JP3201214B2 - Optical disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus for recording a signal on a track of an optical disk or reproducing a signal on the recorded track by using a light spot of a semiconductor laser with a focused light. In particular, the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam is detected and corrected,
The present invention relates to an optical disk apparatus that improves the quality of a light spot on a recording surface of an optical disk and the characteristics of recording and reproducing signals.

[0002]

2. Description of the Related Art In recent years, as one method of detecting and correcting the inclination of a recording surface of an optical disk with respect to the optical axis of a light beam of an optical disk device, an optical head is used to balance reflected light from the optical disk during recording or reproduction. Control combined with a tilt correction method that improves the tilt control accuracy by equalizing the crosstalk components on the inner and outer tracks adjacent to the track on which the test signal was recorded when the optical disk device was started. Have been.

A conventional tilt correction method will be described with reference to a configuration diagram of an optical disk device shown in FIG. In FIG. 8, 1 is an optical disk, 2 is a disk motor, 3 is an optical head for recording and reproducing signals by light from a light source, 4 is an objective lens that narrows down the light of the optical head 3 to generate a light spot, and 5 is an objective lens 4 Are driven in the focus direction and the tracking direction. Reference numeral 6 denotes a light beam for recording and reproducing a signal emitted from a light source (not shown) of the optical head 3.
Return to Reference numeral 7 denotes a light receiver that receives the reflected light beam 6 and that is divided into at least two or four or more divisions. 8
Is a two-divided light beam that detects the inclination emitted from a light source (not shown) of the optical head 3 and is reflected by the optical disk 1; 9 is a two-divided light receiver that detects the two-divided reflected light; A differential amplifier that takes the differential of the light receiver 9 and outputs a differential voltage indicating the slope, and a comparator 11 that compares the reference voltage with the differential voltage to generate a control voltage. Reference numeral 12 denotes a reference voltage generation circuit, and reference numeral 13 denotes a tilt control circuit that drives the tilt motor 14 by the control voltage of the comparator 11 to tilt the optical head 3 and perform tilt control during recording and reproduction. Numeral 15 calculates the output of the photodetector 7 divided by the arithmetic circuit, and outputs a focus error signal FE, a tracking error signal TE, and a reproduction signal RF. A focus control circuit 16 drives the actuator 5 with the focus error signal FE to control the focus of the light spot, and a tracking control circuit 17 drives the actuator 5 with the tracking error signal TE to control the position of the light spot in the track direction. is there. Reference numeral 18 denotes a crosstalk detection circuit which detects a crosstalk component in inner and outer tracks adjacent to a test track on which a predetermined signal is recorded when the optical disk device is started. 19 is such that the amplitudes of the inner and outer crosstalk components are approximately equal,
This is a tilt correction circuit that adjusts the reference voltage of the reference voltage generation circuit 12 to improve the accuracy of tilt control.

Next, a specific configuration of the focus control circuit 16 will be described with reference to FIG.

Reference numeral 50 denotes a differential amplifier for taking a difference between the focus error signal FE and the operation reference voltage VREF. Since the operation reference voltage VREF is based on the focus error signal FE, it can be expressed by the focus error signal FE = FE + VREF. Reference numerals 51 and 52 denote input resistors of the differential amplifier 50, which are resistors R1. 53 and 54 are resistors R2, which are numerator components for gain calculation. The output voltage VO1 of the differential amplifier 50 is V
O1 = (R2 / R1) * FE, and the input FE is multiplied by the gain (R2 / R1). 55 is also an amplifier, 56
The resistor R3 and the capacitor C3 of 57 are connected, and the resistor R4 of 58 and the capacitor C4 of 59 are connected to the feedback system. The output voltage VO2 of the amplifier 55 is VO2 = VO1 *
(R4 / R3) * (1 + sC3R3) / (1 + sC4R)
4) and has a DC gain (R4 / R3) and a phase characteristic (1 + sC3R3) / (1 + sC4R4), and the focus control system is optimized. A current source 60 is driven by the output VO2 of the amplifier 55, and a drive current flows through the actuator 5 so that the light spot is focused.

