JPH0830987A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide a stable and antidefect servo system by providing it with a defect detecting circuit having high sensitivity without being influenced by a wobbly surface of a disk and a variation in the reflectance of the disk, etc. CONSTITUTION:A low band component of an RF signal obtained by photoelectrically converting a reflected light quantity from the disk is extracted by an LPF 13. This low band component is compared with the RF signal by a comparing circuit 14 to generate a defect signal. A low band component is extracted by an LPF 15 from an FE signal showing a focus position error from the disk and a pickup unit. This low band component is compared with the FE signal by a window comparator 16 to generate a defect signal. When either the defect signal generated from the RF signal or the defect signal generated from the FE signal is outputted, a gain of the servo system is changed by an OR circuit 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus, and more specifically, it is stable and has a defect by a highly sensitive defect detection circuit without being affected by surface wobbling or fluctuation of reflectance of a disc. The present invention relates to an optical recording / reproducing device which realizes a strong servo system. For example, C
It is applied to a D-R, a CD-MO, a CD-ROM and the like.

[0002]

2. Description of the Related Art As a known document describing a conventional optical disk reproducing apparatus, for example, Japanese Patent Laid-Open No. 4-1987.
There is publication No. 1. In order to prevent malfunction due to defects (defects) such as scratches and stains existing on the optical disc, the one disclosed in this publication outputs the activation detection signal by detecting the activation state of the drive means for rotationally driving the optical disc. Based on the activation detection signal, a defect existing on the recording surface is detected during the activation state of the drive means, and an operation of performing defect processing based on the defect detection signal is prohibited.

In Japanese Patent Laid-Open No. 3-183030, a scratch / shock judgment circuit outputs a first judgment signal in the case of a scratch on the disk and a second judgment signal in the case of an external shock. A signal is output, and the gain of the tracking servo control is arbitrarily changed by the gain variable circuit based on the first and second determination signals, so that it is strong against both scratches on the disk and external impact, and also prevents dropout. Tracking control having a function is performed.

[0004]

As described above, in the conventional optical disk reproducing apparatus shown in the above-mentioned document, the RF signal (reproducing signal) which is the photoelectric conversion output of the reflected light amount is compared with the reference voltage. However, there were drawbacks such as surface shake and response to the reflectance of the disc, or poor sensitivity.

The present invention has been made in view of the above circumstances, and is stable and resistant to defects due to a highly sensitive defect detection circuit which is not affected by surface wobbling and fluctuations in the reflectance of the disk. It is an object to provide an optical recording / reproducing device having a servo system.

[0006]

In order to achieve the above object, the present invention provides (1) a low-pass filter (13) for extracting a low-frequency component of a reproduction signal obtained by photoelectrically converting the amount of reflected light from the disc (1). And a comparison circuit (14) for generating a defect signal by comparing a low-frequency component extracted by the low-pass filter with the reproduction signal, and the disc (1).
A low-pass filter (15) that extracts a low-pass component from a focusing error signal that is a focus position error between the pickup unit (3) and the pickup unit (3), and compares the low-pass component extracted by the low-pass filter with the focusing error signal. , A window comparator (16) for generating a defect signal and an OR circuit for switching the gain of the servo system if either of the defect signal generated from the reproduction signal is output, or (2) the disk (1) ), A band pass filter (18) for extracting the wobble pre-stamped, and a peak hold circuit (19) and a lower hold circuit (2) for extracting the amplitude of the wobble signal extracted by the band pass filter.
0), a low-pass filter (22) for extracting the low-frequency component of the amplitude, and a comparison circuit for generating a defect signal by comparing the low-frequency component extracted by the low-pass filter with the amplitude of the wobble signal. Or
(3) A peak hold circuit (25) and a lower hold circuit (26) for extracting the amplitude of the reproduced signal, a low pass filter for extracting the low frequency component of the amplitude, and a low frequency band extracted by the low pass filter. A comparison circuit for comparing a component and the amplitude of the reproduction signal to generate a defect signal, and a wobble signal for the peak hold circuit (25)
And a switch means that can be input to the lower hold circuit (26), and the switch means is switched depending on the type of the disk (1).

