JPH117637A - Optical disk drive - Google Patents

Abstract

(57) [Problem] To prevent a dropout detection signal from being erroneously detected for a long time when a dropout occurs in which the amount of light reflected from an optical disk increases. A first switch means is turned off when a charging voltage of a first capacitor holding a peak value of a total reflection light quantity signal corresponding to a reflection light quantity from an optical disk exceeds a first reference voltage. Then, the first resistor 9 is inserted in series with the first capacitor having a predetermined time constant, and the time constant is changed so as to delay the charging time of the first capacitor. In the case where the error occurs or the amount of reflected light temporarily increases at the time of start-up of the apparatus and in a transition state of setting switching, erroneous detection of the dropout detection signal for a long time can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus having a dropout detecting means for detecting a dropout of reproduction information.

[0002]

2. Description of the Related Art In recent years, compact discs (hereinafter referred to as CDs) have been developed.
Abbreviated as MD) or mini-disc (hereinafter abbreviated as MD)
As described above, an optical disk device that records information on a disk-shaped optical recording medium and / or reproduces information recorded on such an optical recording medium is becoming widespread. Generally, in an optical disk device, a loss or a drop-out (hereinafter, simply referred to as a drop-out) of reproduction information due to foreign matter such as dust or dirt adhering to the disk surface,
Dropouts or the like may occur due to scratches or the like generated during the manufacturing process of the disk or during use of the disk. When dropout occurs, there is a possibility that tracking control and focus control of the optical pickup may be lost.

[0003] A CD has a read-only optical disk system. In a read-only optical system, it is guaranteed that an information signal is always recorded.
In general, a method of detecting a dropout of reproduced information based on a lack of a reproduced information signal is employed. (See JP-A-1-92972).

[0004] However, for example, in a disk device capable of recording and reproduction such as an MD, there may be an unrecorded area in a recordable area.
In such a case, the dropout cannot be detected by the method of monitoring the lack of the reproduction information signal. Therefore, in a disk device including a recordable area, dropout is detected by a method of monitoring a decrease in the amount of total reflection from an optical disk.

Hereinafter, an example of an optical disk apparatus having the above-described conventional dropout detecting means for detecting dropout will be described with reference to FIGS. 6 and 7. FIG. FIG. 6 is a block diagram showing a configuration of an example of a conventional optical disk device.
FIG. 7 is a timing chart showing voltage values (waveforms) due to the operation of each unit of the dropout detection means of the optical disk device shown in FIG. In FIG. 6, reference numeral 39 denotes a total reflection light quantity detection means for detecting a total reflection light quantity signal which is a DC voltage signal proportional to the total reflection light quantity by the optical disc. When the total reflection light quantity by the optical disc increases, the total reflection light quantity signal is detected. The voltage rises. Numeral 40 is a dropout detection means for generating a dropout detection signal q.

Reference numeral 41 denotes a diode 44, a capacitor 45, a current source 46 for discharging the charged voltage of the capacitor 45, an amplifier 47, and a voltage dividing means 48. This is low-frequency component detection means for detecting a value and holding it with a large time constant. Here, the diode 44 and the capacitor 45 act so as to hold the peak voltage value of the total reflection light amount signal.
The voltage loss due to the forward voltage of the diode 44 is electrically compensated inside the total reflection light amount detecting means 39.

Reference numeral 46 denotes a current source for gradually discharging the charge of the capacitor 45 to gradually reduce the voltage value n of the charged voltage of the capacitor 45, and reference numeral 48 denotes a resistor 48a and a resistor 48b.
And the voltage value n of the charging voltage of the capacitor 45 is divided through the amplifier 47 at a predetermined voltage dividing ratio by the resistors 48a and 48b, and the voltage value p of the output signal is input to the + input of the comparator 43. The voltage dividing means 42 is composed of a diode 49, a current source 50 and an amplifier 51. The buffer 42 buffers the total reflection light amount signal and inputs the voltage value q of the output signal to the negative input of the comparator 43. Note that the diode 49 and the current source 5 which are components of the buffer 42 are
0 and the amplifier 51 are provided to maintain the electrical characteristics balance between the diode 44, the current source 46, and the amplifier 47, respectively.

As in the case of the diode 44, the voltage loss due to the forward voltage of the diode 49 is electrically compensated inside the total reflection light amount detecting means 39. Also, 4
3 compares the + side input voltage with the − side input voltage, and determines the + side input voltage, that is, the voltage value p of the output signal of the voltage dividing means 48.
Outputs an H level dropout detection signal q when the input voltage is higher than the negative input voltage, that is, the voltage value m of the output signal of the buffer 42, and outputs an L level output when the positive input voltage is lower than the negative input voltage. This is a comparator that outputs a dropout detection signal q.

Reference numeral 52 denotes control means for performing focus control or tracking control of the optical pickup, and the dropout detection means 40 outputs a dropout detection signal q
While the control signal is output as the H level, the control means 52 performs a protection processing operation such as holding the control (maintaining the current state) for the focus control or the tracking control, and prevents the servo from being disengaged due to the occurrence of the dropout. I do. Usually, dropout due to dust on the optical disk surface is short, for example, about 1 ms. Therefore, even if protection processing such as holding of servo control is performed, the servo system may fail. Never.

Hereinafter, the operation of the optical disk apparatus having the above-described conventional dropout detecting means will be described with reference to FIGS. In FIG. 7, the horizontal axis represents time, and the vertical axis represents voltage value. As the voltage value (waveform), m is the voltage value of the output signal of the buffer 42, and n is the capacitor 4
5, the voltage value of the charging voltage, and p is the voltage value of the output signal of the voltage dividing means 48. These symbols represent the operation of the portions indicated by the same symbols as those shown in FIG. Are superimposed on the reference. The rectangular wave signal q is a digital signal having H and L levels indicating a dropout detection signal output from the comparator 43.

