JPH09297925A - Tracking error signal detecting circuit and tracking servo circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable appropriate tracking by preventing detracking even if there is a mirror surface defect in an optical disk medium in an optical disk device. SOLUTION: A tracking error signal TE in which offset is canceled is detected by a tracking error detecting section 20 from light detecting signals A-D outputted from a photodetector 10. A tracking error signal TE is outputted to a tracking servo signal generation section 40 as it is when a RF signal is normally obtained based on a GFS signal indicating that a frame synchronizing signal is detected from a reproduced signal in a tracking error control section 30. When a normal RF signal is not obtained. The tracking error signal is outputted to tracking servo signal generation section 40 as it is when a RF is normally obtained based on a GFS signal indicating that a frame synchronizing signal is detected from a reproduced signal. When a normal signal is not obtained in the case of passing through mirror defect and the like, a signal of a level Vc indicating that tracking error does not exist substantially is outputted to the tracking servo signal generation section 40, a tracking coil 60 and a thread motor 80 are driven based on this output signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to, for example, an optical disk device for reproducing a compact disk (CD), and a tracking error signal detection circuit for performing tracking servo and a tracking error signal detection circuit for detecting the tracking error signal. And a tracking servo circuit that performs tracking servo based on the tracking error signal.

[0002]

2. Description of the Related Art In a tracking servo circuit of an optical disk device for reproducing a so-called optical disk such as a compact disk (CD), first, a tracking error signal is detected and amplified by a predetermined gain to generate a tracking servo signal. Then, the tracking coil is driven by performing phase compensation. In addition, the tracking servo signal is integrated to detect the direct current component, and the sled servo that moves the entire optical pickup in the disc system direction performs a seek operation and a track jump operation. I am able to follow.

By the way, if dust or black spots adhere to the reproducing surface of the optical disk recording medium, the tracking error signal cannot be detected properly, so that proper tracking servo cannot be applied and, in the worst case, detracking occurs. There is a possibility that it will end up. Therefore, when the head passes through such dust or black spots, a defect response circuit (hereinafter referred to as a defect circuit) that holds a tracking error signal is usually provided in the tracking servo circuit. ing.

The defect circuit is shown in FIG. 6 and FIG.
This will be described with reference to FIG. Figure 6 shows the defect circuit
FIG. 3 is a block diagram illustrating a configuration. FIG. 7 shows the communication of each part of FIG.
FIG. 3B is a diagram showing waveforms of signal No., FIG._RFof
Waveform diagram, (B) output of the defect amplifier 210
Signal S₁₁Waveform of Figure, (C) is the first bottom hole
Bottom hold signal S of the drive circuit 221₁₂Waveform and number
2 bottom hold circuit 222 bottom hold signal S
₁₃Of the waveform of the defect comparator 2 shown in FIG.
Defect detection signal S which is the output of 23 ₁₄Shows the waveform of
FIG.

In the defect circuit 200 shown in FIG. 6, first, an input RF signal S _RF as shown in FIG. 7A is amplified by a defect amplifier 210 and inverted, and then shown in FIG. 7B. Such a signal S ₁₁ is generated. This signal S
_A bottom hold is applied to ₁₁ to detect a defect.
At that time, two types of bottom hold are applied by the first bottom hold circuit 221 and the second bottom hold circuit 222. The first bottom hold circuit 221 is a circuit that performs a bottom hold with a fast time constant, that is, a short response, and generates a signal that quickly follows a defect. The second bottom hold circuit 222 has a slow time constant, that is, A bottom-holding circuit with a long response generates a signal that responds slowly to a defect. The bottom hold signals S ₁₂ , S ₁₃ generated respectively are shown in FIG. 7 (C).

Then, those bottom hold signals S ₁₂
And S ₁₃ are compared by the defect comparator 223,
When the difference between them is greater than or equal to a predetermined value, the defect detection signal S ₁₄ as shown in FIG. 7D is output. By holding the tracking error signal while the defect detection signal S ₁₄ is being output, it is possible to prevent the above-mentioned disturbance of the tracking error signal due to dust or the like, and to perform appropriate tracking servo.

[0007]

However, in the defect circuit as described above, the level of the RF signal reproduced from the disc becomes low as shown by a and a'in FIG. 7 (A). RF is effective against various defects
It is impossible to deal with a defect in which a signal is disturbed and output, and a proper modulated signal cannot be obtained. Therefore, when such an RF signal passes through a mirror surface defect to be reproduced, tracking servo is applied according to the disturbed tracking error signal, and in a severe case, detracking occurs. As a result, for example, sound skipping occurs during reproduction of a music CD, and proper reproduction of recorded data cannot be performed. Therefore, improvement is desired.

