JPH0594679A - Track access device - Google Patents

Abstract

PURPOSE:To stably perform seeking by detecting the movement of a fine actuator in addition to both fine and coarse actuators for signals based on errors between reference input and control output. CONSTITUTION:In the case of seeking from a present track to a target track, a highspeed seeking is enabled since control is available in such manners that the vibration of the fine actuator (tracking actuator) 32 is suppresseded to a minimum, a disk eccentricity of sufficiently followed up and a maximum speed is generated in the coarse actuator (feeding motor) 34. In addition, since the fine actuator (tracking actuator) is controlled to be always in a fixed position in relation to the coarse actuator 34, the fine actuator 32 is not vibrated, and the seeking is stably performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track access device for an optical disc of an optical information recording / reproducing device.

[0002]

2. Description of the Related Art Conventionally, as a technique of this kind, there is a track access device disclosed in Japanese Patent Laid-Open No. 61-177640. The track access device is a track access device in an optical disc device having a coarse actuator (feed motor) for driving an optical head and a fine actuator (tracking actuator) for driving a condenser lens in the optical head.

In the track access device, when the light beam is moved from the current track to the target track, the lens position of the condenser lens in the tracking direction with respect to the optical head is detected so that the lens position is always zero by the coarse actuator. In addition, while controlling the position of the optical head, the precise actuator to the target track controls the focusing lens, that is, the speed of the light beam with respect to the track so as to follow the preset reference speed, so that the light beam reaches the target track. Is a device for moving. A similar device is disclosed in Japanese Patent Laid-Open No. 61-28080.

[0004]

In the above-mentioned conventional track access device, when seeking a long distance, the fine actuator is made to seek at a high speed within a range where the coarse actuator can follow, but the seek speed is the position control of the coarse actuator. It depends on the characteristics of the system. At this time, the coarse actuator operates so as to follow the fine actuator at the following speed determined by the position control system, but is not driven at the maximum speed. That is, since the input signal must be suppressed so that the fine actuator does not swing too much, there is a problem that the maximum acceleration of the coarse actuator is not fully achieved.

That is, if the maximum acceleration of the coarse actuator can be derived by suppressing the shake of the fine actuator while making use of the characteristics of both the fine and coarse actuators (without decreasing the gain characteristic in the vicinity of the disk rotation speed), further seek It is thought that the speed can be increased. Further, if the vibration of the precise actuator is suppressed, it is possible to stably switch to the position control at the end of the seek.

The present invention has been made in view of the above points, and an object of the present invention is to provide a track access device for an optical disk which solves the above-mentioned problems and enables seek of a precise actuator at high speed and stably.

[0007]

In order to solve the above problems, the present invention has two fine and coarse actuators and applies a signal based on an error between a reference input and a control output, which is a target speed, to both actuators, Further, it is characterized in that the movement of the fine actuator is detected and the signal is applied to the coarse actuator to control both actuators to search for a desired track.

Further, it is characterized in that reference input or position information at the time of search is used so that the vibration of the fine actuator is reduced at the time of search.

Further, it is characterized in that a change amount of the reference input is applied to the fine actuator so that the vibration of the fine actuator is reduced during the search.

Further, it is characterized in that the gain of the signal applied to the fine actuator is lowered so that the vibration of the fine actuator is reduced during the search.

[0011]

By configuring the track access device as described above, when seeking from the current track to the target track, the vibration of the fine actuator (tracking actuator) is minimized and the disk eccentricity is sufficiently followed. Coarse actuator (feed motor)
Since it is possible to control so that the maximum speed is generated, high-speed seek is possible. Moreover, since the position of the fine actuator (tracking actuator) is always controlled relative to that of the coarse actuator (feed motor), stable seek can be performed without vibration of the fine actuator.

Further, the effect is utilized for the disturbance without lowering the precision actuator sensitivity.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a track access device according to the first embodiment of the present invention. The microprocessor 10 (hereinafter referred to as "MPU") is a single-chip microprocessor having an input port, an output port, a memory, a counter, etc. inside. 10 inside
It operates at MHz and operates at a speed that does not pose a problem for the control system.

