JP2007179693A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the disturbance in TE signals to a minimum, even if a defect exist in the recording surface of an optical disk for reducing the disturbance in tracking due to the defect. <P>SOLUTION: An optical disk device is provided with; a first differential circuit 101 and a second differential circuit 102, to which respective signals acquired from two sub-beams are inputted, respectively; a first comparator 103 and a second comparator 104 which respectively compare the outputs of the first differential circuit 101 and second differential circuit 102 with prescribed reference voltages; a storage circuit 105 which stores values corresponding to the output of the first comparator 103 and second comparator 104; and a first sample holding circuit 106 and a second sample holding circuit 107 which switch between a sample state and a holding state based on the output of the storage circuit 105. Then, the result of subtraction of the output of the first sample holding circuit 106 from the output of the second sample holding circuit 107 is outputted as the TE signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a three-beam optical disc apparatus for reproducing and outputting information recorded on an optical disc.

  In an apparatus for reproducing an optical disk such as a CD (Compact Disk) or a DVD (Digital Versatile Disk), tracking control (tracking servo) for causing a track having a pit row on the disk to follow a reading spot by a beam from an optical pickup. Is essential. The tracking servo is performed based on a tracking error signal generated from a signal based on return light (reflected light) from an optical disc detected by an optical pickup.

  However, if the disc surface is scratched, foreign matter is attached, or the recorded pits are out of phase (such cases are called defects), the beam enters the defect area. In this case, the tracking error signal is disturbed due to the defect, and the tracking of the beam is changed. When the beam escapes from the defect portion, the tracking may be disturbed or removed.

  For this, paying attention to the level change of the RF signal obtained from the optical pickup, the defect period (period during which the beam passes over the defect) is detected, and the tracking error signal is muted (appropriate intermediate level) during that period. An optical disc apparatus that suppresses the disturbance of the tracking error signal during the defect period and reduces the occurrence of tracking deviation due to the defect by fixing the signal to a level immediately before the defect period. Yes (see, for example, Patent Document 1).

  When this is applied to a three-beam type optical disc apparatus, an optical disc apparatus 400 having the configuration shown in FIG. 7 can be considered. In the three-beam type optical disc apparatus, reproduction is performed using a main beam and two sub beams. Here, one of the two sub beams is a beam preceding the main beam (referred to as a preceding sub beam), and the other is a beam subsequent to the main beam (referred to as a subsequent sub beam).

  In FIG. 7, 401 is an optical pickup, which is divided into four main beam sensors (A, B, C, D) for detecting the return light (reflected light) of the main beam, the front and rear of the main beam sensor, and the pits. Are provided with two sub beam sensors (E, F) arranged on both sides (left and right) with respect to the scanning direction. The sub beam sensor is used for tracking servo and detects return light (reflected light) of the sub beam. Here, the sub beam sensor that detects the return light of the preceding sub beam is the sub beam sensor E, the sub beam sensor that detects the return light of the subsequent sub beam is the sub beam sensor F, the signal detected by the sub beam sensor E is the E signal, and the sub beam sensor F is the sub beam sensor F. Let the detected signal be an F signal.

  The optical pickup 401 includes a tracking actuator, and can perform tracking servo when a predetermined signal is supplied to a driver amplifier of the tracking actuator.

  Reference numerals 402 and 403 denote first and second output terminals connected to the optical pickup 401. An E signal is output to the first output terminal 402, and an F signal is output to the second output terminal 403.

  Reference numeral 404 denotes a third output terminal connected to the optical pickup 401, which outputs a signal (RF signal) obtained by adding four electrical signals (referred to as A to D signals) converted into electrical signals by the main beam sensor. It is like that.

  Reference numeral 405 denotes a TE signal generation unit that is connected to the first output terminal 402 and the second output terminal 403 and calculates E-F from the E signal and the F signal to generate a tracking error signal (TE signal).

  Reference numeral 406 denotes an AGC (Automatic Gain Control) that is connected to the third output terminal 404 and normalizes the RF signal to a constant amplitude.

