JP2005158205A - Optical disk unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk unit in which pull-in operation to a track can be stably performed even for an optical disk having a large eccentricity component. <P>SOLUTION: The optical disk unit is provided with: a detecting means 9 detecting that an optical pickup 3 crosses from some track to the next track on an optical disk 1; period measuring means 11, 12 and 13 measuring a period from some track to the next track on the optical disk; and control means 15, 18, 27, 26, 21 and 22 controlling voltage applied to a drive means 10 so as to diminish the voltage by stages in accordance with the value of the measured period. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus that optically reproduces or records and reproduces signals from an optical disc, and more particularly to an optical disc apparatus that performs acceleration / deceleration control of an actuator portion during a pull-in operation to a track.

  Optical disc apparatus for reproducing information from an optical disc having concentric or spiral recording tracks in the radial direction and each track being divided into a plurality of predetermined recording units, and for recording information on the optical disc There is.

  In this type of optical disc apparatus, the tracking control is performed so that the light spot comes right above the recording track. However, before the tracking control is performed, a drawing operation (following operation) to the track is required. At this time, if the light spot crossing the track is controlled by speed control, the track can be stably drawn. Such an optical disk device is described in Patent Document 1, for example.

  In Patent Document 1, immediately after switching from a track to a speed control loop, a kick pulse is applied to an actuator for a predetermined period and moved at a predetermined acceleration immediately before switching to a speed control loop, thereby stabilizing the pull-in operation to the track. It can be carried out.

JP-A-10-320791

  However, in the above prior art, when performing the pulling operation to the track, the kick pulse is once applied to the actuator at a certain level for a certain period, and then the stable pulling operation to the track is performed by speed control. However, since the rotation center of the optical disk in the apparatus and the center of the recording track arranged in a spiral shape (so-called eccentricity) are not taken into consideration, the kick pulse direction is wrong and tracking control runs out of control. There was a problem.

  Furthermore, since the voltage applied to the actuator is constant and the acceleration is not taken into consideration, even if the speed is zero and the track can be pulled in, the track is stably pulled in if the acceleration is large. There was a problem that could not be done.

  An object of the present invention is to provide an optical disc apparatus capable of stably performing a pull-in operation to a track even for an optical disc having a large eccentric component.

  An optical disc apparatus according to claim 1 of the present invention comprises an optical pickup for focusing a laser beam on a recording surface of an optical disc, and a driving means for moving the optical pickup to an arbitrary track position on the optical disc. In addition, in the optical disk apparatus for reproducing or recording / reproducing the optical disk, the optical pickup detects a crossing from a certain track on the optical disk to the next track; It is characterized by comprising period measuring means for measuring the period up to the track, and control means for controlling the voltage applied to the driving means in a stepwise manner in accordance with the value of the measured period.

  According to a second aspect of the present invention, there is provided an optical disc apparatus comprising: an optical pickup for focusing a laser beam on a recording surface of the optical disc; and a driving means for moving the optical pickup to an arbitrary track position on the optical disc. In addition, in the optical disk apparatus for reproducing or recording / reproducing the optical disk, the optical pickup detects a crossing from a certain track on the optical disk to the next track; A period measuring means for measuring the period up to the track; a generating means for generating a difference value between the measured period value and the target period value; and a voltage applied to the driving means in accordance with the generated difference value And control means for controlling it to be small in size.

  According to a third aspect of the present invention, there is provided an optical disc apparatus comprising: an optical pickup for focusing a laser beam on a recording surface of the optical disc; and a driving means for moving the optical pickup to an arbitrary track position on the optical disc. In addition, in the optical disk apparatus for reproducing or recording / reproducing the optical disk, the optical pickup detects a crossing from a certain track on the optical disk to the next track; Period measuring means for measuring the period until the track, reversing means for inverting the polarity of the voltage applied to the driving means according to the value of the measured period, and controlling the applied voltage to the driving means to be small stepwise And a control means.

