JP2001006190A - Optical disk drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce circuit elements and improve a stability by adjusting a gain of a variable amplification circuit to make a signal amplitude of reproduction signals of first and second pit arrays integrated by a low pass filter a specific value, and detecting a displacement of light beams and tracks from the reproduction signals of the integrated first and second pit arrays. SOLUTION: A first signal is sent via an LPF 146, a D/A converter 147 and an adder 148 to a power amplifier 129, whereby a transfer motor 114 is controlled in accordance with a low frequency component of a first TE signal. An output of an adder 130 becomes a total quantity of light received by a photodetector 113 and is sent to an address reproduction circuit 131. The address reproduction circuit 131 reproduces a sector address, sends to a DSP 140, sends a signal synchronous with the address to a gate generation circuit 132. A VFO1 signal and a VFO2 signal are delayed by a delay circuit by a predetermined time, logically synthesized to be a sampling signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tracking control of an optical disk device for recording information on a disk on which tracks are formed or reproducing information from the disk.

[0002]

2. Description of the Related Art As a conventional optical disk device, a light beam generated from a light source such as a semiconductor laser is focused and irradiated on an optical disk rotating at a predetermined number of revolutions to reproduce a signal recorded on the optical disk. There is an optical disk device that performs. An example of the optical disk will be described with reference to FIG. The disk has a plurality of tracks formed in a spiral shape. FIG. 13 is a schematic diagram showing a cross section of the disk.
The track is formed by the groove formed by the unevenness. The concave and convex portions are tracks. The track pitch is 0.74 micrometers (hereinafter referred to as um). A recording film made of a phase change material or the like is provided on the information surface. When information is recorded on a disk, the reflectivity of the recording film is changed by changing the intensity of the light beam according to the information while performing tracking control so that the light beam is always positioned on the track. When reproducing the information on the disk, the light detector receives the reflected light from the optical disk while performing tracking control so that the light beam is always positioned on the track. The information is reproduced by processing the output of the photodetector.

The address will be described with reference to FIG.

[0004] Black portions are convex portions. The portion indicated by the pit string is a sector identifier (hereinafter, referred to as a header field). The pit has a convex shape.

[0005] The header field is located at the head of each sector. The pit row is arranged at an intermediate position between the convex track and the concave track. The structure of this header field is generally a CAPA (Compleme).
nary Allocated Pit Addre
ss). The header field is Varia
ble Frequency Oscillator (hereinafter, referred to as VFO) and a sector address. The VFOs 1 and 2 are recorded at a single frequency, and are recorded in a Phase Locked Loop (hereinafter, PL).
Indicated as L. Used to pull in). Sector address 1 indicates the address of the concave sector, and sector address 2 indicates the address of the convex sector.

[0006] The disk is divided into several zones in the radial direction, and the number of sectors per track in each zone is as follows.
It is constant. The number of sectors per track increases from the inner zone to the outer zone.

When recording and reproducing information, the recording and reproduction are performed after controlling the number of rotations of the disk so that the number of rotations corresponds to each zone. Therefore, the linear velocity in each zone becomes substantially constant. The area other than the header field is a recording area where information can be rewritten (hereinafter, referred to as a rewritable area).

[0008] Similarly, the detection of the track deviation amount for tracking control is obtained from the reflected light from the disk. A tracking error detection method called a general push-pull method will be described. Hereinafter, the tracking error is described as TE. The push-pull method is a method called a far-field method. The TE signal is detected by extracting the light reflected and diffracted by the guide groove on the disk as an output difference at a light receiving section of a two-divided photodetector arranged symmetrically with respect to the track center. As shown in FIG. 11, when the spot of the light beam and the center of the convex portion and the concave portion of the groove coincide with each other, a symmetrical reflection diffraction distribution is obtained. FIG. 12 shows the output difference of the two-segment photodetector when the spot crosses the track. The TE signal becomes zero at the center of the concave portion and the convex portion. In the tracking control, a tracking actuator is driven via a phase compensation circuit and a driving circuit in accordance with the TE signal, and a target track is followed by moving a spot on a disk in a direction perpendicular to the track.

The characteristic of the TE signal shown by a solid line in FIG. 12 is represented by a dotted line when the optical axis of the light beam is perpendicular to the information surface of the disk and when the optical axis of the light beam is inclined in the radial direction of the disk. Show. Hereinafter, the radial tilt of the optical axis of the light beam from a plane perpendicular to the information surface of the disk is referred to as radial tilt.

The phase of the TE signal is shifted due to the radial tilt. That is, even if tracking control is performed so that the TE signal becomes zero, the spot is shifted from the center of the track. In the case of NA = 0.6, wavelength 650 nm, track pitch 0.74 um, groove depth wavelength / 6, and duty of the convex part and the concave part of 50%, a track deviation of about 0.13 um occurs at one degree of inclination. A slight difference occurs depending on the difference in the Gaussian light intensity distribution of the light beam. In the optical disk device, there is a possibility that a radial tilt occurs about once due to the tilt of the disk such as the assembly accuracy or the tilt of the turntable of the disk motor.

