JPH11161968A - Optical head movement controller for optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an optical head carriage using a stepping motor follow the track eccentricity of an optical disk in order to reduce the lens shifting amount of an optical head in an optical disk device. SOLUTION: The rotational cycle of the optical disk is detected in an index signal generator 4 and also the lens position error of the optical head carriage with respect to the optical disk is detected in a lens position detector 1 and an eccentricity maximum position is detected in an eccentricity position specifier 2 from these signals of an index signal 5 and a lens position error signal 3 and also a peak level is detected in a peak level detector 7. A motor controller 8 makes the optical head carriage follow the track eccentricity by starting the revolving of a stepping motor 10 so as to move the carriage toward the eccentricity maximum position and by reversing the motor 10 at the eccentricity maximum point to prevent the lowering of a signal quality due to the eccentricity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk drive for moving an optical head by a stepping motor, and more particularly to an optical head movement control device for controlling the movement of an optical head following the eccentricity of an optical disk.

[0002]

2. Description of the Related Art In an optical disk apparatus, tracking servo is performed to control the position of an optical head with respect to circumferential tracks arranged in a radial direction of an optical disk. A DC motor or a stepping motor is used as a driving source for moving the head carriage. Further, in a general optical disk device, when performing tracking servo of an optical head, in addition to controlling movement of the optical head carriage, tracking control of an optical axis of an objective lens mounted on the optical head carriage is also performed. Normally, the optical axis of the objective lens is finely moved for fine tracking adjustment, and the optical head carriage is roughly moved for large tracking adjustment. In particular, when a large movement such as a seek operation is performed, the optical head carriage moves only greatly, and the actuator of the objective lens is operated near the target track to finely move to follow the target track.

When the optical disc is rotated, there is an eccentricity existing in the optical disc itself and an eccentricity caused by disc chucking which occurs when the optical disc is loaded in the optical disc apparatus. For this reason, in the above-mentioned tracking control, it is necessary to correct the above-mentioned eccentricity. In such tracking control for eccentricity, since the amount of eccentricity is relatively small, it is possible to correct by the tracking control of fine movement in the objective lens described above. However, when the tracking control of the objective lens is approached, the attitude of the actuator for tracking control of the objective lens changes when approaching the operation limit, the lens is tilted, and the optical axis of the objective lens is moved in a direction perpendicular to the optical disk surface. And tilt.
For this reason, when the recording capacity of the optical disc is small and the track density of the optical disc is low, even when the optical axis of the objective lens is inclined, the read / write characteristics when recording / reproducing information on the optical disc are large. Although there is no effect, when the recording capacity is increased and the track density is reduced as in recent optical discs, the beam diameter of the laser beam of the objective lens is also reduced. -The write characteristics are remarkably deteriorated.

For this reason, it is conceivable to perform tracking control of the optical head carriage with respect to the eccentricity of the optical disk. However, in an optical disk device using the above-described DC motor or stepping motor as a driving source for tracking control, Due to the low bandwidth of these motors, it is difficult to finely control the motor at high speed,
It has been difficult to make the carriage of the optical head follow the eccentricity of the optical disk at high speed and with high accuracy.

[0005]

To solve such a problem, if a voice coil motor capable of high-speed and fine operation is used as a driving source for tracking control, this kind of motor is generally expensive. Therefore, it can be applied to a high-priced optical disk device, but it is an obstacle to reducing the price of the optical disk device. In addition, D
When a closed-loop circuit such as feedback control is configured using a C motor or a stepping motor, fine control is theoretically possible, but in reality, control is performed by nonlinear elements such as friction and backlash generated in the optical head cage. Oscillates, and it is difficult to control the eccentricity of the optical disk with high accuracy and stability.

SUMMARY OF THE INVENTION An object of the present invention is to move an optical head of an optical disk apparatus in which an inexpensive stepping motor or DC motor can be used and the optical head carriage can follow the eccentricity of the optical disk with high accuracy and stability. It is to provide a control device.

[0007]

An optical head movement control device for an optical disk apparatus according to the present invention comprises: an optical disk that is driven at a high speed; and an optical disk that is moved in a tracking direction that intersects tracks provided on the optical disk. An optical head for recording / reproducing information through the optical disk, and a thread servo system for causing the optical head to follow a track of the optical disk, wherein the thread servo system is used to move the optical head in the tracking direction. A motor, an index signal generator that detects a rotation period of the optical disc and outputs an index signal, and a lens position detection that detects a displacement between the lens of the optical head and the track and outputs a lens position error signal Based on the index signal and the lens position error signal. And a motor drive signal generating means for generating a motor drive signal for driving the serial motor.
Here, the motor drive signal generating means includes means for specifying the maximum eccentric position of the lens position error signal, means for detecting the maximum eccentric level, and setting a rising time for driving the motor as an advance compensation time. Means for generating a rotation start signal, a reverse rotation start signal, and a reverse rotation end signal of the motor drive signal based on the time of the maximum eccentric position, the maximum eccentric level, and the advance compensation time.

