JP2922124B2 - Optical disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dropout detection in an optical disk device.

[0002]

2. Description of the Related Art In recent years, in optical disk devices, systems capable of recording / reproducing in the field of consumer audio / video have been proposed, such as an audio mini-disc (hereinafter abbreviated as MD). Can be
Compact discs (hereinafter abbreviated as CDs) are already widely accepted as read-only discs for consumer use. They are more resistant to scratches on the disc surface than conventional LP records and are easy to handle. One of them.

In order to take advantage of this feature, in CD players, measures to prevent dropouts on the surface of a disc or the like have been conventionally regarded as important. MD capable of recording / playback
In systems such as this, even if a disc is placed in a cartridge, there are dropouts that occur during the disc manufacturing process and dropouts that occur when the pickup collides with the disc surface during playback on the player. It is necessary to take the same drop-out measures as for CDs.

[0004] In a read-only optical disk system such as a CD, it is guaranteed that an information signal is always recorded. Therefore, a method of detecting a dropout due to a lack of an information signal is generally used (Japanese Patent Laid-Open Publication No. HEI 9-258572). 1-929
No. 72). However, in an optical disk system such as an MD that presupposes recording / reproduction,
Since an information signal is not always recorded, a system problem arises when dropout detection is performed due to lack of the information signal. For example, when a tracking servo is held by a dropout detection signal (Japanese Patent Laid-Open No.
Considering Japanese Patent No. 42775), dropout is always detected in an unrecorded area and the tracking servo is held, making it difficult to access the recording start position. Therefore, in an optical disk system such as an MD that presupposes recording / reproduction,
It is an effective and rational method to detect a dropout based on a decrease in the amount of reflected light from the disc, not a loss of the information signal.

[0005] A conventional optical disk device based on the above method will be described below. FIG. 5 is a block diagram of a conventional optical disk device. In FIG. 5, 1 is an optical disk, 2 is rotating means for rotating the optical disk 1, and 3 is a light beam condensed on a recording surface of the optical disk 1 to form a light spot. , 4, 5, 6, and 7 are constituent elements of the optical pickup 3, and 4 is an optical pickup that transmits a light beam to the optical disc 1.
Condensing lenses 5 and 7 for condensing light on the recording surface of the optical disc 1 for detecting a relative position error between a light beam spot and an information track based on a three-beam method;
A photodetector for detecting the amount of light reflected from the light source;
Is a tracking actuator that moves the light beam spot by moving the light beam spot in the direction perpendicular to the information track of the optical disc 1.
Is a differential amplifier that generates and outputs a three-beam tracking error signal by subtracting the output of the switch, 10 is a switch that opens and closes a tracking control loop, 11 is a control signal input terminal of the switch 10, and the switch 10 is a control signal input terminal. When the input of the terminal 11 is at "H" level, the loop is closed, and when the input is at "L" level, the loop is opened.
Numeral 12 inputs the tracking error signal output from the differential amplifier 9 through the switch 10 and performs a filter process such as phase compensation or low-frequency gain compensation to drive the tracking actuator 8 so that the light beam spot follows the information track. Tracking control means 13 for amplifying the output of the photodetector 6 and outputting a reflected light amount signal; 14 for an NPN transistor; 15 for a constant current source;
Reference numeral 6 denotes a capacitor, and the amplifier 13 and the transistor 14
Further, a peak hold circuit for holding the peak voltage of the reflected light amount signal output from the amplifier 13 by the constant current source 15 is formed (the peak voltage is charged to both ends of the capacitor 16). 17 and 18 are resistors, 19
Is a reference voltage source for generating a reference voltage VR. The peak voltage charged in the capacitor 16 is divided by the resistors 17 and 18 with respect to the reference voltage VR. 20 is NP
The N-type transistor 21 is a constant current source, and the transistor 20 and the constant current source 21 constitute an emitter follower buffer circuit. Reference numeral 22 denotes an emitter voltage of the transistor 20 (a voltage obtained by level-shifting the reflected light amount signal output from the amplifier 13 by the voltage between the base and the emitter of the transistor 20) and a voltage divided by the resistors 17 and 18 (output by the amplifier 13). The level of the reflected light amount signal is shifted by the voltage between the base and the emitter of the transistor 20 and the peak-held voltage is further changed to a reference voltage V
R is a comparator that compares the voltage divided by resistors 17 and 18), outputs a comparison result as a binary signal, and outputs it as a dropout detection signal; 25, a system controller that controls opening and closing of a tracking control loop; 2
Reference numeral 6 denotes a control signal output terminal of the system controller 25.

