JPH06187654A - Defect detecting circuit for optical disk device and optical disk device - Google Patents

Abstract

PURPOSE:To obtain a defect signal by which a tracking servo or a focussing servo is held during the time of recording to an optical disk, as well. CONSTITUTION:A wobble signal is taken out of a band-pass filter 16 and the presence of the wobble signal is detected by a comparater 20. The output of the comparater 20 is inputted to a NOR gate 21 together with a searching signal indicatin that the device is in a track search. The output of the NOR gate 21 becomes to be the defect signal, by which the tracking servo or the focussing servo is held. Thus, the disturbance of the servo due to the damage on the optical disk is prevented except the time of a track-jump.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device, and more particularly to a focus servo in a dusty or scratched area in order to prevent the focus servo or tracking servo from being disturbed by dust or scratches on the disk. And a defect detection circuit for outputting a signal for holding a tracking servo.

Further, the present invention relates to means for preventing the spindle servo from being disturbed at the time of track search of the optical disk device.

[0003]

2. Description of the Related Art An optical disk apparatus performs focusing control so that a laser beam of an optical pickup is focused on a signal recording surface of an optical disk during recording or reproduction, and tracking control so that a laser spot tracks a signal recording track. To do.

The focusing error signal and tracking error signal used for such focusing control and tracking control are obtained from the reflected light from the signal recording surface of the optical disc. If the optical disc is dusty or has scratches, stable focusing error signals and tracking error signals cannot be obtained.

In this case, in order to prevent the focus servo and the tracking servo from being disturbed, the focus servo and the tracking servo are held by a signal from a defect detection circuit that detects a flaw or the like.

FIG. 8 shows an example of a conventional defect detection circuit. As shown in FIG. 8A, the RFO signal is inverted and amplified by the operational amplifier 1. The RFO signal is a signal obtained by reproducing the recording signal of the disc by the optical pickup and includes a DC component.

The RFO signal is inverted and amplified by the operational amplifier 1. 8B and 8C show waveforms of the RFO signal and its inverted and amplified signal. The inverted and amplified signal is subjected to long time constant bottom hold and short time constant bottom hold by the operational amplifiers 2 and 3.

The short-time constant bottom-hold signal is differentiated by C coupling, level-shifted with respect to the long-time constant bottom hold signal, and then compared with the long-time constant bottom hold signal by the comparator 4. Figure 8 (d)
The solid line and the dotted line respectively indicate the signals at the + input terminal and the − input terminal of the comparator 4.

A defect signal as shown in FIG. 8 (e) is output from the comparator 4, and the tracking servo and focusing servo are held by this defect signal.

FIG. 9 shows an example of a spindle servo circuit of a conventional optical disk device. As shown in the figure, the tracking error signal (TE) is amplified by an amplifier 5 having an automatic gain control function, and then a band pass filter 6
The wobble signal component is extracted at. The wobble signal is a signal generated from the waveform of the pre-groove engraved on the optical disk, and the frequency of the wobble signal gives the rotation speed information of the spindle motor.

The wobble signal component extracted by the band pass filter 6 is compared in phase with the signal oscillated by the voltage controlled oscillator 9 in the phase comparator 7. The DC component of the phase difference signal thus phase-compared is extracted by the low-pass filter 8, and the oscillation frequency of the voltage-controlled oscillator 9 is controlled by this signal.

The oscillation frequency of the voltage controlled oscillator 9 is proportional to the carrier frequency of the wobble signal, and thus a stable signal having a frequency proportional to the rotation speed of the spindle motor can be obtained. The output signal of the voltage controlled oscillator 9 is the frequency divider 1
The frequency is divided by 0, and the CLV servo circuit 11 compares the reference frequency signal generated by the timing generator 12 with the frequency and phase.

The CLV servo circuit 11 compares the output signal of the frequency divider 10 with the reference frequency signal in frequency and phase to generate a spindle motor control signal, and the power amplifier 13 power-amplifies the signal to drive the spindle motor 14. To drive. In this way, the C of the signal recording track of the optical disk is
LV (constant linear velocity) control is performed.

[0014]

An RFO signal is input to the conventional defect detection circuit shown in FIG. 8, but when recording on a recording disk having a high reflectance such as a CD-R, the RFO signal is inputted. The signal is saturated by the amplifier at the previous stage that is output to the circuit of FIG. 8, and the RFO signal that enables the defect detection is not input. Therefore, in that case, there is a problem that the defect signal is not generated.

Further, in the optical disk device, when searching for the target position of the signal recording track, a follow-up track jump is performed several times in the vicinity of the target position. Since the wobble signal disappears during the track jump, according to the spindle servo circuit of the conventional optical disk device shown in FIG. 9, the spindle servo becomes unstable and the lock is temporarily stopped.