[0007]

[Function] A method of lowering each control gain so that the focus and tracking control systems are not affected by a defective portion of the disc, adhered dust, or the like, or a value before the disturbance is input is held. The method of is taken. At this time, it is important to accurately detect the disturbance. (1) By comparing the reproduction (RF) signal for detecting the amount of reflected light and the low frequency component thereof, the defect signal is accurately output without responding to the fluctuation of the RF signal due to the surface wobbling or the fluctuation of the reflectance. However, the above method alone responds to a significant decrease in reflectance such as a mirror surface defect of the disk, but in the case of dust or the like, the reflectance may not change significantly and may be almost unchanged from electrical noise. Difficult to detect.
Therefore, by comparing the FE signal and its low frequency component and creating a defect signal, it is possible to detect dust even without responding to fluctuations such as surface wobbling. However, since the FE signal does not respond to a mirror surface defect, stable control can be obtained by reducing the gain so that each control system does not respond when either of the defect signals is output. (2) When wobbles are pre-stamped like CD-WO media, the amplitude of the wobble signal due to beats, eccentricity, etc. is compared by comparing the signal whose amplitude has been detected with its low frequency component. The defect signal is output accurately without responding to the decrease. Further, by using the wobble signal, it is possible to obtain the same effect as the above (1).
(3) In the case of the above (2), it can be used only in the CD-WO medium, but according to the present invention, the same effect can be obtained even in the ordinary CD medium.

[0008]

Embodiments will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining an embodiment of an optical recording / reproducing apparatus according to the present invention, in which 1 is a disk,
2 is a spindle motor, 3 is a pickup unit (P
U), 4 is a reproduction (RF) signal generator, 5 is a focusing error (FE) signal generator, 6 is a tracking error (TE) signal generator, 7 is a binarization circuit, 8 is a selector circuit, and 9 is a decoder. Reference numerals 10 and 11 are drivers / phase compensation circuits, and 12 is a defect detection circuit.

The reflected light from the disk 1 is photoelectrically converted by the PU 3. The current is supplied to the disc by the RF signal generator 4, the FE signal generator 5, and the TE signal generator 6, respectively, and the PU 3 and the disc 1 are written.
The FE signal for controlling the focal position of the disc and the TE signal for controlling the PU3 along the groove of the disc are generated. The RF signal is binarized by the binarization circuit 7,
Data is demodulated by the decoder 9. After passing through the selector 8, the FE signal is current-amplified by the driver / phase compensation circuit 10 and applied to the actuator in the PU 3 for focus control. Similarly to the FE signal, the TE signal also passes through the selector 8 and the driver / phase compensation circuit 11 and is applied to the actuator in the PU 3 to perform tracking control.

The defect detection circuit 12 controls the selector circuit 8 in response to the state of the disc, that is, the defect of the disc or dust adhering to the disc 1. The selector circuit 8 works so as to reduce the gain of each servo system according to the defect signal so that the actuator does not respond to defects, dust and the like.

FIG. 2 is a block diagram for explaining an embodiment of the defect detection circuit in FIG. 1, in which 13 is a low pass filter (LPF), 14 is a comparator, 15 is a low pass filter (LPF), Reference numeral 16 is a window comparator, and 17 is an OR circuit.

Since the RF signal is affected by the surface wobbling of the disk 1 and the fluctuation of the reflectance, it has a low frequency swell. Therefore, LPF1 should take out only the swell.
The high frequency is removed at 3 and compared with the RF signal by the comparator 14. Therefore, the output of the comparator 14 becomes "L" → "H" when the reflectance such as the defect of the disk is lowered, and does not react to the low frequency swell such as surface wobbling. Further, since the FE signal is affected by the surface wobbling of the disk 1 and the like, it also has a low frequency swell. Therefore, the high frequency is removed by the LPF 15 so as to take out the undulations, and is compared with the FE signal by the window comparator 16. Therefore,
The output of the window comparator 16 becomes L → H in response to a rapid change in FE, and does not react to low frequency swell such as surface wobbling.

Further, each output is controlled by the OR circuit 7 so that when either one becomes "H", it is output as a defect signal and the gain of the selector circuit 12 is reduced. As described above, the reason for producing the defect signal from both the RF signal and the FE signal is that when the mirror surface defect of the disk is present, the reflected light disappears, so that the RF signal becomes 0 and the defect signal is output. However, depending on the detection method, the FE signal is not output because it takes the difference between the photodetectors in PU3.

Further, if there is dust adhering to the disk, the amount of reflected light may not change much, and it may not change much with noise, so it is difficult to detect it. However, F
When the difference is taken like the E signal, dust and the like are often in the form of fibers, and the reflected light incident on each photodetector is out of balance and often appears largely in the FE signal. Therefore, it is considered easier to detect dust or the like from the FE signal.

FIG. 3 is a block diagram for explaining another embodiment of the defect detection circuit in FIG.
Is a band pass filter (BPF), 19 is a peak hold circuit, 20 is a lower hold circuit, 21 is a difference amplifier, 22 is a low pass filter (LPF), and 23 is a comparator.