[0006] In the conventional optical disk device comprising the above components, the relationship and operation of the components will be described below. To close the tracking control loop,
The system controller 25 outputs a control signal of “H” from the control signal output terminal 26, and the control signal is input to the control signal input terminal 11 of the switch 10.
Closes. As a result, the tracking error signal output from the differential amplifier 9 is applied to the tracking control means 12, and the light beam spot follows the information track. To open the tracking control loop, the system controller 25 outputs a control signal of “L” from the control signal output terminal 26, and this signal is output to the control signal input terminal 11 of the switch 10.
, The switch 10 is open. In this state, the tracking control is not performed because the tracking error signal output from the differential amplifier 9 is not applied to the tracking control means 12.

The output of the photodetector 6 generates a dropout detection signal. This will be described with reference to FIG. FIG. 6 is a waveform diagram showing an operation signal waveform of a conventional example of dropout detection.

In FIG. 6, the horizontal axis represents time, the vertical axis represents voltage, and a represents an emitter voltage waveform of the NPN transistor 20 and represents a reflected light amount signal from the disk. b is the emitter voltage waveform of the NPN transistor 14 and indicates the peak hold value of the signal of the amount of light reflected from the disk (both a and b are the amplifier 1
3 is shifted in level by the voltage between the base and the emitter of the transistor with respect to the reflected light amount signal output by 3.
Relative level relationships are preserved. ). Symbol c denotes a non-inverting input terminal voltage waveform of the comparator 22, which is a signal obtained by dividing the peak hold value b of the reflected light amount signal with respect to the reference voltage VR by the resistors 17 and 18. V
R indicates a reference voltage generated by the reference voltage source 19, and d indicates an output voltage waveform (dropout detection signal waveform) of the comparator 22. T1 is a period during which the tracking control loop is closed, and T2 is a period during which the tracking control loop is open.

When dropouts such as stains on the disk surface occur during the period (T1) when the tracking control loop is closed, the reflected light amount signal a from the disk temporarily decreases as shown in FIG. At this time, as shown in FIG. 6, the peak hold value b of the reflected light amount holds the reflected light amount immediately before the dropout, and the peak hold signal c obtained by dividing the resistance is held at a voltage value slightly lower than the peak hold value b. By comparing the reflected light amount signal a with the peak-hold signal c obtained by the resistance division by the comparator 22, the portion where the reflected light amount signal a decreases as shown in FIG. Can be.

[0010]

However, the above-described conventional configuration has a problem that when the tracking control loop is opened (period T2 shown in FIG. 6), the dropout detection is erroneously detected. This will be described below with reference to FIGS. 5, 6, and 7.

FIG. 7 is a schematic diagram showing the relationship between the sectional shape of the optical disk and the amount of reflected light. In FIG. 7, A indicates a cross section in the direction perpendicular to the information tracks of the optical disc, a indicates an on-track (groove) area where information signals are recorded,
b denotes an off-track (land) area sandwiched between adjacent on-track areas. B represents the level of the amount of reflected light from the optical disk.

In a system such as an MD, as shown in FIG. 7, the groove width of the on-track area a is smaller than that of the off-track area b.
Greater than the groove width. This is to ensure a sufficient area for recording the information signal. Here, the amount of reflected light when the light beam spot is irradiated on the disk surface changes due to interference by the track grooves. Since the light beam spot diameter is substantially equal to the groove width of the on-track area a, the influence of the interference by the track grooves is larger in the off-track area b than in the on-track area a. Therefore, the amount of reflected light from the disc is lower in the off-track area b than in the on-track area a as shown in FIG. 7B.