According to the present invention, in an optical disc apparatus provided with a lens position detector for detecting a position error of a lens actuator with respect to an optical head carriage, eccentricity is detected from a position error signal of the lens position detector, and the signal is detected. The stepping motor is moved by one step based on. Since one step of the stepping motor is equal to or more than the amount of eccentricity, eccentricity can be canceled within one step of operation. The drive of the stepping motor is started when the amount of eccentricity increases and is reversed when the amount of eccentricity becomes maximum, so that the amount of eccentricity can be approximately followed. The track can be tracked by the lens actuator without accurately following the eccentricity, but the eccentricity is canceled out to some extent, so that the attitude of the lens actuator is not largely changed. Therefore, it is possible to prevent the signal quality from being deteriorated due to the eccentricity.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 3 is a diagram showing a schematic configuration of an optical disk to which the optical head movement control device of the present invention is applied.
The rotation output shaft of the stepping motor 10 is configured as a lead screw 31 having a spiral formed on a peripheral surface thereof, and an optical head carriage 32 is screwed into a screw portion 33 at this screw. Therefore, the stepping motor 1
When the rotation output shaft 0 is driven to rotate, the optical head carriage 32 is screwed along the lead screw 31, and the optical head carriage 32 has a guide shaft extending in parallel to the opposite side of the lead screw 31. The guide shaft 34 is linearly moved in the extension direction of the guide shaft 34 while being guided and supported by the guide shaft 34. The guide shaft 34
Is extended in the radial direction of the optical disk 36 rotated and driven by the spindle motor 35, that is, in the cross-track direction, so that the optical head carriage 32 is moved in the cross-track direction of the optical disk 36, that is, in the tracking direction. become.

The optical head carriage 32 has an objective lens 37 for focusing a laser beam on the recording surface of the optical disk 36. The objective lens 37 includes an actuator that moves the optical axis of the objective lens 37 in the tracking direction and moves the focus position of the laser beam by the objective lens 37 in a direction perpendicular to the recording surface of the optical disc 36, that is, in a focus direction. It is installed. The actuator includes a track actuator having a track coil 38 which cooperates with a magnet 39 provided on the optical head carriage 32 in order to move a lens structure 40 supported by a track leaf spring 37 in the tracking direction. In order to move the objective lens 37 supported by the focus leaf spring 41 in the lens structure 40 in the focus direction, the magnet 3
9 and a track actuator having a focus coil 42 cooperating therewith. Although not shown in FIG. 1, the optical axis of the objective lens 37 is
A lens position detector is provided which outputs a signal corresponding to the amount of positional deviation as a lens position error signal when a positional deviation occurs with respect to track 6. As the lens position detector, for example, a light detection device that receives a laser beam reflected by an optical disk with a divided optical sensor and performs an operation based on each detection value of each divided optical sensor to output a lens position error signal It is possible to use a vessel.

FIG. 2 is a block diagram showing a circuit configuration of an optical head movement control device for performing the tracking control by driving the stepping motor 10 for moving the optical head carriage 32. In this optical head movement control device, as described above, the lens position detector 1 that outputs the lens position error signal 3 indicating the optical axis position of the objective lens with respect to the track of the optical disk 36, and one for each rotation of the optical disk An index signal generator 4 for outputting a pulse index signal 5. The eccentric position specifying device 2 to which the lens position error signal 3 and the index signal 5 are input is used to determine whether the maximum peak of the lens position error signal 3 is positive or negative, that is, the optical disk 36.
When the optical axis of the objective lens 37 is displaced toward the outer circumference of the optical disc with respect to the track No. 3, it is determined as positive. Further, the eccentric position specifying device 2 detects a position on the time axis of the maximum peak, measures a time until the maximum peak time when the index signal 5 is set as a reference time, and holds the time. . Further, the time is measured from the next index signal, and when the time reaches the previously measured time, the eccentric maximum point pulse signal 6 is output. Also,
The peak level detector 7 to which the lens position error signal 3 is input detects the peak level of the lens position error signal 3, holds the detected peak level, and outputs the peak level signal 19 to the eccentric position specifying device. 2 and is output in synchronization with the eccentricity maximum time point pulse signal 6 output. In this case, the peak level detector 7 holds and outputs the positive and negative maximum peak levels, similarly to the eccentric position specifying device 2. Further, the motor controller 8 to which the eccentric maximum time point pulse signal 6 and the peak level signal 19 are inputted, uses the eccentric maximum time pulse signal 6 and the peak level signal 19, and starts the rotation of the motor 10 and the reverse rotation time. Then, the end point of the reverse rotation is specified, and the motor control signal 17 is output. According to the motor control signal 17, the motor driving device 9 causes the stepping motor 1
A motor drive signal 18 for rotating 0 is output.