Since the track position information is modulated into the wobble signal, the track position information cannot be demodulated from the wobble signal unless the spindle servo is locked. Therefore, there is a problem that the track position information cannot be read until the spindle servo is locked, and it takes a long time to search.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a defect detection circuit capable of stably obtaining a defect signal even when recording an optical disk having a high reflectance. To provide.

Another object of the present invention is to provide an optical disk device capable of searching the target position of a signal recording track in a short time by stabilizing the spindle servo during the search.

[0019]

A defect detection circuit of an optical disk device according to the present invention detects the presence or absence of a wobble signal obtained from the waveform during recording or reproduction of an optical disk having a track groove on which a waveform pre-groove is formed. A wobble signal detection circuit and a gate circuit that permits the passage of a signal indicating that there is no wobble signal from the wobble signal detection circuit. By controlling the gate with a signal indicating that a track is being searched, a time other than during a track search The defect signal is output when the wobble signal disappears.

Further, in the optical disk device of the present invention, immediately after the wobble signal disappears, one of the signals flowing in the spindle servo loop due to the signal indicating that there is no wobble signal output from the wobble signal detection circuit of the first aspect. It is configured to be fixed to the signal of No. 1 and to keep the rotation speed of the spindle motor substantially constant during the track search.

[0021]

The servo system of the optical disk device is configured so that the wobble signal can be stably obtained from the tracking error signal even when recording an optical disk having a high reflectance.

Therefore, according to the defect detection circuit of the optical disk device of the present invention, the mirror surface defect is detected by detecting the presence or absence of the wobble signal, and the focus servo and the tracking servo are held by using the signal except when the track is searched. By doing so, even during recording on an optical disc having a high reflectance, each servo can be passed through a scratch or dust area while being kept stable.

Further, according to the optical disk device of the present invention, the spindle servo is held by the signal detecting the mirror surface defect as described above during the period when there is no wobble signal at the time of track adjustment, and the rotation of the disk after the search is prevented. Since it is not disturbed, the spindle servo locks quickly and the track position information can be read. In this way, the time for track search can be shortened.

[0024]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a defect detection circuit of an optical disk device according to an embodiment of the present invention. As shown in the figure, the output current of the two-divided photodiode (PD) is converted into a voltage by the current-voltage converter (IV), and then differentially amplified by the differential amplifier 15 to obtain the tracking error signal ( TE) is obtained.

The tracking error signal is output to the tracking servo circuit via the analog switch 22 and is passed through the Pand Pass Filter 16 so as to be 2
A 2.05 kHz wobble signal is taken out. The wobble signal has a waveform as shown in A of FIG. As shown in the figure, the portion where the amplitude of the wobble signal is 0 corresponds to the defective portion of the optical disc.

The wobble signal is rectified by the rectifier 17 and passes through the low-pass filter 18 to extract the envelope. The envelope output terminal of the wobble signal is connected to the offset voltage source by the connection circuit of the resistors R1 and R2, and the envelope to which the offset voltage is applied is taken out from the connection of the resistors R1 and R2. The voltage waveform becomes the waveform shown in D of FIG.

The envelope of the wobble signal is 2 /
3 Peak hold circuit 19 holds the peak 2
It is divided into / 3. The voltage waveform becomes the waveform shown in C of FIG.

The above-mentioned envelope to which the offset voltage is applied and the 2/3 peak hold voltage are applied to the + input terminal and the-input terminal of the comparator 20, respectively, and are compared. The output of the comparator 20 becomes H level when there is no wobble signal.

The output signal of the comparator 20 is input to the NOR gate 21 together with the search signal indicating that the track search is in progress. The search signal is a signal which becomes H level during the track search as shown in FIG. 3, a track jump is performed during that period, the tracking error signal largely fluctuates, and the number of tracks jumped is counted by the number of the waves. .

The output waveform of the NOR gate 21 becomes the waveform shown in B of FIG. The output of the NOR gate 21 becomes a defect signal, and the analog switch 22 is switched by this signal. That is, when the defect signal is H, the analog switch 22 is switched to the capacitor side, and the tracking error signal output to the tracking servo circuit is held in the state immediately before the output of the defect signal. In this way, the tracking servo is prevented from being disturbed when the optical disc is scratched.

During the search, the output of the defect signal is prohibited as described above to prevent malfunction. Although not shown, the forcing servo is also held by the same defect and signal.

FIG. 4 shows a spindle servo circuit of this optical disk device. In this circuit, the low-pass filter 8 is replaced by the low-pass filter 24 in the circuit shown in FIG. The output of the low-pass filter 24 is held by the output signal of the amplitude detection circuit 23, and the other parts are the same as those shown in FIG.