First, an operation in the case where no dropout occurs as shown in a section t15 in FIG. 7 will be described. That is, at this time, since the voltage of the total reflection light amount signal hardly fluctuates, the voltage value p of the output signal of the voltage dividing means 48 is lower than the voltage value m of the output signal of the buffer 42. Therefore, the comparator 43 outputs the dropout detection signal q
Is output as L level. It indicates that no dropout has occurred. Therefore, the control means 52 performs a normal operation for the focus control or the tracking control.

Next, as shown in a section t16 in FIG. 7, when the total reflection light amount signal temporarily drops suddenly due to the occurrence of dropout due to the attachment of foreign matter such as dust or dirt on the optical disk surface. Will be described. When the total reflection light amount signal temporarily decreases, the voltage value m of the output signal of the buffer 42 sharply decreases as the voltage of the total reflection light amount signal decreases.

On the other hand, the voltage value p of the output signal of the voltage dividing means 48
Is held by the capacitor 45, so that the interval t1
Also in 6, the voltage value hardly changes from the voltage value in the section t15, and only the voltage gradually decreases according to the time constant determined by the capacitor 45 and the current source 46.
Therefore, the voltage value p of the output signal of the voltage dividing means 48 is higher than the voltage value m of the output signal of the buffer 42 in the section t16 in which the dropout occurs due to the attachment of foreign matter such as dust or dirt. Therefore, the comparator 43 outputs an H level indicating the occurrence of dropout as the dropout detection signal q. Therefore, the control unit 52 performs a protection processing operation such as a hold of the servo control for the focus control or the tracking control to prevent the servo from being disengaged.

Next, as shown in the section t17, the voltage value of each signal by the operation of each section after passing through the dropout will be described. Since the voltage value m of the output signal of the buffer 42 returns to the same voltage as that in the section t15 in accordance with the voltage recovery of the total reflection light amount signal, the dropout detection signal q which is the output signal of the comparator 43 indicates that no dropout has occurred. It becomes L level. Therefore, the control means 52 executes the normal operation again for the focus control or the tracking control.

[0015]

In the conventional optical disk apparatus having the above-described dropout detecting means, the reliability of the dropout detection signal is originally required to improve the stability of the servo operation.

Incidentally, in a magneto-optical disk such as an MD (hereinafter collectively referred to as an optical disk), a reflection layer made of a photoreflectivity material such as aluminum is provided on the back side of a recording layer made of a magneto-optical material. The light reflectance of a reflective layer made of aluminum or the like is higher than the light reflectance of a recording layer such as a dielectric or a porcelain material for performing magneto-optical recording. When a pinhole occurs in the recording layer due to a defect in the manufacturing of the optical disc and the aluminum reflective layer is exposed, the signal of the amount of light reflected from the optical disc temporarily increases. This phenomenon is different from the above-described case where dropout occurs due to the attachment of foreign matter such as dust and dirt on the optical disk surface. Such a phenomenon in which the reflected light amount signal temporarily increases may also occur at the time of starting the apparatus and setting switching in a transition period when switching the recording / reproducing operation of the optical disk apparatus.

However, in the optical disk apparatus having the above-mentioned conventional dropout detecting means, there is a case where a dropout in which the amount of reflected light increases due to a scratch on the optical disk such as a pinhole in the recording layer occurs, or when the apparatus is started and the setting is switched. For example, when the amount of reflected light temporarily increases in the transient state, the dropout may be erroneously detected for a long time.

Hereinafter, erroneous detection in the optical disk device having the above-described conventional dropout detecting means will be described with reference to FIGS. 6 and 7. For example, section t1 in FIG.
The voltage value of each signal in 8 indicates the voltage value of each signal changed by the operation of each unit when the amount of reflected light sharply increases due to a scratch on the optical disk or the like as compared to the section t17. The voltage value m of the output signal of the buffer 42 sharply increases as the amount of reflected light increases and reaches a peak. Dividing means 4
The voltage value p of the output signal of No. 8 also sharply increases because the peak voltage value of the total reflection light amount signal held by the capacitor 45 sharply increases.

The section t19 indicates the voltage value of the signal changed by the operation of each section when the reflected light amount returns to the original normal value from the state in which the reflected light amount sharply increases due to a scratch on the optical disk in the section t18. In a section t19, the voltage value m of the output signal of the buffer 42 returns to the original normal value, but the voltage once charged in the capacitor 45 gradually decreases according to a large time constant determined by the capacitor 45 and the current source 46. Therefore, it takes a long time for the voltage value p of the output signal of the voltage dividing means 48 to drop to the original value. Therefore, the comparator 43 keeps outputting the dropout detection signal q as the H level indicating the occurrence of the dropout for a long time. During this time, the control means 52 performs a protection processing operation such as holding servo control for a long period of time with respect to focus control or tracking control. As a result, there is a problem that the servo cannot follow up and servo deviates.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problem, and provides an optical disk apparatus for preventing a dropout detection signal from being erroneously detected for a long time when the amount of reflected light temporarily increases. The purpose is to do.

[0021]

SUMMARY OF THE INVENTION An optical disk apparatus according to the present invention has an envelope waveform of a peak value of a total reflected light amount signal corresponding to a reflected light amount from an optical disk or a peak value of a reproduced signal obtained by reproducing information recorded on an optical disk. When the peak value exceeds the reference voltage, a series resistor is connected to a capacitor having a predetermined time constant and holding the peak value of the total reflection light amount signal or the peak value of the envelope waveform of the peak value of the reproduction signal. Is connected, the time constant is changed so as to delay the charging time, and the rise of the peak value exceeding the reference voltage is suppressed.