FIG. 3 is a block diagram showing details of the motor controller 8. As shown in FIG. Generally, in a stepping motor, the follow-up characteristic of the rotation operation of the motor with respect to the rated current of the motor is as follows.
It is determined by the product specifications of the motor. Therefore,
Based on the specifications, it is possible to know the time from the start of applying the rated drive current to the motor until the motor enters a predetermined rotation state. The lead compensator 11 supplies a rated drive current to the stepping motor 10 based on this,
A follow-up time until the motor enters a predetermined rotation state is set as an advance compensation time, and an advance compensation time signal 20 is output.

The motor rotation start signal generator 12, the motor reverse rotation start signal generator 13, and the motor reverse rotation end signal generator 14 are respectively provided with the eccentric maximum point pulse signal 6 from the eccentric position specifying device 2, and the peak level. The peak level signal 19 from the detector 7 and the advance compensation time signal 20 of the advance compensator 11 are input to the motor control signal generator 16.
To output a time signal. The motor rotation start signal generator 12 is provided with a required driving time corresponding to a required driving amount obtained according to the maximum eccentricity pulse signal 6 and the peak level signal 19 and the advance compensator 1.
The motor rotation start signal 21 is output when the time obtained by adding the advance time of the advance compensation time signal 20 output from 1 is shifted from the maximum eccentricity time. The motor reversal start signal generator 13 outputs a motor reversal start signal 22 at a point in time when the advance compensation time 20 is shifted from the eccentric maximum point indicated by the eccentric maximum point pulse signal 6. The motor reverse rotation end signal generator 14 adds the required drive time according to the required drive amount and the advance compensation time 20 to the motor reverse rotation start signal 22 output from the motor reverse rotation start signal generator 13. The motor reverse rotation end signal 23 is output at the time when it is shifted by the predetermined time.

Further, the polarity determiner 15 determines whether the eccentricity is positive or negative at the time when the eccentricity indicated by the eccentricity maximum time point pulse signal 6 is maximized, and outputs a polarity signal 24 thereof. Further, the motor control signal generator 16 is a motor control signal which starts the rotation of the stepping motor 10 according to the rotation start signal from the motor rotation start signal generator 12 and the polarity signal 24 from the polarity determination unit 15. Signal 1
7 is output. Further, the motor reverse rotation start signal generator 1
The motor control signal 17 is output as a signal for starting the reverse rotation of the motor 10 in response to the reverse rotation start signal 22 from the control signal 3 and the polarity signal 24 from the polarity determination unit 15. Further, a reverse rotation termination signal 23 from the motor reverse rotation termination signal generator 14 and a polarity signal 24 from the polarity determination unit 15
The motor control signal 17 is output as a signal for terminating the reverse rotation of the motor 10 in response to the above. This motor control signal 17
Controls the stepping motor 10 to reduce the relative error between the optical head carriage 32 and the lens 37,
The lens position error signal 3 is compressed.

Next, the operation of the optical head movement control device having the above configuration will be described with reference to FIG. As shown in FIG. 4A, the index signal 5 of one pulse is output from the index signal generator 4 in the circuit of the spindle motor 35 every rotation of the optical disk in synchronization with the rotation of the optical disk. Here, the rising edge of the index signal 2 is defined as an index of one round. Then, while the focus servo and the tracking servo using the focus actuator and the track actuator of the objective lens 37 of the optical head carriage 32 are turned on, the thread servo that controls the optical head carriage 32 in the tracking direction using the stepping motor 10 is used. Is set to OFF, the object lens 37 cannot follow the tracking servo due to the eccentricity of the optical disk 36 with the rotation of the optical disk 36, so that the tracking of the objective lens 37 is periodically shifted with respect to the track. The lens position detector 1 outputs a lens position error signal 3 having a Sin curve as shown in FIG.