Next, in FIG. 6, since the tracking control loop is closed during the period T1, the light beam spot is irradiated on the on-track area. During the period T2, since the tracking control loop is open, the light beam spot irradiates the on-track area and the off-track area alternately due to eccentricity of the disk, external vibration, or the like. Therefore period T2
The reflected light amount signal a periodically decreases as shown in FIG. 6 every time the light beam spot passes through the off-track area. Since this is basically regarded as a phenomenon similar to dropout, a dropout detection signal may be erroneously detected in the off-track area. If the dropout detection signal is erroneously detected when the tracking control loop is opened, a serious problem may occur in the system. For example, if a measure such as holding a focus control signal in response to a dropout detection signal has been taken to prevent a dropout of focus control,
When the tracking control loop is opened at the time of seeking etc.,
The focus control signal is frequently held in response to the erroneously detected dropout signal, causing a situation in which the focus control is disturbed or lost.

The present invention solves the above-mentioned conventional problems, in which the tracking control loop is opened or the light beam spot does not properly follow the on-track area even if the tracking control loop is closed. Another object of the present invention is to provide an optical disk device that prevents erroneous detection of dropout detection.

[0015]

In order to achieve this object, an optical disk apparatus according to the present invention comprises an opening / closing means for opening and closing a tracking control loop, and a dropout detected by a reflected light amount when the tracking control loop is opened. Or if the light spot does not correctly follow the track by the tracking control state determining means, and the light is detected by the reflected light amount. With the configuration of the means for invalidating the dropout, or with the opening and closing means for opening and closing the tracking control loop, and with the configuration of means for reducing the detection sensitivity of the dropout when the tracking control loop is opened, Alternatively, a tracking control state determination means and a tracking control state determination Those having a structure of the means for reducing the sensitivity of the drop-out when the light spot is judged to be not correctly follow a track by means.

[0016]

According to the present invention, the dropout detection is invalidated when the tracking control loop is opened even when the light beam spot passes through the off-track area and the amount of reflected light from the optical disk is reduced. Disable dropout detection if it is determined that the light spot does not correctly follow the track, or reduce the dropout detection sensitivity if the tracking control loop is opened, or if the light spot follows the track correctly. If it is determined that the dropout has not occurred, the dropout detection sensitivity is reduced, thereby preventing erroneous dropout detection.

[0017]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an optical disk device according to a first embodiment of the present invention. In FIG. 1, constituent elements 1 to 22, 25 and 26 are the same as those described with reference to FIG.

The feature of this embodiment is that the output of the comparator 22 is used as the control signal output terminal 26 of the system controller 25.
An AND gate 23 that masks with a control signal output from the controller and outputs the same as a dropout detection signal;
Is provided.

The operation of the optical disk of the first embodiment configured as described above will be described below with reference to the drawings. FIG. 8 is a waveform chart showing an operation signal waveform of dropout detection in the first embodiment.

In FIG. 8, the horizontal axis represents time, and the vertical axis represents voltage values. A, b, c, d, VR and T1, T2
Is the same as that of FIG. 6 described in the conventional example, and the description is omitted. “e” is a control signal waveform output from the control signal output terminal 26 of the system controller 25, and is “H” level when the tracking control loop is closed and “L” level when the tracking control loop is opened. f is AN
The output signal waveform of the D gate 23, that is, the dropout detection signal waveform. g, h, i and VR2 are the second values of the present invention.
Are signal waveforms for explaining the operation of the embodiment, and are not used in the description here.

The tracking control method and the basic operation of dropout detection are the same as in the conventional example. When the tracking control loop is opened, the light beam spot irradiates the on-track area and the off-track area alternately due to the influence of eccentricity or the like. The output d of the comparator 22 intermittently becomes the "H" level, and a dropout is erroneously detected. However, here, the output d of the comparator 22 is output by the AND gate 23.
Is masked by the control signal e, and during the period T2 when the tracking control loop is open, the control signal e becomes "L".
Therefore, the dropout detection signal f is always at "L" level.