Reference numeral 20 is an optical disk, which is rotated at a constant rotation speed by a spindle motor 30. A coarse actuator (feed motor) 34 drives the optical head 31, and a fine actuator (tracking actuator) 32 is incorporated in the optical head 31 to normally control the position of the light beam 36. Reference numeral 33 is a midpoint sensor that detects a midpoint position deviation of the fine actuator 32 with respect to the optical head 31. The optical head 31 outputs a tracking error signal SA and a sum signal SB of reflected light amounts. Reference numeral 11 is a D / A converter, the output of which is connected to the fine actuator 32 and the adder 13
Then, the output of the midpoint sensor 33 is added to drive the coarse actuator 34.

16 is a DC of the tracking error signal SA
It is a track error filter that removes components, and its output is input to the comparator 15 for waveform shaping and obtaining the track pulse TP. Reference numeral 19 is a sum signal filter for removing the DC component of the sum signal SB of the reflected light amount,
Its output is connected to the comparator 18 for waveform shaping and obtaining the sum signal pulse SP. Track pulse TP
Is connected to the counter / input port of the MPU 10.

The track pulse TP has its cycle measured by the cycle counter 14 using a clock of 10 MHz and is taken into the MPU 10. The track pulse TP and the sum signal pulse SP are connected to the direction detector 17, and the direction of the light spot with respect to the track is output by binary logic. Japanese Patent Publication 1
It is described in detail in Japanese Patent Publication No. 50972. This direction signal is connected to the input port of the MPU 10. MP
U10 has a configuration that can be controlled by software.

FIG. 2 is a diagram showing the waveforms of the tracking error signal SA, the sum signal SB, the track pulse TP, the sum signal pulse SP, and the direction detection signal DS. As shown in the figure, it is understood that the rising edge of the track pulse TP should be detected when the optical head 31 moves to the outer circumference, and the falling edge should be detected when the optical head 31 moves to the inner circumference.

The operation of the track access device constructed as described above will be described with reference to the flowchart of FIG. Normally, the disk 20 is rotated at a constant number of rotations, focus servo is applied, and position control called tracking servo is performed. When a seek command is received from a host device (not shown) (step 101), the switch S
W2 is turned off to stop the tracking servo (step 102), and the switch SW1 is set to the D / A converter 11 side. Then, the seek direction and the target number of tracks are set (step 103).

From this time, the MPU 10 obtains the current track by the internal position counter from the number of track pulses TP, obtains the target speed data for moving the optical head 31 according to the difference between the target track and the current track, and the cycle counter. The deviation signal is output from the D / A converter 11 according to the difference between the value of 14 and the actual speed obtained by the MPU 10. M
The position counter inside the PU 10 switches between counting the rising edge and the falling edge of the track pulse depending on the seek direction, and counts when the data area is crossed in either seek direction.

At this time, the fine actuator 32 starts to move, and the coarse actuator 34 follows the output of the midpoint sensor 33, but the output of the D / A converter 11 operates so as to compensate for the following delay (step). 104).
The current position is determined by counting track pulses by using a counter built into the MPU 10 to obtain the number of tracks. By repeating this to the target track, the coarse actuator 34, that is, the light beam can be moved at the target speed (steps 105 and 106).

In this way, the entry speed to the target track is set to be 4 mm / s or less. However, at this time, since it is not known whether the actual speed can stably enter the track (4 mm / s or less), the cycle counter 14 monitors the actual speed (steps 107 and 108). Then, when the speed becomes 4 mm / s or less, the sum signal pulse SP and the track pulse TP are read and switched to the position control in the data section (the switch SW1 is on the servo circuit 12 side and the switch SW2 is on.
Is turned on and the output of the D / A converter 11 is zero). Here, the data section is set so that the sum signal pulse SP is at "H" level and the track pulse TP rises or falls (step 109). If tracking is turned on at such timing (step 1
10) The track can be rushed in in a stable state, and the position control can be switched.

Next, the behavior and seek time of the fine actuator 32 of the truck access device having the above-mentioned structure will be described. 4A and 4B are diagrams showing the shake amount of the fine actuator 32 when the same distance is sought with the same target pattern. FIG. 4A shows the conventional example, and FIG. 4B shows the case of the above embodiment. The required movement time is the same because both servos are applied, but the deflection amount of the fine actuator 32 swings more as the acceleration of the target velocity pattern increases, so that the target velocity pattern does not swing beyond the movable limit of the fine actuator 32. It is necessary to suppress the acceleration of. This is because the precision actuator 32 does not move when it exceeds the movable range, which makes control impossible and seek failure. Therefore, if the track access device is constructed as shown in FIG. 1, the seek speed can be shortened by increasing the acceleration of the target speed pattern, and seek can be performed even if an acceleration about twice that of the prior art is applied. It becomes possible and the seek time can be shortened.