  Reference numeral 407 denotes a defect period detection unit that detects a defect period based on the normalized RF amplitude, and outputs a signal indicating the defect period (defect period signal).

  A tracking control unit 408 performs tracking servo using the TE signal. The tracking control unit 408 includes a servo hold circuit 409. The servo hold circuit 409 is a circuit that holds the TE signal at a value (level) before the defect period based on the defect period signal.

  Reference numeral 410 denotes an AGC hold circuit that holds the gain of the AGC 406 based on the defect period signal.

  Reference numeral 411 denotes a focus control unit that generates a control signal for performing focus servo. Reference numeral 412 denotes an optical disc on which information is recorded.

In the optical disc apparatus 400 described above, the TE signal is supplied to the driver amplifier of the tracking actuator in the optical pickup 401 via the tracking control unit 408. Thus, while tracking servo is performed, an RF signal is generated from information recorded on the optical disc 412, and focus servo is performed by the focus control unit 411 to perform reproduction.
JP-A-61-96529

  However, if the defect period is detected based on the change in the level of the RF signal obtained from the optical pickup 401, it is detected that the defect period is due to a decrease in the level of the RF signal after the beam enters the defect. There is some time lag before it is done.

  FIG. 8 is a diagram showing the positional relationship between the main beam, the sub beam, and the defect on the disk surface. In the figure, 20 is a main beam, 21 is a preceding sub-beam, 22 is a subsequent sub-beam, and 23 is a defect. The preceding sub beam, the main beam, and the subsequent sub beam are arranged in this order with respect to the disk rotation direction. Here, as shown in FIG. 8, when a defect exists on the disk surface, the E signal and the F signal at the time of entering the defect are sharply attenuated as shown in FIG. Therefore, when the defect period is detected based on the level of the RF signal, the amplitude of the TE signal when the tracking servo is held increases. In addition, the fluctuation of the TE signal at the moment when the tracking servo hold is released increases. Therefore, the disturbance of tracking due to the defect becomes large, and in the worst case, the servo may come off.

  The present invention has been made paying attention to the above-described problem, and provides an optical disc apparatus that suppresses disturbance of the TE signal as much as possible even when a defect exists on the recording surface of the optical disc and reduces tracking disturbance due to the defect. The purpose is that.

In order to solve the above problems, the invention of claim 1
An optical disc apparatus for detecting a tracking error signal using two sub beams,
Defects on the optical disc are detected from differential values of the respective signals obtained from the two sub beams, and tracking control is held according to the differential values of the respective signals.

The invention of claim 2
The optical disk apparatus according to claim 1,
A first differentiating circuit for differentiating one of the two signals obtained from the two sub-beams;
A second differentiating circuit for differentiating the other of the two signals obtained from the two sub-beams;
A first comparator for comparing the output of the first differentiating circuit with a predetermined reference voltage;
A second comparator for comparing the output of the second differentiating circuit with a predetermined reference voltage;
A memory circuit for outputting a defect detection signal indicating a period during which the beam passes over the defect in accordance with the outputs of the first and second comparators;
A first sample-and-hold circuit that takes one of two signals obtained from the two sub-beams as an input and switches between a sample state and a hold state according to the output of the memory circuit;
A second sample-and-hold circuit that takes the other of the two signals obtained from the two sub-beams as input and switches between a sample state and a hold state in accordance with the output of the memory circuit;
A subtracting circuit for inputting the outputs of the first and second sample and hold circuits and outputting a subtraction result as the tracking error signal;
It is provided with.

  As a result, it becomes possible to hold the tracking control before the tracking error signal is largely disturbed, so that the tracking disorder can be reduced.