Next, a specific configuration of the tracking control circuit 17 will be described with reference to FIG.

Reference numeral 70 denotes a differential amplifier for taking a difference between the tracking error signal TE and the operation reference voltage VREF. Since the operation reference voltage VREF is based on the tracking error signal TE, the tracking error signal TE = TE + VR
It can be expressed by EF. 71 and 72 are resistors R5 and a differential amplifier 70
Is the input resistance. Reference numerals 73 and 74 denote resistors R6, which are numerator components for gain calculation. Output voltage VO3 of differential amplifier 70
Is VO3 = (R6 / R5) * TE, and the input TE is multiplied by the gain (R6 / R5). 75 is also an amplifier. The input is connected to the resistor R7 of 76 and the capacitor C7 of 77, and the resistor R8 of 78 and the capacitor C8 of 79 are connected to the feedback system. The output voltage VO4 of the amplifier 75 is VO4 = VO
3 * (R8 / R7) * (1 + sC7R7) / (1 + sC
8R8) and has a DC gain (R8 / R7) and a phase characteristic (1 + sC7R7) / (1 + sC8R8),
The tracking control system is optimized. 80 is a current source,
Driven by the output VO4 of the amplifier 75, a drive current flows through the actuator 5 so that the light spot is centered on the track.

The tilt correction method described above basically requires only the tilt control to drive the tilt motor 14 so that the differential output of the light receiver 9 representing the tilt is balanced to zero. That is, the reference voltage may be fixed to zero. However, in practice, even if the differential output of the light receiver 9 is balanced and zero, a mechanical setting deviation of the light receiver 9, a light reception sensitivity deviation of the light receiver divided into two, a deviation of the balance of the reflected light 8, Since there are many error factors such as the offset of the differential amplifier 10, the slope is not zero. To correct these errors, the reference voltage is adjusted so that the crosstalk components on the tracks adjacent to the test track are substantially equal at the time of shipment in the process or at the time of starting up the optical disc apparatus, and the inclination is substantially reduced. Correct to zero. In a conventional correction method, a crosstalk amplitude is monitored by a spectrum analyzer at the time of assembly and shipment in a process, and a reference voltage is manually adjusted. In recent years, the tilt correction circuit 19 automatically adjusts the reference voltage so that the crosstalk amplitudes become equal when the process is shipped or when the optical disk device is started.

The specific operation of the above-described conventional tilt correction method will be described with reference to FIGS. In FIG. 13, 21 is a track, 22 is a pit on which a predetermined signal for detecting crosstalk is recorded, and 23 is a light spot. For the sake of simplicity, a track indicates either a land or a groove, and a light spot does not show a side lobe component that contributes to actual crosstalk detection. In FIG. 13, the track numbers are represented by A-2 to A + 2. A predetermined signal for detecting crosstalk is recorded in the test track A in advance. Tracks A-2 and A-1 are inside test track A. Tracks A + 2 and A + 1 are outside test track A. Light spot 23
However, when the tracks A-1 and A + 1 adjacent to the test track A are reproduced, the signal of the track A is detected as a crosstalk component.

Referring to FIG. 14, inclination correction will be described using the actual amplitude of the crosstalk component. (A) of FIG.
Is a case where a slope exists. At this time, the signal amplitude of the test track A is detected to be about 0 dB, but the inclination occurs and the quality of the light spot is poor, and the amplitude is lower than the original amplitude. The crosstalk signal amplitude of the A-1 track adjacent to the test track is approximately −25 dB, and the crosstalk signal amplitude of the A + 1 track is approximately −35 dB, which is not balanced.