Even if the amount of reflected light increases due to a dropout, or if the amount of reflected light temporarily increases at the time of starting the apparatus and in a transient state of setting switching, the peak value is immediately increased after the end of the dropout. As a result, an optical disk device that can be lowered to prevent the dropout detection signal from being erroneously detected for a long time can be obtained.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical disc apparatus according to the first aspect of the present invention comprises a first waveform peak detecting means for detecting a peak voltage value of a total reflection light amount from a disc-shaped optical recording medium; A first capacitor for holding an output voltage of the first waveform peak detecting means at a first time constant, a first voltage dividing means for dividing and outputting a charging voltage of the first capacitor, and a total reflection light amount A second comparator for detecting that the signal has fallen below the output voltage of the first voltage dividing means and outputting a dropout detection signal indicating a dropout of the total reflection light quantity signal. An optical disc device having first dropout detection means for outputting a signal to a control means for controlling a servo, for recording information on an optical recording medium and / or reproducing recorded information from the optical recording medium The first dropout detecting means further connects a first resistor connected to the first capacitor to delay the charging time thereof, and connects the first resistor to the first capacitor when the first capacitor is opened. When closing the first
A first switch means for short-circuiting and invalidating the resistance of the first capacitor, and comparing the charging voltage of the first capacitor with a first reference voltage to determine that the charging voltage of the first capacitor is equal to the first reference voltage. A first comparator which opens the first switch means when the first switch means is exceeded, and closes the first switch means otherwise, when the first switch means is opened. Is connected to the first capacitor to form a first increasing time constant to delay the charging of the first capacitor. Dropout occurs during information recording and / or reproducing operation. When the total reflected light amount increases and the voltage of the total reflected light amount signal exceeds the reference voltage, the capacitor charging time is delayed to prevent the dropout detection signal from being erroneously detected for a long time.

An optical disc apparatus according to a second aspect of the present invention includes a second waveform peak detecting means for detecting a peak voltage value of a reproduced signal obtained by reproducing information from a disc-shaped optical recording medium; A second capacitor for holding a peak value of the reproduced signal output from the waveform peak detecting means at a second time constant, a second voltage dividing means for dividing and outputting a charging voltage of the second capacitor, A fourth comparator for detecting that the reproduction signal has dropped below the output voltage of the second voltage dividing means and outputting a dropout detection signal indicating a dropout of the reproduction signal. A second dropout detecting unit that outputs a signal to a control unit that controls a servo, and performs recording of information on an optical recording medium and / or reproduction of recorded information from the optical recording medium; A disk device, wherein the second dropout detecting means further includes a second resistor connected to the second capacitor to delay a charging time thereof, and a second resistor connected to the second capacitor when the second capacitor is opened. And a second switch for short-circuiting the second resistor when closed and disabling the second resistor, and comparing the charging voltage of the second capacitor with a second reference voltage to charge the second capacitor. A third comparator that opens the second switch means when the voltage exceeds the second reference voltage and closes the second switch means otherwise; and a reproducing apparatus that reproduces information from the optical recording medium. Third waveform peak detecting means for detecting a peak voltage value of an envelope waveform of a signal peak value, and a third time constant shorter than the second time constant for reproducing a signal output from the third waveform peak detecting means. Hold in the third A capacitor, the second when the second switching means is opened
Is connected to the second capacitor to form a second increasing time constant so as to delay charging of the second capacitor. When the voltage of the signal exceeds the reference voltage, the charging time of the capacitor can be delayed to prevent erroneous detection of the dropout detection signal over a long period of time. By using a reproduction signal of information having a higher sensitivity to a signal level change due to dropout, an effect of making a response of detection of a dropout detection signal faster is provided.

An optical disk device according to a third aspect of the present invention is an optical disk device for recording information on a disk-shaped optical recording medium and / or reproducing recorded information from the optical recording medium. 2. A first drop-out detecting means according to claim 1, wherein the area judging means outputs an area judging signal by judging a recordable area and a reproduction-only area on the medium, and the recordable area in accordance with the area judging signal. Selecting means for selecting the second dropout detecting means according to claim 2 in the reproduction-only area, and outputting a dropout signal obtained from any of the means to a control means for controlling servo. The recording and / or reproducing of an optical disc having both a recordable area such as a pit or a groove and a read-only area. Ku has the effect of and the time of reproduction, by switching selectively the response of the servo operation by the difference between the detection response time of the drop-out detection signal which requires, to optimally improve the detection accuracy of the dropout.

Hereinafter, based on the attached drawings and FIGS. 1 to 5,
An embodiment of the present invention will be described in detail. FIG. 1 is a block diagram showing a configuration of an optical disk device according to a first embodiment of the present invention. FIG. 2 is a timing diagram showing an operation of detecting a dropout based on a voltage value of a signal of each unit of the optical disk device shown in FIG. 3 is a block diagram showing the configuration of the optical disk device according to the second embodiment of the present invention; FIG. 4 is a timing diagram showing the operation of detecting a dropout based on the voltage value of the signal of each part of the optical disk device shown in FIG. FIG. 9 is a block diagram illustrating a configuration of an optical disc device according to a third embodiment of the present invention.

(First Embodiment) First, a configuration of an optical disk device according to a first embodiment of the present invention will be described with reference to FIG. The configuration of the optical disk device according to the present embodiment is roughly divided into a total reflection light amount detection unit 1.
, The first low-frequency component detection means 3, the buffer 4, the second comparator 5, and the control means 18. The total reflection light quantity detection means 1 detects a total reflection light quantity signal which is a DC voltage signal proportional to the total reflection light quantity by an optical disk (optical recording medium), and outputs the output signal to the first low frequency component detection means 3 and a buffer. 4 are output. The voltage of the total reflection light amount signal increases when the total reflection light amount from the optical disk increases.

The first low-frequency component detecting means 3 includes a first waveform peak detecting means 6, a first capacitor 7, a first discharging means (current source) 8, a first resistor 9, The first switch means 10, the first reference voltage 11, the first comparator 12, the first amplifier 13 for the buffer, and the first voltage dividing means 14 are used to detect the total reflection light amount. The peak voltage value of the output signal of the means 1 is detected, held at a large first time constant, and output as the voltage value c of the output signal of the first voltage dividing means 14.

