JPH10320791A - Optical disk drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the runaway of a speed control system in a seek operation for the purpose of recovery of a track following operation without using a light beam moving direction detecting means. SOLUTION: A light beam spot is positioned in an objective track on an optical disk 1 by driving an optical head 4 with a positioning means 3. At this time, a track following control loop, a speed control loop and a means of impressing fixed acceleration by a kick pulse 34 are changed by a control loop changeover means 9, so as to perform each individual operation of the track following operation, the seek operation or the kick pulse impressing operation. When an off-track state is detected by an off-track detecting means 8 during the track following operation, a controller 10 is so operated that at the time of performing the seek operation for the purpose of the recovery of the track following operation by making a changeover to the speed control loop, the control loop is changed once to the kick pulse 34 immediately before performing this speed control, and the positioning means 3 is moved at prescribed acceleration in an arbitrary direction for a prescribed period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical disk for optically recording and reproducing information and an optical disk drive for driving an optical head, and more particularly to a technique for recovering a track following operation of the optical disk drive.

[0002]

2. Description of the Related Art In an optical disk apparatus for recording and reproducing information by irradiating a recording surface of an optical disk with a light beam, an optical disk drive drives an optical disk and an optical head to light a target track on the disk from the optical head. When the beam is made to follow, the track following control is usually performed based on a track error signal (TES) indicating the amount of deviation of the spot position of the light beam from the track center.

In the track following operation mode in which the spot of the light beam follows one track on the disk by drive control of the optical head, the movement of the optical head is controlled so that the value of the track error signal is kept at zero. . However, the track following operation may fail due to disturbance such as mechanical shock or vibration from the outside or disturbance of the track error signal due to scratches or defects on the optical disc.

In such a case, as shown in Japanese Patent Publication No. 7-78975, recovery of the track following operation can be performed for a short time even under conditions that are easily affected by external influences such as disturbance, vibration, and inclination. In order to perform the seek operation reliably, a control method is employed in which after a failure in the track following operation is detected, a seek operation is performed with a track position separated by a predetermined distance as a target position. By performing such a seek operation, the moving speed of the light beam is controlled according to a predetermined speed profile. As a result, at the target track position, the moving speed is zero or non-zero. Moving speed.

When the seek operation is performed, the seek direction is such that when the track following operation fails, the track position is determined when the track following operation mode is being performed. If the mode is in the mode, it is determined by the seek target track position. That is, when the current track position or the target track position is inside the disk, a seek operation for recovering the track following operation is performed to the outside when the current track position or the target track position is outside the disk. Intrusion into the peripheral and outermost mirror portions is avoided.

However, if the seek operation direction is determined in order to recover the track following operation and the seek operation is performed, the direction in which the beam actually moves when the track following operation fails and the track following operation is performed. If the seek operation direction instruction for recovery is reversed, when speed control is performed during a seek operation for the purpose of recovering the track following operation, the polarity of the speed control system becomes positive feedback and a runaway occurs. There was a problem.

In order to avoid the problem that the speed control system runs away due to positive feedback, a control method for controlling a seek operation using a moving direction detecting means of a light beam as disclosed in Japanese Patent Application Laid-Open No. 4-170723. Has been proposed. In this case, when the track following operation fails, the direction in which the beam is moving is detected by the moving direction detecting means, and the direction instruction of the seek operation for the purpose of recovering the track following operation is actually detected by the moving direction detecting means. It should be the same as the direction in which the beam is moving. This can prevent the polarity of the speed control system from becoming positive feedback.

Here, the configuration and operation of the moving direction detecting means will be described. Before that, first, referring to FIGS. 8 and 9, the total reflected light amount signal 61 and the track error signal 6 obtained from the reflected light of the light beam received by the photodetector of the optical head.
2 will be described.

FIG. 8 shows that a laser beam emitted from a semiconductor laser (not shown) of the optical head is
5 shows the distribution of the reflected light incident on the photodetector 54 of the optical head when a light spot is formed on the groove 52 on the optical disk 51 by the method shown in FIG. The circle at the center on the photodetector 54 indicates the case where the focal point is in focus, and the circles on the left and right indicate the case where the tracking is deviated left and right. The detection outputs of the reflected light A55 and the reflected light B56 incident on A and B of the photodetector 54 are input to the total reflected light amount detecting means 57 and the track error signal detecting means 58, and the total reflected light amount signal 61 and the track error signal 62 are provided. Is generated.