Therefore, an object of the present invention is to output a tracking error signal capable of preventing detracking and performing proper tracking even if the optical disk medium has a mirror surface defect, including the above-mentioned defects. It is to provide a tracking error signal detection circuit for Another object of the present invention is to provide a tracking servo circuit capable of preventing detracking and performing appropriate tracking even if the optical disk medium has a mirror surface defect, thereby realizing an optical disk device having excellent playability. To provide.

[0009]

In order to solve the above-mentioned problems, by using a signal generated based on reproduction data obtained from an optical disk as a control signal for holding a tracking error signal, optical disk recording When the signal obtained from the medium is greatly disturbed, that is,
The tracking error signal can be held appropriately when passing through a mirror surface defect. In particular, the tracking error signal is held based on the signal indicating the detection of the frame synchronization signal in the reproduction data.

Therefore, the tracking error signal detection circuit of the present invention detects the reflected light of the light beam applied to the optical disk and generates a tracking error signal, and a reproduction RF signal obtained from the optical disk. When the signal is appropriately detected based on the signal generated by detecting the predetermined reproduction data of, the generated tracking error signal is output as it is, and the signal is not properly detected. And an error signal control circuit for holding the tracking error signal at a predetermined value and outputting the signal (normally, a signal indicating that the tracking error is substantially 0).

Preferably, the error signal control circuit detects the frame synchronization signal based on a signal generated by detecting the frame synchronization signal of the reproduction data obtained from the reproduction RF signal from the optical disk. Outputs the generated tracking error signal as it is, and outputs a signal indicating that the tracking error is substantially 0 when the frame synchronization signal cannot be detected.

Further preferably, the error signal control circuit presets a signal indicating that the tracking error is substantially zero each time a signal indicating that the frame synchronization signal has not been detected is input. Output for a predetermined period. Specifically, the period is approximately 1 msec.

Further, the tracking servo circuit of the present invention detects the reflected light of the light beam applied to the disk-shaped recording medium and generates a tracking error signal, and a tracking error signal generation circuit which is obtained from the disk-shaped recording medium. When a predetermined signal is detected from the reproduced signal, the generated tracking error signal is output as an error signal for tracking servo, and when the predetermined signal is not detected, a tracking error is substantially generated. An error signal control circuit that outputs a signal indicating that is 0 as the tracking servo error signal, and a servo signal generation circuit that generates a tracking servo signal based on the output tracking servo error signal. A tracking actuator is generated based on the generated tracking servo signal. And an actuator drive means for driving the Yueta.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. In the present embodiment, a tracking servo circuit applied to an optical disc device that processes a compact disc (CD) will be described. FIG. 1 is a block diagram showing the configuration of the tracking servo circuit. The tracking servo circuit 1 includes a photodetector 10, a tracking error detector 20, a tracking error controller 30, a tracking servo signal generator 40, a tracking coil drive amplifier 50,
It has a tracking coil 60, a sled motor drive amplifier 70, and a sled motor 80.

In this embodiment, the tracking error is detected by the push-pull method using the light beam of one spot. The push-pull method utilizes the fact that the intensity distribution of light diffracted and reflected by a pit or guide groove and then entering the objective lens again changes depending on the relative positions of the pit or guide groove and the spot. This is a method in which light is received by a photodetector that is divided into a plurality of pieces, and a tracking error is obtained based on the difference in the amount of light received by each photodetector.

Hereinafter, the configuration of each unit will be described. The photodetector 10 is provided in the optical pickup (OP), detects the light diffracted / reflected by the recording medium, and outputs the photodetection signals A to D corresponding to the amount of the light. The photodetector 10 according to the present embodiment has four photodetectors P.
D-A to PD-D are four-division photo detectors arranged as shown. Four photo detectors PD-A to PD
-D, two photo detectors PD-A and PD-B detect the first-order diffracted light reflected on the left side of the data track, and the remaining two photo detectors PD-C and PD-D are on the right side of the data track. The reflected -1st order diffracted light is detected.

The tracking error detector 20 is a circuit for detecting the tracking error signal TE with the offset canceled based on the photodetection signals A to D output from the photodetector 10. In this embodiment, this tracking error signal is detected by the TPP (Top hold Push-Pull) method.

