JP2000200420A - Waveform reshaping device and reproducing signal processor using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To largely reduce a data slice error or jitter by detecting a reproducing signal from an optical pickup circuit with a first detecting time constant, detecting an upper side envelope of the reproducing signal, detecting the reproducing signal with a second detecting time constant, detecting a lower side envelope of the reproducing signal, imparting a weighting coefficient to the upper side and lower side envelopes and calculating an average value. SOLUTION: This device is provided with a first detecting circuit 3 which detects a reproducing signal RS from an optical pickup circuit 2 reproducing a signal recorded on an optical disk 1 with a prescribed time constant and which detects an upper side envelope RSU, and a second detecting circuit 4 which detects the reproducing signal RS with the prescribed time constant and which detects a lower side envelope RSD. When a pre-processed waveform reshaping signal SS is inputted into a binary circuit 130O, a negative feedback binary slice level is hardly varied even when a period of a disturbance owing to a defect is short and is capable of satisfactorily following a disturbance owing to a defect having a short period. Therefore, a slice error is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform shaping device and a reproduced signal processing device using the same, and more particularly to a waveform shaping device for optimally binarizing a reproduced signal obtained from an optical pickup or performing analog-to-digital conversion. The present invention relates to a reproduction signal processing device using the same.

[0002]

2. Description of the Related Art In recent years, optical discs have been used under various conditions, and the manner of storage differs greatly between individuals. In such a situation, the surface of the optical disk often becomes dusty, dusty, or scratched. Even if there is such an optical disk, it is necessary to determine a signal with high accuracy in order to read information stably.

In particular, DVD (Digital Versa)
In an optical disc on which high-density recording is performed, such as TILE DISK, since the SNR at the shortest pit portion is poor, it is required to minimize errors during binarization.

[0004] On the other hand, CD (COMPACT DISK)
Then, as a recording modulation method, EFM modulation (EIGHT T
In the DVD, 8-16 modulation is used, and the data is recorded in a modulation method such that the spectrum of the recording pattern on the disk is substantially DC-free. Taking advantage of this characteristic, the duty ratio of the binary signal is often 50: 5.
Negative feedback control is performed so as to be 0, and reproduction is performed by a binarization circuit that controls a binarization slice level.

[0005] The binarization circuit 1300 will be described with reference to FIG. 13A. The optical pickup circuit 2 outputs a reproduction signal RS reproduced from the optical disk 1. The reproduction signal RS is capacitively coupled by a capacitor C and has a predetermined bias voltage, for example, VCC.
/ 2 is applied to the negative terminal 110 of the comparator 110
A, and is compared with the binarized slice level inputted to the + terminal 110B by the comparator 110 to be digitally binarized.

The charge pump 101 is driven in accordance with the polarity of the binary signal DG1 output from the comparator 110, and the charge capacitor 102 is charged up or charged down. The charge voltage stored in the charge capacitor 102
, And is ripple-removed by the low-pass filter 104 and input to the + terminal 110B of the comparator 100.

For example, the negative terminal 1 of the comparator 100
When the potential of 10A rises with respect to the potential of the + terminal 110B, the output from the comparator 110 becomes 0, the charge pump 101A turns on, and the charge capacitor 1
02 rises, the input potential of the + terminal 110B of the comparator 100 rises, and the + potential of the comparator 110 rises.
Negative feedback control is performed so that the potential difference between the side terminal 110B and the negative terminal 110A is eliminated.

On the other hand, the negative terminal 110 of the comparator
When the potential of A decreases with respect to the potential of the positive terminal 110B, the input potential of the positive terminal 110B of the comparator 110 decreases, and the positive terminal 110B of the comparator 110 decreases.
Negative feedback control is performed so that the potential difference between the negative terminal 110A and the negative terminal 110A disappears.

A high-frequency reproduction signal RS as shown in FIG.
Is input to the binarization circuit 1300, the “0” level L of the binarization signal DG1 output from the binarization circuit 1300
The duty ratio between 0 and the “1” level L1 is 5 on average
The negative feedback binarized slice level SL is controlled so as to be 0:50.

The response of the negative feedback control depends on the charge pump 1
01 drive current value, the capacity of the charge capacitor 102,
It is determined by the time constant of the low-pass filter 104.

