JPH06162662A - Signal regeneration system - Google Patents

Abstract

PURPOSE:To perform binarization at a specified slice level even if signal is recorded only at one part during one track for regenerating a signal properly by detecting low-frequency components from the regenerated signal and then subtracting the low-frequency components from the regenerated signal. CONSTITUTION:A regenerated signal h is input to a detection circuit 8 and the circuit 8 detects the retardation signal components. A subtraction circuit 9 subtracts the retardation signal components from the signal h. The output signal is passed through an amplification circuit 10 and a signal j is regenerated and output via a regeneration circuit 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information reproducing apparatus and an optical information recording / reproducing apparatus, and more particularly to a magneto-optical disk apparatus for reproducing a reproduced signal containing a fluctuation of a low frequency component due to the influence of a recording medium or the like.

[0002]

2. Description of the Related Art In an optical disk drive, due to environmental fluctuations in the semiconductor laser emission power, variations in the sensitivity of the optical disk medium, variations in the sensitivity due to the environment, etc., the shape of the recording marks fluctuates, resulting in even-order distortion during reproduction, and the duty of the reproduction signal Has the drawback of fluctuating. In order to remove this distortion, it is necessary to properly control the slice level of the binarized comparator of the reproduced signal. An example of this method is described in signal processing technology in optical recording, 1989, published by Trikeps Co., Ltd. Kunimaro Tanaka, supervised items 116 to 118.

FIG. 3 shows a conventional signal reproducing circuit.
The laser beam is focused on the track on which the signal of the optical disc is recorded to obtain a reproduction signal, which is amplified by the amplifier 1 to a desired amplitude. This reproduced signal has a low-frequency component fluctuation (hereinafter referred to as retardation) due to fluctuations in the reflectance of the disk, laser beam focusing deviation, deviation from the track center, and the like. In order to remove this fluctuation, it is input to a comparator 3 through a high pass filter (hereinafter referred to as HPF) 2. On the other hand, a peak detection circuit 4 and a bottom detection circuit 5 for detecting the upper and lower envelopes of the amplified reproduction signal.
To the comparator 6 and obtain the difference between the respective outputs by the comparator 6 to obtain a half level of the signal amplitude input to the comparator 3. The slice level of the comparator 3 is set to a half level in a sync signal area (hereinafter referred to as a VFO section) for performing phase synchronization of the demodulation clock at the beginning of the signal. Therefore, the sample-hold circuit 7 is controlled by the VFO gate, and the half level of the VFO section is input as the slice level of the comparator 3.

It should be noted that the reason why the slice level setting is limited to the VFO section is that the VFO section is the reference for the reproduction signal, and the VFO section is also used.
Since the duty of the reproduction signal other than the parts is different,
This is because the peak detection and the bottom detection have different sensitivities, and the proper slice level cannot be obtained for all signals.

[0005]

FIG. 4 shows the waveform of each part of the circuit shown in FIG. Hereinafter, the state of signal reproduction in the case where a signal is recorded in only one part of one track as shown in FIG. 4A will be described.

The waveform shown in FIG. 4a passes through the HPF 2 and is input to the comparator 3 as shown in FIG. 4b. On the other hand, the outputs of the peak detection circuit 4 and the bottom detection circuit 5 are c and d in FIG. 4, and the output to the comparison circuit 6 which is the difference waveform between them is e in FIG.
Therefore, the VFO gate shown in FIG. 4f samples and holds and sends the waveform represented by g in FIG. 4 to the other input of the comparator 3. The waveform shown by the dotted line g in FIG. 4 is the other input signal of the comparator 3 shown in b.

Since the correct slice level is a half level of the signal (broken line of g in FIG. 4), as can be seen from g in FIG. 4, when only one part of the signal is recorded in one track, The problem arises that the signal cannot be read correctly.

[0008]

SUMMARY OF THE INVENTION The present invention is a signal reproducing system having means for detecting a retardation waveform and means for subtracting a retardation component from a reproduced signal.