The amplitude detection circuit 23 is the rectifier 1 of the circuit of FIG.
The circuit from 7 to the comparator 20 holds the output of the low-pass filter 24 by the output signal of the comparator 20.

The details of the low-pass filter 24 are shown in FIG. The output terminal of the phase comparator 7 is connected via an analog switch 25 to a primary filter formed by a circuit of a capacitor and a resistor. The output of the primary filter is amplified by the operational amplifier 26 and output to the voltage controlled oscillator 9. The phase comparator 7 and the voltage controlled oscillator 9 shown in FIG.
The phase comparator 7 and the voltage controlled oscillator 9 shown in FIG.

When the wobble signal disappears, the comparator 2
The output of 0 becomes L and the analog switch 25 is opened at this time. Then, the input voltage of the operational amplifier 26 is held at the charging voltage of the capacitor and the output of the operational amplifier 26 is fixed. That is, the output voltage of the low-pass filter 24 in FIG. 4 becomes constant, and a constant current is supplied to the spindle motor 14.

FIG. 6 shows waveforms of the output of the low-pass filter 24 and the output of the amplitude detecting circuit as A and B, respectively, at the time of track jump. While the output of the amplitude detection circuit is L, the output voltage of the low-pass filter 24 becomes constant, the spindle servo circuit is held, and the rotation of the spindle motor stabilizes. Therefore, the linear velocity of the signal recording track after the search should largely deviate from the target value. Will disappear and the track search can be performed quickly.

FIG. 7 shows the waveforms of the output signal of the bandpass filter 16 and the output signal of the comparator 20 at the time of track jump. No wobble signal is detected during track jump.

[0038]

According to the defect detecting circuit of the optical disk device of the present invention, the mirror surface defect is detected by detecting the presence or absence of the wobble signal, and the focus servo and the tracking servo are held by using the signal when the track search is not performed. By doing so, even during recording on an optical disc having a high reflectance, each servo can be passed through a scratch or dust area while being kept stable.

Further, according to the optical disk device of the present invention, the spindle servo is held by the signal detecting the mirror surface defect as described above during the period when there is no wobble signal at the time of track adjustment, and the rotation of the disk after the search is prevented. Since it is not disturbed, the spindle servo locks quickly and the track position information can be read. In this way, the time for track search can be shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing a defect detection circuit of an optical disc device according to an embodiment of the present invention.

FIG. 2 is a diagram showing signal waveforms of the circuit shown in FIG.

FIG. 3 is a diagram showing waveforms of a search signal and a tracking error signal at the time of searching the optical disk device.

FIG. 4 is a block diagram showing a spindle servo circuit of an optical disk device according to an embodiment of the present invention.

5 is a diagram showing details of a part of blocks shown in FIG. 4;

FIG. 6 is a diagram showing signal waveforms of the circuit shown in FIG.

FIG. 7 is a diagram showing signal waveforms of the circuit shown in FIG.

FIG. 8 is a circuit diagram showing an example of a conventional defect detection circuit.

FIG. 9 is a block diagram showing an example of a spindle servo circuit of a conventional optical disc device.

[Explanation of symbols]

 1 operational amplifier 2 operational amplifier 3 operational amplifier 4 comparator 5 amplifier 6 band pass filter 7 phase comparator 8 low pass filter 9 voltage controlled oscillator 10 frequency divider 11 CLV servo circuit 12 timing generator 13 power amplifier 14 spindle motor 15 differential amplifier 16 Band-pass filter 17 Rectifier 18 Low-pass filter 19 2/3 pic-hold circuit 20 Comparator 21 NOR gate 22 Analog switch 23 Amplitude detection circuit 24 Low-pass filter 25 Analog switch 26 Operational amplifier

Claims (2)

[Claims] 1. A wobble signal detection circuit for detecting the presence or absence of a wobble signal obtained from the waveform during recording or reproduction of an optical disc having a track groove with a waveform pre-groove, and a wobble signal from the wobble signal detection circuit. It is composed of a gate circuit that permits passage of a signal indicating that there is no signal, and by controlling the gate by a signal indicating that a track search is in progress, a defect signal is output when the wobble signal disappears except during track search. Defect detection circuit of the configured optical disk device. 2. The wobble signal detection circuit according to claim 1, wherein one of the signals flowing in the spindle servo loop is fixed to a signal immediately after the wobble signal disappears by a signal indicating that there is no wobble signal and the track is fixed. An optical disk device configured to keep the rotation speed of a spindle motor during a search substantially constant.