When the track shift of about 0.13 μm occurs as described above in the tracking control by the push-pull method, the recording / reproducing characteristics at a narrow track pitch are extremely deteriorated, and in the worst case, the recording information of the adjacent track is erased. It is possible.

Therefore, even if a radial tilt occurs, it is necessary to detect and correct the absolute track center position.

[0013]

As described above, when the radial tilt occurs about once due to the tilt of the disk or the tilt of the turntable of the disk motor,
Since a track shift of 0.13 μm occurs, the reproduction of information becomes unstable, or the information on an adjacent track is erased during recording.

An object of the present invention is to solve the above-mentioned problems by accurately detecting an absolute track center position even when a radial tilt occurs, and mounting an optical disk having a stable track center detecting circuit with a small number of circuit elements. It is to provide a device.

[0015]

In order to achieve the above object, the present invention provides a reproducing signal detecting means for detecting the information recorded on a disk by converging and irradiating a light beam to the disk, a track and an optical signal. First tracking error detecting means for detecting a displacement of a beam by a push-pull method;
And a second tracking error detecting means for detecting a positional deviation between the light beam and the track from the reproduced signals of the first pit train and the second pit train outputted by the reproduced signal detecting means. The detecting means includes a variable amplifier circuit for variably amplifying the output of the reproduced signal detecting means, a gate circuit for extracting the variably amplified reproduction signals of the first pit row and the second pit row, and HP for making each pit row signal AC centered
F, a full-wave rectifier circuit for performing full-wave rectification on the reproduced signals of the first and second pit rows, which are AC-centered, and the first and second full-wave rectified pit rows and the second pit row. LPF for integrating the reproduced signal of the pit train of the first and second pit trains, and a sample and hold circuit for sampling and holding the reproduced signals of the first pit train and the second pit train integrated by the LPF at the time of each pit train. And a differential circuit for obtaining a difference signal between the sampled and held first pit train and the second pit train. The first pit train or the second pit train output from the sample and hold circuit is provided. The gain of the variable amplification amplifier circuit is adjusted so that the signal amplitude of at least one of the signals of the pit train becomes a specified value.

The second tracking error detecting means for detecting the displacement between the light beam and the track includes a variable amplifier circuit for variably amplifying the output of the reproduction signal detecting means, and a variably amplified first pit train. A gate circuit for extracting a reproduced signal of the second pit row, an HPF for centering the extracted signal of each pit row on the AC center,
A full-wave rectifier circuit for performing full-wave rectification on the reproduced signals of the first and second pit rows having an AC center; and the first and second pit rows having been subjected to full-wave rectification. LPF for integrating the reproduction signal of the first pit sequence, a switch for switching the reproduction signal of the first pit train and the second pit train integrated by the LPF, and a reference voltage, and the first pit switched by the switch A pair of sample-and-hold circuits for sampling and holding the reproduction signal and the reference voltage of the row and the second pit row, and obtaining a difference signal between the sample-and-hold signals of the first pit row and the second pit row. And a switching circuit for switching the reproduction signals of the first pit train and the second pit train and the reference voltage at an initial time or at predetermined intervals.

[0017]

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

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to the block diagram of FIG.

The disk 100 is a rotating shaft 1 of a motor 101.
02, and rotates at a predetermined rotation speed.

The disk 100 has tracks formed in a spiral shape with irregularities. The projections and the depressions are both tracks, on which information is recorded. The track pitch is 0.74 um. In addition, the width of the projections and the depressions is about 0.5.
6 um.

The transfer table 115 has a laser 109, a coupling lens 108, a polarizing beam splitter 110,
/ 4 wavelength plate 107, total reflection mirror 105, photodetector 11
3. The actuator 104 is attached, and the transfer table 115 is moved by the transfer motor 114 to the disk 100.
Are configured to move in the radial direction.

The laser 10 mounted on the transfer table 115
9 is converted into parallel light by the coupling lens 108,
10, a 1/4 wavelength plate 107 and a total reflection mirror 10
5 is reflected by the focusing lens 103 and the disc 100
Is focused and illuminated on the information surface of the laser beam.

The light reflected by the information surface of the disk 100 passes through a converging lens 103 and passes through a total reflection mirror 1
The light is reflected at 05, passes through a quarter-wave plate 107, a polarization beam splitter 110, a detection lens 111, and a cylindrical lens 112, and is incident on a photodetector 113 composed of four light receiving units. The focusing lens 103 is attached to a movable part of the actuator 104. Since the focus control is not directly related to the present invention, the description is partially omitted. The actuator 104 includes a focusing coil, a tracking coil, a focusing permanent magnet, and a tracking permanent magnet. Therefore, when a voltage is applied to the focusing coil (not shown) of the actuator 104 using the power amplifier 152, a current flows through the coil, and the coil receives a magnetic force from a focusing permanent magnet (not shown). Therefore, the focusing lens 103 is
Move in the direction perpendicular to the surface (up and down in the figure). The focusing lens 103 is controlled based on a focus error signal indicating a deviation between the focus of the light beam and the information surface of the disk so that the focus of the light beam 106 is always located on the information surface of the disk 100.