FIG. 9 is a view showing the state of the surface of the optical disk 51.
This shows the relationship between the total reflected light amount signal 61 and the track error signal 62, and the reflected light A55 and the reflected light B56.
The total reflected light amount signal 61 is the smallest at the groove 52 and the largest at the center between the tracks. The track error signal 62 indicates the amount of deviation between the center of the track and the center of the light spot, and becomes zero (ground (GND) level) between the track center and the groove 52.

The phase of the track error signal 62 is shifted by 180 degrees when the light spot moves from the inner circumference to the outer circumference and when the light spot moves from the outer circumference to the inner circumference. Therefore, the direction of movement of the light spot can be detected by comparing the phase of the track error signal 62 with the phase of the total reflected light amount signal 61.

FIG. 10 shows an example of a conventional moving direction detecting means 60. The total reflected light amount signal 61 is input to the comparator 63 by AC coupling through the capacitor C1 and the resistor R1,
It is binarized based on the ground level. The track error signal 62 is input to a comparator 64 and binarized based on the ground level. Total reflected light amount signal 61-2
The digitized signal 65 is input as a D input of the D-type latch 67, and the rising edge of the binarized signal 66 of the track error signal 62 is input as a clock signal of the D-type latch 67. In the D-type latch 67, by holding the D input based on the clock signal, the holding result becomes Q
It is output as a direction detection signal 68 from the output.

The direction in which the beam is currently moving is determined from the direction detection signal 68, and a seek operation for the purpose of restoring the track following operation is performed in the same direction.
It is possible to return to the track following operation in a short time while avoiding runaway of the speed control system due to positive feedback.

[0014]

The conventional control method for determining the direction of the seek operation for the purpose of recovering the track following operation using the light beam moving direction detecting means as described above has the following problems. is there.

(1) The circuit scale becomes large. As described above, the total reflected light amount detecting means 57, the comparator 63 for binarizing the detected total reflected light amount signal 61, and the total reflected light amount signal
Many means such as a D-type latch 67 for outputting a direction detection signal 68 from the binary signal 65 of 1 and the binary signal 66 of the track error signal 62 are required. In the field of optical disk devices, downsizing and cost reduction of substrates are essential issues, and it is necessary to adopt a configuration in which means requiring hardware such as analog circuits and logic circuits as described above is used as little as possible. is there.

(2) When the degree of modulation of the total reflected light amount signal is small, the binarization operation cannot be performed normally. As described above, the binarized signal 65 obtained by binarizing the total reflected light amount signal 61 is used for the moving direction detecting means 60. However, when the track pitch becomes smaller as the density of the optical disk increases, the ratio of the track pitch to the spot diameter of the light beam also becomes smaller, so that the degree of modulation of the total reflected light amount signal 61 when traversing the track becomes smaller. If the degree of modulation is small, the binarizing operation of the total reflected light amount signal 61 by the comparator 63 may not be performed normally.

In order to avoid the problem (2), it is conceivable to amplify the total reflected light amount signal 61 and then perform a binarization operation.
Additional means for amplifying 1 is required, and the same problem as (1) described above occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the speed control system can provide positive feedback in a seek operation for recovering a track following operation without using a moving direction detecting means of a light beam. It is an object of the present invention to provide an optical disk drive capable of preventing runaway from occurring and reliably recovering a track following operation.

[0019]