The invention of claim 3
The optical disk apparatus according to claim 1,
A first differentiating circuit for differentiating one of the two signals obtained from the two sub-beams;
A second differentiating circuit for differentiating the other of the two signals obtained from the two sub-beams;
A first comparator for comparing the output of the first differentiating circuit with a predetermined reference voltage;
A second comparator for comparing the output of the second differentiating circuit with a predetermined reference voltage;
A first memory circuit that outputs a signal indicating a period during which one of the sub-beams passes over the defect in accordance with the output of the first comparator;
A second memory circuit that outputs a signal indicating a period during which the other sub-beam passes over the defect in accordance with the output of the second comparator;
The output of the first and second memory circuits is input, and one of two signals obtained from the OR circuit that outputs a defect detection signal indicating a period during which the beam passes over the defect and the two sub beams is input. A first sample-and-hold circuit that switches between a sample state and a hold state according to the output of the OR circuit;
A second sample-and-hold circuit that takes the other of the two signals obtained from the two sub-beams as input and switches between a sample state and a hold state in accordance with the output of the OR circuit;
A subtracting circuit for inputting the outputs of the first and second sample and hold circuits and outputting a subtraction result as the tracking error signal;
It is provided with.

  As a result, since the defect is detected using two sub beams, it is possible to reliably detect the defect period even when only one of the sub beams passes through the defect.

The invention of claim 4
An optical disc apparatus for detecting a tracking error signal using two sub beams,
A first AD converter circuit that AD converts one of the two signals obtained from the two sub-beams;
A second AD conversion circuit that AD converts the other of the two signals obtained from the two sub-beams;
An arithmetic circuit for holding each output at a value before change when a change amount greater than or equal to a certain amount is detected in each output of the first and second AD converter circuits;
A subtracting circuit for inputting the outputs of the first and second AD conversion circuits held by the arithmetic circuit and outputting a subtraction result as the tracking error signal;
It is provided with.

The invention of claim 5
The optical disk apparatus according to claim 4, wherein
The arithmetic circuit is:
A first memory circuit that receives the output of the first AD converter circuit;
A second memory circuit that receives the output of the second AD converter circuit;
A first comparator that receives the output of the first AD converter circuit and the output of the first memory circuit;
A second comparator having the output of the second AD converter circuit and the output of the second memory circuit as inputs;
An OR circuit having the output of the first comparator and the output of the second comparator as inputs;
According to the output of the OR circuit, the first and second storage circuits are configured to be controlled to either a state in which an input signal is sampled or a state in which a value is stored. Features.

The invention of claim 6
6. The optical disc apparatus according to claim 5, wherein
The first comparator obtains a difference between the output level of the first AD conversion circuit sampled at the Nth time and the level sampled at the (N-1) th time, detects a change in the output, and a change greater than a predetermined value is detected. If there is, output is performed so that the output of the first AD converter circuit is held in the first memory circuit, and then the output level of the sampled first AD converter circuit and the first A difference with a value held in one storage circuit is obtained, and when there is a difference greater than or equal to a predetermined value, detection of a change in the output of the first AD converter circuit is resumed;
The second comparator obtains a difference between the output level of the second AD converter circuit sampled at the Nth time and the level sampled at the (N-1) th time, detects a change in the output, and a change of a predetermined value or more is detected. If there is, output is performed so that the output of the second AD converter circuit is held in the second memory circuit, and then the output level of the sampled second AD converter circuit and the second The difference between the value stored in the second storage circuit is obtained, and when there is a difference greater than or equal to a predetermined value, detection of a change in the output of the second AD converter circuit is resumed. Features.

  Thus, the tracking control can be held before the tracking error signal is greatly disturbed.

  According to the present invention, since tracking control can be held before the tracking error signal (TE signal) is largely disturbed, it is possible to reduce tracking disturbance due to defects.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 of the Invention
FIG. 1 is a block diagram showing a configuration of an optical disc apparatus 100 according to Embodiment 1 of the present invention. FIG. 2 shows signal waveforms relating to the optical disc apparatus 100.

  The optical disc apparatus 100 is an example of a three-beam optical disc apparatus, and reproduction is performed using a main beam and two sub beams. Here, one of the two sub beams is a beam preceding the main beam (referred to as a preceding sub beam), and the other is a beam subsequent to the main beam (referred to as a subsequent sub beam). In addition, a signal obtained from the return light of the preceding sub beam is an E signal, and a signal obtained from the return light of the subsequent sub beam is an F signal.

