JP2002183950A - Dropout detecting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dropout detecting circuit, by which the parameter is easily changeable without necessitating an externally attached circuit or an analog circuit and the optimum dropout detection is allowed for an external factor such as the reproduction speed. SOLUTION: The bright-side envelope is extracted by a peak detecting circuit 3 from a digital RF signal formed by A/D conversion of an analog RF signal, and the inclination is detected by an inclination detecting circuit 4, then the dropout is detected by the comparison between the detected inclination level and the reference parameter of inclination being previously set in a parameter switchover circuit 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a CD or a CD-RO.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dropout detection circuit for detecting a dropout that occurs when a disc is reproduced in an apparatus for reproducing an optical disc such as M.

[0002]

2. Description of the Related Art Conventionally, a compact disk (CD) or a compact disk-ROM (CD-R) as a recording medium has been used.
2. Description of the Related Art In an optical disk system for reproducing recorded information from an optical disk such as an OM), a dropout detection circuit for detecting a dropout of an RF signal reproduced from the optical disk is widely used.

[0003] A dropout detection system using such a conventional dropout detection circuit will be described below with reference to FIGS. 6, 7 and 8. FIG. 8 shows a general block configuration of an optical disk system such as a CD. Here, particularly, a pre-processing portion necessary for extracting a data signal (recording data) based on CD recording information will be described.
In FIG. 8, 40 is an optical pickup, 41 is a head amplifier block composed of an analog circuit, and 42 is an optical disk signal processing / controller block composed of a digital circuit.

In an optical disk system such as a CD, an analog RF signal is extracted from a reflection signal of a laser or the like applied to an optical disk by an optical pickup 40, and the analog RF signal is amplified to a certain level by a head amplifier block 41. The data is input to the processing / controller block 42 and the recording data is extracted from the analog RF signal.

[0005] In addition to the amplification of the analog RF signal from the optical pickup 40, the head amplifier block 41 also generates a dropout signal and an off-track signal required for stable reproduction of the optical disk. By adjusting the reading using these drop-out signals and track deviation signals, the analog R of the optical disk can be adjusted.
A data signal can be stably extracted from the F signal.

Here, a method of generating a dropout signal from an analog RF signal will be described. The term “dropout” generally refers to a state in which data read from an optical disk is missing due to a scratch on the surface of the optical disk or the like.
(A)), the high-speed detection signal 37 (FIG. 7 (b-1)), the low-speed detection signal 38 (FIG. 7 (b-2)), and the dropout detection signal 9 (FIG. 7 (c)). Show.

If the bright side of the analog RF signal, that is, the side where the reflection from the optical disk is large is set to the high level of the analog RF signal, and the dark side, that is, the side where the reflection of the optical disk is small, is set to the low level of the RF signal, FIG. As described above, in the non-dropout state, the optical pickup 40 reads the reflection of the portion where the data of the optical disk exists, so that both the light side and the dark side exist, and the light side envelope and the dark side envelope are almost constant. Value.

However, in the case of the dropout state, the optical pickup 40 reads a portion where data is missing, so that the reflection from the optical disk is reduced and the level of the bright side envelope signal is lowered. By utilizing this property, dropout detection can be performed.

A dropout detection circuit for detecting such a dropout will be described below.
FIG. 6 is a block diagram showing a configuration of a conventional dropout detection circuit. In FIG. 6, reference numeral 30 denotes a high-speed detection circuit;
1 is an external circuit (I), 32 is a low-speed detection circuit, 33 is an external circuit (II), 34 is a shift circuit, 35 is a comparison circuit,
1 is an analog RF signal, 37 is a high-speed detection signal, 38 is a low-speed detection signal, 39 is a shift signal, 9 is a dropout detection signal, and 36 is a current switching signal.

The high-speed detection circuit 30 has its output terminal connected to GND.
The external circuit (I) 31 is configured so that an arbitrary predetermined current can flow between the high-speed detection circuit 30 and the high-speed detection circuit 30 so as to provide the high-speed detection circuit 30 with a detection time constant for obtaining a detection speed for high-speed detection. Of the high-speed detection circuit 30 and a current source for flowing a predetermined current between the output terminal of the high-speed detection circuit 30 and GND.