An optical disk drive according to the present invention comprises: an optical head for irradiating a recording / reproducing light beam onto a recording surface of an optical disk; a positioning means for moving the optical head in a radial direction of the optical disk; A track error signal detecting means for generating a track error signal indicating a deviation between the center of the track on the optical disc and the center of the light beam; and causing the optical head to follow a target track according to the track error signal. A track following control loop for controlling the positioning means, a speed control loop for controlling the positioning means so as to seek the optical head to a target track at a predetermined speed using the track error signal, and a constant acceleration for the optical head. A constant acceleration applying means for controlling the positioning means so as to move the track; Control loop switching means for switching between the control loop, the speed control loop, and the constant acceleration applying means; and drive control means for controlling the track following control loop, the speed control loop, the constant acceleration applying means, and the control loop switching means. An off-track detecting means for detecting that the track following control by the track following control loop is deviated based on the track error signal, wherein the drive controlling means comprises: When the off-track detecting means detects an off-rack state during the following operation, when performing a seek operation for the purpose of restoring the track following operation by switching to the speed control loop, once immediately before performing this speed control, Switch to the constant acceleration applying means and change to any direction , A predetermined period is configured to have a function of moving the positioning means at a constant acceleration determined in advance.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an optical disk drive according to an embodiment of the present invention.

The optical disk drive of the present embodiment is disposed to face an optical disk 1 that is driven to rotate by a spindle motor 2, and projects a light beam onto an information track provided on the optical disk 1 to form a light spot. It has an optical head 4 which receives the reflected light and converts it into an electric signal. The optical head 4 is mounted on the positioning means 3,
The optical disk 1 is movable in the radial direction.

The track error signal detecting means 5 is connected to the optical head 4.
Then, a track error signal (TES) 30 indicating the amount of positional deviation of the light spot on the optical disk 1 is generated. The track error signal 30 is input to the track following control means 6, the track counting means 7, and the off-track detecting means 8. The track following control means 6 is connected to the positioning means 3 via the control loop switching means 9, and outputs its output as a drive control signal 36 so that the optical head 4 follows a desired track according to the track error signal 30. It returns to the positioning means 3. A control system including the track following control means 6 constitutes a track following control loop.

As shown in FIG. 2, the off-track detecting means 8 comprises two comparators 21 and 22 to which a track error signal 30 is inputted, and a NAND gate 23. The off-track detecting means 8 deviates from the target track (off-track state) when the positive and negative signal levels of the track error signal 30 exceed the reference value ± E during the track following operation. As NAND gate 2
3 to output a high-level off-track detection signal 31 to the controller 10.

The controller 10 has a control loop switching signal generating means 11 and a direction instruction signal generating means 12. When an off-track is detected during the track following operation by the track following control loop, the controller 10
The control loop switching signal generating means 11 outputs a control loop switching signal 32 to the control loop switching means 9 to switch the control loop, and performs a seek operation for recovering the track following operation (hereinafter referred to as a "recover seek operation"). Start).

The track counting means 7 is internally provided with a track counter, and when the optical head 4 accesses a desired track, the target number 33 of tracks to be traversed is inputted from the controller 10. ing. The track counting means 7 detects the crossing of the track based on the track error signal 30 output from the track error signal detecting means 5, and every time the optical head 4 crosses the track, the track counter counts one by one from the target track number 33. By subtraction, the number of remaining tracks is calculated. The output of the track counting means 7 is input to a period measuring type speed detecting means 13 and a speed commanding means 14.

The period measuring type speed detecting means 13 detects the current moving speed of the positioning means 3 by calculating the period in which the optical head 4 traverses the track. The speed instructing means 14 determines the moving speed of the positioning means 3 for giving a speed instruction based on the number of tracks remaining up to the target at that time according to the contents of the track counter of the track counting means 7. The speed detection value 37 of the output of the period measurement type speed detection means 13 and the speed instruction value 38 of the output of the speed command means 14
Is input to the speed error amplifying means 15, where the error between the two speed values is calculated and amplified.

The speed error amplifying means 15 is connected to the positioning means 3 via the control loop switching means 9 and outputs its output as a drive control signal 36 to the positioning means 3 so as to move the optical head 4 at a predetermined speed. Will return. The track counting means 7, the period measuring type speed detecting means 13,
A control system including the speed command means 14 and the speed error amplifying means 15 forms a speed control loop.

At the end of the seek operation by the speed control loop, the controller 10 switches the control loop switching signal 32 by the control loop switching signal generating means 11 at the timing when the content of the track counter of the track counting means 7 becomes zero. The control loop switching means 9 switches from the speed control loop to the track following control loop to start the track following operation.

In order to move the optical head 4 at a constant acceleration, there is provided acceleration indicating means 16 for generating an instruction signal (hereinafter, referred to as a kick pulse) 34 of a predetermined constant acceleration. Is given to the positioning means 3 through the control loop switching means 9.