  In FIG. 1, reference numerals 101 and 102 denote a first differentiating circuit and a second differentiating circuit to which an E signal and an F signal are input, respectively.

  Reference numerals 103 and 104 denote a first comparator and a second comparator to which outputs of the first differentiation circuit 101 and the second differentiation circuit 102 are connected as inputs.

  The first comparator 103 compares the input output of the first differentiating circuit 101 with the reference voltage Vth1, and outputs the result to the memory circuit 105. On the other hand, the second comparator 104 compares the output of the second differentiating circuit 102 with the reference voltage Vth2, and outputs the result to the memory circuit 105.

  Reference numeral 105 denotes a memory circuit to which outputs of the first comparator 103 and the second comparator 104 are connected as inputs. When the voltage of the output signal of the first differentiating circuit 101 is lower than the reference voltage Vth1 as a result of the comparison by the first comparator 103, the memory circuit 105 is a high level (hereinafter abbreviated as H level) signal. And the first sample hold circuit 106 and the second sample hold circuit 107 are controlled to be in a hold state, and an H level signal is supplied as a signal indicating a defect period (period during which the beam passes over the defect). Output as (defect detection signal).

  Further, the memory circuit 105 has a low level (hereinafter abbreviated as L level) when the voltage of the output signal of the second differentiating circuit 102 exceeds the reference voltage Vth2 as a result of the comparison by the second comparator 104. The first sample hold circuit 106 and the second sample hold circuit 107 are returned to the sample state.

  Reference numerals 106 and 107 denote a first sample hold circuit and a second sample hold circuit to which the output of the memory circuit 105 and the E signal and the F signal are respectively connected as inputs. The first sample hold circuit 106 and the second sample hold circuit 107 include a switch 106a and a switch 107a, respectively. The on / off of the switch 106a and the switch 107a is switched according to the output of the memory circuit 105, and the sample state and the hold state are switched as described above.

  Reference numeral 108 denotes a subtraction circuit to which the outputs of the first sample hold circuit 106 and the second sample hold circuit 107 are connected as inputs, so that the difference between the E signal and the F signal is output as a tracking error signal (TE signal). It has become.

  The operation of the optical disc apparatus 100 configured as described above will be described.

  Normally (when the defect spot does not contain a beam spot), the first sample hold circuit 106 and the second sample hold circuit 107 are fixed to the sample state according to the output of the storage circuit 105. At this time, the E signal and the F signal are input to the subtraction circuit 108 via the first sample hold circuit 106 and the second sample hold circuit 107, respectively. Then, the subtraction circuit 108 outputs the difference between the E signal and the F signal as a TE signal.

  Here, when the beam spot enters the defect on the optical disk surface, the E signal and the F signal are attenuated sharply. At that time, the output signal of the first differentiating circuit 101 has an output amplitude larger than a normal level that is lower than the reference voltage Vth1. The first comparator 103 compares the output of the first differentiating circuit 101 with the reference voltage Vth1. When the voltage of the output signal of the first differentiating circuit 101 is lower than the reference voltage Vth1, the memory circuit 105 outputs an H level signal, and the first sample hold circuit 106 and the second sample hold circuit 107 are output. To the hold status. Further, an H level signal is output as a defect detection signal.

  Further, when the beam spot deviates from the defect, the output signal of the second differentiating circuit 102 can obtain an output amplitude larger than a normal level exceeding the reference voltage Vth2. The second comparator 104 compares the output of the second differentiation circuit 102 with Vth2. When the voltage of the output signal of the second differentiation circuit 102 exceeds the reference voltage Vth2, the storage circuit 105 outputs an L level signal, and the first sample hold circuit 106 and the second sample hold circuit 107 are output. Return to the sample state.

  As described above, according to the present embodiment, since tracking control can be held before the TE signal is greatly disturbed, tracking disturbance can be reduced. Conventionally, since a large number of circuits such as a peak hold circuit and a level shift circuit have been required as the defect detection circuit, the circuit has been complicated. However, this embodiment can simplify the circuit.