Based on the lens position error signal 3, as shown in FIG. 4 (c), the eccentric position specifier 2 is at the peak level of the lens position error signal, that is, at the maximum eccentric time t.
p is determined, the time from the index signal 5 is specified, and the maximum eccentric time pulse signal 6 is output. The peak level detector 7 detects the polarity and value of the peak level. The peak position can be detected, for example, by dividing the analog input for taking in the lens position error signal 3 into several parts between 0 and the peak, measuring the lens position error signal at each set sampling time, and entering the divided range. Or identify.
Then, the identification result is compared with the sampling at the previous time and the data, and the maximum value is detected. It should be noted that the division is made coarse enough not to be affected by noise or the like. The peak level holds the signal level at the peak position of the lens position error signal 3 specified by the eccentric position specifying device 2.

The motor controller 8 includes the eccentric position specifying device 2
The motor control signal 17 is output on the basis of the eccentric maximum time point pulse signal 6 obtained in step (1) and the peak level 19 detected by the peak level detector 7. Further, as described in the configuration of the present invention, in consideration of driving the small stepping motor used in the optical disc device by the control signal of the present application, the stepping motor performs an operation finer than one step of the normal driving method. , Motor control signal generator 1
It is conceivable that the motor control signal 17 output in step 6 generates a reverse rotation signal before the one-step operation. In other words, the motor needs to move in a minute range, unlike normal step drive that moves to reduce the lens position error signal. Therefore, the rotation start time, the reverse rotation start time, and the reverse rotation end time of the motor are realized in a minute range of operation by adjusting the time for supplying the drive current to the stepping motor in consideration of the characteristics of the motor.

The motor rotation start signal generator 12 uses the index signal 5 and the eccentric maximum time pulse signal 6 to move the optical head carriage 32 to follow the eccentric amount of the track, ie, the stepping motor. 10 to calculate the required driving time t1 required to perform the movement. Further, the advance compensation time t2 of the advance compensation time signal 20 corresponding to the delay time with respect to the rated current of the stepping motor 10 is added to the rotation driving time. Then, as shown in FIG.
The time ts, which is obtained by adding the added time from the maximum eccentric time tp, is set as the motor rotation start time ts, and is output. The motor control signal generator 16 outputs a motor control signal 17 to the motor driving device 9 based on the motor rotation start time ts and the polarity of the polarity judgment unit 15. Therefore, at this point, the motor drive 9
Even if the rated current is applied to the stepping motor 10 from
The stepping motor 10 is actually started when the advance compensation time t2 has elapsed. Then, after the stepping motor 10 is started, the maximum eccentric point tp
Thus, the lens reaches the position where the maximum peak of the lens position error signal 3 is canceled. This causes the optical head carriage 32 to follow the eccentric track.

On the other hand, as shown in FIG. 4E, the motor reverse rotation start signal generator 13 generates the motor reverse rotation start signal 22 at a time tr earlier by the time obtained by subtracting the advance compensation time t1 from the maximum eccentricity time tp. The motor control signal generator 16 outputs a motor control signal 17 to the motor drive device 9 in response to the output signal, and the motor drive device 9 has a reverse polarity rating for reverse rotation of the stepping motor 10. Apply current. As a result, the stepping motor 10 is rotated in reverse at the time when the advance compensation time t2 has elapsed from this time tr, that is, at the maximum eccentric time tp, and causes the optical head carriage 32 to follow the eccentric track.

Further, as shown in FIG. 4F, the motor reverse rotation end signal generator 14 moves the stepping motor 10 calculated by the motor rotation start signal generator 12 from the maximum eccentric time point tp. From the time obtained by adding the required driving time t1, the advance compensation time t is calculated.
The time at which 2 is subtracted is obtained, and at this time, a motor reverse rotation end signal is output. In response to this, the motor control signal generator 1
6 outputs a motor control signal 17 to the motor driving device 9,
The motor driving device 9 outputs a signal for stopping the reverse rotation of the stepping motor 10. As a result, the reverse rotation of the stepping motor 10 is stopped at the time when the advance compensation time t2 has elapsed from this time th, that is, at the minimum eccentric time, and the optical head carriage 32 follows the eccentric track. Actually, the optical disk 3
Because the above-mentioned operation is performed periodically by the eccentricity of 6,
The motor reverse rotation end signal is often a motor rotation start signal in the next cycle.

As a result, the optical head carriage 32 executes the thread servo following the eccentric track by the stepping motor 10 as shown in FIG. Therefore, even in an optical disk device using a low-cost stepping motor, high-speed and high-accuracy tracking control for the eccentricity of the optical disk can be performed. Therefore, it is possible to prevent the track actuator of the objective lens from reaching the operation limit and tilting the optical axis,
The read / write characteristics for a high-density optical disk are not degraded.

