JP2002117536A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that a noise component intruding to a radial push-pull signal is increased due to the break of the balance of the radial push- pull signal when a radial tilt or off-track is generated in the case of a DVD-R optical disk. SOLUTION: In the optical disk device mounted with the optical disk having a data recording track wobbled by a wobble signal of a specified frequency component and forming a land prepit having specific phase relation with the wobble signal, the constitution is made in such a manner that two signals optically bisected in the tangential direction of the track by detecting light reflected from the optical disk in a photodetector are inputted respectively to two AGC circuits, then a signal showing the difference of outputs between two AGC circuits is outputted to a wobble detecting circuit and a prepit detecting circuit by a differential circuit so as to extract the wobble signal and the land prepit signal.

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 or reproducing information on a recording medium such as a recordable optical disk, and more particularly, to an optical disk for recording or reproducing a high-density optical disk such as a DVD. Related to the device.

[0002]

2. Description of the Related Art In recent years, the density of optical disks used as recording media has been increasing, and high-density recording disks typified by DVDs, whose recording densities have been dramatically improved from conventional CDs (compact disks), have been used in optical disk devices. Used. Among such high-density recording disks, DVD-R is a write-once recording disk that is recordable.
Is used. Such a DVD-R stores pre-information such as address information, a synchronization signal, and rotation control information necessary for position detection when recording information is recorded. The pre-information as described above is obtained by wobbles formed by wobbling a groove track on a DVD-R and land pre-pits formed on a land track.

As described above, since the wobble signal is used for generating a recording clock and controlling the rotation of the disk, it is very important for the optical disk apparatus to ensure the detection performance of the wobble signal. Since the land pre-pit signal is used for detecting address information, generating a recording clock, and the like, it is also very important to ensure the detection performance of the pre-pit signal. The wobble signal and the land pre-pit signal are reflected by a photodetector optically divided into two in the tangential direction of the track and reflected from a groove track of the optical disk, and are radial push-pull signals which are differential signals of output signals of the photodetector. Detection is performed using signals. Therefore, improving the detection performance of each signal means improving the quality of the radial push-pull signal.

[0004]

However, the recording density of the DVD-R of the optical disk is dramatically improved as compared with the CD or the like. On the other hand, although the laser spot diameter for irradiating the recording surface of the optical disk has become smaller but not as small as the track pitch, the quality of the radial push-pull signal is impaired due to the influence of radial tilt or off-track during recording and reproduction. Was sometimes

If a radial tilt or off-track occurs during recording / reproduction, the balance of reflected light modulated by the recording mark detected by the divided photodetector is lost, and noise mixed into the radial push-pull signal is generated. Ingredients increase. However, with the current mechanical accuracy and control measures against radial tilt or off-track, the noise component mixed in the radial push-pull signal increases, causing false detection of land pre-pits and increased jitter of the wobble signal. There was a problem.

SUMMARY OF THE INVENTION The present invention solves the above problems, and reduces the level of modulation of reflected light by a recording mark superimposed on a radial push-pull signal even if a radial tilt or off-track occurs during recording and reproduction. It is an object of the present invention to obtain an optical disk device capable of detecting land prepits and wobbles with high accuracy.

[0007]

An optical disk drive according to the present invention has a data recording track wobbled with a wobble signal of a predetermined frequency component, and a land having a predetermined phase relationship with the wobble signal. An optical disc device to which an optical disc having pre-pits is mounted, wherein the photo detector detects reflected light from the optical disc and optically divides the light into two in a tangential direction of a track, and a first output of the photo detector. A first AGC circuit which receives a second output of the photodetector; a second AGC circuit which receives a second output of the photodetector;
A differential circuit for detecting a difference between outputs of the C circuit and the second AGC circuit; a wobble detection circuit for detecting a wobble signal based on an output of the differential circuit; and a land based on an output of the differential circuit. A pre-pit detection circuit for detecting a pre-pit signal. The optical disc device of the present invention configured as described above reduces the level of modulation of reflected light by a recording mark superimposed on a radial push-pull signal even when a radial tilt or off-track occurs during recording and reproduction.
Land pre-pits and wobbles can be detected with high accuracy.

In the optical disk drive of the present invention, the first AGC circuit and the second AGC circuit have substantially the same configuration, and each AGC circuit amplifies an input signal according to a gain control signal. A sample-and-hold circuit for holding the output of the variable gain amplifier at a timing at which a land prepit is output, an envelope detection circuit for detecting an envelope waveform of the output of the sample-and-hold circuit, and a smoothing output of the envelope detection circuit. A low-pass filter to be converted, a differential circuit that outputs a difference between an output voltage of the low-pass filter and a reference voltage, and an amplifier that amplifies an output of the differential circuit and outputs the gain control signal to the variable gain amplifier. Is provided. The optical disk device of the present invention configured as above is
The amplitude of each detection signal of the photodetector divided into two in the two AGC circuits is set to a fixed amount, and the difference is taken as a radial push-pull signal to reduce an RF signal component mixed into the radial push-pull signal.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 showing a preferred embodiment of an optical disk device according to the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 FIG. 1 shows Embodiment 1 according to the present invention.
FIG. 2 is a block diagram illustrating a configuration of an optical disk device. In the optical disk device according to the first embodiment, a description will be given using a write-once DVD-R as an example of an optical disk. FIG. 2 is an enlarged perspective view showing a part of a disk recording area of a DVD-R as an optical disk and showing a cross section.