A tracking coil (not shown)
When a voltage is applied using a power amplifier 145 to the coil, a current flows through the coil and receives a magnetic force from a permanent magnet (not shown) for tracking, so that the focusing lens 103 moves in the radial direction of the disk 100, that is, on the disk 100. Move across the track (left and right in the figure).

The photodetector 113 is formed by four light receiving sections. The reflected light from the disk incident on the photodetector 113 is converted into a current, respectively, and the I / V converter 1
16, 117, 118 and 119. The I / V converters 116, 117, 118, and 119 convert the input current into a voltage according to the current level.

Adders 120, 121, 123, 124,
130 adds and outputs the input signals. Subtractor 12
2, 125 subtracts an input signal (also referred to as a differential circuit)
And output.

The output of the subtractor 122 is a focus error signal indicating a deviation between the focal point of the light beam applied to the disk and the information surface of the disk 100. The focus error signal is sent to the analog / digital converter 149, the phase compensation circuit 150, the digital / analog converter 151, and the power amplifier 152. A current flows through the focusing coil of the actuator 104 by the power amplifier 152.

An analog / digital converter 149 (hereinafter, referred to as an A / D converter) converts an analog signal into a digital signal. The digital / analog converter 151 (hereinafter, referred to as a D / A converter) converts a digital signal into an analog signal.

The phase compensation circuit 150 is a digital filter, and performs phase compensation of the focus control system to stabilize the control system. In this way, the focusing lens 103 is driven according to the focus error signal, and the focal point of the light beam is always located on the information surface.

The optical system shown in FIG. 1 constitutes a TE signal detection system generally called a push-pull method. Accordingly, the output of the subtractor 125 becomes a TE signal indicating the deviation between the spot of the light beam irradiated on the disk and the track of the disk 100. Hereinafter, the output of the subtractor 125 is referred to as a first TE signal. The first TE signal is applied to switch 15
5, sent to the A / D converter 143, the adder 142, the phase compensation circuit 144, the D / A converter 170, and the power amplifier 145. A current flows through the tracking coil of the actuator 104 by the power amplifier 145.

The phase compensation circuit 144 is a digital filter, and performs phase compensation of the tracking control system to stabilize the control system. Accordingly, the focusing lens 103 is driven according to the first TE signal, so that the light beam spot always follows the track.

The first TE signal is sent to the power amplifier 129 via the low-pass filter 146, the D / A converter 147, and the adder 148, so that the transfer motor 1
14 is controlled according to the low frequency component of the first TE signal. That is, in the tracking control system, the actuator 104 follows the response of the high frequency, and the transport motor 114 follows the response of the low frequency component.

Next, the adder 130 adds the outputs of the adders 123 and 124. That is, the output of the adder 130 is the total amount of light received by the photodetector 113. Hereinafter, the output signal of the adder 130 is referred to as a total reflection light amount signal. The output of the adder 130 is sent to the address reproducing circuit 131.
The address reproducing circuit 131 reproduces a sector address and outputs the digital signal to the digital signal processor 140 (hereinafter referred to as D).
SP). Further, a signal synchronized with the address is sent to the gate generation circuit 132.

The gate generation circuit 132 has the V
A gate signal which becomes a high level in the FO1 and VFO2 regions is output to the switch 133. Below is VFO
The signals in the 1 area and the VFO2 area are referred to as a VFO1 signal and a VFO2 signal, respectively. Further, the gate generation circuit 132
In this example, the VFO1 signal and the VFO2 signal are delayed by a predetermined time by a delay circuit, and a signal before and after the delay is logically synthesized, and a sampling signal is sampled and held in order to sample the VFO1 signal in the address section. Circuit 136 (hereinafter referred to as S / H circuit)
And outputs a sampling signal to the S / H circuit 137 in order to sample the VFO2 signal in the address section.

Switch 133, HPF 172, full-wave rectifier circuit 134, LPF 135, S / H circuits 136, 137
And the subtractor 138 constitute a circuit for detecting the second TE signal. The output of the subtractor 138 becomes the second TE signal.

The second TE signal is converted to a digital signal by the power amplifier 152 via the switch 153 and sent to the adder 142.

DSP for operating tracking control
The operation of 140 will be described.

In the initial state, the DSP 140 operates with the switch 15
With the switch 3 open, the switch 155 is closed to operate the tracking control. The focusing lens 103 is driven based on the first TE signal.

The address reproducing circuit 131 reads an address and sends an address signal to the DSP 140. DSP1
40 identifies the zone based on the address. Then, a command is sent to the motor control circuit 171 so that the rotation speed of the disk 100 becomes a rotation speed corresponding to the zone. When the rotation speed of the disk 100 reaches a predetermined rotation speed, the address reproduction circuit 131 sends a signal synchronized with the address to the gate generation circuit 132.