The kick pulse 34 is used to start a seek operation (hereinafter, referred to as a normal seek operation) for the purpose of accessing a target track or a recover seek operation immediately before performing the speed control by the speed control loop. To give the positioning means 3 an initial moving speed. After the start of the application of the kick pulse 34, the controller 10 switches the control loop switching signal 32 by the control loop switching signal generating means 11 at a point in time when a predetermined time has elapsed, so that the control loop switching means 9 applies the kick pulse. The operation is switched to the speed control loop, and the operation is shifted to the speed control.

A direction instruction signal 35 is output from the direction instruction signal generation means 12 in the controller 10, and the direction instruction signal 35 is given to the speed error amplification means 15 and the acceleration instruction means 16. The speed error amplifying means 15 switches the polarity of the speed control loop by multiplying the calculation result of the speed error by +1 or -1 according to the direction instruction signal 35.
Similarly, the acceleration instruction means 16 switches the polarity of the kick pulse 34 according to the direction instruction signal 35.

In the case of a normal seek operation, the direction indicating signal 35 moves the positioning means 3 inward if the seek target track position is inside the track position following the current track, and outward if it is outside. The direction of the seek direction is performed. In the case of a recover seek operation, a seek direction is instructed so that the positioning means 3 moves in an arbitrary direction.

FIG. 3 shows a timing chart at the start of the recover seek operation. The above-described recover seek operation is performed by switching the control loop switching signal 32 and the direction instruction signal 35 at the timing shown in FIG. 3 after off-track detection. The direction instruction signal 35 shown in FIG. 3 is an example in the case where the seek operation is instructed to be performed in the outer circumferential direction. Is the same as

Here, in the drive control system of the optical head 4 of the optical disk drive configured as described above, when the recovery control operation is performed, the speed control loop becomes positive feedback and the positioning means 3 runs away. Consider the condition

FIGS. 4 to 7 show a track error signal (TES) 30 during a recovery seek operation, an acceleration instruction signal (A) 36a as a drive control signal 36 fed back to the positioning means 3, and a positioning means moving speed (V). 37 is shown. A0, T, and V0 shown in the figure represent the acceleration command value of the kick pulse 34, the application period, and the moving speed of the positioning means 3 at the time of off-track detection. Here, the moving speed of the positioning means 3 at the start of the speed control is Vc
Then, the relationship of Vc = V0 + A0T holds. | Vr | represents the speed instruction value 38 at the start of the speed control.

4 to 7 show the following states, respectively.

(A) When the moving direction of the positioning means 3 at the time of off-track detection and the recovery seek direction instruction of the acceleration instruction signal 36a based on the direction instruction signal 35 are the same direction (when the signs of V0 and A0 are equal) (FIG. 4) In this case, since the moving direction of the positioning means 3 always coincides with the speed control direction at the time of starting the speed control, the speed control loop becomes a negative feedback and the positioning means 3 does not run away.

(B) When the moving direction of the positioning means 3 at the time of off-track detection is opposite to the direction of the recovery seek direction of the acceleration instruction signal 36a, and the moving speed of the positioning means 3 at the time of off-track detection is low (V0 <0, A0>
When 0, 0 <V0 + A0T, or V0> 0, A0
(0> V0 + A0T when <0) (FIG. 5) In this case, the moving direction of the positioning means 3 is reversed during the application period of the kick pulse 34.
The moving direction of the positioning means 3 matches the speed control direction.
Therefore, the speed control loop becomes a negative feedback, and the positioning means 3 does not run away.

(C) When the moving direction of the positioning means 3 at the time of off-track detection and the recovery seek direction instruction of the acceleration instruction signal 36a are in opposite directions, and the moving speed of the positioning means 3 at the time of off-track detection is high (V0 <0, A0>
0, -│Vr│ <V0 + A0 T <0, or
When V0> 0 and A0 <0, | Vr |> V0 + A0 T>
0) (FIG. 6) In this case, the moving direction of the positioning means 3 does not reverse during the application period of the kick pulse 34.
The moving direction of the positioning means 3 does not coincide with the speed control direction. Therefore, the speed control loop becomes a positive feedback. But,
Since the moving direction of the positioning means 3 is reversed during the speed control period, the speed control loop becomes a negative feedback on the way, and the positioning means 3 does not run away.