[0011]

SUMMARY OF THE INVENTION Dust,
If there are defects such as dust and scratches, these will block the laser light emitted from the optical pickup,
Even if the signal level of the reproduction signal from the optical disc is DC,
It also fluctuates greatly in terms of AC. In order to properly binarize the reproduction signal even with such signal fluctuation, a binarization circuit 1
What is necessary is just to design so that the control responsiveness of the signal 300 may be further improved to follow the signal fluctuation.

However, the spectrum of the recording pattern on the optical disk is close to the defect variation frequency (several K).
(HZ or less), the DC-free operation is not completely performed, so that the cut-off frequency of the low-pass filter 104 is increased in order to enhance the control response of the binarization circuit 1300, and the negative feedback signal, that is, the input of the + input terminal 110B In this case, the DC fluctuation of the reproduced signal is mixed as a disturbance and cannot be properly binarized, and a data slice error occurs to increase jitter.

Further, as shown in FIG.
Before performing the binarization by 00, the high-pass filter 10
5, the low-frequency fluctuation component of the reproduction signal RS is cut, and even if there is a signal fluctuation due to a defect such as a flaw, if the envelope of the reproduction signal RS is vertically symmetrical, the binarization circuit 1300 can be controlled. The burden can be reduced and the data slice error can be reduced.

However, even when there is no defect, since the low-frequency fluctuation component of the reproduction signal RS is constantly cut, a slice error occurs due to lack of low-frequency fluctuation component information, and jitter increases.

An object of the present invention is to provide a waveform shaping device capable of reducing the control load of a binarization circuit and greatly reducing a data slice error or a jitter, and a reproduction signal processing device using the same. It is in.

Another object of the present invention is to provide a waveform shaping device which can correctly binarize a reproduced signal even when the signal level of the reproduced signal from the optical disk largely fluctuates due to a defect on the surface of the optical disk. An object of the present invention is to provide an apparatus and a reproduction signal processing apparatus using the same.

It is still another object of the present invention to provide a waveform shaping device capable of correctly binarizing a reproduced signal even when there is no defect, and a reproduced signal processing device using the same.

[0018]

A waveform shaping device according to the present invention detects a reproduction signal from an optical pickup circuit for reproducing a signal recorded on an optical disk with a first detection time constant, and detects an upper envelope of the reproduction signal. , A second detection circuit for detecting the reproduction signal with a second detection time constant and detecting a lower envelope of the reproduction signal, and a first detection circuit for detecting the lower signal and the upper envelope and the lower envelope. An averaging circuit that calculates an average value by applying a weight represented by a weighting coefficient, and a subtraction circuit that subtracts a signal corresponding to the average value calculated by the averaging circuit from the reproduction signal and outputs a waveform shaping signal. Which achieves the above object.

The waveform shaping device further includes a low-pass filter that smoothes the average value and outputs a smoothed signal, and the subtraction circuit converts the smoothed signal output from the reproduced signal by the low-pass filter circuit. It may be subtracted.

[0020] The weighting factor may be 1: 1.

[0021] The weighting coefficient may be determined based on an asymmetry amount of the reproduced signal.

The waveform shaping device may further include an asymmetry detection circuit for detecting the asymmetry amount.

At least one of the first detection time constant and the second detection time constant may be determined so as to be substantially proportional to a spot diameter of a light spot on the optical disk.

[0024] At least one of the first detection time constant and the second detection time constant may be determined so as to be substantially inversely proportional to the reproduction linear velocity of the optical disk.

[0025] The cutoff frequency of the low-pass filter may be determined so as to be substantially inversely proportional to the spot diameter of a light spot on the optical disc.

[0026] The cutoff frequency of the low-pass filter may be determined so as to be substantially proportional to the reproduction linear velocity of the optical disk.

The waveform shaping device further includes a dropout detecting circuit for detecting a dropout indicating a decrease in the amplitude of the reproduction signal, and when the dropout is detected by the dropout detecting circuit, the first signal is output.
At least one of the detection time constant and the second detection time constant may be set shorter.

The waveform shaping device further includes a dropout detection circuit for detecting a dropout indicating a decrease in the amplitude of the reproduction signal, and when the dropout is detected by the dropout detection circuit, the low-pass filter The cutoff frequency of the circuit may be set higher.

According to one aspect of the present invention, it is possible to suppress a reproduction signal fluctuation occurring at the time of passing a defect, to greatly reduce a control load on a binarization circuit, and to not deteriorate jitter during normal reproduction. Thus, the operation and effect of greatly reducing the data slice error can be achieved.

