JPH1196655A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk device strong against the level fluctuation of a reproducing RF signal and capable of preventing erroneous defect detection, by detecting a defect based on the level fluctuation of the reproducing RF signal read from an optical disk, inputting the reproducing RF signal, comparing this with the output signal of a low-pass filter and masking a detecting operation based on the output signal of a comparator. SOLUTION: A defect detecting circuit 20 supplies a reproducing RF signal passed through a high-pass filter HPF 1 to a short-time constant low-pass filter LPF 11 composed of a resistor R11 and a capacitor C11 and a long-time constant low-pass filter LPF 12 composed of a resistor 12 and a capacitor C12. The output signal of the low-pass filter LPF 11 is supplied to the inversion input terminal of a comparator 6, and the output signal RFLL of the low-pass filter LPF 12 is supplied to the non-inversion input terminal of the comparator 6. In the comparator 6, these signals RFLS and RFLL are compared with each other to obtain a mask signal MS.

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 capable of detecting at least a defect on an optical disk.

[0002]

2. Description of the Related Art Conventionally, a so-called compact disc (CD) has been known as an optical disc. In an optical disk device for reproducing such an optical disk, a tracking servo using a tracking error signal is applied in order to accurately follow a track on the optical disk.

Further, in the conventional optical disk apparatus, the reproduction of the optical disk is prevented so that the tracking servo does not malfunction due to scratches, dust, dirt, etc. existing on the optical disk (hereinafter, collectively referred to as scratches). A level variation of the RF signal is detected, and a tracking error signal when the level variation is detected is not used for tracking servo. That is, as shown in FIG. 4, in the conventional optical disk device, a reproduction RF signal of the optical disk shown in FIG. 4A is passed through a low-pass filter (LPF) as shown in FIG. By comparing with the TL, a level variation Di corresponding to a flaw is detected from the reproduced RF signal, and further, a defect signal as shown in FIG. The tracking error signal corresponding to the portion where the signal has risen (the portion where the level variation exists) is not used for the tracking servo. Note that finding a flaw on the optical disk by detecting the level fluctuation of the reproduced RF signal is called defect detection or interruption detection.

FIG. 5 shows a specific configuration of a defect detection circuit 120 of a conventional optical disk device that detects a flaw using the reproduced RF signal as described above and generates a defect signal.

A reproduction signal from an optical pickup (not shown) is supplied to the RF amplifier 100 and the RF amplifier 1
From 00, a tracking error signal TE and a reproduction RF signal RFO are output. The tracking error signal T
E is sent to a DSP (Digital Signal Processor) 110 as a servo circuit via a low-pass filter LPF 102 including a resistor R103 and a capacitor C103.

The reproduction R from the RF amplifier 100
The F signal RFO is supplied via a terminal 103 to a DS for signal processing.
P and the like, and also to the defect detection circuit 120.

[0007] The reproduction RF signal RFO input to the defect detection circuit 120 passes through a high-pass filter HPF100 including a capacitor C101 and a resistor R101, and then passes through a low-pass filter LPF101 including a resistor R102 and a capacitor C102. The output signal RFL from the low-pass filter LPF 101 is sent to the non-inverting input terminal of the comparator 105.

A comparator voltage (the predetermined threshold level TL) generated by the series resistors R104 and R105 is connected to an inverting input terminal of the comparator 105.
Is supplied. Therefore, the comparator 10
5, the output signal RFL of the low-pass filter LPF101 and the comparison voltage (threshold level T
L). The output from the comparator 105 becomes the defect signal DF. The defect signal DF is generated when the optical disk is damaged and the output signal RFL of the low-pass filter LPF 101 exceeds a predetermined comparator voltage (threshold level TL).
It is a signal that goes to H level and goes to L level when it does not exceed it.

The defect signal DF is generated by the DSP
The switching control signal of the transistor TR102 for switching the tracking error signal TE sent to 110 is provided. Therefore, when the defect signal DF becomes "H" level due to the presence of a scratch on the optical disk (when the defect signal rises),
The tracking error signal TE is not supplied to the DSP 110. More specifically, when the defect signal DF becomes "H" level, the transistor TR102 is turned on and the tracking error signal TE is set to 0 level (or a predetermined level). This is performed based on the value immediately before the defect signal rises. The optical disk apparatus thus prevents the tracking servo from malfunctioning due to the scratches present on the optical disk. However, the above defect signal DF
Since the tracking servo is not working properly while the signal is at the "H" level, detracking (tracking off) may occur.