As described above, according to the present embodiment, the tracking control loop is opened by providing the switch for opening and closing the tracking control loop and the AND gate for masking the output of the comparator when the tracking control loop is opened. In this case, a dropout that is erroneously detected due to a decrease in the amount of reflected light in the off-track area can be invalidated.

FIG. 2 is a block diagram of an optical disk device according to a second embodiment of the present invention. In FIG.
9 and 12 to 22 are the same as those described with reference to FIG. This embodiment is characterized in that a tracking control state determining means 30 for determining whether the light beam spot correctly follows the information track based on the tracking error signal output from the differential amplifier 9 is provided. Reference numerals 31, 32, 33, and 34 denote components of the tracking control state determination means 30, respectively.
Is a reference voltage source that generates a reference voltage VR2, and 31 is a reference voltage VR2 that outputs a tracking error signal output from the differential amplifier 9.
33 is a monomultivibrator for extending the time from the rising edge to the falling edge of the output signal of the comparator 31 to a predetermined time, and 34 is the monomultivibrator 3
3 is an inverter for inverting the polarity of the output signal. 23
Is an AND gate that masks the output of the comparator 22 with the output of the tracking control state determination means 30 and outputs it as a dropout detection signal.
This is a dropout detecting means constituted by 3 to 23.

The operation of the optical disk device of the second embodiment configured as described above will be described below with reference to the drawings. FIG. 8 is a waveform chart showing an operation signal waveform of dropout detection in the second embodiment.

In FIG. 8, the horizontal axis represents time, and the vertical axis represents voltage values. A, b, c, d, VR and T1, T2
Are the same as those described with reference to FIG. g is a tracking error signal waveform output by the differential amplifier 9, VR2 is a reference voltage generated by the reference voltage source 32, h is an output waveform of the comparator 31, and i is an output waveform of the inverter 34 (that is, the tracking control state determining means 30). Output waveform), and f is an output waveform of the AND gate 23 (that is, a dropout detection signal waveform). "e" is a signal waveform for explaining the operation of the first embodiment of the present invention, and is not used in the description here.

The tracking control method and the basic operation of dropout detection are the same as in the conventional example. When the light beam spot crosses the information track due to the tracking control being disturbed by the influence of disturbance vibration or the like, the light beam spot irradiates the on-track area and the off-track area alternately, and accordingly, as shown in a period T2 in FIG. As a result, the reflected light amount signal a periodically decreases, and the output d of the comparator 22 becomes the “H” level intermittently, and a dropout is erroneously detected. This is the same as in the first embodiment in that this is masked by the AND gate 23 and the dropout detection erroneously detected in the off-track area is invalidated.

This embodiment differs from the first embodiment in that the output of the comparator 22 is masked when the tracking control loop is opened according to the control signal of the system controller 25. In the present embodiment, the dropout detection signal is masked when the tracking control state determining means 30 determines that the light beam spot does not correctly follow the information track regardless of whether the tracking control loop is open or closed. It is a point to do. In the first embodiment, the configuration is easy. However, if the tracking control is disturbed due to disturbance vibration or the like when the tracking control loop is closed, a dropout may be erroneously detected. As a serious problem may occur. For example, if measures such as holding the focus control signal in response to the dropout detection signal were taken to prevent the dropout of the focus control, the tracking control was disturbed by disturbance vibration, and the dropout was erroneously detected. When this is done, the focus control signal is held in response to this, and there is a possibility that focus control may be lost. In this embodiment, even in such a case, erroneous detection of dropout can be prevented, so that the focus control system is not affected.

Next, the operation of the tracking control state determining means 30 will be described. When the tracking control is disturbed by disturbance vibration or the like and the light beam spot alternately passes through the on-track area and the off-track area, the tracking error signal g has an S-shaped waveform as shown in a period T2 in FIG. When this is compared with the reference voltage VR2 set to a value slightly lower than the peak value of the tracking error signal by the comparator 31, an intermittent pulse waveform as shown in FIG. When this waveform is extended by the mono-multivibrator 33 to extend the time interval from the rise to the fall and the polarity is inverted by the inverter 34, a tracking control state determination signal as shown in FIG. 8i is obtained. Here, by using the AND gate 23 to mask the output signal d of the comparator 22 with the tracking control state determination signal i, the dropout detection signal erroneously detected in the period T2 in FIG. 8 can be invalidated.