According to another aspect of the present invention, the control load of the binarization circuit can be greatly reduced with a relatively simple circuit configuration, and the data slice error can be reduced without deteriorating the jitter during normal reproduction. This has the effect of greatly reducing the effect.

According to still another aspect of the present invention, the weighting coefficient for the upper and lower envelopes of the averaging operation in the averaging circuit is determined in proportion to the asymmetry amount of the reproduced signal, so that the binarizing circuit is independent of the recording conditions. , The operation load and the effect of greatly reducing the data slice error without deteriorating the jitter at the time of normal reproduction.

According to still another aspect of the present invention, an optimum waveform shaping is performed based on the spot diameter of a light spot, and an operation of greatly reducing a data slice error without deteriorating jitter at the time of steady reproduction. It works.

According to still another aspect of the present invention, the operation and effect of performing the optimum waveform shaping based on the reproduction linear velocity and greatly reducing the data slice error without deteriorating the jitter at the time of steady state reproduction. Play.

According to still another aspect of the present invention, the present invention has an operation and an effect for achieving both the jitter performance at the time of normal reproduction and the waveform shaping performance at the time of passing a defect.

[0035]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) A reproduction signal processing apparatus 200 according to Embodiment 1 of the present invention will be described below with reference to FIG. The reproduction signal processing device 200 includes a waveform shaping device 100 and a binarization circuit 1300.

The waveform shaping device 100 detects a reproduction signal RS from the optical pickup circuit 2 for reproducing a signal recorded on the optical disk 1 with a predetermined time constant, and performs an upper envelope RS
U, a second detection circuit 4 for detecting the reproduced signal RS from the optical pickup circuit 2 with a predetermined time constant to detect a lower envelope RSD, and an upper envelope RSU. Averaging circuit 5 for calculating an average value AVE of the signal and the lower envelope RSD, a low-pass filter 6 for smoothing the average value AVE obtained by the averaging circuit 5, and an optical pickup circuit 2
And a subtraction circuit 7 for subtracting the smoothed signal SM1 obtained by the low-pass filter 6 from the reproduction signal RS from. 2
The binarization circuit 1300 binarizes the waveform shaping signal SS output from the subtraction circuit 7 and outputs a binarized signal.

The operation of the waveform shaping device 100 according to the first embodiment will be described with reference to FIG. The signal recorded on the optical disc 1 is read using the optical pickup circuit 2. If there is a defect such as a scratch on the optical disc 1, a disturbance D1 as shown in FIG. 2A occurs in the reproduction signal RS.

When the reproduction signal RS is directly input to the binarization circuit 1300, the binarization is performed by the negative feedback binarization slice level SL1 which follows approximately the average of the upper envelope RSU and the lower envelope RSD. Will be However, when the period of the disturbance D1 due to the defect is short, the negative feedback binarized slice level SL1 cannot follow the disturbance D1 due to the defect, and a slice error occurs.

Referring to FIG. 2A, the first detection circuit 3 detects the reproduction signal RS from the optical pickup circuit 2 to detect the upper envelope RSU. The second detection circuit 4 detects the lower envelope RSD by detecting the reproduction signal RS from the optical pickup circuit 2.

Referring to FIG. 2B, averaging circuit 5 applies a weighting factor M: N to upper envelope RSU and lower envelope RSD.
The average value AVE is calculated with the weight represented by

Referring to FIG. 2C, low-pass filter 6
Removes the detection noise component contained in the average value AVE,
It outputs a smoothed signal SM1 obtained by extracting only a harmful DC fluctuation component included in the reproduction signal RS when there is a defect.

Referring to FIG. 2D, subtraction circuit 7 subtracts smoothed signal SM1 from reproduced signal RS to output a vertically shaped waveform shaping signal SS.

When the preformed and shaped waveform shaping signal SS is input to the binarization circuit 1300, the negative feedback binarization slice level SL2 has little change even when the period of the disturbance D1 due to the defect is short, and Can sufficiently follow the disturbance D1 due to a short defect, so that a slice error can be greatly reduced. In addition, as an example of the averaging circuit 5, it can be easily realized by a configuration as shown in FIG.