  According to a fourth aspect of the present invention, there is provided an optical disc apparatus comprising: an optical pickup for focusing a laser beam on a recording surface of the optical disc; and a driving means for moving the optical pickup to an arbitrary track position on the optical disc. In addition, in the optical disk apparatus for reproducing or recording / reproducing the optical disk, the optical pickup detects a crossing from a certain track on the optical disk to the next track; A period measuring means for measuring the period up to the track; a first comparing means for comparing the measured period value with a first target period value; and the drive means according to the value of the first comparing means Reversing means for reversing the polarity of the applied voltage, and a second comparator for comparing the measured cycle value with the second target cycle value. When, characterized by comprising and control means for controlling stepwise reduced voltage applied to the drive means in accordance with the value of said second comparison means.

  According to the present invention, it is possible to obtain an optical disc apparatus capable of stably performing a pull-in operation to a track even with an optical disc having a large eccentric component.

  FIG. 1 is a block configuration diagram showing an embodiment of an optical disc apparatus according to the present invention. In FIG. 1, 1 is an optical disk, 2a is a clamper, 2b is a turntable, 3 is an optical pickup, 4 is a lead screw, 5 is a thread motor, 6 is a spindle motor, 7 is an objective lens, 8 is a thread, and 9 is signal processing. Circuit 10, tracking drive circuit 11, edge detection circuit 12, period measurement counter 12, period measurement value 13, tracking pull-in period value 15, brake control period value 16, brake reversal period value 17 The first comparison operator, 18 is a second comparison operator, 19 is a third comparison operator, 20 is a neutral potential, 21 is a microcomputer (hereinafter referred to as a microcomputer), 22 is a first changeover switch, 23 Is a second changeover switch, 24 is an inner circumferential applied voltage value, 25 is an outer circumferential applied voltage value, 26 is a multiplier, and 27 is a variable multiplication coefficient. It is.

  Next, the operation will be described. The optical disk 1 set on the turntable 2b is fixed to the turntable 2b by a clamper 2a. The optical disk 1 rotates as the spindle motor 6 rotates. As the sled motor 5 rotates, the lead screw 4 rotates, whereby the optical pickup 3 mounted on the sled 8 moves to the inner or outer periphery of the optical disc 1.

  A light beam emitted from a laser (not shown) of the optical pickup 3 passes through a half prism (not shown), is focused by the objective lens 7, and forms a beam spot on the optical disk 1. The laser reflected light from the optical disk 1 passes through the objective lens 7 again, is reflected by the half prism, and forms a spot on a photodetector (not shown).

  A signal obtained from the photodetector is supplied to the signal processing circuit 9, and the signal processing circuit 9 controls a focus error signal (hereinafter referred to as a focus error signal) for controlling the focus in the vertical direction with respect to the optical disc 1, or a horizontal direction. A tracking error signal (hereinafter referred to as a tracking error signal) is generated for controlling the tracking.

  Usually, the focus error signal and the tracking error signal are used to perform focus control in the vertical direction and tracking control in the horizontal direction with respect to the optical disc 1 so as to read the data so that the beam spot traces on the track on which information is recorded. .

  When tracking control is being performed, the tracking error signal generated in the signal processing circuit 9 is supplied to the switch 22. The tracking error signal supplied to the switch 22 is supplied to the tracking drive circuit 10 because the signal supplied from the microcomputer 21 instructs the switch 22 to be on the c side.

  The signal supplied to the tracking drive circuit 10 generates a signal for driving the optical pickup 3 in the horizontal direction and supplies it to the optical pickup 3. With the drive signal supplied to the optical pickup 3, the objective lens 7 traces the optical disk 1 on the track in the horizontal direction.

  Here, a case where a state (so-called tracking pull-in) is performed in which the beam spot shifts from a state where focus control is performed to a state where tracking control is performed so as to trace the track on which information is recorded on the optical disc 1. explain.

  In this case, the switch 22 is set to b so that the tracking control loop is opened by an instruction from the microcomputer 21 instead of the state where the tracking control described above is performed. The neutral potential 20 is supplied to b of the switch 22, and the neutral potential 20 is supplied to the tracking drive circuit 10. The tracking drive circuit 10 supplied with the neutral potential 20 generates a signal that causes the optical pickup 3 to be in a neutral position and supplies the signal to the optical pickup 3.