The TPP method will be described with reference to FIG. FIG. 2 is an RF envelope waveform of the first-order diffracted light signal L. In FIG. 2, a waveform P is a peak of the first-order diffracted light signal L, a signal S is a signal obtained by passing an RF envelope used for tracking by a push-pull method through an LPF (low-pass filter), and a signal Q is an offset of the signal S. It is a waveform showing a change. In order to cancel the offset due to the lens shift or the disk skew, the offset change q may be subtracted from the signal S. That is, q
When a coefficient K _t (K _t <1) such that = K _t × p is determined, the offset canceled signal is represented by S−K _t × p. Therefore, the offset value can be obtained by obtaining the peak change p.

FIG. 3 shows the configuration of the tracking error detector 20 for obtaining the tracking error signal TE by the TPP method. The tracking error detector 20 is
First adder 21, first top-hold circuit 22, first coefficient multiplier 23, first subtractor 24, second adder 25, second top-hold circuit 26, second coefficient multiplication And a second subtractor 28 and a third subtractor 29.

The first adder 21 has a photodetector P.
The output signal A from D-A and the output signal B from the photodetector PD-B are added to generate a first-order diffracted light signal L (= A + B) corresponding to the total light amount of the first-order diffracted light. The first top hold circuit 22 detects and holds the top value Lp of the first-order diffracted light signal L generated by the first adder 21. The first coefficient multiplier 23 includes a first top hold circuit 22.
The top value Lp detected and held at is multiplied by a coefficient K _t ,
An offset signal for the first-order diffracted light signal L is obtained. Then, in the first subtractor 24, the input offset value is used as the first-order diffracted light signal L that is further sequentially input.
By further reducing the offset, an output signal corresponding to the light amount of the first-order diffracted light whose offset has been canceled can be obtained.

Similarly, the second adder 25 includes an output signal C from the photodetector PD-C and a photodetector P.
The output signal D from D-D is added to generate a -1st order diffracted light signal R (= C + D) corresponding to the light amount of all -1st order diffracted light. The second top-hold circuit 26 detects and holds the top value Rp of the minus first-order diffracted light signal R, and the second coefficient multiplier 27 multiplies the top value Rp by the coefficient K _t to obtain the minus first-order diffracted light. An offset signal for signal R is determined. Then, in the second subtractor 28, the offset value is subtracted from the −1st-order diffracted light signal R that is sequentially input to obtain an output signal corresponding to the light amount of the −1st-order diffracted light with the offset canceled. Then, in the third subtractor 29, the output signal corresponding to the light amount of the offset canceled first-order diffracted light input from the first subtractor 24 and the offset cancellation input from the second subtractor 28. A difference from the output signal corresponding to the light amount of the −1st order diffracted light thus obtained is obtained and output to the tracking error control unit 30 as a tracking error signal TE.

The tracking error control unit 30 outputs the tracking error signal TE detected by the tracking error detection unit 20 to the tracking servo of the tracking servo based on the GFS signal input from a signal processing circuit (not shown) usually used in the optical disk device. It is output to the tracking servo signal generation unit 40 as a control amount, or the tracking error signal TE detected by the tracking error detection unit 20.
Is disabled and a signal indicating that there is substantially no error is output to the tracking servo signal generation unit 40 or is controlled. Here, the GFS signal is a signal which is usually used in the optical disc device to obtain the reproduction data of a predetermined format from the reproduction bit data and which indicates whether or not the frame synchronization signal is detected. Specifically, GF
S signal is Hi while the frame synchronization signal is being obtained correctly.
gh, and Lo when the frame synchronization signal cannot be obtained
It is a signal that becomes w. That is, the GFS signal becomes Low when the RF signal is disturbed when it passes through a mirror surface defect or the like.

FIG. 4 shows a concrete circuit example of the tracking error control section 30, and FIG. 5 shows signal waveforms of each section. FIG.
As shown in FIG.
Switch 31, a control signal output circuit 32, and a second switch 33. The first switch 31 switches whether to enable the tracking error control unit 30 according to the input recording / reproduction identification signal R / W. The recording / reproduction identification signal R / W becomes Low at the time of data reproduction and becomes High at the time of data recording. Therefore, at the time of data reproduction, the second switch 33, which will be described later, operates as the first switch 32.
Is switched by the output of, that is, the tracking error control unit 30 becomes effective. Since the switching signal of the second switch 33 is always Low at the time of data recording, the tracking error control unit 30 becomes invalid. When the tracking error control unit 30 is invalid, the tracking error signal TE input to the tracking error control unit 30 is output to the tracking servo signal generation unit 40.