[0009]

According to the present invention, in the reproduced signal including the retardation, the means for detecting the retardation waveform and the means for subtracting the retardation component from the reproduced signal provide a constant slice level even if only one part of one track is recorded. It can be binarized to reproduce the signal correctly.

[0010]

1 is a block diagram of an input portion of a signal reproducing system according to a first embodiment of the present invention, and FIG. 2 shows waveforms of respective portions for explaining the operation. The reproduction signal h from the optical disk shows the case where the reproduction signal a in FIG. 4 has retardation. The detection circuit 8 detects the signal component of retardation from the reproduction signal h and outputs the waveform shown as the detection signal i in FIG. A waveform obtained by subtracting the retardation signal component from the reproduction signal h by the subtraction circuit 9 using the detection signal i becomes the reproduction circuit input signal j. As a result, the influence of retardation can be removed from the reproduction signal h, and the HPF2 for removing the influence of retardation shown in the conventional example can be removed.
Even when only one part of the signal is recorded in one track, the signal can be binarized at a constant slice level to correctly reproduce the signal. Alternatively, the cut-off frequency of the HPF 2 can be binarized at a constant slice level and lowered until the signal can be correctly reproduced even when only one part of the track is recorded. Also,
By removing the influence of retardation, the dynamic range of the amplification circuit after the subtraction circuit can be reduced. Specific examples of the detection circuit 8 will be shown in the third and subsequent embodiments.

FIG. 5 shows a second embodiment of the present invention.
The amplifier circuit 10 may be arranged in the input portion as shown in FIG.

FIG. 6 shows a third embodiment of the present invention. Since the frequency of the recording signal and the frequency of the retardation are different from each other, the detection circuit 8 of FIG.
(Referred to as F) is shown, and the same effect as that in FIG. 1 can be obtained.

FIG. 7 shows a fourth embodiment of the present invention.
The amplifier circuit 10 may be arranged in the input portion as shown in FIG.

FIG. 8 shows a fifth embodiment of the present invention. By detecting the bottom portion of the reproduction signal h, the signal component of retardation can be detected. Therefore, a bottom detection circuit is added to the detection circuit of FIG. Fig. 1 shows the case where it is used.
The same effect as can be obtained. The bottom detection circuit is used to detect the envelope of most of the signal shown in FIG. 2h, and is used in the AM detection circuit to perform high-speed charging and low-speed discharging by utilizing the rectification function of the diode.

FIG. 9 shows a sixth embodiment of the present invention.
The amplifier circuit 10 may be arranged in the input portion as shown in FIG.

FIG. 10 shows a seventh embodiment of the present invention, in which the signal component of retardation is almost unchanged at the innermost and outermost circumferences of the disc and the position relative to the disc is recorded. When it can be detected, the unrecorded portion is reproduced in advance, the retardation waveform is stored in the memory 15 by using the AD converter 14, and the retardation waveform data is read from the memory 15 in the portion for reproducing the recording signal, D-A converter 16
By subtracting the signal component of retardation from the reproduced signal h via the LPF 17 and the LPF 17, the same effect as in FIG. 1 can be obtained. In this case, by increasing the resolution and the sampling frequency of the AD converter and the DA converter, there is no phase delay or the like as compared with the LPF or the bottom detection circuit used in the detection circuit 8, so that highly accurate correction is performed. be able to.

FIG. 11 shows an eighth embodiment of the present invention in which the signal component of retardation has a constant change at the innermost and outermost circumferences of the disc, and the position relative to the disc is recorded. If it is detected or can be detected, the innermost unrecorded portion is reproduced in advance, the retardation waveform is stored in the memory 18 by using the A / D converter 14, and the outermost unrecorded portion is reproduced in advance. , The retardation waveform is stored in the memory 19 using the A / D converter 14, the retardation correction waveform is calculated from the memory 19 and the memory 21 using the arithmetic circuit 20, and the memory 15 is used in the portion for reproducing the recording signal. Read out the retardation waveform data from the DA converter 1
By subtracting the signal component of the retardation from the reproduced signal h via 6 and the LPF 17, the same effect as in FIG. 1 can be obtained.