First, a write-once type optical disk DVD-R (hereinafter simply referred to as a disk) 1 used in the optical disk apparatus of the first embodiment will be described. As shown in FIG. 2, land pre-pits 46 representing disc information such as track position information are formed in a disc recording area on the disc 1. Also, a groove track 42 is formed which slightly oscillates (wobbles) at a predetermined period in the radial direction of the disk 1 in accordance with the wobble signal. The rotation speed of the disk 1 is
It is determined by extracting a wobble signal from the reflected light from the spindle motor and controlling the rotation speed of the spindle motor 2 so that this frequency becomes constant.

The disc 1 has a laser beam A
Is formed, and a pre-pit 46 is formed in the land track 43. The groove track 42 is wobbled at a fixed distance along the track, and by extracting a wobble signal from the groove track 42, rotation control of the disk and generation of a recording clock signal are performed. A land prepit 46 provided on the land track 43 indicates a prepit signal indicating disc information and an address, and exists at the maximum displacement position of the wobbled groove track 42. Since the prepit signal does not lose phase information due to crosstalk with an adjacent track, the prepit signal has a higher phase accuracy than the wobble signal.

As shown in FIG. 2, the disk 1 has a recording film 41, a reflective film 45, and a protective film 44 formed of an organic dye material or the like. Recording of data on the disk 1 is performed by irradiating the recording film 41 of the groove track 42 with a laser beam A modulated according to the data. When recording and reproducing data on the disk 1 formed as described above, a laser beam A is applied to the disk recording surface while rotating the disk 1 around the center of the disk 1. At this time, the rotation frequency of the disk 1 is set to a groove track 42 described later.
The wobble signal is extracted in the optical disk device that receives the reflected light from the disk 1, and the rotation speed of the spindle motor is controlled so that the rotation frequency of the disk 1 becomes constant.

In the optical disk device of the first embodiment, a groove track 42, which is a data recording track wobbled with a wobble signal having a predetermined frequency component, and a land prepit 46 having a predetermined phase relationship with the wobble signal are formed. The disc 1 is mounted. In the optical disc device of the first embodiment shown in FIG. 1, the spindle motor 2 rotates the disc 1 at a desired rotation frequency, and is configured to perform recording and reproduction on the disc recording surface by the pickup 50. The pickup 50 has an objective lens 3, a half mirror 4, a photo detector 8, and a laser oscillator 5. The laser beam A from the laser oscillator 5 is applied to the disk 1 by the half mirror 4.
And focused by the objective lens 3 on a target track on the disk recording surface.

The reflected light from the group track 42 for detecting the disk recording surface is received by the photodetector 8 divided into two by a dividing line optically parallel to the tangential direction of the group track 42. When the reflected light from the disk 1 is detected by the push-pull method based on the difference of the photodetector 8, a signal in which a pulse signal corresponding to the land prepit is superimposed on a sine wave corresponding to the wobble is detected. Groove track 42
The wobble signal from is obtained by taking the difference between the output from the photodetector 8 divided into two and extracted from the difference signal. The pickup 50 receives the reflected light from the optical disk 1, generates a detection signal having recording information data including a pre-pit signal of the pre-pit 46 and a wobble signal by the groove track 42, and outputs the detection signal to the head amplifier 9. The head amplifier 9 amplifies detection signals such as a pre-pit signal and a wobble signal, and outputs the amplified signal to a decoder 10.
Output to The decoder 10 decodes the input amplified signal to generate a demodulated signal, and generates a demodulated signal.
6 is output.

On the other hand, the detection signal output from the photodetector 8 is input to a push-pull signal detection circuit 11, where a radial push-pull signal is detected. The push-pull signal detection circuit 11 includes a first AGC (Automatic Ga
in Control) circuit 11A and a second AGC (Automatic Ga
in Control) circuit 11B and a differential unit 11C, and includes a first AGC circuit 11A and a second AGC circuit 11B.
Have substantially the same configuration. In the push-pull signal detection circuit 11, the R of the reflected light output from the photodetector 8 optically divided into two in the tangential direction of the track is obtained.
After the gain is adjusted so that the average value of the F component becomes constant, the difference is calculated to generate a radial push-pull signal. The detected radial push-pull signal is input to the wobble detection circuit 12 and the pre-pit detection circuit 13. The wobble detection circuit 12 extracts a wobble signal from the radial push-pull signal. Prepit detection circuit 13
Detects a land pre-pit signal (LPP) on the outer peripheral side from the radial push-pull signal. The address detector 14 detects the position of the disk 1 from the wobble signal and the land pre-pit signal. The PLL 15 generates a clock signal for recording data from the wobble signal and the land pre-pit signal.

The interface 17 exchanges a command signal from the host computer and data reproduced in the optical disk device. The CPU 16 instructs a reproducing operation and a recording operation using address information obtained from a wobble signal and a land pre-pit signal based on a command signal input via the interface 17. Also,
In response to a command from the CPU 16, the encoder 18 performs code conversion after adding an error correction code to the recording data,
Performs recording modulation. The power control circuit 7 has a pickup 50
The laser oscillator 5 is driven by a laser driving circuit 6.
The phase comparator 19 outputs a phase difference between the wobble signal detected by the wobble detection circuit 12 and the rotation reference signal.
The spindle driver 20 drives the spindle motor 2 to rotate the disk 1 at a constant linear speed based on the output of the phase comparator 19.