The low-speed detection circuit 32 is configured such that an arbitrary current can flow between its output terminal and GND, and that the amount of current can be controlled by a current switching signal 36. The external circuit (II) 33 In order to provide the low-speed detection circuit 32 with a detection time constant for obtaining a detection speed for low-speed detection, the capacitance connected between the output terminal of the low-speed detection circuit 32 and GND and the output of the low-speed detection circuit 32 A current source for flowing an arbitrary current between the end and GND. Here, the current switching signal 36 is a repetitive signal of a level H (high) section and a level L (low) section, and the output terminal of the low-speed detection circuit 32 is changed by changing the ratio of the H section and the L section. And the amount of current between GND and GND can be changed.

In the drop-out detection circuit configured as described above, the high-speed detection circuit 30 uses the detection speed obtained by the capacitance of the external circuit (I) 31 and the current source to generate the analog RF signal 1. On the other hand, analog high-speed detection is performed to generate a high-speed detection signal 37. On the other hand, the low-speed detection circuit 32 performs analog low-speed detection on the analog RF signal 1 using the capacitance of the external circuit (II) 33 and the detection speed obtained from the current source and the current switching signal 36, and outputs the low-speed detection signal. 38 is generated.

Next, a shift circuit 34 shifts the level of the low-speed detection signal 38 to generate a shift signal 39, and a comparison circuit 35 compares the high-speed detection signal 37 with the shift signal 39. A section whose level is higher than the level of the high-speed detection signal 37 is set to a dropout state, a dropout detection signal 9 is generated as a signal that detects the dropout state, and the dropout detection signal 9 is used as an output of the dropout detection circuit. .

By configuring as described above, FIG.
As shown in FIG. 7B, when the level of the bright-side envelope signal is low (dropout state), the shift signal 39 obtained by shifting the low-speed detection signal 38 has little change, but the high-speed detection signal 37 has Since the change is large, the level of the high-speed detection signal 37 is lower than that of the shift signal 39, and it is possible to detect that the level of the bright-side envelope signal has decreased, thereby performing dropout detection.

When the reproduction speed is changed, for example, when the reproduction speed is doubled, the width of the dropout is actually changed to 1/2 as compared with the case of the single speed shown in FIG. FIG. 7 shows the tracking performance of the low-speed detection circuit 32 due to the time constant and the like.
In the case where the level of the low-speed detection signal 38 is higher than that in FIG. 7B and the level of the shift signal 39 is higher when the tracking performance at the 1 × speed of FIG. The width of the section where the level is lower than the shift signal 39 (dotted line section), that is, the width of the section detected as the dropout state becomes wider than the actual dropout width, and the dropout detection signal 9 having a desired width is obtained. Can not.

In the conventional configuration, the amount of current between the output terminal and the GND of the low-speed detection circuit 32 is switched by the current switching signal 36 in response to the change in the reproduction speed as described above.
By controlling the discharge current from the capacitance of the external circuit (II) 33 to change the detection time constant and changing the tracking performance of the low-speed detection circuit 32 (here, improving the tracking performance), low-speed detection is performed. The level of the signal 38 and the level of the shift signal 39 are adjusted (here, lowered) to obtain the dropout detection signal 9 having a desired width.

[0017]

However, in the above-described conventional dropout detection circuit, an external circuit 3 is connected to each of the low-speed detection circuit 32 and the high-speed detection circuit 30.
Since the detection circuits 3 and 31 are required, dedicated terminals for connecting the external circuits 33 and 31 to the detection circuits 32 and 30 are required.

The change in reproduction speed is realized by switching the amount of current flowing from its output terminal to GND in the low-speed detection circuit 32 by the current switching signal 36. However, this method is flexible. And the detection accuracy is poor.
Further, the switching of the current amount has a problem that an external circuit is changed and an analog circuit is increased.