As the first waveform peak detecting means 6, for example, an NPN transistor or a diode can be used. The voltage loss due to the forward voltage of the first waveform peak detecting means 6 is electrically compensated inside the total reflection light quantity detecting means 1. As the first capacitor 7, for example, a multilayer ceramic capacitor or the like can be used. The first discharging means 8 discharges the charging voltage (voltage value b) of the first capacitor 7 with a first time constant, and can use, for example, a current mirror current source circuit or the like.

The first time constant is determined by the first capacitor 7
And the current value of the first discharging means 8,
Even if the output voltage of the total reflection light amount detecting means 1 is suddenly reduced for, for example, 1 ms due to the occurrence of dropout, the charging voltage of the first capacitor 7 is set to a value which is not greatly affected. The first switch means 10 can use, for example, an NPN transistor or the like, and inserts the resistance value of the first resistor 9 into a first time constant at the time of off (open) to switch the first capacitor 7. Try to delay the charging time.

The first comparator 12 includes a first capacitor 7
The voltage value b of the charging voltage and the voltage value e of the first reference voltage 11
When the voltage value b of the charging voltage of the first capacitor 7 exceeds the voltage value e of the first reference voltage 11, the first switch means 10 is turned off (opened). Otherwise, the first switch means 10 is turned on (closed). The voltage value e of the first reference voltage 11 is set higher than the charging voltage of the first capacitor 7 when the total reflected light amount signal is a normal total light amount sum signal. As the first comparator 12, a comparator, a hysteresis comparator, or the like can be used. In particular, the hysteresis comparator is preferable in terms of preventing chattering due to noise.

The first voltage dividing means 14 includes a voltage dividing resistor 14a and a voltage dividing resistor 14b.
Is a resistor that divides the charging voltage through the first amplifier 13 at a predetermined ratio and outputs the divided voltage. As the voltage dividing resistors 14a and 14b, for example, resistors can be used. The output of the first voltage dividing means 14 is input to the plus input of the second comparator 5. On the other hand, the diode 15, the current source 16, and the amplifier 17
Are provided for maintaining the electrical characteristic balance between the first waveform peak detecting means 6, the first discharging means 8, and the first amplifier 13, respectively.

The voltage loss due to the forward voltage of the diode 15 is electrically compensated inside the total reflection light quantity detecting means 1 as in the case of the first waveform peak detecting means 6.
The output of the buffer 4 is input to the negative input of the second comparator 5. The second comparator 5 compares the + input voltage (the voltage value c of the output signal of the first voltage dividing means 14) with the − input voltage (the voltage value a of the output signal of the buffer 4),
When the + input voltage is higher than the − input voltage, an H level is output as the dropout detection signal d. When the + input voltage is lower than the − input voltage, the L level is output.

The control means 18 performs focus control or tracking control of the optical pickup. While the first dropout detection means 2 outputs the H level as the dropout detection signal d, the control means 18 performs protection processing such as holding control (maintaining the current state) for focus control or tracking control. Execute the operation to prevent the servo from coming off due to dropout. Normally, the occurrence of dropout due to dust or the like adhering to the optical disk surface is short, for example, about 1 ms. Therefore, even if a protection processing operation such as holding servo control is performed, the servo system is broken. There is no such thing.

Next, with reference to FIGS. 1 and 2, the operation of the optical disk device according to the present embodiment configured as described above will be described. FIG. 2 is a timing chart showing the operation of detecting the dropout of the optical disk device shown in FIG. 1 by the waveform of each part signal, wherein the horizontal axis represents time and the vertical axis represents voltage value. In FIG. 2, waveforms a, b, c, and e are waveforms showing the operation of the parts denoted by the same reference numerals in FIG.
It is a voltage value superimposed and displayed on the basis. That is,
The waveform a is the voltage value of the output signal of the buffer 4 and the waveform b is the first signal.
The waveform c indicates the voltage value of the output signal of the first voltage dividing means 14, the waveform e indicates the voltage value of the first reference voltage 11, and the waveform d indicates the dropout detection signal. Signal.

First, the operation of each part of the optical disk device in a state where dropout does not occur, as shown by the signal waveform of each part in the section t1 shown in FIG. 2, will be described. At this time, the voltage value of the output signal of the first voltage dividing means 14 is lower than the voltage value a of the output signal of the buffer 4 because the total reflection light amount signal voltage hardly fluctuates. Therefore, the second comparator 5 outputs, as the dropout detection signal d, an L level indicating that no dropout has occurred. Therefore, the control unit 18 executes a normal control operation for the focus control or the tracking control.

As described above, the voltage value e of the first reference voltage 11 is set higher than the voltage value b of the charging voltage of the first capacitor 7 in the case of a normal sum signal of the total light amount. In the interval t1, the voltage value b of the charging voltage of the first capacitor 7 is lower than the voltage value e of the first reference voltage 11, so that the first comparator 12
Remains on (closed). Therefore, the resistance value of the first resistor 9 is not added to the first time constant.

Next, as shown by the signal waveform of each part in the section t2 shown in FIG. 2, the total reflected light amount signal is temporarily suddenly increased due to the occurrence of dropout due to the attachment of foreign matter such as dust and dirt on the optical disk surface. The operation of each unit of the optical disk device in the lowered state will be described. At this time, the voltage value a of the output signal of the buffer 4 sharply decreases as the voltage of the total reflection light amount signal decreases. On the other hand, since the voltage value c of the output signal of the first voltage dividing means 14 is held by the first capacitor 7, it hardly changes from the voltage value in the section t1, and the capacitance of the first capacitor 7 and the Due to the first time constant determined by the current value of the first discharging means 8, only the voltage gradually decreases as shown in FIG.