<< Embodiment 2 of the Invention >>
FIG. 3 is a block diagram showing the configuration of the optical disc apparatus 200 according to Embodiment 2 of the present invention. FIG. 4 shows signal waveforms related to the optical disc apparatus 200. In each embodiment described below, components having the same functions as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 3, the optical disc apparatus 200 includes a first differentiation circuit 101, a second differentiation circuit 102, a first sample hold circuit 106, a second sample hold circuit 107, a subtraction circuit 108, and a first comparator. 201, a second comparator 202, a first memory circuit 203, a second memory circuit 204, and an OR circuit 205.

  The first comparator 201 and the second comparator 202 are comparators to which outputs of the first differentiation circuit 101 and the second differentiation circuit 102 are connected as inputs.

  The first comparator 201 compares the input output of the first differentiating circuit 101 with the reference voltage Vth3 and the reference voltage Vth4, and outputs the result to the first memory circuit 203. On the other hand, the second comparator 202 compares the input output of the second differentiating circuit 102 with the reference voltage Vth5 and the reference voltage Vth6 and outputs the result to the second memory circuit 204.

  The first memory circuit 203 and the second memory circuit 204 are memory circuits to which the outputs of the first comparator 201 and the second comparator 202 are connected as inputs, respectively.

  Specifically, the first memory circuit 203 outputs an H level signal and the output of the first differentiating circuit 101 when the voltage of the output signal of the first differentiating circuit 101 is lower than the reference voltage Vth4. When the signal voltage exceeds the reference voltage Vth3, an L level signal is output.

  The second memory circuit 204 outputs an H-level signal when the voltage of the output signal of the second differentiating circuit 102 is lower than the reference voltage Vth6, and the output signal of the second differentiating circuit 102 is output. When the voltage exceeds the reference voltage Vth5, an L level signal is output.

  The OR circuit 205 is an OR circuit to which the output signals of the first memory circuit 203 and the second memory circuit 204 are input and whose output is connected to the switch 106a and the switch 107a.

  The operation of the optical disc apparatus 200 configured as described above will be described.

  Normally (when no beam spot is included in the defect portion), the first sample hold circuit 106 and the second sample hold circuit 107 are fixed to the sample state in accordance with the output of the OR circuit 205. At this time, the E signal and the F signal are input to the subtraction circuit 108 via the first sample hold circuit 106 and the second sample hold circuit 107, respectively. Then, the subtraction circuit 108 outputs the difference between the E signal and the F signal as a TE signal.

  Here, when the beam spot enters the defect on the optical disk surface, the E signal and the F signal are attenuated sharply. At this time, the output signals of the first differentiating circuit 101 and the second differentiating circuit 102 have an output amplitude larger than a normal level that is lower than the reference voltages Vth4 and Vth6, respectively. The first comparator 201 compares the signal output from the first differentiating circuit 101 with the reference voltage Vth4, and the first comparator 201 compares the signal output from the second differentiating circuit 102 with the reference voltage Vth6. To do.

  The first memory circuit 203 outputs an H level signal when the voltage of the output signal of the first differentiating circuit 101 is lower than the reference voltage Vth4. The second memory circuit 204 outputs an H level signal when the voltage of the output signal of the second differentiating circuit 102 is lower than the reference voltage Vth6.

  The OR circuit 205 obtains a logical sum of the output of the first memory circuit 203 and the output of the second memory circuit 204, and then holds the first sample hold circuit 106 and the second sample hold circuit 107 in a hold state. To. Further, an H level signal is output as the defect detection signal.

  Further, when the beam spot deviates from the defect, the output signals of the first differentiating circuit 101 and the second differentiating circuit 102 have output amplitudes larger than normal levels exceeding the reference voltages Vth3 and Vth5, respectively. It is done.

  The first comparator 201 compares the signal output from the first differentiating circuit 101 with the reference voltage Vth3, and the second comparator 202 compares the signal output from the second differentiating circuit 102 with the reference voltage Vth5. To do.