In the future, when the integration into the optical disk signal processing / controller block 42 shown in FIG. 8 is considered, the analog circuit requires many external circuits and is easily affected by manufacturing variations. There is also a problem that it is difficult to design a circuit and it is difficult to reduce the area even if the process becomes finer in the future.

On the other hand, a method of detecting dropout by detecting the slope of the bright side envelope signal, a method of detecting dropout by detecting a level difference between the bright side and dark side envelope signals, and the like. There is.

However, in these methods, in dropout detection by detecting the inclination of the bright side envelope signal, there is a possibility of erroneous detection in the case of an exceptional envelope signal affected by the state of noise or flaws.

In the dropout detection by detecting the level difference between the envelope signals on the light side and the dark side, the levels on the light side and the dark side must always be detected by the A / D converter, which increases the circuit scale. Or increase in current consumption.

The present invention solves the above-mentioned conventional problems. The parameters can be easily changed without the need for an external circuit or an analog circuit, and the external speed and other external factors such as the reproduction speed can be reliably determined. In addition to performing optimal dropout detection, it is possible to prevent false detection in the case of exceptional envelope signals affected by noise and scratch conditions, and
Provided is a dropout detection circuit which can suppress an increase in circuit scale and current consumption and can be less affected by manufacturing variations.

[0024]

In order to solve the above-mentioned problems, a drop-out detection circuit according to the present invention is provided for converting an analog RF signal corresponding to the information obtained by reproducing a disk serving as an information recording medium from an analog RF signal. A dropout detection circuit for detecting a dropout generated during the reproduction; an A / D converter for converting the analog RF signal into a digital RF signal; and a digital RF signal from the A / D converter. A peak detection circuit for extracting a bright side envelope, a slope detection circuit for detecting a slope of a level of the bright side envelope signal from the peak detection circuit with respect to a lapse of time, and a down state of the slope signal from the slope detection circuit is detected. Means for outputting a slope-down detection signal and a slope-up detection signal that detects an up state of the slope signal; A comparison level parameter setting circuit that generates a level comparison reference signal serving as a comparison reference for the level detection of the light side envelope signal from the detection circuit, and comparing the light side envelope signal from the peak detection circuit with the level comparison reference signal; A first level comparison circuit for detecting that the level of the bright side envelope signal is lower than the level comparison reference signal, and comparing the light side envelope signal from the peak detection circuit with the level comparison reference signal, A second level comparison circuit for detecting that the level of the side envelope signal has exceeded the level comparison reference signal, and a logical AND of the slope down detection signal and a comparison result of the first level comparison circuit; Reset by the logical sum of the slope-up detection signal and the comparison result of the second level comparison circuit A set / reset FF that outputs a drop-out detection signal, wherein the comparison level parameter setting circuit is configured to control the level comparison reference signal based on a level comparison parameter corresponding to a level tendency state of the inclination signal from the inclination detection circuit. Is changed.

With this configuration, the dropout detection is set when both the slope and the detection level of the bright side envelope signal satisfy the dropout detection set condition, and the dropout is detected when one of the dropout detection reset conditions is satisfied. Reset out detection.