As described above, according to the present embodiment, when the tracking control state determining means determines that the light spot does not correctly follow the information track, the output signal of the comparator is masked. By providing an AND gate that performs the above operation, when tracking control is disturbed by disturbance vibration or the like, a dropout that is erroneously detected due to a decrease in the amount of reflected light in the off-track area can be invalidated.

FIG. 3 is a block diagram of an optical disk device according to a third embodiment of the present invention. In FIG. 3, components 1 and 2
2 and 25 and 26 are the same as those described with reference to FIG. The feature of the present embodiment is that the dropout detecting means 24 includes the constituent elements 13 to 22.
And a switch 4 for opening and closing both ends of the resistor 40
1. Control signal output terminal 26 of system controller 25
A control signal input terminal 41 of a switch 41 for inputting a control signal output from the resistor 41 is provided.
0 is closed at both ends and opened at the “L” level.

The operation of the optical disk device of the third embodiment configured as described above will be described below with reference to the drawings. FIG. 9 is a waveform diagram showing operation signal waveforms for dropout detection in the third embodiment.

In FIG. 9, the abscissa represents time, and the ordinate represents voltage. A, b, VR and T1, T2 are the same as those described with reference to FIG. . “e” is a control signal waveform output from the control signal output terminal 26 of the system controller 25, and is “H” level when the tracking control loop is closed and “L” level when the tracking control loop is opened. j is a non-inverting input terminal waveform of the comparator 22, and f is an output waveform of the comparator 22 (that is, a dropout detection signal waveform).

The tracking control method and the basic operation of dropout detection are the same as in the conventional example. When the tracking control loop is opened, the light beam spot irradiates the on-track area and the off-track area alternately due to the influence of eccentricity or the like.
As shown in the figure, the reflected light amount signal a periodically decreases accordingly. In the first and second embodiments, the dropout detection is invalidated by masking the output of the comparator 22 detected by the decrease in the amount of reflected light during the period T2 with an AND gate. By changing the resistance division ratio of the peak hold value of the reflected light amount, dropout detection sensitivity is reduced to prevent erroneous detection. The operation will be described below.

When the tracking control loop is closed, the control signal output terminal 26 of the system controller 25
Outputs an "H" level control signal e from switch 4
1 is closed, the emitter voltage of the transistor 14 (the peak hold voltage b of the amount of reflected light) is divided by the resistors 17 and 18 with respect to the reference voltage VR (the conduction resistance of the switch 41 is assumed to be negligible). The peak hold voltages before and after the voltage division at this time are respectively shown by b and j in the period T1 in FIG. When the tracking control loop is opened, an "L" level control signal e is output from the control signal output terminal 26 of the system controller 25, the switch 41 is opened, and the emitter voltage of the transistor 14 (the peak hold voltage b of the amount of reflected light). Is divided by the resistors 17, 40 and 18 with respect to the reference voltage VR. The peak hold voltages before and after the voltage division at this time are respectively shown by b and j in the period T2 in FIG. In this way, when the tracking control loop is opened, the switch 41 is opened at the same time to change the resistance voltage division ratio, thereby lowering the level of the peak hold voltage j after voltage division as shown in j of FIG. Dropout detection sensitivity is reduced. As a result, even when the light beam spot passes through the off-track area and the reflected light amount signal a decreases as shown in the period T2 in FIG. 9, erroneous detection of dropout can be prevented.

Although the first and second embodiments have a simple structure, the structure is such that the dropout detection signal is masked, so that the dropout exists at the same time as the light beam spot passes through the off-track area. Even so, this could not be detected. On the other hand, in the present embodiment, since the dropout detection sensitivity is reduced, even if a dropout exists simultaneously with the tracking control loop open as shown in a period T2 in FIG. It is possible to detect this only by slightly lowering the detection sensitivity than when closing.