The defect detection circuit 1 shown in FIG.
20 includes a transistor T for switching the output signal RFL from the low-pass filter LPF101.
A signal for controlling R101 is supplied from a terminal 104. The switching control signal of the transistor TR101 is a signal that becomes “H” level when the optical pickup performs an access such as seeking on the optical disk, and becomes “L” level during reproduction (during play) of the optical disk. The defect detection circuit 120 operates only when the switching control signal is at "L" level.

[0011]

As the level fluctuations occurring on the reproduced RF signal due to the scratches on the optical disk, not only the level fluctuations Di as shown in FIG. There is also a level fluctuation Db as shown in FIG. The level fluctuation Db shown in FIG.
Scratches with extremely low reflectivity are caused by scratches with extremely low reflectivity, and scratches with extremely low reflectivity are called black dot scratches.

As shown in FIG. 6A, the level fluctuation Db generated due to the black dot scratches is caused by the reproduction R
The level of the F signal fluctuates downward. Therefore, the reproduced RF signal shown in FIG.
The output signal RFL of the low-pass filter LPF 101 when supplied to the defect detection circuit 120 is basically a level lower than a predetermined threshold level TL (compare voltage) as shown in FIG. Therefore, the defect signal should remain at "L" as shown in FIG.

However, if there is the above-mentioned black dot scratch,
Tracking during this period is often lost, and when tracking is lost due to black dot flaws, detracking is often performed for a short time immediately after passing through the black dot flaw. As described above, when detracking occurs immediately after a black dot flaw, the level of the reproduced RF signal immediately after the black dot flaw rises as shown by Dbu in FIG. 6D.

Thus, the reproduction R immediately after the black dot scratch
When the lower level of the F signal rises, the above-mentioned FIG.
Low-pass filter LP of the defect detection circuit 120
The output signal RFL of F101 also rises upward as indicated by Lu in FIG. 6 (e), which may exceed the threshold level TL (compare voltage).

That is, the defect detection circuit 120 shown in FIG. 5 erroneously detects a defect in the detrack portion immediately after the black dot flaw even though the flaw is not originally present. As a result, a defect signal is generated as shown in FIG.

As described above, in the conventional optical disk apparatus, the detection of the level fluctuation Di of the reproduced RF signal caused by the scratch in the example of FIG.
Defects can be detected based on the output level of F101, and the swell L of the output signal RFL of the low-pass filter LPF101 immediately after black dot damage in the example of FIG.
In order to prevent erroneous detection of defects by u,
The value of the predetermined threshold level TL (compare voltage) is set. This means that the range that can be detected at the above-mentioned predetermined threshold level TL is very narrow, and as a result, the level is weak against fluctuations in the level of the reproduced RF signal and the number of malfunctions increases.

Accordingly, the present invention has been made in view of such circumstances, and has as its object to provide an optical disk apparatus which is strong against fluctuations in the level of a reproduced RF signal and can prevent erroneous defect detection. .

[0018]

SUMMARY OF THE INVENTION The present invention relates to a defect detecting means for detecting a defect based on a level change of a reproduction RF signal read from an optical disk, and a reproduction RF signal.
A first low-pass filter having a short time constant and a second low-pass filter having a long time constant to which signals are input, a comparator for comparing output signals of the second and third low-pass filters, and a signal output from the comparator. And a masking means for masking the detecting operation by the defect detecting means.

That is, according to the present invention, when detecting a defect based on a level change of a reproduction RF signal read from an optical disk, the reproduction RF signal is divided into a first low-pass filter having a short time constant and a second low-pass filter having a long time constant. These output signals are compared with each other through a low-pass filter, and the defect detection operation is masked based on the comparison output signal so that a malfunction does not occur with respect to the level fluctuation of the reproduction RF signal.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

An optical disk device according to an embodiment of the present invention comprises:
When detecting a portion (level fluctuation) corresponding to the above-mentioned scratches such as scratches, dust, and dirt on the optical disk from, for example, a reproduced RF signal as shown in FIG. 1A, FIG. As shown in FIG. 1, a signal obtained by passing the reproduced RF signal through a low-pass filter having a long time constant and a low-pass filter having a short time constant, and comparing the output signals RFLL and RFLS of the low-pass filters (the mask of (c) in FIG. 1). Signal MS) masks the output signal RFL of the original low-pass filter for defect detection, thereby reproducing the RF signal.
It is strong against signal level fluctuations and prevents erroneous detection.

FIG. 2 shows a specific configuration of the defect detection circuit 20 of the optical disk device according to the embodiment of the present invention.