Also, it is possible to digitally set parameters corresponding to changes in external factors such as a change in reproduction speed, to enable flexible setting, and to perform optimum dropout detection by an automatic parameter setting circuit. Parameter setting, and external circuits and large-scale analog circuits required for analog circuits are reduced.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A dropout detection circuit according to a first aspect of the present invention uses a drop-out detection circuit for reproducing an analog RF signal corresponding to the information obtained by reproducing a disk as an information recording medium. A dropout detection circuit for detecting a dropout occurring in the analog RF
An A / D converter for converting a signal into a digital RF signal; a peak detection circuit for extracting a bright envelope of the digital RF signal from the A / D converter; and a bright envelope signal from the peak detection circuit A slope detection circuit that detects a slope of the level with respect to the passage of time, a slope down detection signal that detects a down state of the slope signal from the slope detection circuit, and a slope up detection signal that detects an up state of the slope signal. Means, a comparison level parameter setting circuit for generating a level comparison reference signal serving as a comparison reference for the level detection of the light side envelope signal from the peak detection circuit, and the level comparison of the light side envelope signal from the peak detection circuit. Compare with the reference signal,
A first level comparison circuit for detecting that the level of the bright side envelope signal is lower than the level comparison reference signal, and comparing the light side envelope signal from the peak detection circuit with the level comparison reference signal, A second level comparison circuit for detecting that the level of the side envelope signal has exceeded the level comparison reference signal, and a logical AND of the slope down detection signal and a comparison result of the first level comparison circuit; A set / reset FF for outputting a dropout detection signal reset by a logical sum of the inclination up detection signal and the comparison result of the second level comparison circuit; Based on the level comparison parameter corresponding to the level tendency state of the slope signal from the circuit,
The level comparison reference signal is configured to be changed.

According to a second aspect of the present invention, there is provided a dropout detection circuit including a comparison level parameter switching circuit for switching a level comparison parameter in accordance with the level tendency state of the inclination signal according to the first aspect. As the level comparison parameter, when the level tendency state is down, a logical product signal is used, and when the level tendency state is up, a logical sum signal is used.
It is configured to switch to the slope-up comparison parameter given at the time of the up-up.

According to a third aspect of the present invention, there is provided a dropout detecting circuit for extracting a dark side envelope which is a bottom side of a digital RF signal from the A / D converter according to the first or second aspect, A comparison parameter setting circuit for setting a slope-down comparison parameter and a slope-up comparison parameter based on the bright-side envelope signal and the dark-side envelope signal from the bottom detection circuit; and A level difference between the bright side envelope signal and the dark side envelope signal is detected, and according to the level difference, the slope down comparison parameter and the slope up comparison parameter are automatically set.

According to these configurations, the dropout detection is set when both the inclination and the detection level of the bright side envelope signal satisfy the set condition of the dropout detection, and either one of them satisfies the reset condition of the dropout detection. Reset dropout detection at times.

Also, it is possible to digitally set parameters corresponding to a change in an external factor such as a change in reproduction speed, to enable flexible setting, and to perform an optimum dropout detection by an automatic parameter setting circuit. Parameter setting, and external circuits and large-scale analog circuits required for analog circuits are reduced.

Hereinafter, a dropout detection circuit according to an embodiment of the present invention will be specifically described with reference to the drawings. (First Embodiment) A dropout detection circuit according to a first embodiment of the present invention will be described.

FIG. 1 is a block diagram showing the configuration of the dropout detection circuit according to the first embodiment. In FIG. 1, reference numeral 1 denotes an analog RF signal read from a disc;
Is an A / D converter, 3 is a peak detection circuit, 4 is a slope detection circuit, 5 is a slope down detection circuit, 6 is a slope up detection circuit, 7 is a level comparison circuit, 8 is a comparison level parameter setting circuit, and 9 is logic. A product circuit, 10 is an OR circuit, 11 is a set-reset flip-flop (SR-FF), 12 is a digital RF signal, 13 is a light-side envelope signal, 1
4 is a slope signal, 15 is a slope down detection signal, 16 is a slope up detection signal, 17 is a level comparison result signal (A), 1
8 is a level comparison result signal (B), 19 is a level comparison parameter, 20 is a level comparison reference signal, 21 is a dropout detection set signal, 22 is a dropout detection reset signal, and 23 is a dropout detection signal.

The operation of the dropout detection circuit configured as described above will be described below. FIG.
An analog RF signal 1 shown in FIG. 1A is converted into a digital RF signal 12 by an A / D converter 2 and a peak detection circuit 3
Is input to In the peak detection circuit 3, digital RF
A light-side envelope signal 13 as shown in FIG. 2B is extracted from the signal 12, and the extracted light-side envelope signal 13 is extracted.
Is input to the inclination detection circuit 4 and the level comparison circuit 7.