Next, the push-pull signal detection circuit 11, which is a main component in the optical disk device of the first embodiment, will be described with reference to FIG. FIG. 3 shows the configuration of each of the AGC circuits 11A and 11B in the push-pull signal detection circuit 11. 3, a variable gain amplifier (a VGA (Variable Gain Amplifier) in FIG. 3)
21) adjusts the gain of the input signal based on the gain control voltage from the amplifier 26. The sample hold circuit (denoted by SH in FIG. 3) 22 is based on a sample hold control signal (SH control signal) input from the outside.
The signal from the variable gain amplifier 21 is held. An envelope detection circuit (shown as ENV in FIG. 3) 23 detects the envelope output from the sample hold circuit 22 and outputs it to a low-pass filter (shown as LPF in FIG. 3) 24. The low-pass filter 24 smoothes the output of the envelope detection circuit 23 and outputs it to the differential circuit 25. The differential circuit 25 outputs the difference between the output of the low-pass filter 24 and an externally set reference voltage as a gain control voltage. The amplifier 26 amplifies the output of the differential circuit 25 and controls the gain of the variable gain amplifier 21.

The operation of each of the AGC circuits 11A and 11B of the push-pull signal detection circuit 11 configured as described above will be described with reference to FIG. FIG. 4 shows the AGC shown in FIG.
3 shows signal waveforms at various parts in the circuit. FIG.
(A) shows an input signal of the variable gain amplifier (VGA) 21. The signal waveform of FIG. 4A shows a state in which a pulse signal corresponding to the land prepit is superimposed on a 140 kHz sine wave component corresponding to the wobble. Further, in the recorded disc 1, FIG.
(A), the cross-hatched area is RF-modulated. FIG. 4B shows a sample-and-hold circuit 22.
, A sample-hold control signal (SH) control signal input to the land pre-pit area. FIG. 4C shows an output signal of the sample and hold circuit 22, from which a pulse signal corresponding to a land pre-pit has been removed.

FIG. 4D shows an envelope detection circuit (E).
NV) 23, where the RF signal component is removed and the reflection level of the non-marked part is detected. In FIG. 4E, the solid line is the output signal of the low-pass filter 24,
This is a signal obtained by smoothing the output signal of the envelope detection circuit 23 indicated by a dashed line. The broken line in FIG. 4E indicates the reference level. In the differential circuit 25, the difference between the broken line (reference level) and the solid line (the output signal of the LPF 24) in FIG. FIG.
(F) shows an output signal whose gain has been adjusted in the variable gain amplifier 21. The difference between the reference signal input to the differential circuit 25 and the average level of the input signal from the LPF 24 is amplified and added to the gain control signal input to the variable gain amplifier 21. The variable gain amplifier 21 is controlled so that the average value of the output level of the variable gain amplifier 21 becomes the reference level by inputting the added gain control signal.

In the push-pull signal detection circuit 11 of the first embodiment configured as described above, each RF after AGC
Since the average value of the signal components becomes the reference level, it is possible to suppress the mixing of the RF signal without damaging the wobble signal and the land pre-pit signal. Even if the output of the photodetector 8 divided into two is unbalanced due to radial tilt or off-track, the mixing of the RF signal is suppressed to the maximum.

Next, the sample and hold circuit 22 of the push-pull signal detection circuit 11 in the first embodiment will be described. FIG. 5 is a schematic diagram showing a relative positional relationship between the groove track 42 and the land pre-pits 46. As shown in FIG. The configuration shown on the left side in FIG. 5 is a normal configuration, and a land pre-pit 46 exists at the center of a land track 43 sandwiched between adjacent groove tracks 42, 42.
Apart from such a configuration, as shown in the right side of FIG.
A DVD-R having a configuration in which the position of the land prepit 46 is made closer to the target groove track side is considered.

The operation of the push-pull signal detection circuit 11 in the optical disk device using the DVD-R having such a configuration will be described. FIG. 6 shows a signal waveform in the push-pull signal detection circuit 11. In FIG. 6, the LPP level is a land pre-pit signal level, and the WBL level is a wobble signal level.
The left side of FIG. 6 shows a signal waveform when a normal DVD-R is used, that is, the left side of FIG. 6 shows an output waveform when the land pre-pit 46 exists at the center of the land track 43. 6 is a DV having the configuration shown on the right side of FIG.
The right side of FIG. 6 is an output waveform when the land prepit 46 is formed close to the target groove track 42, that is, the signal waveform when DR is used.

In FIG. 6, (A) and (B) are two input signals of the push-pull signal detection circuit 11, and two output signals from the photodetector 8 divided into two in the tangential direction of the track of the disk 1. It is. FIG. 6C shows a signal waveform when the sample and hold circuit 22 is provided in the push-pull signal detection circuit 11, and FIG. 6D shows the signal waveform when the sample and hold circuit is provided in the push-pull signal detection circuit. This is a signal waveform when there is no signal. The signal waveforms of (C) and (D) in FIG. 6 are output waveforms of the push-pull signal detection circuit 11 that are output through the differential 11C after the AGC processing. FIG. 6D shows a case where each of the sample and hold circuits has no AG.
It is the output waveform of the push-pull signal detection circuit output via the differential after the C processing.

When the land pre-pits 46 are not arranged at the center of the land track 43 in the configuration where the sample hold circuit does not exist (the configuration on the right side of FIG. 5), compared with the case where the land pre-pits 46 are arranged at the center. , The center level of the sine wave is shifted, and the mixing level of the RF signal into the radial push-pull signal increases.
Therefore, by providing the sample and hold circuit 22 in the push-pull signal detection circuit 11, the land pre-pit 4
Even if the arrangement of 6 changes, the center level of the sine wave does not deviate, so that the mixing level of the RF signal can be kept at the minimum level. As described above, by configuring the push-pull signal detection circuit 11 of the first embodiment,
Even when stress such as radial tilt or off-track occurs, a stable wobble signal and land pre-pit signal can be detected.