The gate generation circuit 132 has an address signal,
By outputting the VFO1 signal and the VFO2 signal, the second TE signal is output from the output of the subtractor 138.

The DSP 140 closes the switch 153 and corrects the target position of the tracking control system operating based on the first TE signal according to the second TE signal. That is, the adder 142 adds the second TE signal to the tracking control system based on the first TE signal to add an offset and perform correction.

Hereinafter, each block will be described in detail.

First, a second TE signal detection method (hereinafter, referred to as track center detection) will be described with reference to FIG.

The case where the spot moves on the center of the convex track (the portion painted black) is shown.

The amount of light reflected from the disk is modulated by pits. The output of the adder 130 is shown in the waveform (b). Since the distance between the pit row of VFO1 and the spot is equal to the distance between the pit row of VFO2 and the spot, the amplitude m1 in VFO1 and the amplitude n1 in VFO2 are equal.

FIG. 3 shows a case where the spot moves between tracks between tracks. Adder 1 to waveform (b)
30 shows the output. Since the distance between the pit row of VFO1 and the spot is shorter than the distance between the pit row of VFO2 and the spot, the amplitude m2 is larger than the amplitude n2 of VFO2.

FIG. 4 shows a case where the spot is located at an intermediate position between tracks. The output of the adder 130 is shown in the waveform (b). Since the distance between the pit row of VFO1 and the spot is longer than the distance between the pit row of VFO2 and the spot, the amplitude m3 is smaller than the amplitude n3 of VFO2.

As shown in FIGS. 2, 3, and 4, the deviation between the spot and the track can be detected by detecting the amplitude difference between the VFO1 signal amplitude and the VFO2 signal amplitude of the total reflection light amount signal.

FIG. 5 shows the relationship between the track deviation and the second TE signal. The horizontal axis indicates the amount of deviation from the track center and the vertical axis indicates the voltage value of the second TE signal, and a substantially linear characteristic is obtained with respect to the center of the track. Note that, in the track of the convex portion and the track of the concave portion, the amount of deviation of the VFO1 and VFO2 from the track center is reversed, so that the inclination of the second TE signal with respect to the track deviation is reversed.

Next, the relationship between the signal output from the gate generation circuit 132 and the output waveform of the adder 130 will be described with reference to FIG.

FIG. 6A shows the relationship between a spot and a header field. The waveform (b) is the adder 13
0, the waveform (c) is the timing signal of the VFO1 and VFO2 signals, and the waveform (d) is the VFO1 and VFO obtained by delaying the timing signals of the VFO1 and VFO2 signals by a predetermined time.
The gate signal of the FO2 signal, the waveform (e) is VFO1 and VFO.
The timing signal of the FO2 signal, VFO1 and VFO2
Sampling signals of the VFO1 and VFO2 signals created from the gate signals of the VFO1 and VFO2 signals obtained by delaying the signals by a predetermined time, and a waveform (f) indicates an ID signal or a data acquisition timing signal which becomes a high level in a section including the header field, respectively. .

The gate generation circuit 132 outputs VFO1 and VFO2 in the next sector based on the address synchronization signal output by the address reproduction circuit 131 in the previous sector.
A signal timing signal, an ID signal, or a data acquisition timing signal is generated. It has an oscillator and a counter for counting the output of the oscillator. The counter is cleared according to the address synchronization signal, and a timing signal is generated based on the counter value.

The sampling signals of VFO1 and VFO2 are obtained by taking the logical product of the timing signals of the VFO1 and VFO2 signals inverted in polarity and the timing signals of the VFO1 and VFO2 signals delayed by t10 by mono-multi or the like. Created by

Next, the track center detecting circuit will be described.

First, the total reflection light amount signal output from the adder 130 is input to the variable amplification amplifier circuit 154, variably amplified by the control signal H, and then enters the switch 133. In the switch 133, the above-mentioned VFO1 and VFO
VFO1 and VFO2 are respectively gated by two gate signals. V gated by switch 133
The low frequency components of the FO1 and VFO2 are attenuated by the HPF 172 and enter the full-wave rectifier circuit 134 as the center of amplitude. Here, as shown in FIG. 7, the VFO1 and VFO2 input to the HPF 172 are gated and thus arrive in a stepwise manner, have a differential characteristic at the time of rising of the VFO1 and VFO2, and within the gate time depending on the cutoff frequency of the HPF. There are cases where it is not established. Therefore, it is necessary to set an optimal cutoff frequency in consideration of the gate time and the establishment time. In the present invention, the cutoff frequency is 1 MH
z. Then, VFO1 and VFO2 having the amplitude center in the full-wave rectifier circuit 134 are rectified from the center value of the amplitude and enter the LPF 135. Like the HPF, the LPF 135 needs to consider the gate time and the settling time, and reduce the ripple voltage as much as possible. This is because the sample-and-hold circuit in the next stage is sampled in a short time, so that if the ripple voltage is high, an error is generated only by the ripple voltage, and the accuracy is deteriorated. In the present invention, L
By setting the PF to a cutoff frequency of 1 MHz, which is almost the same as the cutoff frequency of the HPF, in the tertiary LPF, good characteristics were obtained with respect to the setting time and accuracy. In addition, the gate generation circuit 132 makes the delay time for generating the sampling signals of VFO1 and VFO2 substantially the same as the propagation delay time before being sampled by the S / H circuit, thereby reliably sampling the signal amplitude that has been established. Became possible. The VFO1 and VFO2 sufficiently integrated by the LPF 135 are combined with the sample hold circuits 136 and 137.
To sample VFO1 and VFO2 with the sampling signals of VFO1 and VFO2, respectively. Next, the VFO1 and VFO2 sampled and held by the sample and hold circuits 136 and 137 output a difference signal between the amplitudes of VFO1 and VFO2 by a subtractor 138. In the track center control, this VFO1 amplitude and V
Control is performed so that the difference signal of the FO2 amplitude becomes zero.