The frequency spectrum of the reproduction signal RS will be described with reference to FIG. In the method using the high-pass filter 105 as shown in FIG. 14, the component represented by the area A1 is removed from the component of the reproduction signal RS represented by the area S by the high-pass filter 105. The jitter increases due to the missing component.

However, as described in the first embodiment, the average value AVE is calculated by weighting the upper envelope RSU and the lower envelope RSD by a weight represented by a weighting factor M: N. If a method of subtracting the smoothed signal SM1 corresponding to the average value AVE from the signal RS is used, the loss of the component of the reproduction signal RS is reduced as in the region B1. For this reason,
It is possible to minimize the deterioration of jitter, and it is possible to achieve both the slice performance at the time of passing a defect and the jitter performance at the time of normal reproduction.

When the weighting coefficients M: N for the upper and lower envelopes of the averaging operation in the averaging circuit 5 are 1: 1,
A waveform shaping device can be realized with a simple circuit configuration. The averaging circuit 5 can be realized by, for example, an averaging circuit 5A having a circuit configuration as shown in FIG.

(Embodiment 2) FIG. 6 shows a configuration of a reproduction signal processing apparatus 200A according to Embodiment 2. The same components as those of the reproduction signal processing device 200 described above with reference to FIG. 1 are denoted by the same reference numerals. A detailed description of these components will be omitted.

The waveform shaping device 100 A further includes an asymmetry detection circuit 8. The weighting coefficient M: N for the upper and lower envelopes in the averaging operation of the averaging circuit 5 is determined in proportion to the asymmetry amount of the reproduction signal RS.

The asymmetry generally occurs due to disc cutting conditions and recording conditions. If the recording pits tend to be written larger, the negative feedback binarized slice level at which the binarized duty is 50:50 is shifted upward (or lower) from the intermediate level position of the reproduced signal. Conversely, when the recording pits tend to be written smaller, the negative feedback binarized slice level is shifted below (or above) the position of the intermediate level of the reproduced signal. The amount of deviation between the negative feedback binarized slice level and the position of the intermediate level of the reproduced signal is called asymmetry amount.

Referring to FIG. 7A, when asymmetry occurs, the negative feedback binarized slice level SL3 during normal reproduction is shifted from the intermediate level ML of reproduction signal RS by an asymmetry amount ASQ. Negative feedback binarized slice level S
The ratio S between the distance between L3 and the upper envelope RSU and the distance between the negative feedback binarized slice level SL3 and the lower envelope RSD:
T is called asymmetry coefficient ASC.

The negative feedback binarized slice level SL3 fluctuates while maintaining the asymmetry coefficient ASC = S: T during the period corresponding to the disturbance D1 due to the defect. However, when the period of the disturbance D1 due to the defect is short, the negative feedback binarized slice level SL3 cannot follow the disturbance D1 due to the defect, and a slice error occurs.

Referring to FIG. 7B, averaging circuit 5 sets weighting coefficient M: N for upper and lower envelopes RSU and RSD of the averaging operation to asymmetry coefficient ASC (= S: T) output from asymmetry detection circuit 8. Weighted by an asymmetry coefficient ASC (= S: T)
Calculate VE1.

Referring to FIG. 7C, low-pass filter 6
Removes a detection noise component included in the average value AVE1 and outputs a smoothed signal SM2. Referring to FIG. 7D,
The subtraction circuit 7 outputs a waveform shaping signal SS1 by subtracting the smoothing signal SM2 from the reproduction signal RS.

As shown in FIG. 7D, a weighting coefficient M: N
Is set to the asymmetry coefficient ASC (= S: T), the fluctuation of the negative feedback binarized slice level SL3 is minimized,
The slice performance when the light beam passes through the defect can be further improved.

When the asymmetry occurs, even if the weighting coefficient M: N = 1: 1, the swing of the negative feedback binarized slice level SL3 shown in FIG. 7D is slightly increased, but there is no practical problem. Fits in.

The asymmetry detection circuit 8 can have, for example, the configuration shown in FIG. The asymmetry detection circuit 8 includes a peak detection circuit 9 for detecting a peak of the reproduction signal RS, and a second low-pass filter 1 for obtaining a DC level of the reproduction signal RS.
0, bottom detection circuit 1 for detecting the bottom of the reproduction signal RS
1. It includes first and second subtraction circuits 12A and 12B and an asymmetry coefficient operation circuit 12C. The asymmetry coefficient calculation circuit 12C calculates an asymmetry coefficient ASC (= S: T) from the difference between the peak detection circuit 9 and the low-pass filter circuit 10 and the difference between the peak detection circuit 9 and the low-pass filter circuit 10.