On the other hand, in the case of FIG. 14B in which the reference voltage is adjusted so that the amplitude of the crosstalk signal is substantially equal to -30 dB in the A-1 track and the A + 1 track, the slope becomes almost zero. Has been corrected. Therefore, the quality of the light spot is good, and the signal amplitude of the test track A is +
The amplitude is 2 dB, and the amplitude is improved as compared with the case where there is a slope.

[0012]

However, in the conventional optical disk apparatus using the tilt correction method for balancing the crosstalk component, the signal amplitude of the crosstalk component is reduced from -30 dB to the signal amplitude of the test track.
Since the amplitude is very small, about 40 dB, there is a problem that amplitude fluctuation is large, and it is difficult to detect reliably and stably.

The present invention solves such a problem. When a crosstalk component is detected, an offset is added to a focus control circuit to bring a light spot into a defocus state, whereby the crosstalk component is detected. It is an object of the present invention to provide an optical disc apparatus that detects a signal amplitude by increasing the signal amplitude and ensures tilt correction to improve the quality of a light spot and the signal quality of recording and reproduction.

[0014]

In order to achieve this object, an optical disc apparatus according to a first aspect of the present invention reproduces an inner or outer track adjacent to a predetermined track to reduce the amplitude of a crosstalk component of a predetermined signal. Crosstalk detecting means for detecting and outputting; tilt detecting means for detecting the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam from the differential output of the two-part photodetector; The tilt control means that drives the optical head by the control voltage generated by comparing the voltage and makes the inclination substantially zero, and the amplitude of the crosstalk component inside and outside the predetermined track detected by the crosstalk detection means are substantially equal. The tilt control means adjusts the reference voltage of the tilt control means so that the focus control is performed when the signal amplitude of the crosstalk component is detected by the crosstalk detection means. And a defocusing means for the light spot to the defocused state by adding an offset to the means.

According to a second aspect of the present invention, there is provided an optical disk apparatus according to the first aspect of the present invention, wherein the offset to be added to the focus control means is set to both positive and negative polarities instead of the defocusing means in the optical disk apparatus of the first invention, thereby performing bipolar defocusing. It has a defocus means for generating.

According to a third aspect of the present invention, there is provided an optical disk apparatus according to the first aspect of the present invention, wherein an offset added to the tracking control means when the signal amplitude of the crosstalk component is detected by the crosstalk detection means instead of the defocus means. Are set to positive and negative polarities to generate off-tracks of both polarities, and off-track means for switching the offset between inner and outer tracks so that the light spot is closer to a predetermined track.

[0017]

According to the optical disk device of the first aspect of the present invention, when the crosstalk detecting means reproduces an inner or outer track adjacent to a predetermined track to detect a crosstalk component, the defocus means operates at the light spot. To a defocused state. Since the light spot is defocused, the diameter of the spot increases, and the detection amplitude of the crosstalk component of the adjacent track increases. The tilt correction means adjusts the reference voltage so as to correct the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam so that the amplitude of the crosstalk component having the increased signal amplitude becomes substantially equal between the inner and outer tracks.

According to the optical disk apparatus of the second aspect of the present invention, when the crosstalk detecting means detects a crosstalk component, the defocus means sets the light spot to a defocus state of both positive and negative polarities. Even if the direction in which the light spot increases due to astigmatism has directionality with respect to the track, the spot diameter in the crosstalk detection direction increases due to positive or negative defocus, and the crosstalk component of the adjacent track The detection amplitude increases. In the case of the defocus polarity in which the signal amplitude is increased between the inner track and the outer track, the tilt correction means adjusts the reference voltage so as to correct the tilt so that the amplitude of the crosstalk component becomes substantially equal.