If dropouts can be reliably detected when the tracking control loop is opened, it is extremely useful systematically. For example, when a seek operation is performed by opening a tracking control loop, if a dropout detection signal can be reliably detected even during a seek, the focus control signal is held in accordance with this, and the focus control is performed due to a scratch on the disk surface during the seek. Departure can be prevented, and the stability of the access operation can be improved.

As described above, according to the present embodiment, by providing the switch for opening and closing the tracking control loop and the means for lowering the dropout detection sensitivity when the tracking control loop is opened, the tracking control loop is provided. When opened, it is possible to prevent erroneous detection of dropout due to a decrease in the amount of reflected light in the off-track area, and to detect dropout if simultaneous dropout exists in that state.

FIG. 4 is a block diagram of an optical disk device according to a fourth embodiment of the present invention. In FIG.
9 and 12 to 22 are the same as those described with reference to FIG. The components 30 to 34 are the same as those described in the second embodiment with reference to FIG. Also, the components 40 to 42 are the same as those described in the third embodiment, and thus description thereof will be omitted. This embodiment is characterized in that the switch 4 in the dropout detecting means 24 is used.
The first control signal input terminal 42 receives the output signal of the tracking control state discriminating means 30 so that both ends of the resistor 40 are closed at "H" level and opened at "L" level.

The operation of the optical disk device of the fourth embodiment configured as described above will be described below with reference to the drawings. FIG. 10 is a waveform diagram showing an operation signal waveform of dropout detection in the fourth embodiment.

In FIG. 10, the horizontal axis represents time, and the vertical axis represents voltage value. A, b, VR and T1, T2 are the same as those described in FIG. i and VR2 are the same as those described with reference to FIG. 8 of the second embodiment, and j and f are the same as those described with reference to FIG. 9 of the third embodiment.

The tracking control method and the basic operation of dropout detection are the same as in the conventional example. When the tracking control is deviated by the influence of disturbance vibration and the light beam spot crosses the information track, the light beam spot irradiates the on-track area and the off-track area alternately, and accordingly, as shown in a period T2 in FIG. As a result, the reflected light amount signal a periodically decreases. In the present embodiment, when the tracking control state determination means 30 determines that the light beam spot does not correctly follow the information track, the dropout detection sensitivity is changed by changing the resistance division ratio of the peak hold value of the reflected light amount. To prevent false detection. The operation will be described below.

The operation of the tracking control state discriminating means 30 is the same as in the second embodiment, and will not be described. When it is determined by the tracking control state determination means 30 that the light beam spot is correctly following the information track, an “H” level is input to the control input terminal of the switch 41, and the switch 41 is closed. The emitter voltage of the transistor 14 (the peak hold voltage b of the reflected light amount) is divided by the resistors 17 and 18 with respect to the reference voltage VR (the conduction resistance of the switch 41 is assumed to be negligible). The peak hold voltages before and after the voltage division at this time are shown by b and j in the period T1 in FIG. When it is determined by the tracking control state determination means 30 that the light beam spot does not correctly follow the information track, an “L” level is input to the control input terminal of the switch 41, and the switch 41 is opened. The emitter voltage (peak hold voltage b of the amount of reflected light) is divided by the resistors 17, 40 and 18 with respect to the reference voltage VR. The peak hold voltages before and after the voltage division at this time are b in the period T2 in FIG.
And j, respectively. As described above, by opening the switch 41 according to the output of the tracking control state determination means 30 and changing the resistance voltage division ratio, the level of the peak hold voltage j after voltage division is reduced as shown in j of FIG. , Dropout detection sensitivity can be reduced. Thereby, even if the reflected light amount signal a decreases when the light beam spot passes through the off-track area as shown in the period T2 in FIG. 10, erroneous detection of dropout can be prevented.

Since the dropout detection sensitivity is reduced as in the third embodiment, the tracking control is deviated due to disturbance vibration or the like as shown in a period T2 in FIG. Even if there is a dropout at the same time in the state of crossing, it is possible to detect this.