The VFO1 amplitude and the VFO2 amplitude under the tracking control based on the first TE signal are originally close to each other as the amplitude difference. Therefore, in the detection of the amplitude difference, the input / output characteristics of the circuit, that is, the linearity of the output amplitude with respect to the input amplitude level and the variation in the circuit greatly affect the detection accuracy. Therefore, the switch 133, the HPF 172 and the LPF 1
By amplifying the gain for obtaining the required detection sensitivity in each of the circuits 35, the linearity of the input / output characteristics can be kept within a range with a good linearity even in a narrow state.
It is necessary to transmit VFO1 and VFO2 signals.

The sample-and-hold circuit performs current amplification to charge the capacitor for charging and holding at a high speed with a voltage value input during the high level period of the sampling signal, and charges the capacitor. The current amplification is cut off at the time when the low level period is reached from the period, and the state is set to the hold state. Further, in order to keep the hold state for a long time, a buffer circuit is connected to the charge and hold capacity to minimize the leakage current. As the circuit, a bias current compensating circuit for compensating the input bias current of the buffer circuit is inserted as shown in FIG. However, since the bias current cannot be completely reduced to zero even by the bias compensation circuit, the hold time is affected to some extent. In addition, the bias current compensation also changes according to the input voltage, and an error occurs in the hold characteristics at the voltage to be held. Therefore, a slight error occurs in the charging characteristics depending on the charged voltage, and an error also occurs in the hold characteristics depending on the charged voltage, that is, the held voltage. Even if this error occurs, for example, 5 mv, it may be 0.
There is a position error of 005um.

In order to minimize the detection error, it is necessary to transmit the VFO1 and VFO2 signals within a good linearity range of the switch 133, the HPF 172 and the LPF 135, and the sample and hold circuits 136 and 137
The amplitude values of VFO1 and VFO2 input to the controller are changed to substantially the same level even if the signal amplitude of the total reflection light signal increases or decreases due to variations in the reflectivity of the disk, etc. Should be. For this purpose, the amplitude of one of the VFO1 and VFO2 signals is detected. Detection is performed by the sample and hold circuits 136 and 13
7 is detected. The switch 156 is closed, the output of the sample and hold circuit 137 is converted to digital data by the A / D converter 157,
The amplitude is determined by 140, and the variable amplifier circuit 154 is controlled by the control signal H so that the output of the sample hold circuit 137 becomes a predetermined value. The variable amplification amplifier circuit 154 has no problem as long as the amplification factor changes with an analog voltage, or a circuit whose amplification factor can be changed, such as a circuit whose amplification factor changes stepwise.

As described above, the amplitude of one of the VFO1 and VFO2 signals is detected, and even if the signal amplitude of the total reflection light amount signal changes, the amplitude of one of the VFO1 and VFO2 signals is set to a desired amplitude. Switch 133, HPF by changing the gain of the variable amplification amplifier circuit.
VF within the good linearity range of 172 and LPF135
By transmitting the O1 and VFO2 signals and sampling and holding the sample and hold circuit at a substantially constant voltage, it is possible to provide an optical disc apparatus having a track center detection circuit with high detection accuracy.

(Embodiment 2) Hereinafter, Embodiment 2 of the present invention will be described with reference to the block diagram of FIG. The same blocks as in the above-described first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The difference from the first embodiment is that the switch 158
, 160, reference voltage generation circuit 159, A / D converter 1
61, a D / A converter 162, a subtractor 163, a temperature sensor 165, a reset signal I, a switching signal J, and a switching signal K are added.

In the second embodiment, a configuration for further reducing the detection error is provided. The configuration will be described with reference to FIG.

The part where a detection error easily occurs in the track center detection of the present invention is the S / H circuit. In order to reduce the detection error of the S / H circuit, the S / H circuits 136 and 1
A switch 158 is provided at the input of 37 to switch between the reference voltage generation circuit 159 and the LPF 135.