  The first memory circuit 203 outputs an L level signal when the voltage of the output signal of the first differentiating circuit 101 exceeds the reference voltage Vth3. Further, the second memory circuit 204 outputs an L level signal when the voltage of the output signal of the second differentiating circuit 102 exceeds the reference voltage Vth5. The OR circuit 205 obtains a logical sum of the output of the first memory circuit 203 and the output of the second memory circuit 204, and then sets the first sample hold circuit 106 and the second sample hold circuit 107 to the sample state. Return.

  As described above, in the present embodiment as well, as in the first embodiment, since tracking control can be held before the TE signal is greatly disturbed, the tracking disorder can be achieved with a relatively simple circuit configuration. Can be reduced.

  In addition, since the defect is detected using both the E signal and the F signal, even when only one of the sub beams passes the defect, the defect period is detected more reliably than the optical disc apparatus 100 of the first embodiment. It becomes possible.

<< Embodiment 3 of the Invention >>
FIG. 5 is a block diagram showing a configuration of an optical disc apparatus 300 according to Embodiment 3 of the present invention. FIG. 6 shows signal waveforms related to the optical disc apparatus 300.

  As shown in FIG. 5, the optical disc apparatus 300 includes a first A / D converter 301, a second A / D converter 302, a first comparator 303, a second comparator 304, and a first storage circuit 305. , A second memory circuit 306, an OR circuit 307, and a subtraction circuit 308.

  The first A / D converter 301 and the second A / D converter 302 AD convert the E signal and the F signal, respectively, in synchronization with the bright levels of the E signal and the F signal, respectively. It has become. Here, the signals AD-converted by the first A / D converter 301 and the second A / D converter 302 are referred to as a signal E ′ and a signal F ′, respectively.

  The first comparator 303 samples the output of the first A / D converter 301 at a predetermined timing, compares the signal E ′ at time t with the signal E ′ at time (t−1), and exceeds a predetermined value. If there is a difference between them, an H level signal is output, and thereafter, the signal E ′ output from the first A / D converter 301 and the first storage circuit 305 are stored at a predetermined timing. The signal E ′ is compared with the signal E ′, and if there is a difference greater than a predetermined value, an L level signal is output. Here, for example, time t indicates the time when the t-th sampling is performed.

  The second comparator 304 is a circuit having the same configuration as the first comparator 303, and is different in that the input signal is the signal F 'and the output of the second memory circuit 306.

  The first storage circuit 305 is a circuit that stores the signal E ′, and is controlled to be either the sample state of the signal E ′ or the state in which the value is stored in accordance with the input control signal. It has become. The second memory circuit 306 is a circuit that stores the signal F ′, and is controlled to either the sample state of the signal F ′ or the state in which the value is stored in accordance with the input control signal. It has become so. A control signal for controlling the states of the first memory circuit 305 and the second memory circuit 306 is an output signal of the OR circuit 307.

  The OR circuit 307 is an OR circuit to which the output of the first comparator 303 and the output of the second comparator 304 are input.

  The first A / D converter 301 and the second A / D are combined by the first comparator 303, the second comparator 304, the first storage circuit 305, the second storage circuit 306, and the OR circuit 307. An arithmetic circuit is configured to hold each output at a value before the change when a certain amount of change is detected in each output of the converter 302.

  The subtraction circuit 308 is a subtraction circuit that receives the output signals of the first memory circuit 305 and the second memory circuit 306 as inputs.

  The operation of the optical disc apparatus 300 configured as described above will be described.

  The first A / D converter 301 and the second A / D converter 302 perform AD conversion in synchronization with the bright levels of the E signal and F signal, respectively. As a result, a signal in which the RF signal component is removed can be obtained.

  Normally (when a defect spot does not contain a beam spot), the signal E ′ and the signal F ′ are input to the subtraction circuit 308 via the first storage circuit 305 and the second storage circuit 306, respectively. Then, the subtraction circuit 308 outputs the difference between the signal E ′ and the signal F ′ as a TE signal.

  At this time, the first memory circuit 305 and the second memory circuit 306 are in the sample state, and the signal E ′ and the signal F ′ at the time T are input to the subtraction circuit 308 at the time (T + 1).