In the above control operation of the present invention, considering that the stepping motor used in the optical disk drive is driven, the stepping motor performs a finer operation than one step of the normal driving method. It is considered that most of the motor control signals output from the signal generator generate a reverse rotation signal before the one-step operation. In addition, the peak level detector is configured to output a signal only when the eccentricity is larger than the set value, so that the above-described control is not performed unless the eccentricity is large to some extent, thereby preventing unnecessary operation. I do. Further, the present invention can be similarly applied to an optical disk device using a DC motor, in which case the start signal, the reverse rotation signal, and the end signal
What is necessary is just to apply as a signal which has a continuous time width.

[0023]

As described above, according to the present invention, the maximum eccentric position is specified from the lens position error signal, the maximum eccentric level is detected, and the rise time in driving the motor for controlling the movement of the optical head is reduced. After setting the advance compensation time, a rotation start signal, a reverse rotation start signal, and a reverse rotation end signal of the motor drive signal are generated based on the maximum eccentric position, the maximum eccentric level, and the advance compensation time to control the movement of the optical head. The lens tracking control can be realized without driving the track actuator of the lens to the drive limit, and the deterioration of the read / write characteristics due to the tilt of the lens optical axis with respect to the recording surface of the optical disk is prevented beforehand. And it can be applied to a high-capacity optical disk device. Also, in this case, even when a stepping motor or a DC motor is used as a motor for driving the optical head, the optical head can follow the track eccentricity of the optical disk at high speed and with high accuracy, and the optical disk device is inexpensive. Can be configured. Further, since control of the motor can be performed in an open loop, oscillation in a control system in a closed loop can be prevented, and stable control can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an optical disk device to which the present invention is applied.

FIG. 2 is a block diagram of an optical head movement control device according to the present invention.

FIG. 3 is a block circuit diagram of a motor drive signal generation circuit according to the present invention.

FIG. 4 is a time chart for explaining the operation of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 lens position detector 2 eccentric position specifying device 3 lens position error signal 4 index signal generator 5 index signal 6 eccentric maximum time pulse signal 7 peak level detector 8 motor controller 9 motor drive device 10 stepping motor 11 advance compensator 12 Motor rotation start signal generator 13 Motor reverse rotation start signal generator 14 Motor reverse rotation end signal generator 15 Polarity determiner 16 Motor control signal generator 32 Optical head carriage 36 Optical disk 37 Objective lens

Claims (4)

[Claims] 1. An optical disk which is driven at high speed, an optical head which is moved in a tracking direction intersecting a track provided on the optical disk and records / reproduces information on / from the optical disk, and the optical head In an optical disc device including a thread servo system for following a track, the thread servo system includes:
A motor for moving the optical head in the tracking direction, an index signal generator for detecting a rotation cycle of the optical disc and outputting an index signal, and detecting a positional shift between a lens of the optical head and the track. A lens position detector that outputs a lens position error signal, and a motor drive signal generation unit that generates a motor drive signal for driving the motor based on the index signal and the lens position error signal. A drive signal generation unit, a unit for specifying an eccentric maximum position of the lens position error signal, a unit for detecting the eccentric maximum level, a unit for setting a rising time at the time of driving the motor as an advance compensation time, Based on the time of the maximum eccentric position, the maximum eccentric level and the advance compensation time, Rolling start signal, reverse rotation start signal, the optical head moving control device of an optical disk apparatus characterized by comprising a means for generating a reverse termination signal. 2. A means for generating a rotation start signal of the motor drive signal calculates a required movement amount of the optical head from the index signal and a maximum eccentric position, and calculates a required drive amount of the motor from the required movement amount. Calculate the time, calculate the time obtained by adding the advance compensation time to the required drive time,
The rotation start signal is output at a time point before the time point of the maximum eccentric position by the added time, and the means for generating the reverse rotation start signal of the motor is configured to output the rotation start signal at a time point ahead of the time point of the maximum eccentric position. The reverse rotation start signal is output at a time point prior to the compensation time, and the means for generating the reverse rotation end signal includes the advance compensation time from the calculated required driving time of the motor from the time point of the eccentric maximum position. 2. The optical head movement control device for an optical disk device according to claim 1, wherein said reverse rotation end signal is output at a time point when said difference is subtracted. 3. The optical head movement control device according to claim 1, wherein the motor is a stepping motor or a DC motor. 4. The optical head has an optical head carriage moved in the tracking direction by the motor, and the lens is provided on the optical head carriage so that focus control and tracking control can be performed by a focus actuator and a track actuator, respectively. 4. An optical head movement control device for an optical disk device according to claim 1, which is mounted.