At least one detection time constant of the first detection circuit 3 and the second detection circuit 4 can be determined substantially in proportion to the spot diameter of the light spot on the surface of the optical disc 1.

FIGS. 9A and 9C show how light spots SP1 and SP2 having different spot diameters D1 and D2 pass over the same size defect DF on the surface of the optical disc 1. FIG. 9B and 9D show the fluctuation of the reproduction signal RS in each case.

It is assumed that the spot diameter D1 of the light spot SP1 is n times the spot diameter D2 of the light spot SP2 (n> 1). If the spot diameter D1 is n times the spot diameter D2, the fall speed of the reproduction signal RS1 shown in FIG. 9B is 1/1 / the speed of the fall of the reproduction signal RS2 shown in FIG. 9D.
It becomes n times, and the reproduction signal RS1 falls more slowly than the reproduction signal RS2.

The first detection circuit 3 detects the detection signals DS1, D
The reproduction signals RS1 and RS2 are detected using S2. The detection time constant T1 of the detection signal DS1 is equal to the detection signal DS.
2 is determined to be n times the detection time constant T2. As described above, the detection time constant of the first detection circuit 3 is determined substantially in proportion to the spot diameter of the light spot. Similarly, the detection time constant of the second detection circuit 4 is determined substantially in proportion to the spot diameter of the light spot.

The detection time constants T1 and T2 are the reproduction signals RS1 and
Since the detection time constants T1 and T2 need only be determined so as to detect the drop of RS2, the detection time constants T1 and T2 may be determined to be short so that the slopes of the detection signals DS1 and DS2 in FIGS. 9B and 9D can be secured.

However, if the detection time constant is made shorter than necessary to detect a reproduced signal which drops sharply, an unnecessary detection noise is picked up. Therefore, an appropriate detection time constant is set in consideration of the light spot shape. There is a need.

If the detection time constant is determined substantially in proportion to the spot diameter of the light spot, the slice performance at the time of passing a defect and the jitter performance at the time of normal reproduction can be obtained without picking up unnecessary detection noise. Can be compatible.

The detection time constant of the first detection circuit 3 or the second detection circuit 4 can be determined so as to be substantially inversely proportional to the reproduction linear velocity. FIG. 10A and FIG. 10B show the fluctuation of the reproduction signal RS when the light beam passes through a defect having the same size while changing the linear velocity. FIG.
A indicates the fluctuation of the reproduction signal RS during 1 × speed reproduction. FIG. 10B shows the fluctuation of the reproduction signal RS at the time of n-times speed reproduction.

As shown in FIG. 10B, when the reproduction linear velocity becomes n times as large as that of FIG. 10A, the drop rate of the reproduction signal also becomes n.
Therefore, the optimum detection time constant becomes 1 / n. Thus, the detection time constant is determined so as to be substantially inversely proportional to the reproduction linear velocity.

The cutoff frequency of the low-pass filter circuit 6 can be determined so as to be substantially inversely proportional to the spot diameter of the light spot on the optical disk surface. As shown in FIGS. 9A and 9B, when the light spot diameter increases by n times, the drop rate of the reproduction signal becomes 1 / n times, and when the light spot diameter of the light spot becomes 1 / n times, the reproduction signal drops. The speed is increased n times.

When the falling speed of the reproduced signal becomes n times,
Harmful signal fluctuation included in smoothed signal SM1 (FIG. 7C)
Becomes n times as high. In order to pass an n-fold signal fluctuation, the cutoff frequency of the low-pass filter circuit 6 needs to be set to n times.

Therefore, when the light spot diameter becomes 1 / n times, the cutoff frequency of the low-pass filter circuit 6 is set to n times. Thus, the cutoff frequency of the low-pass filter circuit 6 is determined so as to be substantially inversely proportional to the spot diameter of the light spot.

When the cut-off frequency of the low-pass filter circuit 6 is determined so as to be substantially inversely proportional to the spot diameter of the light spot, the slicing performance at the time of passing through the defect,
Jitter performance during normal reproduction can be compatible.