  For example, when a beam spot enters a defect on the optical disk surface at time t, the E signal and the F signal attenuate sharply.

  The first comparator 303 compares the signal E ′ at the time t with the signal E ′ at the time (t−1), and the second comparator 304 compares the signal F ′ at the time t with the time (t−1). Is compared with the signal F ′.

  As a result of the comparison, when there is a difference of a certain value or more, the first comparator 303 and the second comparator 304 output an H level signal. Accordingly, the OR circuit 307 outputs an H level signal, and the first memory circuit 305 and the second memory circuit 306 are controlled to be in a state where the value of time (t−1) is stored. . The OR circuit 307 outputs an H level signal as a defect detection signal.

  When the beam spot deviates from the defect, the first comparator 303 compares the signal E ′ at time (t−1) with the signal E ′ at time (t + n), and the second comparator 304 The signal F ′ at time (t−1) is compared with the signal F ′ at time (t + n). As a result of the comparison, if the difference is within a certain value, the first comparator 303 and the second comparator 304 output an L level signal. Accordingly, the OR circuit 307 outputs an L level signal, and the first memory circuit 305 and the second memory circuit 306 are controlled to be in the sample state.

  As described above, also in this embodiment, since tracking control can be held before the TE signal is largely disturbed, the tracking disorder can be reduced. Conventionally, since a large number of circuits such as a peak hold circuit and a level shift circuit have been required as the defect detection circuit, the circuit has been complicated. However, this embodiment can simplify the circuit.

  The optical disc apparatus according to the present invention can hold the tracking control before the TE signal is greatly disturbed, so that it is possible to reduce the tracking disorder due to the defect. It is useful as a three-beam optical disk device for reproducing and outputting recorded information.

1 is a block diagram showing a configuration of an optical disc device according to Embodiment 1. FIG. 2 shows signal waveforms related to the optical disc apparatus according to the first embodiment. 6 is a block diagram illustrating a configuration of an optical disc device according to Embodiment 2. FIG. 7 shows signal waveforms related to the optical disc apparatus according to the second embodiment. FIG. 6 is a block diagram illustrating a configuration of an optical disc device according to a third embodiment. It is a figure which shows the signal waveform regarding the optical disk apparatus which concerns on Embodiment 3. FIG. It is a block diagram which shows the structure of the conventional 3 beam system optical disk apparatus. It is a figure which shows the positional relationship of a main beam, a sub beam, and a defect on a disc surface. It is a figure which shows the signal waveform of each part in the conventional optical disk apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Optical disk apparatus 101 1st differentiation circuit 102 2nd differentiation circuit 103 1st comparator 104 2nd comparator 105 Memory circuit 106 1st sample hold circuit 106a Switch 107 2nd sample hold circuit 107a Switch 108 Subtraction circuit 200 Optical disk apparatus 201 First comparator 202 Second comparator 203 First storage circuit 204 Second storage circuit 205 OR circuit 300 Optical disk apparatus 301 First A / D converter 302 Second A / D converter 303 Second 1 comparator 304 second comparator 305 first storage circuit 306 second storage circuit 307 OR circuit 308 subtraction circuit 400 optical disc device 401 optical pickup 402 first output terminal 403 second output terminal 404 second 3 output terminals 405 TE signal generation unit 406 AGC circuit 407 defect period detection unit 408 tracking control unit 409 servo hold circuit 410 AGC hold circuit 411 focus control unit 412 optical disc

Claims (6)