Second Embodiment Next, a second embodiment of the optical disk apparatus according to the present invention will be described with reference to FIG. FIG. 7 is a block diagram illustrating the configuration of the optical disk device according to the second embodiment. In FIG. 7, components having the same configuration and function as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the following description, a portion different from that of the first embodiment will be mainly described. 7, the first push-pull signal detection circuit 11 has substantially the same configuration as the push-pull signal detection circuit 11 of the first embodiment,
The two signals of the reflected light output from the photodetector 8 optically divided into two in the tangential direction of the track are received, and the gain is adjusted so that the average value of the RF components of the signals becomes constant. After the first push-pull signal detection circuit 11 adjusts the gain of each signal, the first push-pull signal detection circuit 11 generates a radial push-pull signal by taking the difference between the signals.

The second push-pull signal detection circuit 27
It has a first AGC circuit 27A, a second AGC circuit 27B, and a differential unit 27C, and the first AGC circuit 27A and the second AGC circuit 27B have substantially the same configuration. The second push-pull signal detection circuit 27 receives two signals of the reflected light output from the photodetector 8 optically divided into two in the tangential direction of the track, and the RF components of those signals become constant. Adjust the gain as follows. After adjusting the gain of each signal, the second push-pull signal detection circuit 27 calculates a difference between the signals to generate a radial push-pull signal.

The wobble detection circuit 12 extracts a wobble signal component from the radial push-pull signal output from the first push-pull signal detection circuit 11. The prepit detection circuit (PLL) 13 detects land prepits on the outer peripheral side from the radial push-pull signal output from the second push-pull signal detection circuit 27. In the second embodiment, components other than those described above are provided with the same functions as those of the above-described first embodiment, and thus description thereof will be omitted.

Next, the first push-pull signal detection circuit 11 and the second push-pull signal detection circuit 27, which are main components in the second embodiment, will be described with reference to FIG. The configuration of the first push-pull signal detection circuit 11 according to the second embodiment is substantially the same as the configuration of the push-pull signal detection circuit 11 according to the above-described first embodiment, and a description thereof will be omitted. FIG. 8 is a block diagram showing a configuration of each AGC circuit in the second push-pull signal detection circuit 27. FIG.
, The variable gain amplifier (VGA) 21
6, the gain of the input signal is adjusted based on the gain control voltage. The sample hold circuit (SH) 22 holds a signal from the variable gain amplifier 21 based on a sample hold control signal (SH control signal) input from the outside. The envelope detection circuit (ENV) 23 detects the envelope output of the output signal of the sample and hold circuit 22.
The differential circuit 25 outputs a difference between the output of the envelope detection circuit 23 and an externally set reference voltage. The amplifier 26 amplifies the output of the differential circuit 25 and controls the gain of the variable gain amplifier. The AGC circuit of the first push-pull signal detection circuit 11 and the AGC circuit of the second push-pull signal detection circuit 27
The difference from the GC circuit is that the control band of the AGC circuit of the second push-pull signal detection circuit 27 is higher than the wobble frequency.

The operation of the AGC circuit in the second push-pull signal detection circuit 27 configured as described above will be described with reference to FIG. FIG. 9 shows signal waveforms at various parts of the AGC circuit shown in FIG. FIG. 9A
Denotes an input signal of the variable gain amplifier 21. The signal waveform in (A) of FIG.
A state is shown in which a pulse signal corresponding to a land prepit is superimposed on a sine wave component of 40 kHz. In the case of the recorded optical disc 1, the cross-hatched area in FIG. 9A is RF-modulated. FIG. 9B shows a sample / hold control signal (SH control signal) input to the sample / hold circuit 22, which is a signal which becomes a hold level around the land prepit. FIG. 9C shows the sample hold circuit 2.
2, the pulse signal corresponding to the land pre-pit has been removed. FIG. 9D shows the output signal of the envelope detection circuit 23, from which the RF signal component is removed and the reflection level of the non-mark portion is detected. The broken line in FIG. 9D indicates the level of the reference voltage.
In the differential circuit 25, the difference between the reference voltage level indicated by the broken line and the reflection level indicated by the solid line in FIG. 9D is output.

FIG. 9E shows an output signal of the variable gain amplifier 21. The difference between the reference signal detected by the differential circuit 25 and the average level of the input signal is amplified by the amplifier 26 and input to the variable gain amplifier 21 as a gain control signal. The variable gain amplifier 21 controls an output level to be a reference level by a gain control signal. FIG. 9F shows a radial push-pull signal that is controlled and output to the reference level in the variable gain amplifier 21. By configuring the second push-pull signal detection circuit 27 in this way, it is possible to minimize the mixing of the RF signal in any part of the AGC circuit of the second push-pull signal detection circuit 27. . In the first and second push-pull signal detection circuits 11 and 27 according to the second embodiment configured as described above, the RF signal component after the AGC processing is adjusted to the reference signal level. It is possible to suppress the RF from being mixed into the radial push-pull signal. As a result, the optical disk device according to the second embodiment can detect a stable wobble signal and land pre-pit signal even when stress such as radial tilt or off-track occurs.

Third Embodiment Next, a third embodiment of the optical disk device according to the present invention will be described with reference to FIG. FIG. 10 is a block diagram illustrating the configuration of the optical disk device according to the third embodiment. In FIG. 10, components having the same configuration and function as those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. In the following description, the first embodiment will be described.
The following description focuses on the parts different from the above. In FIG. 10, the first
The push-pull signal detection circuit 11 of the first embodiment has substantially the same configuration as that of the push-pull signal detection circuit 11 of the first embodiment, and the reflection output from the photodetector 8 optically divided into two in the tangential direction of the track. The two signals of light are received, and gain adjustment is performed so that the average value of the RF components of those signals is constant. After the first push-pull signal detection circuit 11 adjusts the gain of each signal, the first push-pull signal detection circuit 11 generates a radial push-pull signal by taking the difference between the signals.