The control signal output circuit 32 detects the trailing edge of the input GFS signal, generates a one-shot trigger having a predetermined pulse width from the trailing edge, and applies it to the second switch 33 as an error switching signal S. To do. For example, when the RF signal as shown in FIG. 5A is obtained from the optical disc, the GFS signal as shown in FIG. 5B is input to the control signal output circuit 32. In the control signal output circuit 32, as shown in FIG. 5C, the error switching signal S is output for 1 msec after the fall.

The second switch 33 outputs the tracking error signal TE input to the tracking servo signal generator 40 based on the error switching signal S input from the control signal output circuit 32, or the tracking error signal TE. It is selected whether to invalidate the signal TE and output a signal indicating that there is substantially no error. That is, when the error switching signal S is Low, the output error signal TE 'is a signal based on the input tracking error signal TE, and when the error switching signal S is High, the second switch 3
3 becomes conductive and the output error signal TE 'is maintained at a predetermined level Vc. When the signal as shown in FIG. 5 is input, the output error signal TE ′ as shown in FIG. 5D is output from the tracking error control unit 30 to the tracking servo signal generation unit 40.

The tracking servo signal generation section 40 applies a predetermined gain to the error signal TE 'input from the tracking error control section 30 and further performs phase compensation to actually perform tracking servo. The servo signal TS and the sled servo signal SS are generated. Tracking coil drive amplifier 5
0 increases the current of the tracking servo signal TS output from the tracking servo signal generation unit 40 to actually drive the tracking coil 60, generates a tracking coil drive signal TD, and applies the tracking coil drive signal TD to the tracking coil 60. Thread motor drive Ambu 70
Applies a current to the sled motor 80 to drive the sled motor 80, generates a sled motor drive signal SD, and applies the sled motor drive signal SD to the sled motor 80.

The operation of the tracking servo circuit 1 will be summarized based on the configuration of each unit described above. First, based on the photodetection signals A to D output from the photodetector 10, the offset cancellation in the tracking error detection unit 20 is performed. Tracking error signal TE
Is detected. The obtained tracking error signal TE,
GF obtained based on the reproduction RF signal from the optical disc
Based on the S signal, the tracking error control unit 30 determines an error signal TE ′ to be output to the tracking servo signal generation unit 40 as a tracking servo control amount. That is, when the RF signal is normally obtained, the tracking error signal TE obtained by the tracking error detection unit 20 is output to the tracking servo signal generation unit 40 as it is, and a normal RF signal is obtained when passing through a mirror surface defect or the like. When not obtained, a signal of level Vc indicating that there is substantially no tracking error is output to the tracking servo signal generation unit 40.

Based on the error signal TE ', the tracking servo signal generator 40 determines the tracking servo signal TS and the sled servo signal SS, which are the manipulated variables for the tracking coil 60 and the sled motor 80. Then, the tracking servo signal TS
The current is amplified in the tracking coil drive amplifier 50 and applied to the tracking coil 60 to actually drive the tracking coil 60. The sled servo signal SS is current-amplified in the sled motor drive amp 70 and applied to the sled motor 80 to actually drive the sled motor 80.

As described above, according to the tracking servo circuit 1 of the present embodiment, the GFS indicating whether or not the frame sync signal is detected from the reproduction RF signal when passing through the mirror surface defect.
Since it is detected by the signal, no matter what RF signal is output depending on the state of the defect, if the RF signal is abnormal, the passage of the mirror surface defect can be immediately detected. At that time, since the tracking error signal is held at the level of error 0 for a predetermined period,
It is possible to prevent detracking due to the tracking servo being disturbed by the tracking error. If detracking is not performed, proper reproduction can be maintained by error correction, etc., so that it is possible to configure an optical disc device with excellent playability that can properly reproduce recorded data even if there is a mirror surface defect.

The present invention is not limited to the present embodiment, and various modifications are possible. For example, in the present embodiment, the disturbance of the RF signal is detected using the GFS signal indicating whether or not the frame synchronization signal is detected. However, a signal indicating detection of a signal other than this synchronization signal is detected. It may be used to detect the disturbance of the RF signal.