Therefore, in the section t2 where the dropout occurs due to the attachment of foreign matter such as dust or dirt, the voltage value c of the output signal of the first voltage dividing means 14 is not
Is higher than the voltage value a of the output signal. Therefore, the second comparator 5 sets the dropout detection signal d to the H level to notify the occurrence of the dropout. Therefore, the control unit 18 executes a protection processing operation such as holding (maintaining a current state) the servo control operation for the focus control or the tracking control, and prevents the servo from being disengaged due to the occurrence of dropout. Also in the section t2, since the voltage value b of the charging voltage of the first capacitor 7 is lower than the voltage value e of the first reference voltage 11, the first comparator 1
2 keeps the first switch means 10 turned on.

Next, the operation of each part of the optical disk device after passing through the dropout in the section t2 as shown by the signal waveform of each part in the section t3 shown in FIG. 2 will be described.
Since the voltage value a of the output signal of the buffer 4 returns to the same voltage as that in the section t1 with the recovery of the voltage of the total reflection light amount signal,
The second comparator 5 sets the dropout detection signal d to L level to notify that no dropout has occurred. Therefore, the control means 18 executes the normal control operation again for the focus control or the tracking control.

Next, the operation of the optical disk apparatus in the case where the total reflected light amount signal temporarily increases due to a defect in the manufacturing of the optical disk as shown by the signal waveform of each part in the section t4 shown in FIG. 2 will be described. In the dropout section in which the total reflection light amount signal increases, the voltage value a of the output signal of the buffer 4 sharply increases and reaches a peak with the increase in the total reflection light amount. The voltage value b of the charging voltage of the first capacitor 7 also starts to increase rapidly, but when the voltage value e of the first reference voltage 11 is reached, the first comparator 12 turns off the first switch means 10. (Open).

When the first switch means 10 is turned off,
A first resistor 9 is inserted in series with the first capacitor 7. Therefore, the charging time constant (hereinafter, referred to as a first increasing time constant) becomes large, so that the charging time is delayed, and the voltage value b of the charging voltage of the first capacitor 7 and the output voltage of the first voltage dividing means 14 are reduced. The voltage value c becomes a very gentle voltage increase while the voltage value a of the output signal of the buffer 4 increases rapidly. As a result, the rise of the voltage value b of the charging voltage of the first capacitor 7 in the dropout section t4 is suppressed very low, and the voltage value c of the output signal of the first voltage dividing means 14
Is also very low.

Next, the operation of the optical disk device in a state after the dropout, in which the total reflection light amount signal increases, as shown by the signal waveform of each part in the section t5 shown in FIG. 2, will be described. In this state, the voltage value a of the output signal of the buffer 4 returns from the peak to the original normal value. At the same time, the voltage value b of the charging voltage of the first capacitor 7 is determined by the capacity of the first capacitor 7, the current value of the first discharging means 8, and the resistance value of the first resistor 9. Falls very slowly from the value slightly increased in the section t4 based on the increasing time constant of

Accordingly, the voltage value a of the output signal of the buffer 4
Returns to the original normal value, the first switch means 10 is turned off during the interval t6 in which the voltage value b of the charging voltage of the first capacitor 7 exceeds the voltage value e of the first reference voltage 11. (Open). Therefore, at the beginning of the section t5, a period occurs in which the voltage value c of the output signal of the first voltage dividing means 14 is higher than the voltage value a of the output signal of the buffer 4, and the second comparator 5 During this period, an H level indicating the occurrence of dropout is output as the dropout detection signal d.

However, since the rise of the output voltage of the first voltage dividing means 14 is suppressed very low in the section t4, the erroneous detection of the dropout is performed in a very short section as shown by t7 in FIG. Can be suppressed. As described above, if the section t7 is equal to or shorter than the section t2, an erroneous detection of a dropout in the section t7 does not exert an influence due to a servo disconnection or the like.

(Second Embodiment) Hereinafter, FIGS. 3 and 4
The optical disk device according to the second embodiment of the present invention will be described with reference to FIG. In the optical disc device according to the first embodiment of the present invention, the dropout is detected by using the total reflection light quantity signal as a signal proportional to the total reflection light quantity by the optical disc, but in the present embodiment, the dropout is recorded on the optical disc. Dropout is detected using the peak value of the envelope waveform of the peak value of the reproduced signal (hereinafter abbreviated as RF signal) obtained by reproducing the reproduced information.

First, the configuration of the optical disk device according to the present embodiment will be described with reference to FIG. The configuration of the optical disk device according to the present embodiment is roughly divided into an information reproduction signal detection unit 19, a second low frequency component detection unit 21, an envelope detection unit 22, a fourth comparator 23, and a control unit 1.
8 The information reproduction signal detecting means 19 reproduces and amplifies the information signal of the optical disk and outputs it as an RF signal. When the amount of light reflected by the optical disk increases, the peak voltage of the RF signal, which is the output voltage of the information reproduction signal detecting means 19, increases, and when it decreases, the peak voltage decreases.

The output of the information reproduction signal detecting means 19 is
Low frequency component detecting means 21 and envelope detecting means 22
Is input to both. Second low frequency component detecting means 21
The second waveform peak detecting means 24, the second capacitor 25, the second discharging means 26, the second resistor 27,
A second switch means 28, a second reference voltage 29, a third comparator 30, a second amplifier 31 for a buffer,
The second voltage dividing means 32 detects the peak value of the RF signal output from the information reproduction signal detecting means 19 and holds it at a second time constant. Output as the voltage value i of the output signal.

As the second waveform peak detecting means 24,
For example, an NPN transistor or a diode can be used. The voltage loss due to the forward voltage of the second waveform peak detecting means 24 is electrically compensated inside the information reproduction signal detecting means 19. As the second capacitor 25, for example, a multilayer ceramic capacitor or the like can be used. The second discharging means 26 discharges the charging voltage (voltage value h) of the second capacitor 25 with a second time constant, and can use, for example, a current mirror current source circuit or the like.

The second time constant is equal to the second capacitor 2
5 and the current value of the second discharging means 26, and even if the output voltage of the information reproduction signal detecting means 19 suddenly decreases for, for example, 1 ms due to the occurrence of dropout, the second capacitor 25 The charging voltage is set to a value that is not greatly affected. Second switch means 28
For example, an NPN transistor or the like can be used, and when the transistor is off (open), the resistance of the second resistor 27 is changed to the second value.
And the charging time of the second capacitor 25 is delayed.