The third push-pull signal detection circuit 28
It has a first AGC circuit 28A, a second AGC circuit 28B, and a differential 28C. The third push-pull signal detection circuit 28 receives two signals of the reflected light output from the photodetector 8 optically divided into two in the tangential direction of the track, and converts the RF components of those signals into land pre-pits. The gain is adjusted to be constant at the position corresponding to. After adjusting the gain of each signal, the second push-pull signal detection circuit 28 generates a radial push-pull signal by taking the difference between the signals.

The wobble detection circuit 12 extracts a wobble signal component from the radial push-pull signal output from the first push-pull signal detection circuit 11. The prepit detection circuit (PLL) 13 detects land prepits on the outer peripheral side from the radial push-pull signal output from the third push-pull signal detection circuit 28. In the third embodiment, components other than those described above are provided with the same functions as the components of the above-described first embodiment, and a description thereof will be omitted.

Next, the first push-pull signal detection circuit 11 and the third push-pull signal detection circuit 28, which are the main components in the optical disk device of the third embodiment, will be described.
This will be described with reference to FIG. FIG. 11 is a block diagram showing a configuration of the first AGC circuit 28A and the second AGC circuit 28B in the third push-pull signal detection circuit 28. In the first AGC circuit 28A shown in FIG. 11, the first variable gain amplifier (VGA1) 21A is
The gain of the input signal is adjusted based on the gain control signal from A. The sample hold circuit (SH) 22A holds the output signal of the variable gain amplifier 21A based on a sample hold control signal (SH control signal) input from the outside. The envelope detection circuit (ENV) 23A detects an envelope output in the output from the sample and hold circuit 22A. The output signal of the envelope detection circuit 23A is input to the differential circuit 25A via the peak detection circuit 29A. The peak detection circuit 29A detects the peak of the output signal of the envelope detection circuit 23A and outputs the detected signal to the differential circuit 25A. The differential circuit 25A outputs a difference between the output of the peak detection circuit 29A and an externally set reference voltage. Amplifier 26A amplifies the output from differential circuit 25A and outputs it to variable gain amplifier 21A. Variable gain amplifier 2
The gain of the input signal is controlled by the gain control signal input to 1A.

In the second AGC circuit 28B,
The second variable gain amplifier (VGA2) 21B is an amplifier 2
The gain of the input signal is adjusted based on the gain control signal from 6B. The sample hold circuit (SH) 22B holds an output signal of the variable gain amplifier 21B based on a sample hold control signal (SH control signal) input from the outside. The envelope detection circuit 23B (ENV) detects an envelope output in the output from the sample and hold circuit 22B. The output signal of the envelope detection circuit 23B is input to the differential circuit 25B via the bottom detection circuit 30B. The bottom detection circuit 30 is an envelope detection circuit 23
The peak of the output signal of B is detected and output to the differential circuit 25B. The differential circuit 25B outputs a difference between the output of the bottom detection circuit 30B and an externally set reference voltage. Amplifier 26B amplifies the output from differential circuit 25B and outputs it to variable gain amplifier 21B. Variable gain amplifier 21
The gain of the input signal is controlled by the gain control signal input to B.

A of the first push-pull signal detection circuit 11
The AG of the GC circuit and the third push-pull signal detection circuit 28
The difference from the C circuit is that the comparison target in each circuit is different. AG of the first push-pull signal detection circuit 11
In the C circuit, the comparison target is the same in each AGC circuit. In the third push-pull signal detection circuit 28, the output signal of the peak detection circuit 29A is compared with the differential circuit 25A of the first AGC circuit 28A, and the bottom signal is output in the differential circuit 25B of the second AGC circuit 28B. This is an output signal of the detection circuit 30B.

Each of the AGC circuits 28A, 28 in the third push-pull signal detection circuit 28 configured as described above
The operation of B will be described with reference to FIG. FIG.
Is the third push-pull signal detection circuit 2 shown in FIG.
8 shows an example of a signal waveform of a main part of each of the AGC circuits 28A and 28B of FIG. In FIG. 9, (A) shows the first
(B) is an input signal of the variable gain amplifier (VGA1) 21A.
B shows the input signal. The signal waveform shown in FIG. 12A is a signal detected by the photodetector 8 arranged on the outer peripheral side of the disk 1, and includes a 140 kHz sine wave component corresponding to the wobble and a pulse signal corresponding to the land prepit. Are superimposed. FIG. 12C shows a first variable gain amplifier (VGA1) 2
1A, which is controlled so that the peak of the envelope output of the RF signal becomes the reference potential. (D) of FIG.
Indicates the output signal of the second variable gain amplifier (VGA2) 21B, and is controlled so that the bottom of the envelope output of the RF signal becomes the reference potential. FIG. 12E shows a radial push-pull signal output from the third push-pull signal detection circuit 28.

In the third push-pull signal detection circuit 28 configured as described above, since the RF signal component after the AGC processing becomes the reference signal level in the land pre-pit area, the radial push after the difference is obtained. The RF signal component mixed in the pull signal is minimized in the land pre-pit area. As a result, in the optical disc device of the third embodiment, the land pre-pit detection performance is dramatically improved. As a result, the optical disk device according to the third embodiment can detect a stable wobble signal and land pre-pit signal even when stress such as radial tilt or off-track occurs.

