to be a prescribed value or below by a deflection decision circuit and releases the tracking servo loop control of a slide mechanism 3 by a slide servo circuit 6. Moreover, the servo switching circuit 7 uses the tracking servo circuit 5 to control the optical pickup 4 for the tracking servo in response to the fact that the deflection of the optical disk 2 is decided to be a prescribed value or over and incorporates a slide servo circuit 6 in the tracking servo loop to apply tracking servo control to the slide mechanism 3. Thus, number of revolutions for check and the check mode are selected optimizingly.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical disc inspection device, and particularly to an optical disc inspection device for inspecting scratches on an optical disc from which information is read by an optical pickup having a servo system using a tracking actuator. The present invention relates to an optical disc inspection device.

[Prior Art] An optical disc inspection device applies tracking servo to grooves for recording information on an optical disc, and inspects all grooves for scratches and the like in the grooves of the optical disc. In these optical disk devices, an optical pickup having a servo system using a tracking actuator is used.

It is desired that the optical disk inspected by such an optical inspection device has as little eccentricity as possible when attached to the rotating shaft.

[Problems to be Solved by the Invention] However, normally, when an optical disk is fitted onto a shaft based on the inner diameter, eccentricity of several tens of microns cannot be avoided. Furthermore, in the manufacturing process of the optical disk itself, the groove is eccentric by several tens of microns with respect to the inner diameter. Therefore, in the worst case, the groove will be approximately 10
This means that it is eccentric by about 0 microns. in this way,
In an apparatus that tests the characteristics of an optical disk by applying a tracking servo to an eccentric groove, the relationship between the allowable eccentricity and the number of revolutions is as shown in FIG. 6, due to the characteristics of the optical pickup. That is, as is clear from FIG. 6, it is impossible to inspect an optical disk with a large amount of eccentricity at high speed rotation. The amount of eccentricity of an optical disk differs for each optical disk and also varies depending on the production lot, so the rotation speed of the optical disk must be lower than the worst case eccentricity, which increases the time required for inspection. There was a problem with this.

Therefore, the main object of the present invention is to be able to inspect an optical disk at a high speed rotation even if the amount of eccentricity is large, to fix the amount of eccentricity n1 of the optical disk at the initial stage of the inspection, and to adjust the number of inspection rotations according to the size of the eccentricity n1. An object of the present invention is to provide an optical disk inspection device that can select the optimum inspection mode.

[Specific Means for Solving the Problems] This invention includes a coarse movement actuator and a fine movement actuator that constitute a tracking servo loop in order to follow the grooves of an optical disk and apply a tracking servo. An optical disc inspection device for determining n1,
The eccentricity determining means for determining the eccentricity of the optical disc at the start of measurement, the detecting means for detecting the position of the coarse movement actuator, and the eccentricity determining means determine that the eccentricity of the optical disc is less than or equal to a predetermined value. In response to this, the tracking servo loop of the coarse movement actuator is canceled and the detection output of the detection means is switched to be applied to the coarse movement actuator, and in response to it being determined that the amount of eccentricity is greater than or equal to a predetermined value, The structure includes switching control means for switching to close the servo loop of the coarse movement actuator.

More preferably, it is configured to include a linear slide mechanism capable of linearly moving the coarse movement actuator, and a linear motor for driving the linear slide mechanism.

Furthermore, the fine movement actuator is installed on the slide mechanism and includes an optical pickup that irradiates a light beam onto the groove of the optical disc, receives the reflected light, and applies tracking servo based on the received light output. be done.

[Function] The optical disk inspection device according to the present invention, if the measured eccentricity at the start of measurement is less than a predetermined value, configures a tracking servo loop using only the fine movement actuator to rotate the previous disk at high speed, and corrects the eccentricity. If is equal to or greater than a predetermined value, the coarse movement actuator and the fine movement actuator constitute a tracking servo loop to rotate the optical disk at a relatively slow speed. - [Embodiment of the invention] FIG. 1 is a schematic block diagram of an embodiment of the invention.

First, referring to FIG. 1, a general configuration of an embodiment of the present invention will be described. An optical disk 2 is rotationally driven by a drive motor 1, and a slide mechanism 3 as a coarse movement actuator and an optical pickup 4 as a fine movement actuator are provided to apply tracking servo to the optical disk 2. The slide mechanism 3 is controlled by a slide servo circuit 6, and the optical pickup 4 is controlled by a tracking servo circuit 5. The eccentricity determination circuit 8 determines the amount of eccentricity at the initial stage of inspection of the optical disc 2. The servo switching circuit 7 causes the tracking servo circuit 5 to perform tracking servo control on the optical pickup 4 in response to the eccentricity determination circuit determining that the amount of eccentricity of the optical disc 2 is less than a predetermined value, and also controls the slide servo circuit 6 The tracking servo loop control of the slide mechanism 3 is canceled.