When wobbles are stamped on the disc 1 in advance like a CD-WO, the wobble signal is extracted from the TE signal by the BPF 18 and the magnitude of the wobble signal is determined by the peak hold circuit 19 and the lower hold circuit 20. The peak is detected and the magnitude is taken out by the differential amplifier. Also, the wobble signal is the disc 1
Due to the eccentricity and beat of the, the low frequency swell occurs. Therefore, the low frequency swell is taken out by the LPF 22,
The comparator 23 compares the wobble level with the wobble level.
Thus, when there is a defect or dust on the disc, it is possible to accurately output the defect signal and to output the defect signal without being affected by the eccentricity or the beat.

FIG. 4 is a configuration diagram for explaining still another embodiment of the defect detection circuit in FIG.
24 is a band pass filter (BPF), 25 is a peak hold circuit, 26 is a lower hold circuit, 27 is a differential amplifier, 28 is a low pass filter, 29 is a comparator, and 30 is a switch. After detecting the type of the disk, the switch 30 is set to S1 if the disk 1 has wobble, and the switch 30 is set to S2 if the disk 1 does not have wobble. Subsequent processing is the same as in FIG.

[0018]

As is apparent from the above description, the present invention has the following effects. (1) Effect corresponding to claim 1: R for detecting the amount of reflected light
By comparing the F signal with the low-frequency component, the defect signal can be accurately output without responding to the fluctuation of the RF signal due to the surface fluctuation or the fluctuation of the reflectance. (2) Effect corresponding to claim 2: When the wobble is pre-stamped as in the CD-WO medium, by comparing the signal whose amplitude is detected with the low frequency component,
The defect signal is accurately output without responding to the amplitude reduction due to the beat or eccentricity of the wobble signal. or,
By using the wobble signal, it is possible to obtain the same effect as the above (1). (3) Effect corresponding to claim 3: In the case of (2), CD-
Although it can be used only in WO media, according to the present invention, the same effect can be obtained even in ordinary CD media.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of an optical recording / reproducing apparatus according to the present invention.

FIG. 2 is a configuration diagram for explaining an embodiment of the defect detection circuit in FIG.

FIG. 3 is a configuration diagram for explaining another embodiment of the defect detection circuit in FIG.

4 is a configuration diagram for explaining yet another embodiment of the defect detection circuit in FIG. 1. FIG.

[Explanation of symbols]

1 ... Disc, 2 ... Spindle motor, 3 ... Pickup unit (PU), 4 ... Playback (RF) signal generator, 5
... Focusing error (FE) signal generator, 6 ... Tracking error (TE) signal generator, 7 ... Binarization circuit,
8 ... Selector circuit, 9 ... Decoder, 10, 11 ... Driver / phase compensation circuit, 12 ... Defect detection circuit, 13
... Low-pass filter (LPF), 14 ... Comparator, 15 ...
Low pass filter (LPF), 16 ... Window comparator, 17 ... OR circuit.

Claims (3)

[Claims] 1. A low-pass filter for extracting a low-pass component of a reproduction signal obtained by photoelectrically converting the amount of reflected light from a disc, and a low-pass component extracted by the low-pass filter and the reproduction signal are compared to generate a defect signal. Comparing circuit, a low-pass filter for extracting a low-pass component from a focusing error signal which is a focus position error between the disc and the pickup unit 3, and a low-pass component extracted by the low-pass filter and the focusing error signal. An optical recording / reproducing apparatus comprising: a window comparator for comparing and generating a defect signal; and an OR circuit for switching the gain of a servo system when either of the defect signal generated from the reproduction signal is output. 2. A bandpass filter for extracting a wobble pre-stamped on a disk, a peak hold circuit and a lower hold circuit for extracting the amplitude of a wobble signal extracted by the bandpass filter, and the amplitude of the amplitude. An optical recording comprising a low-pass filter for extracting a low-pass component, and a comparison circuit for comparing the low-pass component extracted by the low-pass filter with the amplitude of the wobble signal to generate a defect signal. Playback device. 3. A peak hold circuit and a lower hold circuit for extracting the amplitude of a reproduced signal, a low pass filter for extracting a low frequency component of the amplitude, a low frequency component extracted by the low pass filter and the reproduction. It has a comparison circuit for comparing a signal amplitude and a defect signal and a switch means for inputting a wobble signal to the peak hold circuit and the lower hold circuit, and switches the switch means depending on the type of disk. An optical recording / reproducing apparatus characterized by the above.