The tilt detection circuit 4 holds the data of the light-side envelope signal 13 one sample before, and generates a tilt signal 14 by taking the difference from the light-side envelope signal 13 input this time.

On the other hand, the level comparison circuit 7 compares the level comparison reference signal 20 set by the comparison level parameter setting circuit 8 as shown in FIG. It is determined whether or not the level of the currently input analog RF signal 1 has dropped. When the bright side envelope signal 13 is at a lower level than the level comparison reference signal 20, FIG.
A level comparison result signal (A) 17 as shown in (d) is output, and the bright side envelope signal 13 is
If the level is higher than 0, a level comparison result signal (B) 18 as shown in FIG.

When the level of the input tilt signal 14 is in a down direction with respect to the passage of time, the tilt down detection circuit 5 outputs a tilt down detection signal 15 as shown in FIG. When the level of the input tilt signal 14 is in the upward direction with respect to the passage of time, the tilt-up detection circuit 6 outputs a tilt-up detection signal 16 as shown in FIG.

The AND circuit 9 takes the logical product of the slope down detection signal 15 output from the slope down detection circuit 5 and the level comparison result signal (A) 17, and outputs the FF 11 by the output dropout detection set signal 21. Is set. The OR circuit 10 performs a logical OR operation of the slope-up detection signal 16 output from the slope-up detection circuit 6 and the level comparison result signal (B) 18, and outputs the FF 11 by the output dropout detection reset signal 22. Reset.

The output signal of the FF 11 is output as a dropout detection signal 23 as shown in FIG. As described above, the conventional analog circuit is changed to a digital circuit, and the combination of the two conditions of the inclination detection and the level comparison of the RF signal for dropout detection and the comparison level parameter setting circuit 8 are provided. Since the level comparison reference signal 20 can be digitally set on the basis of the level comparison parameter 19, the level comparison reference signal 20 can be set flexibly, and the optimum drop can always be optimized for external factors such as a change in reproduction speed. Out detection can be performed.

Next, an example of dropout detection in the case of being affected by an external factor such as noise will be described. FIGS. 9A and 9B are waveform diagrams showing an example of dropout detection when noise occurs. FIG. 9A shows a light-side envelope signal with noise, FIG. 9B shows a dark-side envelope signal, and FIG.
Is a level comparison reference signal serving as a detection level determination reference for dropout detection, (d) is a dropout detection signal obtained by detecting inclination with respect to the bright side envelope signal, and (e) is inclination detection and level judgment with respect to the bright side envelope signal. 7 is a dropout detection signal under the following two conditions.

The slope of the bright side envelope signal is detected by the noise generated as shown in FIG. 9 (a). In the dropout detection by detecting the slope with respect to the bright side envelope signal, this noise is detected as shown in FIG. 9 (d). The waveform is detected as a dropout state. On the other hand, in dropout detection under the two conditions of the gradient of the light-side envelope signal and the detection level, the detection level of the light-side envelope signal does not satisfy the condition of dropout detection.
This noise waveform is not detected as a dropout state as in (e).

FIGS. 10A and 10B are waveform diagrams showing examples in which the bright side envelope signal cannot be obtained in an ideal state due to the influence of the scratches on the disk. FIG. 10A shows the bright side envelope signal, and FIG. Is a dark side envelope signal, (c) is a level comparison reference signal serving as a detection level determination reference for dropout detection, (d) is a dropout detection signal obtained by detecting a slope with respect to the light side envelope signal, and (e) is a light side detection signal. Is a dropout detection signal under two conditions of a gradient with respect to the envelope signal and a detection level.

The operation at the time of setting the dropout detection (timing t1) is as follows.
(D)), and dropout detection (FIG. 10 (e)) based on two conditions of the gradient and the detection level for the bright side envelope signal, are performed without any problem.

However, with respect to the operation at the time of resetting the dropout detection (timing t2), since the slope of the signal at this reset is smaller than the assumed slope, the up state of the slope is not detected. As a result, in the dropout detection based only on the inclination detection for the bright side envelope signal, the reset of the dropout detection is not performed as shown in FIG.