Fourth Embodiment Next, a fourth embodiment of the optical disk apparatus according to the present invention will be described with reference to FIG. FIG. 13 is a block diagram illustrating the configuration of the optical disk device according to the fourth embodiment. In FIG. 13, components having the same configuration and function as those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. In the following description, the first embodiment will be described.
The following description focuses on the parts different from the above.

In FIG. 13, the third push-pull signal detection circuit 28 includes a first AGC circuit 28A and a second AGC circuit 28A.
It has a C circuit 28B and a differential 28C, and has the configuration shown in FIG. The third push-pull signal detection circuit 28 receives two signals of the reflected light output from the photodetector 8 optically divided into two in the tangential direction of the track, and converts the RF components of those signals to land prepits. Adjust the gain so that it becomes constant at the corresponding position. The third push-pull signal detection circuit 28
After the gain of each signal is adjusted, a radial push-pull signal is generated by taking the difference between the signals.

The wobble detection circuit 12 extracts a wobble signal component from the radial push-pull signal output from the third push-pull signal detection circuit 28. The pre-pit detection circuit (PLL) 13 detects land pre-pits from the radial push-pull signal output from the third push-pull signal detection circuit 28. In the fourth embodiment, components other than those described above are provided with the same functions as the components of the above-described first embodiment, and a description thereof will be omitted.

The third push-pull signal detection circuit 28 in the optical disk device of the fourth embodiment configured as described above.
In, the RF signal component after the AGC processing becomes the reference signal level in the land pre-pit area. For this reason,
The RF signal component mixed into the radial push-pull signal after taking the difference is minimum in the land pre-pit area,
Land pre-pit detection performance is improved.

In the fourth embodiment, the radial push-pull signal output from the third push-pull signal detection circuit 28 is used for wobble detection. In the third push-pull signal detection circuit 28, the average amount of mixing of the RF signal increases, but in the wobble detection,
It is possible to improve the SN ratio by narrowing the band of the band pass filter. Therefore, in the fourth embodiment, it is possible to omit a push-pull signal detection circuit specially configured for wobbles for the purpose of simplifying the circuit.

Fifth Embodiment Next, a fifth embodiment of the optical disk apparatus according to the present invention will be described with reference to FIG. FIG. 14 is a block diagram showing the configuration of the optical disk device of the fifth embodiment. In FIG. 14, components having the same configuration and function as those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. In the following description, the first embodiment will be described.
The following description focuses on the parts different from the above.

In FIG. 14, the fourth push-pull signal detection circuit 31 includes a first AGC circuit 31A and a second AGC circuit 31A.
It has a C circuit 31B and a differential unit 31C. First A
The GC circuit 31A and the second AGC circuit 31B have substantially the same configuration. The fourth push-pull signal detection circuit 31 receives two signals of the reflected light output from the photodetector 8 optically divided into two in the tangential direction of the track, and converts the RF components of those signals into land prepits. Adjust the gain so that it becomes constant at the corresponding position. After adjusting the gain of each signal, the fourth push-pull signal detection circuit 31 generates a radial push-pull signal by taking the difference between the signals.

The wobble detection circuit 12 extracts a wobble signal component from the radial push-pull signal output from the fourth push-pull signal detection circuit 31. The pre-pit detection circuit 13 detects land pre-pits from the radial push-pull signal output from the fourth push-pull signal detection circuit 31. In the fifth embodiment, components other than those described above are provided with the same functions as those of the above-described first embodiment, and thus description thereof will be omitted.

Next, a fourth push-pull signal detection circuit 31, which is a main component in the optical disk device of the fifth embodiment, will be described with reference to FIG. FIG.
3 is a block diagram showing a configuration of each AGC circuit in the push-pull signal detection circuit 31 of FIG. Variable gain amplifier 2
1 adjusts the gain of the input signal based on the gain control voltage from the amplifier 26. Variable gain amplifier (VGA) 2
The output signal of 1 is input to a low-pass filter (LPF) 24 via a sample-and-hold circuit (SH). The differential circuit 25 outputs a difference between the output of the low-pass filter 24 and an externally set reference voltage. The amplifier 26 amplifies the output of the differential circuit 25 and inputs the amplified gain control signal to the variable gain amplifier 21. With this gain control signal, the variable gain amplifier 21 controls the gain of the input signal.

The operation of the fourth push-pull signal detection circuit 31, particularly the operation of the AGC circuit, of the optical disk device of Embodiment 5 configured as described above will be described with reference to FIG. FIG. 16 shows a signal waveform of a main part in the AGC circuit shown in FIG. FIG. 16A shows an input signal of the variable gain amplifier (VGA) 21. This input signal is 140 kHz corresponding to the wobble.
A pulse signal corresponding to a land pre-pit is superimposed on the sine wave component of FIG. FIG. 16B shows an output signal of the low-pass filter (LPF) 24, which smoothes the input signal. FIG. 16C shows an output signal of the variable gain amplifier (VGA) 21. The average voltage of the input signal is controlled so that it becomes a reference potential in the variable gain amplifier.

In the fourth push-pull signal detection circuit 31 according to the fifth embodiment configured as described above, AG
Since the average value of each RF signal component after the C processing becomes the reference signal level, it is possible to suppress RF mixing without damaging the wobble signal and the land prepit signal.
Even if an unbalance occurs in the output signal from the photodetector 8 divided into two by radial tilt or off-track, the average value of each RF signal component becomes the reference signal level, so that mixing of the RF signal is suppressed, The wobble signal and the land pre-pit signal can be extracted with high accuracy.