The cut-off frequency of the low-pass filter circuit 6 can be determined so as to be substantially proportional to the reproduction linear velocity. As shown in FIG. 10B, when the reproduction linear velocity increases by n times, the drop rate of the reproduction signal at the time of passing the defect also increases by n times.

When the falling speed of the reproduced signal becomes n times,
Harmful signal fluctuation included in smoothed signal SM1 (FIG. 7C)
Becomes n times as high. In order to pass an n-fold signal fluctuation, the cutoff frequency of the low-pass filter circuit 6 needs to be set to n times.

Therefore, when the reproduction linear velocity becomes n times, the cutoff frequency of the low-pass filter circuit 6 is set to n times. Thus, the cut-off frequency of the low-pass filter circuit 6 is determined so as to be substantially proportional to the reproduction linear velocity.

When the cutoff frequency of the low-pass filter circuit 6 is determined to be substantially proportional to the reproduction linear velocity,
It is possible to achieve both the slice performance at the time of passing a defect and the jitter performance at the time of normal reproduction.

(Embodiment 3) FIG. 11 shows Embodiment 3 of the present invention.
1 shows a configuration of a reproduction signal processing device 200B according to the first embodiment. The same components as those of the reproduction signal processing device 200 described above with reference to FIG. 1 are denoted by the same reference numerals. A detailed description of these components will be omitted.

The waveform shaping device 100B further includes a dropout detection circuit 13 for detecting a dropout indicating a decrease in the amplitude of the reproduction signal RS.

When the dropout detection circuit 13 detects a dropout, at least one detection time constant of the first detection circuit 3 and the second detection circuit 4 is set short.
Thereby, when dropout is detected, the follow-up property of envelope detection for a reproduced signal that fluctuates greatly in a defect section can be improved, and at the time of normal reproduction in which dropout is not detected, the first or second signal is used.
Since the detection noise and the like generated in the detection circuits 3 and 4 can be suppressed, it is possible to achieve both the jitter performance at the time of normal reproduction and the waveform shaping performance at the time of passing a defect.

FIG. 12 shows the configuration of another reproduction signal processing device 200C according to the third embodiment. The same components as those of the reproduction signal processing device 200B described above with reference to FIG. 11 are denoted by the same reference numerals. A detailed description of these components will be omitted.

When the dropout detection circuit 13 detects a dropout, the cutoff frequency of the low-pass filter 6 is set high. As a result, when a dropout is detected, a harmful signal fluctuation occurring in a defect section in which the reproduction signal fluctuates greatly can be passed, and during normal reproduction in which no dropout is detected, the first or second detection circuit 3 can be used. , 4 can suppress both the jitter performance at the time of normal reproduction and the waveform shaping performance at the time of passing a defect.

[0080]

As described above, according to the present invention, even when the signal level of the reproduction signal from the optical disk greatly fluctuates due to a defect on the optical disk surface, it is possible to correctly binarize the reproduction signal. Can be provided.

Further, according to the present invention, it is possible to provide a waveform shaping device which can correctly binarize a reproduced signal even in a state where there is no defect.

[Brief description of the drawings]

FIG. 1 is a block diagram of a waveform shaping device according to a first embodiment.

FIG. 2A is a diagram showing an example of a reproduction signal waveform of an optical disk having a defect.

FIG. 2B is a diagram showing an average value obtained by weighting a reproduction signal waveform of an optical disc having a defect according to the first embodiment;

FIG. 2C is a diagram showing a fluctuation component included in a reproduction signal waveform of the optical disk having a defect according to the first embodiment.

FIG. 2D is a diagram in which the reproduction signal waveform of the optical disk having a defect in the first embodiment is vertically symmetric.

FIG. 3 illustrates an example of an averaging circuit in Embodiment 1.

FIG. 4A is a diagram showing a frequency spectrum of a reproduction signal.

FIG. 4B is a diagram showing a frequency spectrum of a reproduced signal in the first embodiment.

FIG. 5 is a diagram showing an example of an averaging circuit when a weighting coefficient is 1: 1 in the first embodiment.

FIG. 6 is a diagram showing a waveform shaping device according to a second embodiment.

FIG. 7A is a diagram showing an example of a reproduction signal waveform.

FIG. 7B is a diagram showing an average value obtained by weighting a reproduced signal waveform in the second embodiment.

FIG. 7C is a diagram showing a fluctuation component included in a reproduced signal waveform according to the second embodiment.