On the other hand, in the dropout detection based on the two conditions of the gradient of the envelope signal on the light side and the detection level, the dropout detection reset by the level detection is performed although the dropout detection reset by the tilt detection is not performed. Therefore, dropout detection is normally performed as shown in FIG. (Second Embodiment) A dropout detection circuit according to a second embodiment of the present invention will be described.

The dropout detection circuit according to the second embodiment sets the level comparison parameter at the time of dropout detection setting and the level comparison parameter at the time of resetting dropout detection in the first embodiment separately. It is an improved version that can be flexibly used in many systems.

FIG. 3 is a block diagram showing the configuration of the dropout detection circuit according to the second embodiment. In FIG. 3, reference numeral 1 denotes an analog RF signal read from a disc;
Is an A / D converter, 3 is a peak detection circuit, 4 is a slope detection circuit, 5 is a slope down detection circuit, 6 is a slope up detection circuit, 7 is a level comparison circuit, 8 is a comparison level parameter setting circuit, and 9 is logic. A product circuit, 10 is an OR circuit, 11 is a set / reset FF, 12 is a digital RF signal, 13 is a bright side envelope signal, 14 is a slope signal, 15 is a slope down detection signal, 16 is a slope up detection signal, and 17 is a level. A comparison result signal (A), 18 is a level comparison result signal (B), 19 is a level comparison parameter, 20 is a level comparison reference signal, 21 is a dropout detection set signal, 2
2 is a dropout detection reset signal, 23 is a dropout detection signal, 24 is a comparison level parameter switching circuit, 25 is a slope down comparison parameter, and 26 is a slope up comparison parameter.

With respect to the dropout detection circuit configured as described above, only the operation of the circuit different from that of the first embodiment will be described. The comparison parameter 25 at the time of inclination down and the comparison parameter 26 at the time of inclination up are set in the comparison level parameter switching circuit 24. Normally, the comparison level parameter switching circuit 24 sets the comparison parameter 25 at the time of inclination down to the level comparison parameter 19.
Is output as

When the dropout detection set signal 21 is output, the comparison level parameter switching circuit 24
The level comparison parameter 19 is switched to the tilt-up comparison parameter 26. Next, when the dropout detection reset signal 22 is output, the level comparison parameter 19 is returned to the inclination down comparison parameter 25.

Other operations are the same as those in the first embodiment. The difference between the operation of the second embodiment and the operation of the first embodiment will be described below.

FIG. 11 is a waveform diagram showing an example in which the light-side envelope signal could not be obtained in an ideal state due to the effect of the state of the scratch on the disk. FIG. 11 (a) is a light-side envelope signal, and FIG. Is a envelope signal on the dark side, (c-1) is a set level comparison reference signal serving as a detection level determination criterion when dropout detection is set, and (c-2) is a reset level reference criterion when dropout detection is reset. The level comparison reference signal, (d) is the dropout detection signal according to the first embodiment, and (e) is the dropout detection signal according to the second embodiment.

As shown in FIG. 11A, the rising edge of the bright side envelope signal has a gentle slope due to the influence of the flaw. Therefore, dropout detection is not reset by tilt detection. In the case of the first embodiment in which the level comparison parameter is only (c-1), the dropout detection state becomes longer (timing t3).

On the other hand, in the case of the second embodiment in which the level comparison parameter can be set separately for two types, that is, at the time of setting the dropout detection and at the time of resetting, the reset comparison parameter of FIG. By setting it lower than the reset comparison parameter of -1), the timing at the time of resetting the dropout detection can be advanced (timing t2).

If the dropout state becomes too long, the system may become unstable. Thus, by separately setting the level comparison parameters at the time of setting the dropout detection and at the time of resetting, It is necessary to make settings so that dropout detection that is optimal for the system to be used can be performed. (Third Embodiment) A dropout detection circuit according to a third embodiment of the present invention will be described.

In the third embodiment, the level comparison parameter is automatically set to improve the setting of dropout detection as compared with the first and second embodiments. .