  The horizontal optical pickup 3 supplied with a neutral signal is fixed at a fixed position, and the beam spot cannot be traced on the track. In this state, since the beam spot cannot be traced on the track, when the optical disc 1 is rotated, the track crosses the beam spot fixed by the eccentric component of the optical disc 1.

  Here, the eccentric component is a component that occurs because the center of rotation of the optical disk and the center of the track that is actually recorded on the spiral on the optical disk is deviated. Will cross. Since the eccentric component is related to the rotational speed of the optical disc as described above, when the optical disc is rotated at a high speed for reading or writing data from the optical disc, the frequency across the track is increased accordingly.

  Next, a step of shifting from a state where the beam spot cannot be traced on the track to a state where the beam spot can be traced will be described.

  In advance, the tracking control loop can be closed to the tracking pull-in period value 14, and the tracking period can be closed to the period when the beam spot moves across the track when the beam spot crosses the track, that is, the time. Brake control to the cycle of moving between the tracks when the beam spot for applying the brake control to the objective lens 7 crosses the track, that is, the time, and the brake reversal cycle value 16 so that the control loop can be closed. A period, that is, a time for moving the beam spot between the tracks when the beam spot crosses the track for detecting a case where the brake voltage is different from the control direction is set.

  A tracking zero cross signal (hereinafter referred to as TZC signal) generated by the signal processing circuit 9 from the signal obtained by the optical pickup 3 is supplied to the edge detection circuit 11. Here, the TZC signal is, for example, a signal obtained by binarizing the tracking error signal generated by the signal processing circuit 9 and having a polarity that rises or falls every time the light beam crosses the track.

  The TZC signal supplied to the edge detection circuit 11 detects a rising or falling edge of the TZC signal and supplies edge information to the period measurement counter 12 and the period measurement value 13. The period measurement counter 12 starts the count with the edge information supplied from the edge detection circuit 11 and measures the period from the edge information to the next input edge information.

  Here, the period from the current periodic edge information to the next inputted periodic edge information is the edge information generated when the light beam crosses the track, so that there is a gap between the current track and the adjacent track. This is the time that the light beam travels.

  The period value measured by the period measurement counter 12 is sequentially input to the period measurement value 13, but the value is not updated until the edge information is input from the edge detection circuit 11. For this reason, the value of the period measurement value 13 stores the period value from the current edge information to the previously input edge information. The value stored as the period measurement value 13 is supplied to the first comparison calculator 17, the second comparison calculator 18, and the third comparison calculator 19.

  On the other hand, a preset tracking pull-in period value 14 is set in the first comparison calculator 17, a preset brake control period value 15 is set in the second comparison calculator 18, and a preset brake inversion period is set. The value 16 is supplied to the third comparator 19.

  The first comparator 17 compares the value supplied from the period measurement value 13 with the value supplied from the tracking pullable period value 14, calculates the difference value, and supplies the output value to the switch 22. The second comparison calculator 18 compares the value supplied from the cycle measurement value 13 with the value supplied from the brake control cycle value 15, calculates the difference value, and supplies the output value to the variable multiplication coefficient value 27. . The third comparator 19 compares the value supplied from the cycle measurement value 13 with the value supplied from the brake reversal cycle value 16, calculates the difference value, and supplies the output value to the switch 23.

  The microcomputer 21 closes the tracking control loop from the state in which the switch 22 is b, that is, the state in which the tracking control is not performed, to the state in which the tracking control is performed. At this time, the tracking control can be performed by setting the switch 22 to c. However, if the rotational speed of the optical disk 1 is large, the track crossing frequency due to eccentricity is high. The crossing frequency exceeds the bandwidth of tracking control, and tracking cannot be controlled by a feedback loop.

  Therefore, once the brake voltage of a constant voltage is applied to drive the objective lens 7 of the optical pickup 3 to relatively reduce the track crossing frequency, the frequency is reduced to a band where the tracking control of the feedback loop is possible. For this purpose, the switch 22 is switched to a.