Further, in response to the determination that the amount of eccentricity is greater than or equal to a predetermined value, the servo switching circuit 7 causes the tracking servo circuit 5 to perform tracking servo control on the optical pickup 4, and also causes the slide servo circuit 6 to enter the tracking servo loop. The slide mechanism 3 is controlled by tracking servo. That is, when the amount of eccentricity of the optical disk is small, a one-stage control is performed in which only the optical pickup 4 is subjected to tracking servo control, and when the amount of eccentricity is large, a two-stage configuration is performed in which tracking servo control is performed on the slide mechanism 3 and the optical pickup 4.

FIG. 2 is a perspective view of essential parts of an example of the slide mechanism shown in FIG. 1, and FIG. 3 is a diagram schematically showing the optical pickup.

Next, referring to FIGS. 2 and 3, the slide mechanism 3
The configuration of the optical pickup 4 will now be explained. The slide mechanism 3 includes a linear motor 31.

This linear motor 31 moves the slide section 32 to the optical disk 2.
The object is to be slid linearly toward the center of the object. The optical pickup 4 is placed on the slide portion 32.

As shown in FIG. 3, the optical pickup 4 includes a semiconductor laser 41, a collimator lens 42, a beam splitter 43, a quarter-wave plate 44, a fixed mirror 45, a two-dimensional actuator 46, an objective lens 47, a lens 48, and a half mirror.
49, a photodetector 50, a cylindrical lens 51, and a photodetector 52. The semiconductor laser 41 emits laser light, and this laser light passes through the collimator lens 42. Beam splitter 43. 1/4 wavelength plate 44. The light is irradiated onto the optical disc 2 via the fixed mirror 45 and the objective lens 47. The laser beam reflected by the optical disk 2 passes through the objective lens 47. Fixed mirror 45. 1/4 wavelength plate 44. Beam splitter 43. Lens 48. It is detected by the photodetector 50 via the half mirror 49, and
It is reflected by the half mirror 49, and the cylindrical lens 5
1 and is detected by a photodetector 52. The two-dimensional actuator 46 moves the objective lens 47 as shown in FIG.
, move in the b direction to adjust the focus, and c
, d direction to perform tracking control. Incidentally, since the optical pickup 4 as shown in FIG. 3 is already known, detailed explanation will be omitted.

FIG. 4 is a concrete block diagram of one embodiment of the present invention, which more specifically shows the configuration shown in FIG. 1.

In FIG. 4, a position detector 9 for detecting the position of the linear motor 31 is provided near the linear motor 31. The position of the linear motor 31 detected by the position detector 9 is given to a positioning command circuit 10.

The positioning command circuit 10 is supplied with a position command signal. The positioning command circuit 10 outputs the deviation between the position of the linear motor 31 detected by the position detector 9 and the position command signal, and provides it to the servo switching circuit 7 . The servo switching circuit 7 switches to the output side of the positioning command circuit 10 or the output side of the gain adjustment circuit 67 based on the determination output of the eccentricity determination circuit 8 shown in FIG.

The slide servo circuit 6 includes a gain adjustment circuit 61, a phase compensation circuit 62, a notch filter 63, a power amplifier 64, a low-pass filter 66, and a gain adjustment circuit 67, and the tracking servo circuit 5 includes a tracking error detection circuit 51 and a phase compensation circuit. 52, a gain adjustment circuit 53, and a power amplifier 54. The tracking error detection circuit 51 detects whether or not there is an error based on the tracking signal given from the optical pickup 4. The tracking error detection signal detected by the tracking error detection circuit 51 is given to the phase compensation circuit 52 to perform phase compensation, and after the gain is adjusted by the gain adjustment circuit 53, it is sent to the power amplifier 54.
given to.

The power amplifier 54 applies tracking servo to the optical pickup 4 based on the tracking error detection signal.

Further, the tracking error signal detected by the tracking error detection circuit 51 is given to a low-pass filter 66, and after high frequency components are attenuated, the gain is adjusted by a gain adjustment circuit 67. Further, the signal is applied to the gain adjustment circuit 61 via the servo switching circuit 7 for gain adjustment again, and after phase compensation is performed by the phase compensation circuit 62, the resonance peak is attenuated by the filter 63. Further, the tracking error detection signal is amplified by a power amplifier 64, and the linear motor 31 is driven based on the output of the power amplifier 64.

FIG. 5 is a diagram showing the relationship between the number of rotations and the amount of eccentricity that can be inspected in one embodiment of the present invention.

Next, with reference to FIGS. 1 to 5, a specific operation of an embodiment of the present invention will be described.