If dropouts can be reliably detected in such a state, it is extremely useful systematically.
If a dropout exists at the same time when tracking control is deviated due to disturbance vibration and the light beam spot crosses the information track, focus control is deviated by detecting this as a dropout and holding the focus control signal. Can be prevented, and the stability of the system can be improved.

As described above, according to this embodiment, the dropout detection sensitivity is reduced when the tracking control state determining means determines that the light spot does not correctly follow the track. Means to prevent erroneous detection of dropout due to a decrease in the amount of reflected light in the off-track area when tracking control is disturbed by disturbance vibration or the like, and simultaneously drop in that state. If an out exists, it can be detected.

Although the tracking error signal is detected by the three-beam method in the first to fourth embodiments of the present invention, any method such as a push-pull method, a wobbling method, and a phase difference method may be used.

In the first to fourth embodiments of the present invention, a decrease in the amount of reflected light due to dropout is detected using a peak detection circuit using a transistor, a resistor and a capacitor, and a comparator. Any means can be used as long as it can be detected, and it can be realized not only by an analog circuit but also by any method such as a digital circuit or software processing.

Although the output signal of the comparator 22 is masked by the AND gate in the first and second embodiments of the present invention, any means for invalidating the output signal of the comparator 22 can be used. It may be realized by any method such as an analog circuit, a digital circuit, and software processing.

Further, in the first and third embodiments of the present invention, the switch for opening and closing the tracking control loop is disposed before the tracking control means, but may be located at any position in the tracking control loop. Not limited to this, any means may be used as long as it can open and close the tracking control loop.

In the first and third embodiments of the present invention, the switches for opening and closing the tracking control loop are controlled by the system controller. However, this is a system controller in a broad sense, and is used in ordinary equipment. It is not limited to a microcomputer, but can be realized by any method such as an analog circuit, a digital circuit, and software processing as long as it controls the system.

In the second and fourth embodiments of the present invention, the tracking control state discriminating means compares the tracking error signal with a reference value by a comparator and extends the pulse width by a mono-multivibrator.
This may be any means as long as it is means for determining whether or not the light beam spot correctly follows the information track, and can be realized by any method such as an analog circuit, a digital circuit, and software processing.

In the third and fourth embodiments of the present invention, the resistance division ratio of the peak hold value of the reflected light amount is switched in order to lower the dropout detection sensitivity. This is just one example. In addition, the transistor 14 or 2 that applies an offset to one of the inputs of the comparator 22
Level-shift any one of the 0 emitter voltage outputs,
Various methods are conceivable, such as switching the reference value VR generated by the reference voltage source 19, attenuating the periodic fluctuation component of the reflected light amount caused by crossing the track through the reflected light signal through the low-puff filter, and the like. No matter what method is used as long as it reduces the effect, the gist of the present invention is not affected at all. Also, the realization method is not limited to the analog circuit, but can be realized by any method such as a digital circuit and software processing.

[0053]

As is apparent from the above description of the embodiment, the present invention provides an opening / closing means for opening and closing a tracking control loop, and invalidates a dropout detected by the amount of reflected light when the tracking control loop is opened. Or if the tracking control state determining means determines that the light spot does not correctly follow the track, the dropout detected by the reflected light amount is invalidated. Means for opening and closing the tracking control loop, and means for lowering the dropout detection sensitivity when the tracking control loop is opened, or a tracking control state determining means, and a tracking control state. The light spot is correctly positioned on the track by the discriminating means. By providing a means to reduce the dropout detection sensitivity when it is determined that the tracking error is not observed, the light beam spot is correctly placed in the on-track area even if the tracking control loop is opened or the tracking control loop is closed. When the tracking is not performed, erroneous detection of dropout detection can be prevented, so that the stability of the optical disk system can be improved.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of an optical disc device according to a second embodiment of the present invention;

FIG. 3 is a block diagram of an optical disc device according to a third embodiment of the present invention.

FIG. 4 is a block diagram of an optical disc device according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram of a conventional optical disk device.