  An outer peripheral direction applied voltage 25 to be applied in the outer peripheral direction in the radial direction of the optical disc 1 is supplied to the input of e of the switch 23. On the other hand, d of the switch 23 is supplied with an inner circumferential applied voltage 24 applied in the inner circumferential direction in the radial direction of the optical disk.

  Further, the microcomputer 21 switches the switch 23 to e. In response to an instruction from the microcomputer 21, the switch 23 outputs an outer circumferential applied voltage 25 and supplies it to the multiplier 26. The multiplier 26 is supplied with a variable multiplication coefficient value 27. The multiplier 26 multiplies the value applied from the outer peripheral direction applied voltage value 25 supplied from the switch 23 and the variable multiplication coefficient value 27 and supplies the result to the switch 22.

  Since the switch 22 is switched to “a” in response to an instruction from the microcomputer 21, the signal for driving the optical pickup 3 to the outer periphery multiplied by the multiplier 26 is supplied to the tracking drive circuit 10. The signal for driving in the outer circumferential direction supplied to the tracking drive circuit 10 generates a signal for driving the optical pickup 3 in the horizontal direction and supplies it to the optical pickup 3. With the drive signal supplied to the optical pickup 3, the objective lens 7 is driven on the optical disc 1 in the horizontal direction in the outer peripheral direction.

  On the other hand, the third comparator 19 compares the value supplied from the cycle measurement value 13 with the value supplied from the brake inversion cycle value 16, and the cycle measurement value 13 is smaller than the brake inversion cycle value 16. If (brake reversal cycle value> cycle measurement value), that is, if the speed of movement between tracks increases, a “HIGH” signal is output and supplied to the switch 23.

  The third comparator 19 compares the value supplied from the cycle measurement value 13 with the value supplied from the brake reversal cycle value 16, and whether the cycle measurement value 13 is greater than the brake reversal cycle value 16. If they are equal (brake reversal cycle value ≦ cycle measurement value), that is, if the speed of movement between tracks becomes slow, a “LOW” signal is output and supplied to the switch 23.

  In the switch 23, the switch 23 is switched to the opposite of the current one by the “HIGH” signal from the third comparison calculator 19. For example, when the current switch position is d, the operation is switched to e, and when the current switch position is e, the operation is switched to d. In the case of the “LOW” signal from the third comparator 19, the switch 23 is not switched.

  Further, the second comparator 18 compares the value supplied from the cycle measurement value 13 with the value supplied from the brake control cycle value 15, and the cycle measurement value 13 is larger than the brake control cycle value 15. If they are equal (brake control cycle value ≦ cycle measurement value), that is, if the speed of movement between tracks becomes slow, a “HIGH” signal is output and supplied to the variable multiplication coefficient value 27.

  The second comparator 18 compares the value supplied from the cycle measurement value 13 with the value supplied from the brake control cycle value 15, and the cycle measurement value 13 is smaller than the brake control cycle value 15. In the case of (brake reversal cycle value> cycle measurement value), that is, when the speed of movement between tracks increases, a “LOW” signal is output and supplied to the variable multiplication system numerical value 27.

  In the variable multiplication system numerical value 27, the multiplication coefficient value is gradually reduced by the “HIGH” signal from the second comparison calculator 18. For example, when the initial value is 1, the coefficient value is decreased as 0.9, 0.8, 0.7. However, the sign should not be reversed. In the case of the “LOW” signal from the second comparison calculator 18, the variable multiplication coefficient value 27 is not changed. In general, when a constant applied voltage is applied to the optical pickup 3, a constant acceleration occurs in the objective lens 7, and the speed of the objective lens 7 gradually increases.

  In the case of the present embodiment, the purpose is to reduce the speed of the objective lens 7 by applying an applied voltage. However, if acceleration is continuously generated by always applying a constant voltage, the speed is gradually reduced to zero. However, this time it will have a speed in the reverse direction and will accelerate in the reverse direction. In this case, the frequency cannot be reduced to a band where the feedback loop tracking control is possible, and eventually the tracking control cannot be performed.