According to the optical disk apparatus of the third aspect of the present invention, when the crosstalk detecting means detects a crosstalk component, the off-track means sets a positive / negative offset in the tracking control means to set the light spot in the off-track state. To In switching the offset between positive and negative, when detecting crosstalk between outer tracks adjacent to the predetermined track, a positive offset is set in a direction in which the light spot approaches the predetermined track. When detecting crosstalk between inner tracks adjacent to a predetermined track, a negative offset is set in a direction in which the light spot approaches the predetermined track. In this way, the polarity of the offset is switched between the inside and outside tracks of the predetermined track to generate an off-track where the light spot approaches the predetermined track, thereby increasing the amplitude of the crosstalk component. The tilt correcting means adjusts the reference voltage so as to correct the tilt so that the amplitude of the crosstalk component between the inner and outer tracks having the increased amplitude becomes substantially equal.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows that when a crosstalk component is detected,
FIG. 3 is a configuration diagram of an optical disc device in an embodiment of the first invention in which a tilt correction circuit adjusts a reference voltage to correct a tilt by setting a light spot in a defocused state. The defocusing circuit 30 is a portion which is added to the configuration of the conventional example described above and shown in FIG. The defocus circuit 30 gives an offset to the focus control circuit 16 to bring the light spot into a defocus state when the crosstalk detection circuit 18 detects the crosstalk amplitude between the inner track and the outer track adjacent to a predetermined track.

The configuration of the defocus circuit will be described with reference to FIG. In the defocus circuit 30 surrounded by the broken line, 90
Outputs an offset voltage VOF1 by a DA converter. 9
Reference numeral 1 denotes a high-impedance resistor R10,
Is connected to the input stage of the differential amplifier 50 of the focus control circuit 16. When the offset voltage VOF1 enters the focus control system, the light spot defocuses during tilt correction. The offset voltage VOF1 is DA
The tilt correction circuit 19 connected to the converter 90 controls.

This situation will be described with reference to FIG. In FIG. 3, reference numeral 31 denotes a track, 32 denotes a pit on which a predetermined signal for detecting crosstalk is recorded, 33 denotes a normal unfocused light spot, and 34 denotes a defocused light spot. Since the defocus circuit 30 defocuses the light spot, the diameter of the light spot on the track A-1 increases, and the amplitude of the crosstalk component of the predetermined track A can be detected large.

As shown in the graph of FIG. 4, when the focus is in focus and the diameter of the light spot is small, the amplitude of the crosstalk component is about -30 dB. On the other hand, when the focus is defocused by about +1 μm, the diameter of the light spot becomes large, and the amplitude of the crosstalk component becomes approximately −2.
It is about 0 dB. This is because the signal amplitude is improved by +10 dB as compared with the case where the focus is in focus, and the tilt correction is ensured by the tilt correction circuit 19 making the inner and outer crosstalk amplitudes adjacent to the predetermined track substantially equal. . Thereby, the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam can be made almost zero, and the signal recording / reproducing characteristics can be improved.

After the reference voltage corrected by the tilt correction circuit 19 is held by the reference voltage generation circuit 12 and the tilt correction is completed, the offset voltage VO of the defocus circuit 30 is set.
F1 is not output, and the defocus of the light spot disappears. The tilt control circuit 13 suppresses the tilt to zero by tilt control for driving the tilt motor 14 with a control voltage obtained by comparing a reference voltage and a differential voltage indicating the tilt.

Next, an embodiment of the second invention will be described. According to a second aspect of the present invention, there is provided a defocus circuit for setting a light spot to a defocus state of both positive and negative polarities when crosstalk is detected to correct the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam.