The eccentricity determining circuit 8 determines how eccentric the optical disc 2 is based on the eccentricity signal at the initial stage of testing the optical disc 2 . When the amount of eccentricity is relatively small as shown at point A in FIG. 5, the eccentricity determination circuit 8 switches the servo switching circuit 7 shown in FIG. 4 to the positioning command circuit 10 side. The positioning command circuit 10 outputs a signal corresponding to the eccentricity difference between the position of the slide portion 32 detected by the position detector 9 and the position command signal. This signal is transmitted to the gain adjustment circuit 61° and the phase compensation circuit 62. The signal is applied to a power amplifier 64 via a notch filter 63. Power amplifier 64 drives linear motor 31.

At this time, the tracking error detection circuit 51 detects a tracking error based on the signal output from the optical pickup 4, and transmits the tracking error detection signal to the phase compensation circuit 52. Power amplifier 5 via gain adjustment circuit 53
Give to 4. In response, the power amplifier 54 drives the optical pickup 4.

In this case, as shown in FIG. 5, even if the optical disk 2 is rotated at a relatively high speed, the optical pickup 4 can sufficiently follow the eccentricity using just the tracking servo.

Conversely, when the amount of eccentricity is relatively large as shown at point B in FIG. 5, the eccentricity determination circuit 8 switches the servo switching circuit 7 to the output side of the gain adjustment circuit 67.

The tracking error signal detected by the tracking error detection circuit 51 is given to the tracking servo circuit 5, and is also applied to a low-pass filter 66, a gain adjustment circuit 67, a servo switching circuit 7, a gain adjustment circuit 611, a phase compensation circuit 62. The signal is applied to a power amplifier 64 via a notch filter 63. The power amplifier 64 amplifies the tracking error detection signal and drives the linear motor 31.

On the other hand, the tracking servo circuit 5 performs tracking servo on the optical pickup 4 according to the tracking error detection signal. That is, when the amount of eccentricity is large, two stages of servo are applied: servo by the slide servo circuit 6 and tracking servo by the tracking servo circuit 5.

In this case, as shown in FIG. 5, by rotating the optical disk 2 at a relatively low speed and applying tracking servo and slide servo, it is possible to sufficiently follow the eccentricity.

[Effects of the Invention] As described above, according to the present invention, when the amount of eccentricity is small, the coarse actuator is separated from the tracking servo loop system, and the coarse actuator is controlled based on the position detection output of the coarse actuator. In addition, tracking servo is applied to the fine movement actuator, and when the amount of eccentricity is large, tracking servo is applied to the coarse movement actuator and fine movement actuator, so the inspection rotation speed and inspection mode can be optimally selected.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of an embodiment of the present invention. FIG. 2 is an external perspective view showing a linear slide mechanism for inspecting optical discs. FIG. 3 is a diagram showing the tracking actuator. FIG. 4 is a concrete block diagram of an embodiment of the present invention. FIG. 5 is a diagram showing the relationship between the number of rotations of an optical disk and the amount of eccentricity that can be tested in one embodiment of the present invention. 6th
The figure is a diagram showing the relationship between the rotational speed and the amount of eccentricity that can be tested in a conventional disk testing device. In the figure, 1 is a drive motor, 2 is an optical disk, 3 is a slide mechanism, 4 is an optical pickup, 5 is a tracking servo circuit, 6 is a slide servo circuit, size 7 is a servo switching circuit, 8 is an eccentricity illusion circuit, and 9 is an eccentricity illusion circuit. Position detector, 51 is a tracking error detection circuit, 52.62 is a phase compensation circuit, 53.61.67 is a gain adjustment circuit, 5
4.64 is a power amplifier, and 66 is a low-pass filter.

Claims (3)

[Claims] (1) An optical disc inspection device for measuring the characteristics of the optical disc, including a coarse movement actuator and a fine movement actuator forming a tracking servo loop in order to follow the grooves of the optical disc and apply a tracking servo, an eccentricity determining means for determining the eccentricity of the optical disc at the start of measurement; a detecting means for detecting the position of the coarse movement actuator; In response to the determination, the tracking servo loop of the coarse movement actuator is canceled and the detection output of the detection means is switched to be applied to the coarse movement actuator, and the eccentricity is determined to be equal to or greater than a predetermined value. An optical disc inspection device comprising a switching control means for switching to close a servo loop of the coarse movement actuator in accordance with the determination. (2) The optical disc inspection apparatus according to claim 1, wherein the coarse movement actuator includes: a linear slide mechanism capable of moving linearly; and a linear motor for driving the linear slide mechanism. (3) The fine movement actuator is provided on the slide mechanism, irradiates the groove of the optical disk with a light beam, receives the reflected light, and applies a tracking servo based on the received light output. The optical disc inspection device according to claim 2, further comprising a pickup.