(D) When the moving direction of the positioning means 3 at the time of off-track detection is opposite to the direction of the recovery seek direction of the acceleration instruction signal 36a, and the moving speed of the positioning means 3 at the time of off-track detection is even higher ( V0 <0,
V0 + A0T <-| Vr | when A0> 0, or V0 + A0T> | Vr when V0> 0 and A0 <0
(FIG. 7) In this case, the moving direction of the positioning means 3 does not reverse during the application period of the kick pulse 34.
The moving direction of the positioning means 3 does not coincide with the speed control direction. Therefore, the speed control loop becomes a positive feedback. Also, since the moving direction of the positioning means 3 does not reverse during the speed control period, the speed control loop remains positive feedback,
The positioning means 3 runs away.

As described above, only in the case of (d), the speed control loop remains positive feedback during the speed control period, and the positioning means 3 runs away.

The condition for preventing the state (d) from occurring is a case where one of the following relationships (I) and (II) is satisfied.

(I) The signs of V0 and A0 are equal. (II) When V0 <0, A0> 0, V0 + A0T>-| V
r | or V0 + A0 T when V0> 0 and A0 <0
<│Vr│. That is, the signs of V0 and A0 are different,
| V0 |-| A0T | <| Vr | (1) Therefore, | A0 | and T always satisfy the above expression (1).
Is determined in advance, even if the recover seek operation is instructed in an arbitrary direction, either of the above-mentioned relations (I) and (II) is satisfied, so that runaway of the positioning means 3 can be avoided.

By the way, | A0 |, which satisfies the expression (1),
To determine T, | V0 | and | Vr | must each be a known value. | Vr | is known because it is a value arbitrarily determined by the target speed profile during the speed control period. | V0 | can be known by replacing it with the maximum moving speed | Vmax | of the positioning means 3 that can actually occur at the time of off-track detection.

The movement speed of the positioning means 3 becomes the highest when the off-track is detected in the actual operation, when the target track fails to enter at the end of the seek operation and the track goes off-track, or a strong impact is applied during the track following operation. For example, it is a case where the player goes off track. The maximum moving speed can be obtained by measuring the speed indicating value 38 immediately before the end of the seek operation, or measuring the moving speed of the positioning means 3 when off-tracking is performed in an impact experiment or the like. In practice, | A0 |, T satisfying the expression (1) is obtained as follows.

First, the value of | A0 |, T must be as small as possible within the range that satisfies the relationship (I). This is because, in the case of (a) described above, when the off-track occurs, the moving direction of the positioning means 3 and the direction instruction of the recovery seek operation are the same, so that during the application period of the kick pulse 34, the positioning means 3 is more speedy. It is accelerated in the direction to increase. Therefore, if the value of | A0 |, T is larger than necessary, the speed control loop does not become a positive feedback by satisfying the relationship (I), but the operation at the start of the speed control may become unstable. .

Therefore, the estimated value of | V0 |
In this case, it suffices to find | A0 |, T satisfying the following equation (2).

| Ve | − | A0T | = | Vr | → | Ve | − | Vr | = | A0T | (2) In the equation (2), if | Ve | is large, | A0 |, T Is large, and | A0 | and T are small if | Ve | is small. By the way, from the relationship of equation (2),
When calculating A0 |, T, when the estimated value | Ve | of | V0 | is smaller than the maximum moving speed | Vmax | that can actually occur, | A0 |
Because of the relationship of the expression, the relationship of the expression (1) cannot be satisfied.

| V0 |-| A0T | = | Vmax |-| Ve | + | Vr |> | Vr | (3) That is, the positioning means 3 goes into the state (d) and runs away. Therefore, by setting the value of | Ve | to the estimated value of the maximum moving speed | Vmax | that can occur at the time of off-track detection, the condition of expression (1) is always satisfied, and | A0 of the necessary minimum size is always satisfied. |, T can be obtained.