Further, as the tracking error detecting method, the push-pull method using the light beam of one spot is used in the present embodiment, but other methods may be used. For example, a three-spot method or the like may be used in which the amounts of reflected light from two sub-beams arranged with the main beam in between are compared. In addition, the method of detecting the tracking error signal TE, the configuration of the tracking actuator, the sled actuator, and the like are arbitrary.

[0032]

As described above, according to the present invention,
It is possible to provide a tracking error signal detection circuit that outputs a tracking error signal that can prevent detracking and perform appropriate tracking even if an optical disk medium has a mirror surface defect. Further, it is possible to provide a tracking servo circuit capable of preventing detracking and performing appropriate tracking even if the optical disc medium has a mirror surface defect, and thereby realizing an optical disc device having excellent playability.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a tracking servo circuit according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a tracking error detection method performed by a tracking error detection unit of the tracking servo circuit shown in FIG.
It is a figure which shows an F envelope waveform.

3 is a block diagram showing a configuration of a tracking error detection unit of the tracking servo circuit shown in FIG.

4 is a diagram showing a specific circuit example of a tracking error control unit of the tracking servo circuit shown in FIG.

5A and 5B are diagrams showing signal waveforms of respective parts in the circuit of the tracking error control unit shown in FIG. 4, where FIG. 5A is a diagram showing a waveform of a reproduction RF signal, and FIG. 5B is a diagram showing a waveform of a GFS signal. , (C) are diagrams showing the waveform of the error switching signal S,
(D) is a diagram showing a waveform of the output error signal TE '.

FIG. 6 is a circuit diagram showing a configuration of a defect handling circuit provided in a conventional tracking servo circuit.

7 is a diagram showing a signal waveform of each part shown in FIG. 6,
(A) is a diagram showing the waveform of the input RF signal S _RF , (B) is a diagram showing the waveform of the output signal S ₁₁ of the defect amplifier, (C)
Is the bottom hold signal S ₁₂ of the first bottom hold circuit.
And a waveform of the bottom hold signal S ₁₃ of the second bottom hold circuit, and (D) is a diagram showing the waveform of the defect detection signal S ₁₄ which is the output of the defect comparator.

[Explanation of symbols]

1 ... Tracking servo processing circuit, 10 ... Photo detector, 20 ... Tracking error detection unit 21, 25 ...
Adder, 22, 26 ... Top hold circuit, 23, 27
... coefficient multiplier, 24, 28, 29 ... subtractor, 30 ... tracking error control section, 31 ... first switch, 32 ...
Control signal output circuit, 33 ... Second switch, 40 ... Tracking servo signal generator, 50 ... Tracking coil drive amp, 60 ... Tracking coil, 70 ... Sled motor drive amp, 80 ... Sled motor

Claims (5)

[Claims] 1. A tracking error signal generation circuit for detecting a reflected light of a light beam applied to a disc-shaped recording medium and generating a tracking error signal, and a predetermined signal from a reproduction signal obtained from the disc-shaped recording medium. If the tracking error signal is detected, the generated tracking error signal is output as an error signal for tracking servo, and if the predetermined signal is not detected, a signal indicating that the tracking error is substantially 0 is output. A tracking error signal detection circuit having an error signal control circuit that outputs the error signal for the tracking servo. 2. The tracking error signal detection circuit according to claim 1, wherein the error signal control circuit controls the output of the error signal for the tracking servo depending on whether or not a frame synchronization signal is detected from the reproduction signal. . 3. The error signal control circuit outputs a signal indicating that the tracking error is substantially zero for a predetermined period after a signal indicating that the frame synchronization signal has not been detected is input. The tracking error signal detection circuit according to claim 2, wherein the tracking error signal detection circuit outputs the tracking servo error signal. 4. The tracking error signal detection circuit according to claim 3, wherein the period is approximately 1 msec. 5. A tracking error signal generating circuit for detecting a reflected light of a light beam applied to a disc-shaped recording medium and generating a tracking error signal, and a predetermined signal from a reproduction signal obtained from the disc-shaped recording medium. If the tracking error signal is detected, the generated tracking error signal is output as an error signal for tracking servo, and if the predetermined signal is not detected, a signal indicating that the tracking error is substantially 0 is output. An error signal control circuit that outputs an error signal for the tracking servo, a servo signal generation circuit that generates a tracking servo signal based on the output error signal for the tracking servo, and a tracking servo signal that is generated. Actuator driver that drives the tracking actuator based on Tracking servo circuit and a blanking means.