Further, the place for storing the retardation waveform is not limited to the innermost and outermost positions, and when the recording track is divided into several zones, the correction can be performed more accurately in each zone.

For example, when the reproduction signal (hereinafter referred to as MO signal) obtained by the change of the magnetic field of the recording medium in the magneto-optical disk device is used, it is obtained from the strength of the reflected light amount from the recording medium from the viewpoint of the MO signal detecting method. The reproduction signal (hereinafter referred to as WO signal) may be included, and the detection circuit 8 may malfunction. At this time, the detection circuit 8 is
By providing the hold circuit so as to perform only the signal portion, the same effect as in FIG. 1 can be obtained.

[0020]

According to the present invention, in an optical disc having a large retardation, the HPF for removing the influence of the retardation can be removed, and even if only one part of one track has a signal recorded, it can be reproduced at a constant slice level. There is an effect that the value can be converted and the signal can be correctly reproduced. Alternatively, the HPF cutoff frequency can be binarized at a constant slice level even if only one part of a track has a signal recorded, and the signal can be lowered until it can be correctly reproduced. Further, by removing the influence of retardation, there is an effect that the dynamic range of the amplification circuit after the subtraction circuit can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of an input portion of a signal reproduction system according to a first embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of FIG.

FIG. 3 is a block diagram of a conventional signal reproduction system.

FIG. 4 is an operation explanatory diagram of FIG. 2;

FIG. 5 is a block diagram showing a second embodiment of the present invention.

FIG. 6 is a block diagram showing a third exemplary embodiment of the present invention.

FIG. 7 is a block diagram showing a fourth exemplary embodiment of the present invention.

FIG. 8 is a block diagram showing a fifth embodiment of the present invention.

FIG. 9 is a block diagram showing a sixth embodiment of the present invention.

FIG. 10 is a block diagram showing a seventh embodiment of the present invention.

FIG. 11 is a block diagram showing an eighth embodiment of the present invention.

[Explanation of symbols]

 1 ... Amplifier, 2 ... HPF, 3 ... Waveform shaping circuit, 4 ... Peak detection circuit, 5 ... Bottom detection circuit, 6 ... Comparator, 7 ... Sample hold circuit, 8 ... Detection circuit, 9 ... Subtractor, 11 ... Reproduction Circuit, 12 ... LPF, 14 ... AD converter, 15 ... Memory, 16 ... DA converter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toru Kawashima, Tohru Kawashima, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Stock Information, Hitachi Imaging Information Systems Co., Ltd. Hitachi, Ltd. Central Research Laboratory (72) Inventor Seiichi Mita 2880 Kozu, Odawara-shi, Kanagawa Hitachi Storage Systems Division

Claims (5)

[Claims] 1. An optical information reproducing apparatus and an optical information recording / reproducing apparatus, wherein a detecting means for detecting a low frequency component from a reproduced signal including a fluctuation of the low frequency component, and a means for subtracting the detected signal from the reproduced signal. A signal reproducing method characterized by having. 2. An optical information reproducing apparatus and an optical information recording / reproducing apparatus, wherein means for reproducing an unrecorded portion in advance from a reproduction signal containing fluctuations of a low frequency component and storing the low frequency component, A signal reproducing system characterized by having means for subtracting a stored signal from a reproduced signal at the time of reproducing. 3. The signal reproducing method according to claim 1, wherein a low pass filter is used. 4. A signal reproducing system according to claim 1, wherein an unrecorded level detecting circuit is used. 5. A signal reproducing system according to claim 2, further comprising subtraction means for storing a plurality of low frequency components and using a result of computing them.