FIG. 5 is a block diagram of the control system of the track access device of the present invention, in which the open loop transfer function is {(G1 (s) H (s) + K (s) G2 (s) + G1 (s )} S.

FIG. 6 is a block diagram of a control system of a conventional track access device, in which the open loop transfer function is {G1 (s) H (s) G2 (s) + G1 (s)} s. .. From the above two equations, in the present invention, K (s)
It can be seen that the gain increases by G2 (s).

FIG. 7 is a block diagram showing a second embodiment of the present invention. In FIG. 7, the same reference numerals as those in FIG. 1 indicate the same or corresponding portions. The MPU 10 is the MPU of FIG.
It is a single-chip microprocessor with internal input port, output port, memory, counter, etc. The inside operates at 10MHz and operates at a speed that does not pose a problem for the control system.

Reference numeral 44 denotes a coarse actuator (feed motor) for driving the movable part optical head 41, and the movable part optical head 4 is provided.
1 is installed. A fine actuator (tracking actuator) 42 is incorporated in the fixed portion optical head 45 to normally control the position of the light beam 36. Reference numeral 43 is a midpoint sensor for detecting the midpoint position shift of the fine actuator 42 with respect to the fixed portion optical head 45. The movable portion optical head 41 outputs a tracking error signal SA and a reflected light amount sum signal SB.

The output of the D / A converter 11 is connected to the fine actuator 42, and is added to the output of the midpoint sensor 43 by the adder 13 to drive the coarse actuator 44. The output of the track error filter 16 is connected to the comparator 15 and waveform-shaped to obtain a track pulse TP. The output of the sum signal filter 19 is connected to the comparator 18 and waveform-shaped to obtain the sum signal pulse SP.

The track pulse TP is connected to the counter / input port of the MPU 10. In addition, the track pulse SP uses a clock of 10 MHz and the cycle counter 1
The period is measured at 4 and is taken into the MPU 10.

The track pulse TP and the sum signal pulse SP are connected to the direction detector 17, and the direction of the light spot with respect to the track is output by binary logic. This direction detecting method is described in detail in Japanese Patent Publication No. 1-50972. This direction signal is connected to the input port of the MPU 10. The MPU 10 has a configuration that can be controlled by software.

Tracking error signal SA and sum signal S
The waveforms of B, the track pulse TP, the sum signal pulse SP, and the direction detection signal DS are the same as those in FIG. As shown in the figure, it is understood that the rising edge of the track pulse TP should be detected when the movable head 41 moves to the outer circumference, and the falling edge should be detected when the movable head 41 moves to the inner circumference.

The operation of the track access device configured as described above is similar to that of the flowchart of FIG. 3, and its description is omitted.

FIG. 8 is a block diagram of the control system of the present invention. At this time, the open loop transfer function becomes [{G1 (s) H (s) + K (s)} G2 (s) + G1 (s)] {1-exp (-sT)}.

FIG. 9 is a block diagram of a conventional control system. At this time, the open loop transfer function is {G1 (s) H (s) G2 (s) + G1 (s)} {1-exp (-sT)}.

From the above two equations, the control system of the present invention is K (s) G2 (s) {1-exp (-s
It can be seen that the gain increases by T)}. Here, the control target is the same for comparison. FIG. 10 compares these two gain characteristics. It can be seen that the present invention has a larger gain in both the low range and the high range.

The behavior of the fine actuator 42 and the shortening of the seek time will be described with reference to FIG. FIG. 11 is a simulation of the deflection amount (output of the midpoint sensor) of the precise actuator 42 when seeking the same distance with the same target pattern according to the related art and the present invention.

The required moving time is substantially the same because both are servo-driven, but the shake amount of the fine actuator 42 is about 1.5 times larger in the prior art. Here, the shake amount of the fine actuator 42 shakes more as the acceleration of the target speed pattern increases, so it is necessary to suppress the acceleration of the target speed pattern to the extent that it does not shake beyond the movable limit of the fine actuator 42. This is because the precision actuator does not move when it exceeds the movable range, which makes control impossible and seek failure.

FIG. 12 is a graph in which the shake amount of the fine actuator 42 is calculated using the acceleration of the target speed pattern during seek as a parameter. If the movable range of the fine actuator 42 is 100 μm or less, it is possible to perform a seek by applying an acceleration of 1 G in the conventional method and 2 G in the present invention.