  Therefore, by gradually reducing the voltage value to be driven by the variable multiplication coefficient as described above, the acceleration is reduced when the frequency is reduced to a band where the feedback loop tracking control is possible.

  Further, the first comparator 17 compares the value supplied from the period measurement value 13 with the value supplied from the tracking pull-in period value 14, and the period measurement value 13 is more than the tracking pull-in period value 14. When it becomes larger or equal (tracking pullable period value ≦ period measurement value), that is, when the moving speed between tracks becomes slow, a “HIGH” signal is output and supplied to the switch 22.

  The first comparator 17 compares the value supplied from the period measurement value 13 with the value supplied from the tracking pull-in period value 14, and the period measurement value 13 is smaller than the tracking pull-in period value 14. When (tracking pullable period value> period measurement value), that is, when the speed of movement between tracks increases, a “LOW” signal is output and supplied to the switch 22. In the switch 22, the switch 22 is switched to c by the “HIGH” signal from the first comparison calculator 17.

  As a result, the tracking control becomes a feedback loop, and the objective lens 7 traces the optical disk on the track in the horizontal direction by the drive signal supplied to the optical pickup 3. In the case of the “LOW” signal from the first comparison calculator 17, the switch 22 is not switched.

  By configuring as described above, even in an optical disk having a large eccentricity component, a direction in which tracking control does not deviate from the band of the feedback loop is detected from the period of traversing between tracks, and the speed (period) control is performed to the track. When the speed at which the pull-in operation can be performed is reduced, the acceleration can be reduced to stably perform the pull-in operation to the track.

  In the above embodiment, the voltage applied first is the outer peripheral direction, but it goes without saying that it may be the inner peripheral direction.

  Here, the case of performing the tracking pull-in operation will be described with reference to FIGS.

  FIG. 2 shows a case where the direction in which a constant voltage is first applied coincides with the direction in which the moving speed between tracks is decelerated in order to perform tracking pull-in while the optical disk 1 having an eccentric component is rotated. FIG.

  In FIG. 2, “A”, “B”, “C”, “D”, “E”, and “F” are the time between rising edges of the tracking zero cross (TZC), which is a signal obtained by binarizing the tracking error signal, that is, a periodic value. (Hereinafter referred to as TZC period). This is the period measurement value 13 measured by the period measurement counter 12. In this case, the relationship between the cycle value, the tracking pullable cycle value 14, the brake control cycle value 15, and the brake reverse cycle value 16 is “brake reverse cycle value” <“A” <“brake control cycle value” <“B” < It is assumed that “C” <“D” <“E” <“tracking pull-in period value” <“F”.

  When tracking control is not performed, the switch 22 is “b”, and the state is loop-off. A neutral voltage is output as the tracking drive signal.

  Here, a process for performing tracking control is started in accordance with an instruction from the microcomputer 21. First, the switch 22 is set to “a” and the switch 23 is set to “e” at the same time. As a result, the outer peripheral direction applied voltage value 25 is output as the tracking drive signal. At this time, the TZC period is still “A”, which is the same as when the loop is off. In the case of FIG. 2, the direction in which the track moves with respect to the beam spot is decelerated by the applied voltage value 25 in the outer circumferential direction because the direction in which the track moves with respect to the beam spot is the inner circumferential direction. For this reason, the TZC period gradually becomes larger than “A”.

  Due to the deceleration, the TZC cycle becomes larger than the “brake control cycle value”. When the TZC cycle becomes “B”, the comparison operator 18 outputs a “HIGH” signal. As a result, the value of the variable multiplication coefficient 27 is decreased, and the value of the applied voltage in the outer circumferential direction of the tracking drive signal is decreased. Thereafter, the value of the applied voltage in the outer circumferential direction is reduced by the variable multiplication coefficient 27 but is in the deceleration direction, so that the TZC cycle becomes larger and larger, “C”, “D”, and “E”.