The third comparator 30 includes a second capacitor 2
5 is compared with the voltage value k of the second reference voltage 29, the voltage value h of the charging voltage of the second capacitor 25 exceeds the voltage value k of the second reference voltage 29. Then, the second switch means 28 is turned off, and otherwise, the second switch means 28 is turned on (closed).
The voltage value k of the second reference voltage 29 is set higher than the charging voltage of the second capacitor 25 at the time of a normal RF signal. As the third comparator 30, a comparator, a hysteresis comparator, or the like can be used. In particular, the hysteresis comparator is preferable in terms of preventing chattering due to noise.

The second voltage dividing means 32 is composed of a voltage dividing resistor 32a and a voltage dividing resistor 32b.
5 is a resistor that divides the charging voltage of No. 5 through the second amplifier 31 at a predetermined ratio and outputs it. As the voltage dividing resistors 32a and 32b, for example, resistors can be used. The output of the second voltage dividing means 32 is input to the plus input of the fourth comparator 23.

On the other hand, the envelope detecting means 22
, A current peak source, an amplifier, and a third capacitor. The third waveform peak detecting means 33 and the third capacitor 36 detect the peak voltage value of the envelope waveform of the peak value of the reproduced signal obtained by reproducing the information recorded on the optical disk. The third waveform peak detecting means 33, the current source 34, and the amplifier 35 are used to maintain an electrical characteristic balance with the second waveform peak detecting means 24, the second discharging means 26, and the second amplifier 31, respectively. Provided.

The capacity of the third capacitor 36 is set to an extremely small value compared to the capacity of the second capacitor 25. Therefore, the third capacitor 36 sets the output voltage of the third waveform peak detecting means 33 to the third voltage shorter than the second time constant.
, And the voltage value g of the output signal of the envelope detecting means 22 has a waveform that rapidly responds to dropout, as described later. Further, the voltage loss due to the forward voltage of the third waveform peak detecting means 33 is electrically compensated inside the information reproduction signal detecting means 19, similarly to the second waveform peak detecting means 24.

The output of the envelope detecting means 22 is input to the negative input of the fourth comparator 23. The fourth comparator 23 has a positive input voltage (voltage value i of the output signal of the second voltage dividing means 32) and a negative input voltage (envelope detecting means 2).
2 is compared with the output signal voltage value g), and when the + input voltage is higher than the − input voltage, an H level is output as the dropout detection signal j. + Side input voltage is-
When the input voltage is lower than the side input voltage, an L level is output. The control unit 18 is the same as the control unit 18 shown in FIG. 1 and executes a control operation of focus control or tracking control of the optical pickup.

While the second dropout detection means 20 detects the H level as the dropout detection signal j, the control means 18 holds the control (maintains the current state) for the focus control or the tracking control. To prevent the servo from coming off due to the dropout. Normally, the occurrence of dropout due to dust or the like adhering to the optical disk surface is short, for example, about 1 ms. Therefore, even if a protection processing operation such as holding servo control is performed, the servo system is broken. There is no such thing.

Next, with reference to FIGS. 3 and 4, the operation of the optical disk device according to the present embodiment configured as described above will be described. FIG. 4 is a timing chart showing the operation of detecting the dropout of the optical disk apparatus shown in FIG. 3 by the waveform of each part signal, where the horizontal axis represents time and the vertical axis represents voltage value. In FIG. 4, waveforms f, g, h, and i are waveforms showing the operation of the parts denoted by the same reference numerals in FIG.
It is a voltage value superimposed and displayed on the basis.

That is, the waveform f is the waveform of the RF signal which is the output signal of the information reproduction signal detecting means 19, the waveform g is the voltage value of the output signal of the envelope detecting means 22, and the waveform h is the second signal.
, The waveform i is the voltage value of the output signal of the second voltage dividing means 32, the waveform k is the voltage value of the second reference voltage 29, and the waveform j is the digital value indicating the dropout detection signal. Signal.

First, the operation of each part of the optical disk device in a state where dropout does not occur, as shown by the signal waveform of each part in the section t8 shown in FIG. 4, will be described. At this time, since the level of the RF signal hardly fluctuates, the second voltage dividing means 3
2, the voltage value i of the output signal is lower than the voltage value g of the output signal of the envelope detecting means 22. Therefore, the fourth comparator 2
3 outputs an L level indicating that no dropout has occurred as the dropout detection signal j. Therefore, the control unit 18 executes a normal control operation for the focus control or the tracking control.

As described above, the voltage value k of the second reference voltage 29 is set higher than the voltage value h of the charging voltage of the second capacitor 25 in the case of a normal RF signal. Since the voltage value h of the charging voltage of the second capacitor 25 is lower than the voltage value k of the second reference voltage 29, the third comparator 30 turns on (closes) the second switch means 28. Remains. Therefore, the resistance value of the second resistor 27 is not added to the second time constant.

Next, as shown by the signal waveform of each part in the section t9 shown in FIG. 4, the total reflection light amount signal is temporarily sharply increased due to the occurrence of dropout due to the attachment of foreign matter such as dust and dirt on the optical disk surface. The operation of each unit of the optical disk device in the lowered state will be described. At this time, the voltage value g of the output signal of the envelope detection means 22 sharply decreases as the RF signal level decreases. On the other hand, the second pressure dividing means 32
Since the voltage value i of the output signal is held by the second capacitor 25, it hardly changes from the voltage value in the section t8, and depends on the capacity of the second capacitor 25 and the current value of the second discharging means 26. Due to the determined second time constant, only the voltage gradually decreases as shown in FIG.