First, the total reflection light quantity signal is input to the variable amplification amplifier circuit 154, variably amplified by the control signal H, and then enters the switch 133. The switch 133 gates VFO1 and VFO2 with the gate signals of the VFO1 and VFO2 signals, respectively. Switch 133
VFO1 and VFO2 gated by HPF
The low frequency component is attenuated by 172 and enters the full-wave rectifier circuit 134 as the center of amplitude. The amplitude signals of VFO1 and VFO2 rectified by the full-wave rectifier circuit 134 enter the tertiary LPF 135, and VFO1 and VF are subjected to full-wave rectification.
The O2 amplitude signal is sufficiently integrated and output.

Next, VFO1 and VFO from the LPF 135 are
Before sampling and holding the signal of the FO2 amplitude, the switch 158 switches between the output of the LPF 135 and the reference voltage generating circuit 159, and when the track center is detected, the switch 158 is set to the LPF 135 side.
When performing offset learning, the switch 158 is switched to the reference voltage generating circuit 159 by the switching signal K. Therefore, the S / H circuits 136 and 137
There are both cases where the integrated amplitude signals of VFO1 and VFO2 from F135 are sampled, respectively, and where the reference voltage from reference voltage generation circuit 159 is sampled. Since the amplitude signals of VFO1 and VFO2 must be updated without error for each sector,
Before sampling VFO1 and VFO2, the reset signal I initializes the held voltages of the S / H circuits 136 and 137 to a voltage lower than the sampled voltage and to a constant voltage. The reset signal I is basically output after the DSP 140 acquires the information of the amplitude signals of VFO1 and VFO2 sampled and held by the S / H circuits 136 and 137. Immediately before sampling VFO1, there is a method of generating and resetting a reset signal I using the VFO1 signal and a signal obtained by delaying the VFO1 signal. Further, for example, the rising timing of the ID signal is detected using the ID signal or the data acquisition timing signal which becomes the high level in the section including the header field, and a reset signal is generated from the ID signal before VFO1 and VFO2 arrive. Various configurations such as a reset method and the like can be considered.

Next, the offset learning will be described.
As described above, a circuit in which an error easily occurs in the track center detection is the S / H circuit. Although it is natural to reduce this error in terms of a circuit, the circuit scale and the number of elements are not infinite, and ultimately pose a problem in terms of cost. Therefore, it is conceivable that the fixed error of the circuit is operated based on the fixed error, and the error of the circuit is simplified as the error without complicating the circuit configuration.

First, in FIG. 9, the switch 158 switches the reference voltage generation circuit 159 to a reference voltage value S.
/ H circuits 136 and 137 sample and hold.
It is preferable that the voltage value of the reference voltage be closer to the voltage sampled by the S / H circuit. The sampled and held reference voltage is output including an error in the S / H circuits 136 and 137, is subtracted by the subtractor 138, and is then switched by the switch 160 via the A / D converter 161 to the DSP 14.
Input to 0. The switch 160 is switched by the switching signal J. The DSP 140 outputs the switching signal K to switch to the reference voltage generation circuit 159, and then outputs the switching signal J. The output of the subtractor 138 that samples and holds the reference voltage switched by the switch 160 is processed by the DSP 140 as a reference value for a control operation or an S / H circuit 13 from the control reference value to obtain a target value.
6, 137 and the offset value generated by the subtractor 138 are measured and held. The offset value held by the DSP 140 is converted into an analog voltage by the D / A converter 162 and output to the subtractor 163. The subtractor 163 is
Switches 158 and 160 are respectively switched, and VF
The amplitude signals of O1 and VFO2 are subtracted from the offset voltage held by the DSP 140 and output. Thus S /
The offset voltages of the H circuits 136 and 137 and the subtractor 138 are once captured and held, and the actual VFO1 and V
By subtracting the offset voltage of the S / H circuit and the subtractor included when sampling and holding the FO2 amplitude signal and outputting the same, the offset voltage which is an error generated in the S / H circuit and the subtractor can be compensated. It becomes possible.

A series of operations for holding the errors of the S / H circuit and the subtractor by switching the switches 158 and 160 are performed by the track center signals VFO1 and VFO2.
Before taking in the amplitude signal of For example, fortunately, VFO1 and VFO2 arrive at a sector cycle, and thus the VFO of the next sector after VFO1 and VFO2.
This offset learning can be performed using the time until 1 and VFO2 arrive. In addition, if it is not possible for each sector, offset learning can be performed at an early stage before extracting the amplitude signals of VFO1 and VFO2.
When control is actually performed by a DSP or the like, offset learning for each sector may be difficult due to the processing time.
What is problematic when the offset learning is performed at the beginning is the temperature characteristic. It goes without saying that the S / H circuit and the subtractor also change with temperature. Therefore, the temperature at the time when the offset learning is initially performed is stored by the temperature sensor 165, and the offset learning is performed again when a predetermined temperature difference occurs, thereby compensating the temperature characteristics. Further, the offset learning can be performed not only by the relative temperature but also by the absolute temperature. Simply say 0 degrees, 2
It is also possible to perform offset learning at every 20 degrees of 0, 40, and 60 degrees.