FIG. 6 is a waveform diagram showing operation signal waveforms of a conventional optical disc device.

FIG. 7 is a schematic diagram showing the relationship between the cross-sectional shape of an optical disc and the amount of reflected light.

FIG. 8 is a waveform chart showing operation signal waveforms in the optical disk devices of the first and second embodiments of the present invention.

FIG. 9 is a waveform chart showing operation signal waveforms in the optical disc device of the third embodiment of the present invention.

FIG. 10 is a waveform chart showing operation signal waveforms in the optical disc device according to the fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Switch 12 Tracking control means 23 AND gate 24 Dropout detection means 25 System controller 30 Tracking control state determination means 41 Switch

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Claims (4)

(57) [Claims] A rotating means for rotating an optical disk on which an information signal is recorded in a predetermined track form; a light beam formed on an information surface of the optical disk by forming a light spot; An optical pickup that receives light at
Tracking error signal generating means for detecting a relative position error between the track and the light spot in the disk radial direction based on an output of the photodetector and outputting as a tracking error signal; a tracking actuator for moving the light spot in the disk radial direction A tracking control unit that configures a tracking control loop by driving the tracking actuator with the tracking error signal as an input to cause the light spot to follow the track; an opening and closing unit that opens and closes the tracking control loop; Dropout detection means for detecting dropout on the optical disk surface based on the output of a photodetector, wherein the dropout detection means drops when the opening / closing means opens the tracking control loop. Optical disc apparatus characterized by a disable output. 2. A rotating means for rotating an optical disk on which an information signal is recorded in a predetermined track form, and a light beam is focused on an information surface of the optical disk to form a light spot, and the reflected light is detected by a photodetector. An optical pickup that receives light at
Tracking error signal generating means for detecting a relative position error between the track and the light spot in the disk radial direction based on an output of the photodetector and outputting as a tracking error signal; a tracking actuator for moving the light spot in the disk radial direction A tracking control means for configuring the tracking control loop by driving the tracking actuator with the tracking error signal as an input to cause the light spot to follow the track; and whether the light spot correctly follows the track. A tracking control state determining means for determining whether the tracking control is performed, and a dropout detecting means for detecting a dropout on the optical disk surface based on an output of the photodetector. When the light spot in the state discriminating means is determined not to be correctly follows the track, the optical disk apparatus characterized by a disabling dropout detection. 3. A rotating means for rotating an optical disk on which an information signal is recorded in a predetermined track form, and a light beam is focused on an information surface of the optical disk to form a light spot, and the reflected light is detected by a photodetector. An optical pickup that receives light at
Tracking error signal generating means for detecting a relative position error between the track and the light spot in the disk radial direction based on an output of the photodetector and outputting as a tracking error signal; a tracking actuator for moving the light spot in the disk radial direction A tracking control unit that configures a tracking control loop by driving the tracking actuator with the tracking error signal as an input to cause the light spot to follow the track; an opening and closing unit that opens and closes the tracking control loop; Dropout detection means for detecting dropout on the optical disk surface based on the output of a photodetector, wherein the dropout detection means drops when the opening / closing means opens the tracking control loop. Optical disc apparatus characterized by reducing the output sensitivity. 4. A rotating means for rotating an optical disk on which an information signal is recorded in a predetermined track form, and a light beam is focused on an information surface of the optical disk to form a light spot, and the reflected light is detected by a photodetector. An optical pickup that receives light at
Tracking error signal generating means for detecting a relative position error between the track and the light spot in the disk radial direction based on an output of the photodetector and outputting as a tracking error signal; a tracking actuator for moving the light spot in the disk radial direction A tracking control means for configuring the tracking control loop by driving the tracking actuator with the tracking error signal as an input to cause the light spot to follow the track; and whether the light spot correctly follows the track. A tracking control state determining means for determining whether the tracking control is performed, and a dropout detecting means for detecting a dropout on the optical disk surface based on an output of the photodetector. When the light spot in the state discriminating means is determined not to be correctly follows the track, the optical disk apparatus characterized by reducing the dropout detection sensitivity.