  If the deceleration continues and the TZC cycle becomes “F”, the cycle value becomes larger than the “tracking pull-in possible cycle”, and thus the “HIGH” signal is output from the comparison calculator 17. As a result, the switch 22 is set to “C”. Since the TZC period “F” is longer than the tracking pull-in period, when tracking control is turned on by setting the switch 22 to “C”, tracking can be stably pulled in by the gain and bandwidth of the feedback loop.

  Further, since the tracking drive signal immediately before the tracking control loop-on is applied has a small applied voltage due to the variable multiplication coefficient 27, the acceleration is also small. After the tracking is pulled in, the vehicle runs away from the track due to the acceleration. There is nothing.

  Next, in FIG. 3, in order to perform tracking pull-in while the optical disk 1 having an eccentric component is rotated, the direction in which a constant voltage is first applied coincides with the direction in which the moving speed between tracks is reduced. It is the figure which showed the case where there is no.

  In FIG. 3, “A”, “B”, “C”, “D”, “E”, “F”, “G”, “H”, and “I” are the rising edges of the tracking zero cross (TZC), which is a binarized signal of the tracking signal. The time between them, that is, the TZC cycle value. This is the period measurement value 13 measured by the period measurement counter 12. In this case, the relationship between the cycle value and the tracking pullable cycle value 14, the brake control cycle value 15, and the brake reverse cycle value 16 is “C” <“brake reverse cycle value” <“B” <“D” <“A”. <“Brake control cycle value” <“E” <“F” <“G” <“H” <“Tracking pull-in period value” <“I”.

  When tracking control is not performed, the switch 22 is “b”, and the state is loop-off. A neutral voltage is output as the tracking drive signal.

  Here, a process for performing tracking control is started in accordance with an instruction from the microcomputer 21. First, the switch 22 is set to “a” and the switch 23 is set to “e” at the same time. As a result, the outer peripheral direction applied voltage value 25 is output as the tracking drive signal. At this time, the TZC period is still “A”, which is the same as when the loop is off. In the case of FIG. 3, since the direction in which the track moves with respect to the beam spot is the outer peripheral direction, the velocity in the direction in which the track moves with respect to the beam spot is accelerated by the applied voltage value 25 in the outer peripheral direction. For this reason, the TZC cycle becomes gradually smaller than “A”.

  When the TZC cycle becomes “C” which is shorter than the “brake reversal cycle value” through the “B” by acceleration, the “HIGH” signal is output from the comparator 19. As a result, the switch 23 is changed from “e” to “d”. As a result, the applied voltage value 24 in the inner circumference direction, which is opposite to the applied voltage polarity in the outer circumference direction, is supplied to the tracking drive circuit 10, so the speed in the direction in which the track is moving with respect to the beam spot Is slowed down.

  For this reason, the TZC period gradually becomes larger than “C”. When the TZC cycle becomes “E”, which is greater than the “brake control cycle value” through the “D” due to deceleration, the “HIGH” signal is output from the comparator 18. As a result, the value of the variable multiplication coefficient 27 becomes small, and the value applied to the inner circumferential direction of the tracking drive signal becomes small. Thereafter, the value of the applied voltage in the inner circumferential direction is reduced by the variable multiplication coefficient 27 but is in the decelerating direction, so that the TZC cycle becomes increasingly larger “F”, “G”, and “H”.

  If the deceleration continues and the TZC cycle becomes “I”, the cycle value becomes larger than the “tracking pull-in possible cycle”, and therefore the “HIGH” signal is output from the comparison calculator 17. As a result, the switch 22 is set to “C”. Since the TZC period “I” is longer than the tracking pull-in period, when tracking control is turned on by setting the switch 22 to “C”, tracking can be stably pulled in by the gain and bandwidth of the feedback loop.

  Further, since the tracking drive signal immediately before the tracking control loop-on is applied has a small applied voltage due to the variable multiplication coefficient 27, the acceleration is also small. After the tracking is pulled in, the vehicle runs away from the track due to the acceleration. There is nothing.