[0069]

As is apparent from the above description,
According to the present invention, a first pit row formed at a position shifted in one direction perpendicular to the track and a second pit row formed at a position shifted in the other direction perpendicular to the track are provided. The track center detection circuit detects the positional deviation between the light beam and the track based on the reflected light from the disk when the light beam passes, and the variable amplification amplifier circuit variably amplifies the reproduction signal from the disk. A gate circuit for extracting reproduced signals of the first and second pit rows, an HPF for centering the extracted signals of each pit row on the AC center, and the first circuit on the AC center. A full-wave rectifier circuit for full-wave rectification of the reproduction signals of the pit train and the second pit train, and an LPF for integrating the full-wave rectified reproduction signals of the first pit train and the second pit train When It said integrated by LPF first
A pair of sample-and-hold circuits for respectively sample-holding the reproduced signals of the pit train and the second pit train,
It is possible to provide a circuit having high detection accuracy and excellent stability with a simple configuration such as a differential circuit for obtaining a difference signal between both signals of the first pit row and the second pit row sampled and held. .

Further, the offset voltage, which is an error of the S / H circuit, is detected by switching to a reference voltage at the input of the S / H circuit and sampled and held, and the error is further detected by compensating for the error of the S / H circuit. It is possible to provide an optical disk device having a track center detection circuit with high accuracy and excellent temperature characteristics.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical disc device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a header field and a total reflection light amount according to the first embodiment.

FIG. 3 is a diagram showing a configuration of a header field and a total reflection light amount according to the first embodiment.

FIG. 4 is a diagram showing a configuration of a header field and a total reflection light amount in the first embodiment.

FIG. 5 is a diagram for explaining a track center detection signal according to the first embodiment.

FIG. 6 is a diagram for explaining a gate signal of the gate signal generation circuit according to the first embodiment.

FIG. 7 is a waveform chart for explaining the detection circuit according to the first embodiment.

FIG. 8 is a block diagram illustrating an S / H circuit according to the first embodiment.

FIG. 9 is a block diagram of an optical disk device according to the second embodiment.

FIG. 10 is a block diagram illustrating a detection circuit according to the second embodiment.

FIG. 11 is a schematic diagram of a disk when describing the above-described conventional optical disk device.

FIG. 12 is a schematic diagram of a header field for explaining the above-described conventional optical disk device.

FIG. 13 is a schematic diagram for explaining a TE signal detection method by a push-pull method when describing the above-described conventional optical disk device.

FIG. 14 is a schematic diagram for explaining a relationship between a TE signal and a radial tilt by a push-pull method when describing the above-described conventional optical disk device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 disc 101 motor 103 focusing lens 104 actuator 105 total reflection mirror 106 light beam 107 quarter-wave plate 108 coupling lens 109 laser 110 deflection beam splitter 111 detection lens 112 cylindrical lens 113 photodetector 114 transfer motor 115 transfer table 116, 117, 118, 119 I / V converter 120, 121 Adder 122 Subtractor 123, 124 Adder 125 Subtractor 131 Address regeneration circuit 132 Gate generation circuit 133 Switch 134 Full-wave rectification circuit 135 LPF 136, 137 S / H circuit 138 Subtractor (differential circuit) 140 DSP 142 Adder 143 A / D converter 144 Phase compensation circuit 145 Power amplifier 146 LPF 147 D / A converter 149 A / D converter 150 Phase compensation filter 151 D / A converter 152 power amplifier 154 variable amplifier circuit 156 switches 157 A / D converter 165 a temperature sensor 171 the motor control circuit 172 HPF 175 laser drive circuit

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kotoshi Konno 1006 Kazuma Kadoma, Osaka Pref.Matsushita Electric Industrial Co., Ltd. F term (reference) 5D118 AA13 BA01 CA13 CA26 CD03

Claims (9)