FIG. 7D is a diagram showing a relationship between a reproduction signal waveform and a negative feedback binary slice level according to the second embodiment;

FIG. 8 illustrates an example of an asymmetry detection circuit in Embodiment 2.

FIG. 9A is an explanatory diagram of a light spot having a large spot diameter that passes through a defect.

FIG. 9B is an explanatory diagram of a drop in a reproduction signal when a light spot having a large spot diameter passes through a defect.

FIG. 9C is an explanatory diagram of a light spot having a small spot diameter that passes through a defect.

FIG. 9D is an explanatory diagram of a drop in a reproduction signal when a light spot having a small spot diameter passes through a defect.

FIG. 10A is a diagram showing a change in a reproduction signal when the reproduction linear velocity is normal.

FIG. 10B is a diagram showing a change in a reproduction signal when the reproduction linear velocity is high.

FIG. 11 is a diagram showing a waveform shaping device according to a third embodiment.

FIG. 12 is a diagram showing another waveform shaping device according to the third embodiment.

FIG. 13A is a block diagram of a binarization circuit.

FIG. 13B is an explanatory diagram of a high-frequency reproduction signal input to the binarization circuit.

FIG. 14 is a diagram for explaining a conventional waveform shaping circuit.

[Explanation of symbols]

 Reference Signs List 1 optical disk 2 optical pickup circuit 3 first detection circuit 4 second detection circuit 5 averaging circuit 6 low-pass filter 7 subtraction circuit 8 asymmetry detection circuit 9 peak detection circuit 10 second low-pass filter 11 bottom detection circuits 12A, 12B second Subtraction circuit 13 dropout detection circuit 110 comparator 101 charge pump 102 charge capacitor 103 buffer 104 low-pass filter 105 high-pass filter

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kazuhiro Aoki 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd.

Claims (11)

[Claims] A first detection circuit for detecting a reproduction signal from an optical pickup circuit for reproducing a signal recorded on an optical disk with a first detection time constant and detecting an upper envelope of the reproduction signal; A second detection circuit that detects the lower envelope of the reproduced signal by detecting the second envelope with a second detection time constant; and weights the upper envelope and the lower envelope with weights represented by weighting coefficients to calculate an average value. A waveform shaping device comprising: an averaging circuit for calculating; and a subtraction circuit for subtracting a signal corresponding to the average value calculated by the averaging circuit from the reproduced signal and outputting a waveform shaping signal. 2. The waveform shaping device further includes a low-pass filter that smoothes the average value and outputs a smoothed signal, and the subtraction circuit outputs the smoothed signal output from the reproduced signal by the low-pass filter circuit. The waveform shaping device according to claim 1, wherein the signal is subtracted. 3. The waveform shaping device according to claim 1, wherein the weighting factor is 1: 1. 4. The waveform shaping device according to claim 1, wherein the weighting coefficient is determined based on an asymmetry amount of the reproduced signal. 5. The waveform shaping device according to claim 4, wherein said waveform shaping device further comprises an asymmetry detection circuit for detecting said asymmetry amount. 6. At least one of the first detection time constant and the second detection time constant is determined so as to be substantially proportional to a spot diameter of a light spot on the optical disk.
The waveform shaping device according to claim 1. 7. The waveform shaping device according to claim 1, wherein at least one of the first detection time constant and the second detection time constant is determined so as to be substantially inversely proportional to a reproduction linear velocity of the optical disk. . 8. The waveform shaping device according to claim 2, wherein a cutoff frequency of the low-pass filter is determined so as to be substantially inversely proportional to a spot diameter of a light spot on the optical disk. 9. The waveform shaping device according to claim 2, wherein a cutoff frequency of the low-pass filter is determined so as to be substantially proportional to a reproduction linear velocity of the optical disc. 10. The waveform shaping device further includes a dropout detection circuit for detecting a dropout indicating a decrease in the amplitude of the reproduction signal, and when the dropout is detected by the dropout detection circuit, The first detection time constant and the second detection time constant
The waveform shaping device according to claim 1, wherein at least one of the detection time constant and the detection time constant is set to be short. 11. The waveform shaping device further includes a dropout detection circuit for detecting a dropout indicating a decrease in the amplitude of the reproduced signal, and when the dropout is detected by the dropout detection circuit, 3. The waveform shaping device according to claim 2, wherein the cutoff frequency of the low-pass filter circuit is set high.