In the above description of each embodiment,
Although the reference signal level is shown as a fixed potential set from the outside, as shown in FIG. 17, a configuration may be used in which the result of adding two input signals to the push-pull signal detection circuit is input to each AGC as a reference. . FIG. 17 is a block diagram showing a configuration of the push-pull signal detection circuit. As shown in FIG. 17, two signals of reflected light output from the photodetector are input to the two AGCs 32 and 32, respectively. The two input signals are input to the adder 34, and the result is used as a reference signal level for each AGC3.
2, 32. The AGC 32 of the push-pull signal detection circuit used here has the configuration described in each of the above embodiments. Further, in the above description of each embodiment, the case of reproducing a recorded DVD-R has been described as an example. However, even during recording, the same configuration can be used. Has an effect.

[0052]

As apparent from the detailed description of the embodiments, the present invention has the following effects.
The optical disc device of the present invention reduces the level of the modulation of the reflected light by the recording mark superimposed on the radial push-pull signal even when a radial tilt or off-track occurs during recording / reproduction, thereby enabling land pre-pits and wobbles to have high precision. Can be detected. According to the present invention, even in a bad environment such as radial tilt or off-track, the RF signal mixed into the radial push-pull signal can be suppressed, so that land pre-pits and wobbles can be reliably detected, and high reliability is obtained. An optical disk device can be obtained.

[Brief description of the drawings]

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

FIG. 2 is an enlarged perspective view of a DVD-R, which is an example of an optical disk.

FIG. 3 is a block diagram illustrating an AGC circuit of a push-pull signal detection circuit in the optical disc device according to the first embodiment.

FIG. 4 is a signal waveform diagram in the AGC circuit of the push-pull signal detection circuit of the optical disc device of the first embodiment.

FIG. 5 is a schematic diagram showing a positional relationship between a groove track and a land prepit.

FIG. 6 is a signal waveform diagram in the optical disc device of the first embodiment.

FIG. 7 is a block diagram illustrating a configuration of an optical disc device according to a second embodiment of the present invention.

FIG. 8 is a block diagram illustrating an AGC circuit of a push-pull signal detection circuit in the optical disc device according to the second embodiment.

FIG. 9 is a signal waveform diagram in the AGC circuit of the push-pull signal detection circuit of the optical disc device of the second embodiment.

FIG. 10 is a block diagram illustrating a configuration of an optical disc device according to a third embodiment of the present invention.

FIG. 11 is a block diagram illustrating an AGC circuit of a push-pull signal detection circuit in the optical disc device of the third embodiment.

FIG. 12 is a signal waveform diagram in the AGC circuit of the push-pull signal detection circuit of the optical disc device of the third embodiment.

FIG. 13 is a block diagram illustrating a configuration of an optical disc device according to a fourth embodiment of the present invention.

FIG. 14 is a block diagram illustrating a configuration of an optical disc device according to a fifth embodiment of the present invention.

FIG. 15 is a block diagram illustrating an AGC circuit of a push-pull signal detection circuit in the optical disc device of the fifth embodiment.

FIG. 16 is a signal waveform diagram in the AGC circuit of the push-pull signal detection circuit of the optical disc device of the fifth embodiment.

FIG. 17 is a block diagram showing a configuration of an optical disc device according to another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 DVD-R 2 Spindle motor 3 Objective lens 4 Half mirror 5 Laser oscillator 6 Laser drive circuit 7 Power control circuit 8 Photodetector 9 Head amplifier 10 Decoder 11 Push-pull signal detection circuit 12 Wobble detection circuit 13 Prepit detection circuit 14 Address detector Reference Signs List 15 PLL 16 CPU 17 Interface 18 Encoder 19 Phase comparator 20 Spindle driver 21 Variable gain amplifier 22 Sample hold circuit 23 Envelope detection circuit 24 Low-pass filter 25 Differential circuit 26 Amplifier

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Kazuo Fujimoto 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 5D090 AA01 BB04 CC01 DD03 FF07 GG09 GG23

Claims (13)