A reproduction signal from an optical pickup (not shown) is supplied to the RF amplifier 10 and the RF amplifier 10
From the tracking error signal TE and the reproduction RF signal RF
O and the like are output. The tracking error signal TE is sent to a DSP (digital signal processor) 11 as a servo circuit via a low-pass filter LPF2 including a resistor R3 and a capacitor C3.

The reproduced RF from the RF amplifier 10
The signal RFO is sent to a signal processing DSP or the like via the terminal 3 and is also sent to the defect detection circuit 20.

The reproduced RF signal RFO input to the defect detection circuit 20 includes a capacitor C1 and a resistor R1.
After passing through a high-pass filter HPF1 composed of a low-pass filter LP composed of a resistor R2 and a capacitor C2.
Go through F1. The output signal RFL from the low-pass filter LPF1 is sent to the non-inverting input terminal of the comparator 5.

The inverting input terminal of the comparator 5 has
A comparator voltage (predetermined threshold level TL) generated by the series resistors R4 and R5 is supplied. Therefore, the comparator 5 compares the output signal RFL of the low-pass filter LPF1 with the comparator voltage (threshold level TL). The output from the comparator 5 becomes the defect signal DF. The defect signal DF becomes "H" level when the output signal RFL of the low-pass filter LPF1 exceeds a predetermined comparator voltage (threshold level TL) due to a scratch on the optical disk, and becomes "L" level when the output signal RFL does not exceed the comparator voltage. This is the signal.

The defect signal DF is generated by the DSP
The switching control signal is a switching control signal for the transistor TR2 for switching the tracking error signal TE sent to the reference numeral 11. Therefore, when the defect signal DF becomes “H” level due to the presence of a scratch on the optical disk (when the defect signal rises),
The tracking error signal TE is not supplied to SP11. More specifically, the defect signal D
When F becomes “H” level, the transistor TR
2 turns on, and the tracking error signal TE is set to the 0 level (or a predetermined level).
In this case, the tracking servo is performed based on the value immediately before the defect signal rises. The optical disk device of the present embodiment thus prevents the tracking servo from malfunctioning due to the scratches present on the optical disk. However, the defect signal DF is "H".
While the level is at the level, the tracking servo is not working properly, so that detracking (out of tracking) may occur.

Here, the reproduction R from the RF amplifier 10
The F signal RFO has a level fluctuation Db caused by a black dot flaw as shown in FIG. 3A and a signal whose lower level rises as shown by Dbu in the figure immediately after the black dot flaw. In FIG. 3B,
As shown in the figure, the output signal R of the low-pass filter LPF1 is
In the FL, an upward swelling of the level indicated by Lu in the figure occurs, and the level exceeds the threshold level TL (compare voltage). This low pass filter LPF
If the output signal RFL of 1 is supplied to the comparator 5 as it is, an erroneous defect signal will rise as in the configuration of the conventional example described above.

The defect detection circuit 20 of this embodiment shown in FIG. 2 has the following configuration to prevent such a situation.

That is, in the defect detection circuit 20 of the optical disk device of the present embodiment, the reproduced RF signal passed through the high-pass filter HPF1 is converted into a short-time constant low-pass filter LPF11 composed of a resistor R11 and a capacitor C11, and a resistor R12 and a resistor R12. It is also supplied to a long time constant low-pass filter LPF12 composed of a capacitor C12. Here, the low-pass filter LP
The time constant of F11 should be sufficiently delayed from the level fluctuation Db due to the black dot flaw, and the time constant of low-pass filter LPF12 should be R
It is set to follow the F level fluctuation. Since the low-pass filter LPF11 has a short time constant, its output signal is as shown by RFLS in FIG. 3C.
Further, since the low-pass filter LPF12 has a long time constant, the output signal thereof is as shown by RFLL in the diagram of FIG. 3C.

The output signal RFLS of the low-pass filter LPF11 is supplied to the inverting input terminal of the comparator 6, and the output signal RFLL of the low-pass filter LPF12 is supplied to the non-inverting input terminal of the comparator 6. The comparator 6 outputs these signals RFLS and RFLL. Are compared. As a result, a mask signal MS as shown by MS in FIG. 3D is obtained from the comparator 6.