Therefore, in the section t9 in which the dropout occurs due to the attachment of foreign matter such as dust or dirt, the voltage value i of the output signal of the second voltage dividing means 23 is equal to the voltage of the output signal of the envelope detecting means 22. It becomes higher than the value g. Therefore, the fourth comparator 23 sets the dropout detection signal j to the H level to notify the occurrence of the dropout. Therefore, the control means 18 executes a protection processing operation such as holding (maintaining the current state) the servo control operation for the focus control or the tracking control,
Prevents the servo from coming off due to dropout. Also in the section t9, since the voltage value h of the charging voltage of the second capacitor 25 is lower than the voltage value k of the second reference voltage 29, the third comparator 30 turns on the second switch means 28. Keep it as it is.

Next, the operation of each part of the optical disk device after passing through the dropout in the section t9 as shown by the signal waveform of each part in the section t10 shown in FIG. 4 will be described. Since the voltage value g of the output signal of the envelope detection means 22 returns to the same voltage as that in the section t8 according to the recovery of the level of the RF signal, the fourth comparator 23 sets the dropout detection signal j to the L level, Notify no occurrence. Therefore, the control means 18 executes the normal control operation again for the focus control or the tracking control.

Next, the operation of the optical disk apparatus when the RF signal level temporarily increases due to a defect in the manufacturing of the optical disk as shown by the signal waveform of each section in the section t11 shown in FIG. 4 will be described. In such a dropout section in which the RF signal level increases, the voltage value g of the output signal of the envelope detection means 22 sharply increases and reaches a peak with the increase in the RF signal level. Second
The voltage value h of the charging voltage of the capacitor 25 starts to rapidly increase at the same time, but when the voltage value k of the second reference voltage 29 is reached,
The third comparator 30 turns off (opens) the second switch means 28.

When the second switch means 28 is turned off,
A second resistor 27 is inserted in series with the second capacitor 25. As a result, the charging time constant (hereinafter, referred to as a second increasing time constant) increases, so that the charging time is delayed, and the voltage value h of the charging voltage of the second capacitor 25 and the output voltage of the second voltage dividing means 32 are reduced. The voltage value i becomes a very gradual increase while the voltage value g of the output signal of the envelope detecting means 22 sharply increases. As a result, the rise of the voltage value h of the charging voltage of the second capacitor 25 in the dropout section t11 is suppressed very low, and the second voltage dividing means 3
The rise of the voltage value i of the output signal of No. 2 is also very low.

Next, the operation of the optical disk device in a state after the dropout in which the RF signal level increases as shown by the signal waveforms of the respective sections in the section t12 shown in FIG. 4 will be described. In this state, the voltage value g of the output signal of the envelope detecting means 22 returns from the peak to the original normal value. At the same time, the voltage value h of the charging voltage of the second capacitor 25
Is the capacity of the second capacitor 25 and the second discharging means 2
6, the value gradually decreases from the value slightly increased in the section t11 based on the second increasing time constant determined by the current value of the second resistor 27 and the resistance value of the second resistor 27.

Therefore, even if the voltage value g of the output signal of the envelope detecting means 22 returns to the original normal value, the voltage value h of the charging voltage of the second capacitor 25 becomes equal to the voltage value k of the second reference voltage 29. During the interval t13, the second switch means 28 remains off. Therefore, at the beginning of the section t12, the voltage value i of the output signal of the second voltage dividing means 32 is smaller than the voltage value g of the output signal of the envelope detecting means 22.
Occurs, and the fourth comparator 23 outputs an H level indicating the occurrence of dropout as the dropout detection signal j during that period.

However, in the section t11, the second voltage dividing means 32
Since the rise of the voltage value i of the output signal is extremely low, the erroneous detection of the dropout is suppressed to a very short section as shown by t14 in FIG. in this way,
If the section t14 is equal to or shorter than the section t9, an erroneous detection of a dropout in the section t14 does not exert an influence such as a servo disconnection.

In the optical disk device according to the second embodiment of the present invention, since the RF signal whose signal level change sensitivity due to dropout is higher than the total reflection light amount signal is used, the response sensitivity of the detection of the dropout detection signal is high. .

However, in a recordable disk such as a magneto-optical disk, if there is no recording history in the recordable area of the optical disk, there is no RF signal there. No detection. Therefore, the present embodiment can be implemented in a reproduction area of a read-only disc and / or a recordable disc.

(Third Embodiment) Hereinafter, an optical disk device according to a third embodiment of the present invention will be described with reference to FIG. The configuration of the optical disk device according to the present embodiment is shown in FIG. 5. In FIG. 5, components having the same reference numerals as those shown in FIGS. 1 and 3 have the same functions, and therefore, are further described in detail. Detailed description is omitted.

In FIG. 5, reference numeral 37 denotes an area judging means for judging a recordable area and a read-only area on the optical disk and outputting an area judging signal. And / or knows whether to reproduce information or to reproduce information in a reproduction-only area.
Is a selection means for switching to select the second dropout detection means 20 when the information is reproduced in the reproduction-only area by selecting the dropout detection means 2 of FIG.

Next, the operation of the optical disk device according to the present embodiment will be described. First dropout detecting means 2
Can be applied to a recordable area in which no information has been recorded yet, and the second dropout detection means 20 has a good detection response sensitivity but can be applied only to a reproduction-only area. Both areas are determined by 37, and the first or second dropout detecting means 2 or 20 is appropriately selected by the selecting means 38, and the first or second dropout detecting means 2 or 20 is generated in the first or second dropout detecting means 2 or 20, respectively. Control means 1 for dropout detection signal
8 Then, a control operation such as focus control or tracking control is performed.

In the present embodiment, the dropout detecting means can be selected according to the recordable area and / or the read-only area of the optical disk, so that the dropout detection accuracy can be optimally improved. In the present embodiment, the recordable area and the read-only area of the optical disk may be on the same optical disk or may be separate optical disks.