[Claims] 1. An optical disc apparatus having a data recording track wobbled with a wobble signal of a predetermined frequency component, and an optical disk having land prepits having a predetermined phase relationship with the wobble signal mounted thereon. A photodetector that detects reflected light from the optical disk and optically divides the light into two in a tangential direction of a track; and a first output having a first output of the photodetector as an input.
An AGC circuit, and a second output having a second output of the photodetector as an input.
An AGC circuit; a differential circuit that detects a difference between outputs of the first AGC circuit and the second AGC circuit; a wobble detection circuit that detects a wobble signal based on an output of the differential circuit; An optical disc device comprising: a pre-pit detection circuit that detects a land pre-pit signal based on an output of a differential circuit. 2. The first AGC circuit and the second AGC circuit have substantially the same configuration, each AGC circuit amplifying an input signal according to a gain control signal, and the variable gain amplifier. Sample and hold circuit that holds the output of the land pre-pit at the output timing, an envelope detection circuit that detects the envelope waveform of the output of the sample and hold circuit, and a low-pass filter that smoothes the output of the envelope detection circuit, A differential circuit that outputs a difference between an output voltage of the low-pass filter and a reference voltage, and an amplifier that amplifies an output of the differential circuit and outputs the gain control signal to the variable gain amplifier. 2. The optical disk device according to claim 1, wherein: 3. The first AGC circuit and the second AGC circuit have substantially the same configuration, each AGC circuit amplifying an input signal according to a gain control signal, and the variable gain amplifier. And a low-pass filter for smoothing the output of the sample-and-hold circuit, and a differential for outputting a difference between an output voltage of the low-pass filter and a reference voltage. 2. The optical disk device according to claim 1, further comprising: a circuit; and an amplifier that amplifies an output of the differential circuit and outputs the output to the variable gain amplifier as the gain control signal. 4. The first AGC circuit holds a first variable gain amplifier for amplifying an input signal in accordance with a gain control signal, and holds an output of the first variable gain amplifier at a timing at which a land prepit is output. A first sample and hold circuit, a first envelope detection circuit for detecting an envelope waveform of an output of the first sample and hold circuit, a peak detection circuit for detecting a peak level of the first envelope detection circuit, A first differential circuit that outputs a difference between an output voltage of the peak detection circuit and a reference voltage, and an output of the first differential circuit that is amplified and output as a gain control signal to the first variable gain amplifier. First
The second AGC circuit comprises: a second variable gain amplifier that amplifies an input signal according to a gain control signal; and a timing at which a land prepit is output from the output of the second variable gain amplifier. A second sample and hold circuit, a second envelope detection circuit for detecting an envelope waveform of an output of the second sample and hold circuit, and a bottom detection circuit for detecting a bottom level of the second envelope detection circuit A second differential circuit for outputting a difference between an output voltage of the bottom detection circuit and a reference voltage;
2. The optical disk device according to claim 1, further comprising: a second amplifier that amplifies an output of the differential circuit and outputs the amplified output to the second variable gain amplifier as a gain control signal. 5. The optical disk device according to claim 2, wherein the reference voltage applied to each differential circuit in the first AGC circuit and the second AGC circuit is the same. 6. A method according to claim 1, wherein a reference voltage applied to each differential circuit in said first AGC circuit and said second AGC circuit is an average voltage of input signals of said first AGC circuit and said second AGC circuit. The optical disk device according to claim 5, wherein: 7. An optical disc device having a data recording track wobbled with a wobble signal of a predetermined frequency component, and an optical disk on which land prepits having a predetermined phase relationship with the wobble signal are mounted. A photodetector that detects reflected light from the optical disc and optically divides the light into two in a tangential direction of a track; and two outputs from the photodetector,
A first push-pull signal detection circuit for performing the difference processing, and two outputs from the photodetector,
A second push-pull signal detection circuit that performs the difference processing; a wobble detection circuit that detects a wobble signal based on an output of the first push-pull signal detection circuit; and an output of the second push-pull signal detection circuit And a pre-pit detection circuit for detecting a land pre-pit signal on the basis of the following. 8. The first push-pull signal detecting circuit, wherein the output amplitude of the photodetector is the same.
Two AGC circuits and a differential circuit for detecting a difference between outputs of the two AGC circuits, wherein the second push-pull signal detection circuit has the same output of the photodetector in a land prepit area. AGC circuits whose gains are controlled as described above,
An optical disc device comprising: a differential circuit for detecting a difference between outputs of two AGC circuits. 9. Each of the AGC circuits includes a variable gain amplifier that amplifies an input signal in accordance with an output of a gain control terminal, a sample and hold circuit that holds an output of the variable gain amplifier at a timing at which a land prepit is output, An envelope detection circuit that detects an envelope waveform of an output of the sample and hold circuit, a low-pass filter that smoothes an output of the envelope detection circuit, and a differential circuit that outputs a difference between an output voltage of the low-pass filter and a reference voltage, 9. The optical disk device according to claim 7, further comprising: an amplifier for amplifying an output of the differential circuit and outputting the amplified output to a variable gain amplifier as a gain control signal. 10. One of the two AGC circuits is a first variable gain amplifier that amplifies an input signal according to a gain control signal, and outputs an output of the first variable gain amplifier at a timing at which a land prepit is output. 1st to hold
A sample and hold circuit, a first envelope detection circuit for detecting an envelope waveform of an output of the first sample and hold circuit, the peak detection circuit for detecting a peak level of the first envelope detection circuit, A first differential circuit that outputs a difference between an output voltage of the detection circuit and a reference voltage, and a second differential circuit that amplifies an output of the first differential circuit and outputs the amplified output to the first variable gain amplifier as a gain control signal. A second variable gain amplifier that amplifies an input signal according to an output of a gain control terminal;
A second sample-and-hold circuit for holding an output of the second variable gain amplifier at a timing at which a land prepit is output, and a second envelope detection circuit for detecting an envelope waveform of an output of the second sample-and-hold circuit A bottom detection circuit for detecting a bottom level of the second envelope detection circuit; a second differential circuit for outputting a difference between an output voltage of the bottom detection circuit and a reference voltage; 9. The optical disk device according to claim 7, further comprising: an amplifier for amplifying an output of a circuit and outputting the amplified output to the second variable gain amplifier as a gain control signal. 11. An optical disc apparatus having a data recording track wobbling with a wobble signal of a predetermined frequency component, and mounting an optical disk on which land prepits having a predetermined phase relationship with the wobble signal are mounted. A photodetector that detects reflected light from an optical disc and optically divides the light into two in a tangential direction of a track; a first AGC circuit that outputs a voltage level of one output of the photodetector; A second AGC circuit that sets a voltage level of the other output of the detector as an output target; a differential circuit that outputs a difference between an output of the first AGC circuit and an output of the second AGC circuit; A wobble detection circuit for detecting a wobble signal based on an output of the driving circuit; and a land pre-pit signal based on an output of the differential circuit. An optical disc device, comprising: a pre-pit detection circuit for detecting. 12. The optical disk device according to claim 11, wherein a reference voltage applied to said differential circuit in said first AGC circuit and said second AGC circuit is made equal. 13. A reference voltage applied to the differential circuit in the first AGC circuit and the second AGC circuit,
13. The optical disk device according to claim 12, wherein an average voltage of each input signal of the first AGC circuit and the second AGC circuit is set.