FIG. 4 is a block diagram showing the configuration of the dropout detection circuit according to the third embodiment. In FIG. 4, reference numeral 1 denotes an analog RF signal read from a disc;
Is an A / D converter, 3 is a peak detection circuit, 4 is a slope detection circuit, 5 is a slope down detection circuit, 6 is a slope up detection circuit, 7 is a level comparison circuit, 8 is a comparison level parameter setting circuit, and 9 is logic. A product circuit, 10 is an OR circuit, 11 is a set / reset FF, 12 is a digital RF signal, 13 is a bright side envelope signal, 14 is a slope signal, 15 is a slope down detection signal, 16 is a slope up detection signal, and 17 is a level. The comparison result signals (A), 18 are level comparison result signals (B), 19 is a level comparison parameter, 20 is a level comparison reference signal, 21 is a dropout detection set signal, 2
2 is a dropout detection reset signal, 23 is a dropout detection signal, 24 is a comparison level parameter switching circuit, 25 is a slope down comparison parameter, 26 is a slope up comparison parameter, 27 is a bottom detection circuit, 28
Is a comparison parameter automatic setting circuit, and 29 is a dark side envelope signal.

With respect to the dropout detection circuit configured as described above, only the operation of the circuit different from that of the second embodiment will be described. The digital RF signal 12 converted from the analog RF signal 1 by the A / D converter 2 is input to the bottom detection circuit 27. This bottom detection circuit 2
At 7, the dark side envelope signal 29 as shown in FIG. 5 (e) is detected. The dark side envelope signal 29 detected by the bottom detection circuit 27 and the light side envelope signal 13 detected by the peak detection circuit 3 are input to a comparison parameter automatic setting circuit 28.

In the comparison parameter automatic setting circuit 28, the difference between the light side envelope signal 13 and the dark side envelope signal 29 is obtained, and the slope between the light side envelope and the dark side envelope as shown in FIG. Downtime comparison parameter 2
5 and a tilt-up comparison parameter 26 as shown in FIG.

The subsequent operation is the same as in the second embodiment. As described above, in the third embodiment,
The comparison parameter 25 at the time of inclination down and the comparison parameter 26 at the time of inclination up can be automatically set, and simplification of level comparison parameter setting can be easily realized.

[0060]

As described above, according to the present invention, dropout detection is set when both of the gradient and the detection level of the bright side envelope signal satisfy the set conditions of dropout detection, and either of them sets the dropout detection. Can be reset when the reset condition is satisfied.

In addition, parameters can be set digitally in response to changes in external factors such as changes in reproduction speed, so that flexible settings can be made. An optimum parameter setting circuit detects an optimum dropout. Can be simplified, and an external circuit and a large-scale analog circuit required for an analog circuit can be reduced.

As described above, the parameters can be easily changed without the need for an external circuit or an analog circuit. It is possible to prevent erroneous detection in the case of an exceptional envelope signal affected by the state of a flaw, suppress an increase in circuit scale and current consumption, and reduce the influence of manufacturing variations. be able to.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a dropout detection circuit according to a first embodiment of the present invention;

FIG. 2 is a waveform chart of each part showing an operation in the first embodiment.

FIG. 3 is a configuration block diagram of a dropout detection circuit according to a second embodiment of the present invention;

FIG. 4 is a configuration block diagram of a dropout detection circuit according to a third embodiment of the present invention.

FIG. 5 is a waveform chart showing a level comparison parameter automatic setting operation in the third embodiment.

FIG. 6 is a configuration block diagram of a conventional dropout detection circuit.

FIG. 7 is a waveform chart of each part showing an operation in the conventional example.

FIG. 8 is a block diagram showing a configuration of a general optical disk system.

FIG. 9 is a waveform diagram for explaining comparison of dropout detection when noise occurs.

FIG. 10 is a waveform chart for comparing and explaining dropout detection when the signal is not an ideal bright side envelope signal.