Therefore, in order to shorten the seek time, if the acceleration of the target velocity pattern is to be increased, it is possible to perform the seek even if the configuration of the present invention is applied and about twice the acceleration of the prior art is applied. , Seek time can be shortened.

FIG. 13 is an example of a block diagram showing the configuration of the track access device of the third embodiment of the present invention. MP
U10 is a single-chip microprocessor having an input port, an output port, a memory, a counter, etc. as in FIGS. The inside operates at 10MHz and operates at a speed that does not pose a problem for the control system. In FIG. 13, parts given the same reference numerals as those in FIGS. 1 and 7 indicate the same or corresponding parts.

The optical disc 20 is rotated at a constant rotation speed by a spindle motor 30. The optical head 31 is driven by a coarse actuator (feed motor) 34. A fine actuator (tracking actuator) 32 is incorporated in the optical head 31 to normally control the position of the light beam. The midpoint sensor 33 detects the midpoint position shift of the fine actuator 32 with respect to the optical head 31. The tracking error signal SA is output from the optical head 31.
And a reflected light amount sum signal SB is output.

The output of the D / A converter 11 is connected to the fine actuator 32, and is added to the output of the midpoint sensor 33 by the adder 13 to drive the coarse actuator 34. The output of the D / A converter 21 is the precision actuator 3
Connected to 2. It is added to the output of the D / A converter 11.

The DC component of the tracking error signal SA is removed by the tracking error filter 16, the waveform is shaped, and the comparator 15 is used to obtain the track pulse TP.
It is connected to the. The DC component of the reflected light amount sum signal SB is
It is connected to a comparator 18 to obtain a sum signal pulse that has been removed by the sum signal filter 19 and has undergone waveform shaping.

The track pulse TP is connected to the counter / input port of the MPU 10, and the track pulse TP is 1
The cycle is measured by the cycle counter 14 using a clock of 0 MHz and is taken into the MPU 10. The track pulse signal TP and the sum signal pulse SP are connected to the direction detector 17, and the direction of the light spot with respect to the track is output by binary logic. This direction detecting method is described in detail in Japanese Patent Publication No. 1-50972. This direction signal is connected to the input port of the MPU 10. The MPU 10 has a configuration that can be controlled by software.

Tracking error signal SA and sum signal S
The waveforms of B, the sum signal pulse SP, and the direction detection signal DS are the same as those shown in FIG. As shown in the figure, it is understood that the rising edge of the track pulse TP should be detected when the optical head 31 moves to the outer circumference, and the falling edge should be detected when the optical head 31 moves to the inner circumference.

The operation of the track access device constructed as described above will be described with reference to the flowchart of FIG. Normally, the disk 20 rotates at a constant rotation speed, is subjected to focus servo, and is in a state of being subjected to position control called tracking servo.

When a seek command is received from a higher position (not shown) (step 101), SW1 is set to the D / A converter 1
It is set to the side of 1 and 21 and the tracking servo is stopped (step 102). Then, the seek direction and the target number of tracks are set (step 103).

From this time, the MPU 10 obtains the present track from the position pulse inside the MPU 10 from the number of track pulses TP,
Depending on the difference between the target track and the current track, the optical head 31
Target speed data, which is a reference input to be moved, is obtained, and a deviation signal is output from the D / A converter 11 according to the difference between the value of the cycle counter 14 and the actual speed obtained by the MPU 10. The position counter inside the MPU 10 switches whether to count the rising edge or the falling edge of the track pulse according to the seek direction, and counts when the data area is crossed in either seek direction.

At this time, the speed servo is driven, the fine actuator 32 starts to operate, and the coarse actuator 34 follows the output of the midpoint sensor 33. Further, the output of the D / A converter 11 causes the following delay. It is operated to compensate (step 104).

Normally, maximum acceleration is performed during acceleration in order to shorten the seek time, but at this time, since the fine actuator 32 vibrates, a change in the target speed is added via the D / A converter 21, and the fine actuator operates. Perform feed-forward compensation to prevent vibration. Even in this case, the fine actuator follows the eccentricity of the optical disc (step 105).

The current position is obtained by counting track pulses using a counter built in the MPU 10. By repeating this to the target track, the coarse actuator 34, that is, the light beam can be moved at the target speed (steps 106 and 107).