[Claims] 1. A first pit row formed at a position shifted in one direction of a direction perpendicular to a track and a second pit row formed at a position shifted in the other direction are arranged. Reproduction signal detection means for converging and irradiating a light beam on the disk to detect information recorded on the disk; a variable amplification amplifier circuit for variably amplifying an output of the reproduction signal detection means; A gate circuit for extracting a portion corresponding to the pit row and the second pit row, an HPF for centering the extracted signal of each pit row on the AC center, and a first pit row and the AC center. A full-wave rectifier circuit for full-wave rectification of the reproduction signal of the second pit row; and an LPF for integrating the reproduction signals of the first and second pit rows subjected to full-wave rectification. ,
A first pit train integrated by the LPF and a second pit train;
The first and second pit trains integrated by the LPF are adjusted by adjusting the gain of the variable amplification amplifier circuit so that the signal amplitude of at least one of the reproduced signals of the pit train has a prescribed value. An optical disc device for detecting a displacement between a light beam and a track from a reproduced signal of the optical disc. 2. A pair of sample-and-hold circuits for respectively sample-holding reproduction signals of a first pit row and a second pit row integrated by an LPF, and a first pit row and a second pit sampled and held. And a differential circuit for obtaining a difference signal between the two signals in the row. The LPF is provided by a sampling signal generated from the reproduced signals of the first pit row and the second pit row output from the reproduced signal detecting means. 2. The optical disc apparatus according to claim 1, wherein a position shift between the light beam and the track is detected based on a result obtained by sampling and holding the reproduced signals of the first pit train and the second pit train outputted from the optical disc. 3. A first pit row formed at a position shifted in one direction of a direction perpendicular to a track and a second pit row formed at a position shifted in the other direction are arranged. A variable amplification amplifier circuit for variably amplifying the output of a reproduction signal detecting means for detecting information recorded on the disk by converging and irradiating the disk with a light beam; and a first pit train and a second pit train based on the output of the variable amplification amplifier. A gate circuit for extracting a portion corresponding to the pit row, an HPF for making the extracted signal of each pit row the AC center, and reproduction of the first pit row and the second pit row which become the AC center A full-wave rectifier circuit for full-wave rectification of a signal, an LPF for integrating reproduction signals of the first and second pit arrays subjected to full-wave rectification, and a first pit integrated by the LPF Column and second A switch for switching between a reproduced signal of the pit train and a reference voltage, a pair of sample and hold circuits for sampling and holding the reproduced signals and the reference voltage of the first pit train and the second pit train switched by the switches, An optical disk device, comprising: a differential circuit for obtaining a difference signal between outputs of a sample and hold circuit, wherein an output of the differential circuit when the switch is switched and a reference voltage is sampled and held is used as a reference value. . 4. A first pit row formed at a position deviated in one direction of a direction perpendicular to a track and a second pit row formed at a position deviated in the other direction are arranged. A variable amplification amplifier circuit for variably amplifying an output of a reproduction signal detecting means for detecting information recorded on the disk by converging and irradiating the disk with a light beam; A gate circuit for extracting a portion corresponding to the pit row of FIG. 1, an HPF for centering the extracted signal of each pit row on the AC center, and an AC
A full-wave rectifier circuit for full-wave rectification of the reproduced signals of the first and second pit strings at the center; and a reproduced signal of the first and second pit strings that have been subjected to full-wave rectification. And the first integrated by the LPF.
And a pair of samples for sampling and holding the reproduced signals and the reference voltages of the first and second pit strings switched by the switches. A hold circuit; and a differential circuit for obtaining a difference signal between the outputs of the pair of sample and hold circuits.
An optical disk device which moves a light beam in accordance with an output of the differential circuit when switching to a reproduction signal of the pit train and the second pit train and positions the light beam substantially at the center of the track. 5. The method according to claim 1, further comprising, after obtaining a reference value based on the reference voltage, switching a switch to a reproduction signal of the first pit row and the second pit row to detect a positional shift between the light beam and the track. 3. The optical disk device according to 3. 6. When a predetermined temperature difference is generated from the temperature at the time when the reference value based on the predetermined temperature and the reference voltage is obtained, the switch is switched again to the reference voltage to obtain the reference value again. 3. The optical disk device according to 3. 7. The optical disk device according to claim 1, wherein a cutoff frequency of the HPF and a cutoff frequency of the LPF are set to be substantially equal. 8. A first pit row formed at a position shifted in one direction of a direction perpendicular to a track and a second pit row formed at a position shifted in the other direction. Reproduction signal detection means for detecting information recorded on the disk by converging and irradiating the disk with a light beam; and extracting portions corresponding to the first pit row and the second pit row from the output of the reproduction signal detection means And a H circuit for centering the signal of each extracted pit row on the AC center
A PF, a full-wave rectifier circuit for performing full-wave rectification on the reproduced signals of the first and second pit rows centered on the AC, and a first and second pit rows that have been subjected to full-wave rectification. An LPF for integrating the reproduced signals of the columns, a pair of sample and hold circuits for respectively sampling and holding the reproduced signals of the first and second pit arrays integrated by the LPF, and a first sampled and held circuit A differential circuit for obtaining a difference signal between both signals of the pit train and the second pit train and the first pit train and the second pit train are obtained from the reproduced signal detecting means.
A timing signal generating circuit for generating a timing signal corresponding to the pit train of the first and second embodiments, a delay circuit for generating a delay signal in which the timing signals corresponding to the first pit train and the second pit train are respectively delayed by a predetermined time; An optical disc having a logic circuit for performing logic synthesis of a timing signal and a delay signal, wherein the gate circuit is gated by the delay signal and the pair of sample-and-hold circuits are operated by an output of the logic circuit. apparatus. 9. The optical disk device according to claim 8, wherein a delay time delayed by the delay circuit is substantially equal to a propagation delay time from the gate circuit to the pair of sample and hold circuits.