FIG. 11 is a waveform diagram for dropout detection when level comparison parameters for dropout detection are set separately for set and reset.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 analog RF signal 2 A / D converter 3 peak detection circuit 4 inclination detection circuit 5 inclination down detection circuit 6 inclination up detection circuit 7 level comparison circuit 8 comparison level parameter setting circuit 9 AND circuit 10 OR circuit 11 set reset flip-flop (FF) 12 Digital RF signal 13 Bright side envelope signal 14 Slope signal 15 Slope down detection signal 16 Slope up detection signal 17 Level comparison result signal (A) 18 Level comparison result signal (B) 19 Level comparison parameter 20 Level comparison reference Signal 21 Dropout detection set signal 22 Dropout detection reset signal 23 Dropout detection signal 24 Comparison level parameter switching circuit 25 Comparison parameter at the time of inclination down 26 Comparison parameter at the time of inclination up 27 Bottom detection circuit 28 Automatic comparison parameter setting circuit 29 Dark side envelope signal 30 High speed detection circuit 31 External circuit (I) 32 Low speed detection circuit 33 External circuit (II) 34 Shift circuit 35 Comparison circuit 36 Current switching signal 37 High speed detection signal 38 Low speed detection signal 39 shift signal 40 optical pickup 41 head amplifier block 42 optical disk signal processing / controller block

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Tateo Doi 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. F term (reference) 5C053 FA23 HB07 KA21 KA25 5D044 AB05 BC03 CC04 FG05 FG16 5D080 AA07 DA06 FA15 FA37 5D090 AA01 BB02 CC04 DD03 DD05 EE12 FF37 FF38

Claims (3)

[Claims] 1. An analog RF signal corresponding to information obtained by reproducing a disk which is a recording medium of information,
An A / D converter for converting the analog RF signal into a digital RF signal in a dropout detection circuit for detecting a dropout generated during the reproduction;
A peak detection circuit for extracting a light-side envelope of the digital RF signal from the A / D converter; a slope detection circuit for detecting a level slope of the light-side envelope signal from the peak detection circuit over time; Means for outputting a slope-down detection signal that detects a down state of the slope signal from the detection circuit, and a slope-up detection signal that detects an up state of the slope signal, and level detection of a bright-side envelope signal from the peak detection circuit A comparison level parameter setting circuit for generating a level comparison reference signal serving as a comparison reference for comparing the bright side envelope signal from the peak detection circuit with the level comparison reference signal, and comparing the level of the light side envelope signal with the level comparison A first level comparison circuit for detecting that the signal level has dropped below the reference signal;
A second level comparison circuit that compares the light side envelope signal from the peak detection circuit with the level comparison reference signal, and detects that the level of the light side envelope signal exceeds the level comparison reference signal; A dropout detection signal that is set by the logical product of the down detection signal and the comparison result of the first level comparison circuit, and is reset by the logical sum of the inclination up detection signal and the comparison result of the second level comparison circuit And a set / reset FF for outputting the reference level signal. A dropout detection circuit characterized by comprising. And a comparison level parameter switching circuit for switching a level comparison parameter in accordance with a level tendency state of the inclination signal, wherein the comparison level parameter switching circuit is used as the level comparison parameter when the level tendency state is down. By the AND signal, the slope down comparison parameter given at the time of the down, when the level tendency state is up, by the OR signal, the slope up comparison parameter given at the time of the up,
2. The dropout detection circuit according to claim 1, wherein the dropout detection circuit is configured to switch between them. 3. A bottom detection circuit for extracting a dark side envelope which is a bottom side of the digital RF signal from the A / D converter, based on a light side envelope signal and a dark side envelope signal from the bottom detection circuit. A comparison parameter setting circuit for setting a comparison parameter at the time of inclination down and a comparison parameter at the time of inclination up, the comparison parameter setting circuit detects a level difference between the bright side envelope signal and the dark side envelope signal, and 3. The drop-out detection circuit according to claim 1, wherein the comparison parameter at the time of inclination-down and the comparison parameter at the time of inclination-up are automatically set according to a level difference.