The defocus circuit 30 according to the first aspect of the invention corrects the tilt by improving the crosstalk amplitude in the defocus state where only the positive polarity is +1 μm. The light spot is ideally in the positive / negative defocus state and the spot diameter is the same, and there is no difference in the crosstalk amplitude detection level. However, if there is astigmatism, the direction in which the spot diameter increases in the positive / negative defocus state is rotated by 90 degrees, so that the detection level of the crosstalk detection greatly differs.
The crosstalk detection at the time of positive and negative defocus will be described with reference to FIG. The graph of FIG. 5A shows the case where the light spot is ideal. When the light spot is defocused in the positive and negative directions, the diameter of the light spot remains a perfect circle and the diameter becomes the same and becomes larger. At this time, when ± 1 μm is defocused in the positive and negative directions,
The detected crosstalk amplitude is approximately -20 dB.
When the image is not defocused, the amplitude is −30 dB.
It is improved by dB. In this case, the inclination may be corrected by setting the defocus to only one of the positive and negative sides.

On the other hand, FIG. 5B shows a light spot having astigmatism, and the positive and negative defocusing directions are different from positive and negative directions in which the light spot does not become a perfect circle and an ellipse extends. For this reason, in the negative defocus state of -1 μm, the direction in which the diameter of the light spot increases is the track direction in which crosstalk is detected.
B is improved. However, in the positive defocus state of +1 μm, the direction in which the diameter of the light spot extends is the pit direction of the track, so that it is difficult to detect crosstalk in the adjacent track, and the amplitude decreases to −33 dB. That is, when the light spot is asymmetric to positive and negative defocus when the defocus state is set to increase the amplitude of the crosstalk detection, it is necessary to set the defocus to both positive and negative polarities.

The defocus circuit 30 according to the second aspect of the present invention adds both positive and negative offsets to the focus control circuit 16 to change the defocus state of the light spot to both positive and negative polarities. The tilt correction circuit 19 includes a crosstalk detection circuit 18.
The inclination of the recording surface of the optical disc with respect to the optical axis can be surely corrected with the defocus polarity at which the crosstalk amplitude detected by the above becomes large. After performing the inclination correction, the defocus circuit 30 stops the offset output, and the defocus state of the light spot is released.

In the second invention, if the crosstalk amplitude is at a predetermined level by giving a positive defocus first, the correction time can be shortened by directly performing the tilt correction, and the rise time of the system can be improved. Of course, if the crosstalk amplitude is low and not at a predetermined level due to positive defocus,
Improve crosstalk amplitude with negative defocus,
What is necessary is just to perform inclination correction.

Next, the third invention will be described. According to a third aspect of the present invention, there is provided an off-track circuit for setting a light spot to an off-track state of both positive and negative polarities when crosstalk is detected to correct the inclination of the recording surface of the optical disk with respect to the optical axis. FIG. 6 is a configuration diagram of the optical disc device of the third invention. The part added and changed to FIG. 10 which is the configuration diagram of the conventional example described above is an off-track circuit 40. The off-track circuit 40 gives a positive / negative offset to the tracking control circuit 17 when the crosstalk detection circuit 18 detects the crosstalk amplitude of the inner track and the outer track adjacent to the predetermined track, and sets the light spot to the off-track state. I do.

The configuration of the off-track circuit 40 will be described with reference to FIG. In the off-track circuit 40 surrounded by a broken line, reference numeral 92 denotes a DA converter which outputs an offset voltage VOF2. 93 is a high-impedance resistor R11 that connects the output VOF2 of the DA converter to the input stage of the differential amplifier 70 of the tracking control circuit 17. Offset voltage VOF
2 enters the tracking control system, so that the light spot goes off-track during tilt correction. Offset voltage VOF
2 is controlled by the tilt correction circuit 19 connected to the DA converter 92.

This situation will be described with reference to FIG. (A) of FIG.
FIG. 8B shows a normal state where the light spot is not off-track, and FIG. 8B shows a state where the light spot is positively or negatively off-tracked by the off-track circuit 40 at the tracks A + 1 and A-1. In FIG. 8A, 41 is a track, 42 is a pit on which a predetermined signal for detecting crosstalk is recorded, 43 and 44 are light spots for detecting crosstalk, and lines 11 and 12 in the middle of the track. I'm on top. Here, A-
Although light spots are shown on both track 1 and track A + 1, actually, in one light spot, A-
After reproducing one track, A + 1 track is reproduced.
Of course, in a system with multiple light spots, A
Track -1 and track A + 1 can be reproduced.