As described above, by setting the acceleration instruction value | A0 | of the kick pulse 34 and the application period T in advance so as to satisfy the condition that the positioning means 3 does not run away, the moving direction detecting means of the light beam can be used. Without using the components, it is possible to prevent runaway of the positioning means 3 in the seek operation while minimizing the number of components.

According to the first embodiment, when performing the recovery seek operation, the control system is configured to move the positioning means at a predetermined constant acceleration for a predetermined period immediately before shifting to the speed control. As a result, even if the moving direction detecting means of the light beam is not used, the speed control loop becomes positive feedback and the positioning means can be prevented from going out of control, and the track following operation can be surely recovered.

Next, a modified example in which the control method shown in the first embodiment is changed as a second embodiment will be described.

In the second embodiment, the direction instruction of the recover seek operation is set in the same direction as the direction instruction of the seek operation (normal seek operation or recover seek operation) performed immediately before.

When the entry of the target track fails in the seek operation and an off-track occurs, there is a high possibility that the positioning means 3 moves in the same direction as the seek operation direction due to inertial force. Therefore, when performing the recover seek operation in response to the occurrence of off-track, the direction instruction of the recover seek operation is set to the same direction as the direction instruction of the seek operation performed immediately before, so that the positioning means 3 at the time of off-track detection is performed. Is more likely to be in the same direction as the moving direction of the target and the direction instruction of the recover seek operation. Therefore, the possibility of occurrence of the state (a) shown in the first embodiment increases.

That is, if the direction of movement of the positioning means 3 at the time of off-track detection is the same as the direction instruction of the recover seek operation, the speed control loop always becomes negative feedback.
It is possible to avoid the possibility that the positioning means 3 goes into the state of (d) shown in the first embodiment and runs away.

Further, according to the control method of the second embodiment, as shown in the first embodiment, when estimating the value of | Vmax | to determine the values of | A0 | It is not necessary to consider the moving speed of the positioning means 3 in the case of failing to enter the track and going off-track. That is, as the maximum moving speed | Vmax |, it is sufficient to consider only the moving speed of the positioning means 3 in the case of off-tracking due to an impact or the like during the track following operation.

In general, the moving speed of the positioning means 3 at the time of off-track detection is better when off-tracking during track following operation than when the target track fails to enter the target track due to seek operation. It is thought to be slower. Therefore, the maximum moving speed | Vmax | is smaller than that of the first embodiment. That is, since the value of | A0 |, T can be set smaller than that of the first embodiment, the movement of the positioning means 3 when switching to the speed control loop immediately after the kick pulse is applied in the recover seek operation. The velocity distribution becomes smaller. Therefore, the operation at the start of the speed control is more stable than in the case of the first embodiment.

According to the second embodiment, by configuring the control system so that the direction of the recovery seek operation is set in the same direction as the seek operation performed immediately before, the speed control loop becomes positive feedback and the positioning means runs away. Can be more reliably avoided, and the operation at the start of speed control can be made more stable.

Next, another modified example of the third embodiment in which the control method shown in the first embodiment is changed will be described.

In the third embodiment, when the seek operation performed immediately before is a recover seek operation, a direction operation for performing the recover seek operation again is performed immediately before (recover seek operation). So that the direction is the opposite of the direction indication.

As shown in the first embodiment, the recover seek operation is different from the normal seek operation.
When the movement direction of the positioning means 3 and the movement direction instruction during the speed control period are reversed, and the speed control loop becomes a positive feedback, the positioning means 3 may run away and the track pull-in operation may fail. In the control methods of the first and second embodiments described above, since the direction of the recover seek operation is specified in an arbitrary direction or in the same direction as the immediately preceding seek operation, the recover seek operation is performed by the positive feedback of the speed control loop. Therefore, when the recovery seek operation is performed again, there is a high possibility that the moving direction of the positioning means 3 and the speed control direction instruction are reversed. That is, the recover seek operation is likely to fail again due to runaway.

In order to avoid this problem, if the seek operation performed immediately before is the recover seek operation, a direction instruction for performing the recover seek operation again is given in the direction of the seek operation performed immediately before. Reverse the direction. As a result, when the recover seek operation is performed again, there is a high possibility that the moving direction of the positioning means 3 and the speed control direction instruction are in the same direction, so that there is no possibility that the recover seek operation fails again due to runaway as described above. be able to.