Thus, the speed of entry into the target track
Set it to 4 mm / s or less. However, at this time, since it is not known whether the actual speed can stably enter the track (4 mm / s or less), the cycle counter 14 monitors the actual speed (steps 108 and 109). And the speed is 4m
When it becomes m / s or less, the sum signal pulse SP and the track pulse TP are read and switched to position control in the data section (switch SW1 is connected to the servo circuit 36 side, and the output of the D / A converter 11 is zero). Here, the data section is set so that the sum signal pulse SP is at "H" level and the track pulse TP rises or falls (step 110).

If the tracking is turned on at such a timing (step 111), stable track entry can be performed and position control can be switched. However, the data area is configured so that the rising edge of the track pulse may be detected when the optical head moves to the outer circumference, and the falling edge may be detected when the optical head moves to the inner circumference.

If the fine actuator 32 moves due to inertial force when the coarse actuator 34 is moved, the feedforward compensation must also consider the inertial force.

FIG. 15 is a block diagram of the control system of this embodiment. The open loop transfer function of the feedback loop is {(G1 (s) H (s) + K (s)) G2 (s) + G1 (s)} {1-exp (-sT)}.

FIG. 16 is a block diagram of a conventional control system. At this time, the open-loop transfer function is {(G1 (s) H (s) G2 (s) + G1 (s)} {1-exp (-sT)}.

From the above two equations, K (s) G2 (s)
It can be seen that the gain increases by {1-exp (-sT}).
Here, the control target is the same for comparison. The comparison of these two gain characteristics is the same as in FIG. It can be seen that the present invention has a larger gain in both the low range and the high range. In both cases, the gain near the disk rotation speed (40 Hz) is high, and the effect of suppressing the disk eccentricity is large.

The effect of the feedforward compensation F (s) on the behavior of the precise (tracking) actuator 32 with respect to the reference input (target speed) is as follows. FIG. 17 shows the prior art, the feedforward compensation F of the present invention.
(S) is included. This is a simulation of the shake amount (output of the midpoint sensor) of the precise (tracking) actuator 32 when the same distance is sought with the same target pattern. Here, F (s) = {s / (K _f ) +
s)}.

In FIG. 15, the fine actuator transmission characteristic G1 (s) and the coarse actuator transmission characteristic G2 are shown.
(S), the phase compensation circuit transfer characteristic H (s) and the feedforward compensation characteristic F (s) are as follows: G1 (s) = K ₁ ωn ₁ / (s ² + 2ζ ₁ sωn ₁ + ωn ₁ ² ) G 2 (s) = ( K ₂ / s ² ) (ωn ₂ ² ) / (s ² + 2ζ ₂ sωn ₂ + ωn ₂ ² ) H (s) = (1 + Tbs) / (1 + Tas) K (s) = K _k / (1 + T _k s) F ( s) = s / (K _f + s).

The required moving time is almost the same because both are servoed, but the shake amount of the fine (tracking) actuator 32 is about 10 times larger in the prior art. Here, since the shake amount of the fine (tracking) actuator 32 swings more as the acceleration of the target velocity pattern increases, it is necessary to suppress the acceleration of the target velocity pattern to the extent that it does not swing beyond the movable limit of the fine (tracking) actuator 32. This is because the precision (tracking) actuator does not move when it exceeds the movable range, so that control becomes impossible and seek fails.

FIG. 18 is a diagram showing the shake amount of the fine actuator when the disk eccentricity of ± 50 μm and 40 Hz are applied. It can be seen that the precise actuator follows the disk eccentricity and the track pulse TP can be counted without being affected by the eccentricity. The coarse actuator also follows the eccentricity.

FIG. 19 shows the amount of shake of the precise (tracking) actuator 32 calculated using the acceleration of the target velocity pattern during seek as a parameter. If the movable range of the precision (tracking) actuator 32 is 100 μm or less, 1.4 G in the conventional method and 14 G in the present invention (about 10 times).
You can seek by adding the acceleration of. (This figure was performed at an acceleration of 1.4G.)

Therefore, in order to reduce the seek time, if the acceleration of the target velocity pattern is to be increased, the structure of the present invention is adopted, and even if the acceleration of about 10 times is applied to the prior art, the fine (tracking) actuator. It is possible to seek without vibrating, and it is possible to shorten the seek time.

FIG. 20 is a block diagram of a track access device according to the fourth embodiment of the present invention. At this time, the open loop transfer function is {(G1 (s) H (s) + Kvk (s)) G2 (s) + G1 (s)} {1−exp (-sT)} K1 is a variable gain, and Kv at maximum acceleration
If you reduce the
It can be seen that the shake amount of 2 can be suppressed to be small. At this time, it is necessary to reduce the gain up to 100 tracks before the target track, set a normal gain thereafter, and follow the disc eccentricity.