In FIG. 8B, the off-track circuit 40 works. When crosstalk is detected in the A-1 track inside the predetermined track A, the off-track circuit 40 gives a negative off-track by a negative offset. Therefore, as shown by the line 13, the light spot 43 approaches the track A, and a large amplitude of the crosstalk component of the track A can be detected. When crosstalk is detected on track A + 1 outside track A,
An off-track circuit 40 sets a positive offset of the negative polarity and the opposite polarity to give a positive off-track. Therefore, as shown by the line 14, the light spot 44 approaches the track A, and it is possible to detect a large amplitude of the crosstalk component of the track A.

As shown in the graph of FIG. 9, when the tracking is off-track 0 μm, the inclination is corrected,
The crosstalk amplitude becomes approximately −30 dB between the A-1 track and the A + 1 track. On the other hand, off-track +
In the state of 0.1 μm, the light spot on the track A + 1 is off-track toward the track A, and the crosstalk amplitude is improved to about -20 dB. Track A +
When the light spot on the track No. 1 is off-tracked by -0.1 μm, it leaves the track A, so that the crosstalk amplitude is -30d
B is lower than B.

On the contrary, the light spot on the track A-1 is-
When the track is off-tracked by 0.1 μm, it becomes closer to track A,
The crosstalk amplitude is improved to -20 dB. +0.1
When the track is off-tracked by μm, the track A is separated from the track A and the crosstalk amplitude becomes −30 dB or less. The off-track circuit 40 according to the third aspect of the invention controls the tracking control circuit 17 so that the light spots on the A-1 and A + 1 tracks adjacent to the predetermined track A become off-tracks of a polarity approaching the track A.
Is set to improve the amplitude of crosstalk detection. Thereby, the tilt correction circuit 19
Can reliably correct the inclination of the recording surface of the optical disc with respect to the optical axis at the off-track polarity at which the crosstalk amplitude detected by the crosstalk detection circuit 18 becomes large. After performing the tilt correction, the off-track circuit 40 stops outputting the offset voltage VOF2, and the off-track of the light spot is released.

In the case of the defocus circuit 30, since the polarity of positive and negative defocus is set respectively, the time for tilt correction becomes long. However, the off-track circuit 40 only needs to perform one combination of positive and negative off-tracks. In addition, the time for tilt correction can be reduced.

[0038]

As described above, the first aspect of the present invention includes the defocus circuit 30 for adding an offset to the focus control circuit 16 to make the light spot in a defocus state when detecting a crosstalk component. , The signal amplitude of the crosstalk component is greatly improved, and the tilt correction circuit 19
As a result, the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam can be reliably corrected, and the quality of the light spot on the recording surface of the optical disk and the signal quality of recording and reproduction can be improved.

In the second invention, the focus control circuit 16
A defocus circuit 3 that adds a positive and negative bipolar offset to the light spot to make the defocus state of the light spot both positive and negative.
0, the tilt correction circuit 19 can surely correct the tilt with the defocus polarity at which the crosstalk amplitude detected by the crosstalk detection circuit 18 becomes large, even when the light spot is asymmetric to positive and negative defocus. it can.

In the third invention, the tracking control circuit 1
7 is provided with an off-track circuit 40 for adding a positive / negative offset of a polarity in which the light spot is closer to the predetermined track inside and outside the predetermined track, and the tilt correction circuit 19 is provided with a crosstalk amplitude detected by the crosstalk detection circuit 18. The inclination can be reliably corrected at the off-track polarity where increases. In addition, in the case of the defocus circuit 30, since the polarity of the positive and negative defocus is set respectively, the time of the inclination correction becomes long. However, the off-track circuit 40 only needs to perform one combination of the positive and negative off-tracks, Time can be shortened.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical disk device according to an embodiment of the first invention.