  As described above, according to the present embodiment, even in an optical disc having a large eccentric component, the direction in which tracking control does not deviate from the bandwidth of the feedback loop is detected from the period crossing between tracks, and the speed control is performed. By reducing the acceleration when the speed at which the track pull-in operation can be performed is reduced, it is possible to realize an optical disc apparatus that can stably perform the track pull-in operation.

1 is a block configuration diagram showing an embodiment of an optical disc apparatus according to the present invention. FIG. 10 is a diagram showing a case where the direction in which a constant voltage is first applied coincides with the direction in which the moving speed between tracks is decelerated in order to perform tracking pull-in while rotating an optical disk having an eccentric component. . FIG. 10 is a diagram showing a case where the direction in which a constant voltage is first applied does not coincide with the direction in which the speed of movement between tracks is decelerated in order to perform tracking pull-in while rotating an optical disk having an eccentric component. .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2a ... Clamper, 2b ... Turntable, 3 ... Optical pick-up, 4 ... Lead screw, 5 ... Thread motor, 6 ... Spindle motor, 7 ... Objective lens, 8 ... Thread, 9 ... Signal processing circuit, 10 ... Tracking drive circuit, 11 ... Edge detection circuit, 12 ... Period measurement counter, 13 ... Period measurement value, 14 ... Tracking pull-in period value, 15 ... Brake control period value, 16 ... Brake reversal period value, 17 ... First comparison Arithmetic unit, 18 ... second comparison arithmetic unit, 19 ... third comparison arithmetic unit, 20 ... neutral potential, 21 ... microcomputer, 22 ... first changeover switch, 23 ... second changeover switch, 24 ... inside Circumferential applied voltage value, 25... Peripheral applied voltage value, 26... Multiplier, 27.

Claims (4)

An optical disc apparatus comprising an optical pickup for focusing a laser beam on a recording surface of an optical disc, and a driving means for moving the optical pickup to an arbitrary track position on the optical disc, and optically reproducing or recording / reproducing the optical disc In
Detection means for the optical pickup to detect a crossing from one track to the next track on the optical disc;
A period measuring means for measuring a period from one track to the next track on the detected optical disc;
An optical disc apparatus comprising: control means for controlling the applied voltage to the driving means in a stepwise manner in accordance with the measured period value. An optical disc apparatus comprising an optical pickup for focusing a laser beam on a recording surface of an optical disc, and a driving means for moving the optical pickup to an arbitrary track position on the optical disc, and optically reproducing or recording / reproducing the optical disc In
Detection means for the optical pickup to detect a crossing from one track to the next track on the optical disc;
A period measuring means for measuring a period from one track to the next track on the detected optical disc;
Generating means for generating a difference value between the measured period value and the target period value;
An optical disc apparatus comprising: control means for controlling the applied voltage to the driving means in a stepwise manner in accordance with the generated difference value. An optical disc apparatus comprising an optical pickup for focusing a laser beam on a recording surface of an optical disc, and a driving means for moving the optical pickup to an arbitrary track position on the optical disc, and optically reproducing or recording / reproducing the optical disc In
Detection means for the optical pickup to detect a crossing from one track to the next track on the optical disc;
A period measuring means for measuring a period from one track to the next track on the detected optical disc;
Reversing means for reversing the polarity of the voltage applied to the driving means according to the measured period value;
An optical disk apparatus comprising: control means for controlling the voltage applied to the driving means to be small in a stepwise manner. An optical disc apparatus comprising an optical pickup for focusing a laser beam on a recording surface of an optical disc, and a driving means for moving the optical pickup to an arbitrary track position on the optical disc, and optically reproducing or recording / reproducing the optical disc In
Detection means for the optical pickup to detect a crossing from one track to the next track on the optical disc;
A period measuring means for measuring a period from one track to the next track on the detected optical disc;
First comparing means for comparing the measured period value with a first target period value;
Reversing means for reversing the polarity of the voltage applied to the driving means according to the value of the first comparing means;
A second comparison means for comparing the measured period value with a second target period value;
An optical disc apparatus comprising: control means for controlling the voltage applied to the driving means to be reduced stepwise according to the value of the second comparing means.

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