[0064]

As described above, according to the present invention, the following excellent effects can be obtained. (1) Since the maximum acceleration of the coarse actuator can be extracted while suppressing the vibration of the fine actuator during seek (about 10 times that of the conventional method), there is an effect that it is possible to perform fast and stable track access to the optical disc. (2) Further, by utilizing the precise actuator characteristic at the time of seek, the eccentricity of the disk can be followed, and the effect of suppressing the disturbance can be maintained, so that there is an effect that stable optical disk track access that is resistant to the eccentricity and the disturbance can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a track access device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing each waveform of a tracking error signal SA, a sum signal SB, a track pulse TP, a sum signal pulse SP, and a direction detection signal DS in the track access device of the first embodiment.

FIG. 3 is a diagram showing a track access processing flow of the track access device of the first embodiment.

4A and 4B are diagrams showing the deflection amount of the tracking actuator when the same distance is sought with the same target pattern in the track access device of FIG. 1, where FIG. 4A is a conventional example and FIG. It is a figure which shows the case of the Example of.

5 is a block diagram of a control system of the track access device of FIG.

FIG. 6 is a block diagram of a control system of a conventional track access device.

FIG. 7 is a block diagram showing a configuration of a track access device according to a second embodiment of the present invention.

FIG. 8 is a block diagram of a control system of the track access device of FIG.

FIG. 9 is a block diagram of a control system of a conventional track access device.

FIG. 10 is a diagram showing gain characteristics of a control system of a track access device according to a second embodiment of the present invention and a conventional control system.

FIG. 11 is a diagram showing a simulation example of the shake amount of the precise actuator when seeking the same distance with the same target pattern according to the second embodiment of the present invention and the prior art.

FIG. 12 is a diagram showing calculation results of shake of the fine actuator using the acceleration of the target velocity pattern at the time of seek according to the second embodiment of the present invention and the prior art.

FIG. 13 is a block diagram showing a configuration of a track access device according to a third embodiment of the present invention.

FIG. 14 is a diagram showing a track access processing flow of the track access device of the third embodiment of the present invention.

FIG. 15 is a block diagram of a control system of a track access device according to a third embodiment of the present invention.

FIG. 16 is a block diagram of a control system of a conventional track access device.

FIG. 17 is a diagram showing a simulation of a shake amount of a fine actuator according to a third embodiment of the present invention and a conventional example.

FIG. 18 is a diagram showing the result of calculation of shake of the fine actuator using the acceleration of the target speed pattern at the time of seek as a parameter.

FIG. 19 is a diagram showing a shake amount of a fine actuator according to a third embodiment of the present invention and a conventional example.

FIG. 20 is a block diagram of a control system of a track access device according to a fourth embodiment of the present invention.

[Explanation of symbols]

 10 MPU 11 D / A converter 12 Servo circuit 13 Adder 14 Cycle counter 15 Comparator 16 Track error filter 17 Direction detection circuit 18 Comparator 19 Sum signal filter 20 Optical disk 21 D / A converter 30 Spindle motor 31 Optical head 32 Precision actuator 33 Medium Point sensor 34 Coarse actuator 35 Condenser lens 36 Light beam 41 Movable head 42 Fine actuator 43 Midpoint sensor 44 Coarse actuator SW1 switch SW2 switch SA Tracking error signal SB Sum signal TP Track pulse SP Sum signal pulse DS Direction detection signal

Claims (4)

[Claims] 1. A fine and coarse actuator, which applies a signal based on an error between a reference input and a control output to both actuators, further detects the movement of the fine actuator, and applies the signal to a coarse actuator. A track access device that controls both actuators to search for a desired track. 2. The position information at the time of reference input or search is used so that the vibration of the fine actuator due to reference input is reduced while the fine actuator is made to follow the track eccentricity component at the time of search. The described truck access device. 3. The precision actuator according to claim 1, wherein a change amount of the reference input is added to the precision actuator so as to reduce vibration of the precision actuator due to the reference input while allowing the precision actuator to follow the track eccentricity component at the time of search. Truck access equipment. 4. The gain of the signal applied to the fine actuator is lowered so that the fine actuator is made to follow the track eccentricity component at the time of search and the vibration of the fine actuator due to the reference input is reduced. Truck access equipment.