FIG. 2 is a configuration diagram of a defocus circuit of the optical disc device in the embodiment of the first invention.

FIG. 3 is a diagram for explaining a defocused light spot;

FIG. 4 is a diagram illustrating a relationship between defocus and crosstalk amplitude.

5A is a diagram illustrating a relationship between a light spot symmetric to positive and negative defocus and a crosstalk amplitude. FIG. 5B is a diagram illustrating a relationship between a light spot asymmetric to positive and negative defocus and a crosstalk amplitude.

FIG. 6 is a configuration diagram of an optical disk device according to an embodiment of the third invention.

FIG. 7 is a configuration diagram of an off-track circuit of an optical disc device according to an embodiment of the third invention.

FIG. 8 is a diagram for explaining an off-track light spot.

FIG. 9 is a diagram showing a relationship between off-track and crosstalk amplitude.

FIG. 10 is a configuration diagram of a conventional optical disk device.

FIG. 11 is a configuration diagram of a focus control circuit of a conventional optical disc device.

FIG. 12 is a configuration diagram of a tracking control circuit of a conventional optical disk device.

FIG. 13 is a diagram for explaining tracks, pits, and light spots.

FIG. 14 is a diagram showing a relationship between tilt and crosstalk balance;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical disk 2 Disk motor 3 Optical head 4 Objective lens 5 Actuator 6 Light beam 7 Receiver 8 Divided light 9 Divided light receiver 10 Differential amplifier 11 Comparator 12 Reference voltage generation circuit 13 Tilt control circuit 16 Focus control circuit 17 Tracking control circuit 18 Crosstalk detection circuit 19 Tilt correction circuit 30 Defocus circuit 40 Off-track circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B ^7/ 09-7/22

Claims (4)

(57) [Claims] 1. An optical head for recording and reproducing a signal by irradiating a light spot with a light beam focused on an optical disk, a focus control unit for controlling a focal position of the light spot on an optical disk surface, and a light source for positioning the light spot on a track. Tracking control means for controlling position; crosstalk detecting means for reproducing an inner or outer track adjacent to a predetermined track on which a predetermined signal is recorded, detecting the amplitude of a crosstalk component of the predetermined signal, and outputting the crosstalk; The optical disk is irradiated with light for detecting the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam, and the inclination of the recording surface of the optical disk is obtained from the differential output of the two-segment photodetector that receives the light reflected by the optical disk. A comparator for generating a control voltage by comparing a differential output of the two-divided photodetector with a reference voltage, Tilt control means for tilting the optical head by the control voltage to make the inclination of the recording surface of the optical disc with respect to the optical axis of the light beam substantially zero; and inside and outside of the predetermined track detected by the crosstalk detection means Tilt correction means for adjusting the reference voltage of the tilt control means so as to make the amplitude of the crosstalk components substantially equal to each other to correct the inclination; reference voltage output means for holding and outputting the adjusted reference voltage; An optical disc apparatus comprising: a defocus unit that adds an offset to the focus control unit to set a light spot in a defocus state when a signal amplitude of a crosstalk component is detected by a talk detection unit. 2. The optical disc device according to claim 1, wherein the defocusing means sets the offset to be added to the focus control means to both positive and negative polarities so as to generate bipolar defocusing. apparatus. 3. An off-track light spot is added to the tracking control means when the signal amplitude of the crosstalk component is detected by the crosstalk detection means in place of the defocus means of the optical disk device according to claim 1. An optical disk device including an off-track means for setting a state. 4. The off-track means according to claim 3, wherein the offset to be added to the tracking control means is set to both positive and negative polarities to generate bipolar off-track, and a light spot is detected when crosstalk is detected. An optical disc apparatus characterized in that the polarity of an offset is switched between inner and outer tracks to a polarity closer to a predetermined track.