According to the third embodiment, when the seek operation performed immediately before is the recover seek operation, a direction instruction for performing the recover seek operation again in the opposite direction to the seek operation performed immediately before. By configuring the control system so as to perform the above operation, it is possible to prevent the positioning means from running out of control and the recovery seek operation from continuously failing.

[0064]

As described above, according to the present invention, the speed control system becomes positive feedback in the seek operation for recovering the track following operation without using the moving direction detecting means of the light beam. Runaway can be prevented, and the track following operation can be surely recovered.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an optical disk drive according to an embodiment of the present invention.

FIG. 2 is a circuit block diagram illustrating a configuration of an off-track detection unit.

FIG. 3 is a timing chart showing an off-track detection signal, a control loop switching signal, and a direction instruction signal at the start of a recovery seek operation.

FIG. 4 is a timing chart showing a track error signal, an acceleration instruction signal, and a moving speed of a positioning unit during a recover seek operation;

FIG. 5 is a timing chart showing a track error signal, an acceleration instruction signal, and a positioning unit moving speed during a recover seek operation;

FIG. 6 is a timing chart showing a track error signal, an acceleration instruction signal, and a moving speed of a positioning unit during a recover seek operation;

FIG. 7 is a timing chart showing a track error signal, an acceleration instruction signal, and a moving speed of a positioning unit during a recover seek operation;

FIG. 8 is an explanatory diagram showing a configuration of a photodetector, a total reflected light amount detection unit, and a track error signal detection unit in the optical head.

9 is an operation waveform diagram showing a total reflected light amount signal and a track error signal in the configuration of FIG. 8;

FIG. 10 is a circuit block diagram showing a configuration of a light beam moving direction detecting unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical disk 3 ... Positioning means 4 ... Optical head 5 ... Track error signal detecting means 6 ... Track following control means 8 ... Off-track detecting means 9 ... Control loop switching means 10 ... Controller 11 ... Control loop switching signal generating means 12 ... Direction Instruction signal generating means 14 Speed command means 15 Speed error amplifying means 16 Acceleration instruction means

Claims (3)

[Claims] An optical head for irradiating a recording / reproducing light beam on a recording surface of the optical disk; positioning means for moving the optical head in a radial direction of the optical disk; a center of a track on the optical disk and the light beam; A track error signal detecting means for generating a track error signal indicating a deviation from the center of the track, a track following control loop for controlling the positioning means to cause the optical head to follow a target track according to the track error signal, A speed control loop for controlling the positioning means so as to seek the optical head to a target track at a predetermined speed using the track error signal; and a constant control loop for controlling the positioning means so as to move the optical head at a constant acceleration. Acceleration applying means, the track following control loop, the speed control loop, and the constant acceleration mark. Control loop switching means for switching the addition means, drive control means for controlling the track following control loop, the speed control loop, the constant acceleration applying means and the control loop switching means, and the track following based on the track error signal. An off-track detecting means for detecting that the track following control by the control loop has deviated, wherein the drive controlling means turns off the off-track detecting means during the track following operation by the track following control loop. When the track state is detected, when performing the seek operation for the purpose of restoring the track following operation by switching to the speed control loop, temporarily switch to the constant acceleration applying means immediately before performing the speed control, and , A predetermined period of time, a predetermined constant acceleration An optical disk drive having a function of moving the positioning means. 2. The method according to claim 1, wherein when the off-track detecting unit detects an off-track state during the track following operation by the track following control loop, the drive control unit switches to the speed control loop to recover the track following operation. When the target seek operation is performed, a function to perform the direction instruction of the seek operation for the purpose of recovering the track following operation so as to be in the same direction as the direction instruction of the immediately preceding seek operation is provided. The optical disk drive according to claim 1, wherein: 3. When the off-track detecting means detects an off-track state during a track following operation by the track following control loop, the drive control means switches to the speed control loop to recover the track following operation. When performing a desired seek operation, if the seek operation performed immediately before is a seek operation for the purpose of recovering the track following operation, a direction instruction of the seek operation for the purpose of recovering the track following operation again. 2. The optical disk drive according to claim 1, further comprising a function of performing a direction opposite to a direction instruction of a seek operation performed immediately before.