[0075]

The present invention is constructed as described above, and in particular, the envelope waveform of the peak value of the total reflection light quantity signal corresponding to the reflection light quantity from the optical disc or the peak value of the reproduction signal obtained by reproducing the information recorded on the optical disc. Of a capacitor having a predetermined time constant and holding the peak value of the total reflection light amount signal or the peak value of the envelope waveform of the crest value of the reproduction signal upon detecting that the peak value exceeds the reference voltage. By changing the time constant so as to delay the time, even when a dropout occurs in which the amount of reflected light increases, or when the amount of reflected light temporarily increases during the start-up of the device and in a transition state of setting switching, Long-term erroneous detection of the dropout detection signal can be prevented, and problems such as the servo coming off or becoming unstable can be prevented. Kill.

Further, by using an envelope waveform of a peak value of a reproduction signal obtained by reproducing information recorded on the optical disk as a signal corresponding to the amount of light reflected from the optical disk, the response sensitivity of the detection of the dropout detection signal can be improved. Can be improved.

In addition, by selecting the dropout detecting means depending on the difference between the recording area and / or the read-only area of the optical disk, the dropout detection accuracy can be improved optimally.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optical disc device according to a first embodiment of the present invention.

FIG. 2 is a timing chart showing a dropout detection operation based on voltage values of signals of respective parts of the optical disc apparatus shown in FIG. 1;

FIG. 3 is a block diagram showing a configuration of an optical disk device according to a second embodiment of the present invention.

FIG. 4 is a timing chart showing an operation of detecting dropout based on voltage values of signals of respective parts of the optical disk device shown in FIG.

FIG. 5 is a block diagram showing a configuration of an optical disc device according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing an example of a configuration of a conventional optical disk device.

FIG. 7 is a timing chart showing voltage values (waveforms) due to the operation of each unit of the dropout detection means of the optical disk device shown in FIG. 6;

[Explanation of symbols]

 1, 39 total reflection light amount detection means 2 first dropout detection means 3 first low frequency component detection means 4, 42 buffer 5 second comparator 6 first waveform peak detection means 7 first capacitor 8th 1 discharging means 9 first resistor 10 first switching means 11 first reference voltage 12 first comparator 13 first amplifier 14 first voltage dividing means 15, 44, 49 diodes 16, 34, 46 , 50 current source 17, 35, 47, 51 amplifier 18, 52 control means 19 information reproduction signal detection means 20 second dropout detection means 21 second low frequency component detection means 22 envelope detection means 23 fourth comparator 24 Second Waveform Peak Detecting Means 25 Second Capacitor 27 Second Resistor 28 Second Switching Means 29 Second Reference Voltage 30 Third Comparator 31 Second Amplifier 32 and the second voltage divider 33 third waveform peak detector 36 the third capacitor 37 area determination means 38 the selection means 40 dropout detector 41 low-frequency component detecting unit 43 comparator 45 capacitor 48 minutes pressure means

Claims (3)

[Claims] 1. A first waveform peak detecting means for detecting a peak voltage value of a total reflection light amount from an optical recording medium having a disk shape, and an output voltage of the first waveform peak detecting means is determined by a first time constant. A first capacitor to be held, first voltage dividing means for dividing and outputting a charging voltage of the first capacitor,
A second comparator for detecting that the total reflection light quantity signal has fallen below the output voltage of the first voltage dividing means and outputting a dropout detection signal indicating a dropout of the total reflection light quantity signal. An optical disc device having first dropout detection means for outputting a dropout detection signal to control means for controlling a servo, and recording information on an optical recording medium and / or reproducing recorded information from the optical recording medium. The first dropout detecting means includes:
A first resistor connected to the first capacitor to delay its charging time; and a first resistor connected to the first capacitor when opened and the first resistor short-circuited when closed. Switching means for comparing the charging voltage of the first capacitor with a first reference voltage, and when the charging voltage of the first capacitor exceeds the first reference voltage,
And a first comparator that closes the first switch means when the switch means is open and otherwise closes the first switch means. When the first switch means is opened, the first resistor is connected to the first capacitor. An optical disc device, wherein the first capacitor is connected to form a first increasing time constant to delay charging of the first capacitor. 2. A second waveform peak detecting means for detecting a peak voltage value of a reproduced signal obtained by reproducing information from a disk-shaped optical recording medium, and a peak value of the reproduced signal output from the second waveform peak detecting means. A second time constant, a second voltage dividing means for dividing and outputting the charging voltage of the second capacitor, and an output of the second voltage dividing means for outputting the reproduced signal. A fourth comparator for detecting that the voltage has dropped below and outputting a dropout detection signal indicating a dropout of the reproduction signal, and outputting the dropout detection signal to control means for controlling servo.
An optical disc device for recording information on an optical recording medium and / or reproducing recorded information from the optical recording medium, wherein the second dropout detecting means further comprises the second dropout detecting means. A second resistor connected to the second capacitor to delay its charging time, and second switch means for connecting the second resistor to the second capacitor when open and short-circuiting the second resistor when closed, The charge voltage of the second capacitor is compared with a second reference voltage, and when the charge voltage of the second capacitor exceeds the second reference voltage, the second switch means is opened. A third comparator for closing the second switch means, and a third waveform peak detecting means for detecting a peak voltage value of an envelope waveform of a peak value of a reproduced signal obtained by reproducing information from the optical recording medium. , And a third capacitor which holds the reproduction signal output from the waveform peak detection means of the third time constant of said second time shorter than the constant third, the second
When the switch means is opened, the second resistor is connected to the second capacitor to form a second increasing time constant to delay charging of the second capacitor. Optical disk device. 3. An optical disk device for recording information on a disk-shaped optical recording medium and / or reproducing recorded information from the optical recording medium, wherein a recordable area and a reproduction-only area on the optical recording medium are distinguished. 3. An area judging means for outputting an area judging signal, and selecting the first dropout detecting means according to claim 1 in the recordable area according to the area judging signal, and selecting the first dropout detecting means in the read-only area. An optical disk device, comprising: a selector for selecting the second dropout detecting means described in (1) and outputting a dropout signal obtained from any of the second dropout detecting means to a control means for controlling servo.