An optical disc apparatus for detecting a tracking error signal using two sub beams,
An optical disc apparatus, wherein a defect on an optical disc is detected from a differential value of each signal obtained from two sub beams, and tracking control is held according to the differential value of each signal. The optical disk apparatus according to claim 1,
A first differentiating circuit for differentiating one of the two signals obtained from the two sub-beams;
A second differentiating circuit for differentiating the other of the two signals obtained from the two sub-beams;
A first comparator for comparing the output of the first differentiating circuit with a predetermined reference voltage;
A second comparator for comparing the output of the second differentiating circuit with a predetermined reference voltage;
A memory circuit for outputting a defect detection signal indicating a period during which the beam passes over the defect in accordance with the outputs of the first and second comparators;
A first sample-and-hold circuit that takes one of two signals obtained from the two sub-beams as an input and switches between a sample state and a hold state according to the output of the memory circuit;
A second sample-and-hold circuit that takes the other of the two signals obtained from the two sub-beams as input and switches between a sample state and a hold state in accordance with the output of the memory circuit;
A subtracting circuit for inputting the outputs of the first and second sample and hold circuits and outputting a subtraction result as the tracking error signal;
An optical disc apparatus comprising: The optical disk apparatus according to claim 1,
A first differentiating circuit for differentiating one of the two signals obtained from the two sub-beams;
A second differentiating circuit for differentiating the other of the two signals obtained from the two sub-beams;
A first comparator for comparing the output of the first differentiating circuit with a predetermined reference voltage;
A second comparator for comparing the output of the second differentiating circuit with a predetermined reference voltage;
A first memory circuit that outputs a signal indicating a period during which one of the sub-beams passes over the defect in accordance with the output of the first comparator;
A second memory circuit that outputs a signal indicating a period during which the other sub-beam passes over the defect in accordance with the output of the second comparator;
The output of the first and second memory circuits is input, and one of two signals obtained from the OR circuit that outputs a defect detection signal indicating a period during which the beam passes over the defect and the two sub beams is input. A first sample-and-hold circuit that switches between a sample state and a hold state according to the output of the OR circuit;
A second sample-and-hold circuit that takes the other of the two signals obtained from the two sub-beams as input and switches between a sample state and a hold state in accordance with the output of the OR circuit;
A subtracting circuit for inputting the outputs of the first and second sample and hold circuits and outputting a subtraction result as the tracking error signal;
An optical disc apparatus comprising: An optical disc apparatus for detecting a tracking error signal using two sub beams,
A first AD converter circuit that AD converts one of the two signals obtained from the two sub-beams;
A second AD conversion circuit that AD converts the other of the two signals obtained from the two sub-beams;
An arithmetic circuit for holding each output at a value before change when a change amount greater than or equal to a certain amount is detected in each output of the first and second AD converter circuits;
A subtracting circuit for inputting the outputs of the first and second AD conversion circuits held by the arithmetic circuit and outputting a subtraction result as the tracking error signal;
An optical disc apparatus comprising: The optical disk apparatus according to claim 4, wherein
The arithmetic circuit is:
A first memory circuit that receives the output of the first AD converter circuit;
A second memory circuit that receives the output of the second AD converter circuit;
A first comparator that receives the output of the first AD converter circuit and the output of the first memory circuit;
A second comparator having the output of the second AD converter circuit and the output of the second memory circuit as inputs;
An OR circuit having the output of the first comparator and the output of the second comparator as inputs;
According to the output of the OR circuit, the first and second storage circuits are configured to be controlled to either a state in which an input signal is sampled or a state in which a value is stored. An optical disc device characterized. 6. The optical disc apparatus according to claim 5, wherein
The first comparator obtains a difference between the output level of the first AD conversion circuit sampled at the Nth time and the level sampled at the (N-1) th time, detects a change in the output, and a change greater than a predetermined value is detected. If there is, output is performed so that the output of the first AD converter circuit is held in the first memory circuit, and then the output level of the sampled first AD converter circuit and the first A difference with a value held in one storage circuit is obtained, and when there is a difference greater than or equal to a predetermined value, detection of a change in the output of the first AD converter circuit is resumed;
The second comparator obtains a difference between the output level of the second AD converter circuit sampled at the Nth time and the level sampled at the (N-1) th time, detects a change in the output, and a change of a predetermined value or more is detected. If there is, output is performed so that the output of the second AD converter circuit is held in the second memory circuit, and then the output level of the sampled second AD converter circuit and the second The difference between the value stored in the second storage circuit is obtained, and when there is a difference greater than or equal to a predetermined value, detection of a change in the output of the second AD converter circuit is resumed. An optical disc device characterized.

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