The mask signal MS from the comparator 6
Is a low-pass filter L sent to the comparator 5
This is a switching control signal for the transistor TR3 for switching the output signal RFL of the PF1. Therefore, when the mask signal MS is at "H" level, the transistor TR3 is turned on, and the low-pass filter LPF is connected to the non-inverting input terminal of the comparator 5.
No output signal RFL will be supplied. In other words, while the mask signal MS is at the "H" level, the output signal RFL of the low-pass filter LPF1 is at the 0 level (or a predetermined low level). Even if an upward swell as shown by Lu in the figure b) occurs, the comparator 5 supplies the swell portion Lu of the output signal RFL of the low-pass filter LPF1 to the comparator 5.
Is not supplied, so that an erroneous defect signal can be prevented from rising from the comparator 5 as described above. The defect signal at this time is as shown in FIG.

Further, according to the present embodiment, there is no possibility of erroneously detecting an upwardly rising level as indicated by Lu in FIG. 3B from the above description. , The predetermined threshold level TL (compare voltage) can be made lower than the level limited by the upwardly rising portion Lu, and
The detection level (threshold level TL) of the output signal RFL of the low-pass filter LPF1 similar to that shown in FIG. 4B can be reduced, and as a result, the level of the reproduced RF signal is strong and the malfunction is reduced.

The defect detection circuit 2 shown in FIG.
To 0, a signal for controlling the transistor TR1 for switching the output signal RFL from the low-pass filter LPF1 is supplied from the terminal 4. The switching control signal of the transistor TR1 is a signal that becomes “H” level when the optical pickup performs an access such as seeking on the optical disk, and becomes “L” level during reproduction of the optical disk (during play). The defect detection circuit 20 operates only when the switching control signal is at "L" level.

As described above, according to the present embodiment,
A level variation Db occurs in the reproduced RF signal due to the black dot flaw as shown in FIG. 3A, and the lower level of the reproduced RF signal immediately after the black dot flaw is D in the figure.
Even if it is lifted as shown by bu, a defect signal is not erroneously raised as shown in FIG. 3E, and the level of defect detection can be widened. An optical disk device that is strong against signal level fluctuation and does not cause erroneous defect detection is realized.

[0036]

As is apparent from the above description, according to the present invention, when detecting a defect based on the level fluctuation of the reproduction RF signal read from the optical disk, the reproduction RF signal is converted to the first low-pass signal having a short time constant. These output signals are compared with each other through a filter and a second low-pass filter having a long time constant, and the defect detection operation is masked based on the comparison output signal. Erroneous defect detection can be prevented.

[Brief description of the drawings]

FIG. 1 is a waveform chart used for describing a basic operation of an optical disc device according to an embodiment of the present invention.

FIG. 2 is a block circuit diagram illustrating a schematic configuration of a defect detection circuit that is a main part of the optical disc device according to the present embodiment.

FIG. 3 is a waveform diagram used for describing a specific operation of the optical disc device according to the embodiment of the present invention.

FIG. 4 is a waveform chart used for explaining a basic operation of a conventional optical disc device.

FIG. 5 is a block circuit diagram showing a schematic configuration of a defect detection circuit which is a main part of a conventional optical disk device.

FIG. 6 is a waveform diagram used to explain a defect of a conventional optical disk device.

[Explanation of symbols]

5, 6 Comparator, 10 RF amplifier, 11
DSP, LPF1, LPF2, LPF11, LPF1
2 Low-pass filter, TR1, TR2, TR3 transistor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 20/18 572 G11B 20/18 572F

Claims (5)

[Claims] 1. A defect detection means for detecting a defect based on a level change of a reproduction RF signal read from an optical disk; a first low-pass filter having a short time constant to which the reproduction RF signal is input; A second low-pass filter having a long time constant to be inputted, a comparator for comparing an output signal of the first low-pass filter with an output signal of the second low-pass filter, and the defect detection means based on an output signal of the comparator An optical disk device, comprising: a mask means for masking a detection operation in the optical disk. 2. The apparatus according to claim 1, wherein said defect detecting means includes a low-pass filter to which said reproduced RF signal is inputted, and a comparator for comparing an output signal of said low-pass filter with a predetermined threshold level. Item 2. The optical disk device according to item 1. 3. The time constant of the first low-pass filter is a time constant that is sufficiently delayed from the duration of the level change of the reproduction RF signal, which is caused by a black dot flaw on the optical disk. 2. The optical disc apparatus according to claim 1, wherein the time constant of the second low-pass filter is a time constant that can follow a level fluctuation of a reproduction RF signal in a rotation cycle of the optical disc. 4. The optical disk apparatus according to claim 2, wherein the predetermined threshold level is lower than a level of a reproduction RF signal generated due to a black dot flaw on the optical disk. 5. The apparatus according to claim 2, wherein said masking means includes switching means for switching an output signal of a low-pass filter of said defect detecting means.
An optical disk device as described in the above.