JPH043373A - Access controller for optical head - Google Patents

Abstract

PURPOSE:To perform the stable seek operation by driving and controlling an actuator based on the result of comparison between the acceleration profile signal outputted from an acceleration command means and the relative speed between a light spot and a track in the direction orthogonal to the track. CONSTITUTION:A speed command means 10 successively outputs a speed profile signal corresponding to the number of residual tracks each time when the counted value of a track counter 14 is inputted, and the speed profile signal is inputted to an error amplifier 12, and the relative speed in the direction orthogonal to the track between the light spot detected by a speed detector 11 and the track is subtracted, and the result is inputted to a fine actuator 13 as a speed error signal to eliminate the speed error. An acceleration command means 15 receives the number of tracks from the counter 14 to output the acceleration profile signal corresponding to the number of residual tracks, and this signal is added to the signal, which is obtained by compensating the output signal of a position detector 16 by a phase compensator 17, by a summing amplifier 18, and the result is inputted to a rough actuator 19. The actuator 19 is so controlled that an objective lens 20 is placed in a certain position to an optical head 21.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention controls an optical head that records and/or reproduces information on a track on an information recording medium using a minute light spot, and changes the light spot from one track to another. This invention relates to an access control device for an optical head that moves and positions an optical head to a track.

[Conventional technology]

A conventional example of an access control device for an optical head is shown in FIG. 4, for example. This conventional device was published in Japanese Unexamined Patent Publication No. 62
This corresponds to the one disclosed in No. 231430, and performs two-stage speed control using a coarse actuator 30 and a fine actuator 31 as positioning means, and in detail, the output of the speed detection means 33 is controlled from the output of the speed command means 32. The output of the error amplification means 34, that is, the speed deviation, obtained by subtracting the
are input to the coarse actuator 30 and fine actuator 31 respectively to actuate both actuators 30 and 31, and the spot position of the light spot that moves accordingly is detected by the position detection means 37 to obtain a tracking error signal, and the tracking is performed. The error signal is fed back to the speed command means 32 and the speed detection means 33 to perform speed control so that the speed deviation becomes zero.

In this conventional device, when accessing a track at high speed, commands for sudden acceleration and sudden deceleration are issued from the speed command means 32.
The high frequency components included in such command input act on the fine actuator 31 through the high-pass filter 36 and cause the optical spot to move excessively, making it necessary to re-access the target track, which reduces the access time. There was a problem with the length of time.

As a countermeasure to this problem, the applicant of the present application has already proposed a device shown in FIG. This device includes a speed command means 40 for outputting the speed at which the light spot should move in the direction perpendicular to the track with respect to the track of the recording medium, and a speed detection means for detecting the relative speed of the light spot and the recording medium in the direction perpendicular to the track. 41, and a subtracter 4 that subtracts the signal related to the relative speed from the speed command signal of the speed command means 40 and outputs a speed error signal.
2, an amplifier 43 that amplifies this speed error signal, a fine actuator 44 that finely adjusts the position of the optical spot by moving the objective lens according to the output of this amplifier, and a fine actuator position that detects the amount of displacement of the fine actuator. A detector 45, a filter 46 which receives the speed command signal and outputs an acceleration command signal, an adder 47 which adds this acceleration command signal and the signal related to the displacement amount, and amplifies the output of the adder 47. It is comprised of an amplifier 48 which inputs the signal to the phase compensation circuit 49, and a coarse actuator 50 which receives the signal whose phase has been compensated by the phase compensation circuit 49 and coarsely adjusts the optical spot position accordingly. The precision actuator 44 is placed on an optical head (not shown) that is moved by the actuator. Here, the sum of the amount of movement of the light spot by the coarse actuator 50 and the amount of movement of the light spot by the fine actuator 44 defines the position of the light spot with respect to the recording medium.

According to this device, a feedback control system inputs a speed error, which is the difference between the output of the speed command means 4o and the output of the speed detection means 41, to the fine actuator 44. The coarse actuator 50 operates so that the relative speed in the direction matches the speed command of the speed command means 40, and the coarse actuator 50 receives the displacement amount of the fine actuator from the fine actuator position detector 45 and detects the deviation of the fine actuator 44 from the reference position. Since the operation is performed such that the speed decreases, there is no problem that the access time becomes longer due to the high-pass filter during high-speed access as in the conventional device. Although feed forward control is performed to add to the drive signal, the steady deviation of the fine actuator 44 from the reference position during the seek operation can be reduced.

[Problem to be solved by the invention]

In the apparatus shown in FIG. 5 above, the speed command means is generally C
The speed command signal output according to the number of remaining tracks up to the target track is actually the sixth
As shown in the enlarged figure, the signal becomes step-like. On the other hand, the filter that converts the speed command signal into the acceleration command signal has differential characteristics, so if the input signal is step-like, the output signal will be a pulse-like signal, and if left as is, the saturation of the electric circuit may occur. This makes it impossible to use it as a regular acceleration command signal. For this reason, an integral characteristic is also added to this filter to prevent the output signal from becoming a pulse.

Generally, in order to stabilize the seek operation, the speed command means decreases the rate of change of the speed command signal, that is, the acceleration, as the target track approaches, and at this time, the relative speed also decreases. In such a state, the width of the stepped portion of the speed command signal (indicated by T in Figure 6) increases, so in order to generate a sufficiently smooth acceleration command signal from this speed command signal, the integral characteristic of the filter must be adjusted. It is necessary to make it effective in the low frequency range.

However, when the integral characteristic is set in this way, as shown by the dotted line in Figure 7, at the start of a seek operation or when the acceleration suddenly changes, the acceleration command is The signal waveform for signal generation becomes like the dotted line, and the waveform change of the filter output signal is delayed and becomes a distorted waveform, which impedes the original effect of feedforward control and causes a large deviation from the reference position of the precision actuator. Therefore, as with the conventional example shown in FIG. 4, the time required to access the target track may become longer.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an access control device that can overcome these conventional problems, fully exhibit the effects of feedforward control, and perform stable seek operations.

[Means and operations for solving the problem] For this purpose, an access control device for an optical head according to the present invention includes an optical head access control device that controls optical head access along a track on an information recording medium. An access control device for an optical head that records and/or reproduces information using a spot includes a speed detection means that detects a relative speed between a light spot and a track in a direction perpendicular to the track, and a speed detection means that detects a relative speed of a light spot and a track in a direction perpendicular to the track. a first actuator capable of moving over a range; a second actuator that moves in conjunction with the operation of the first actuator and capable of moving a light spot within a minute range; and a distance to which the light spot is to be moved. speed command means for outputting a preset speed profile signal according to the distance; and acceleration command means for outputting a preset acceleration profile signal according to the distance; the first actuator and/or the acceleration profile signal based on the comparison result and the acceleration profile signal;
Alternatively, the second actuator may be drive-controlled.

As a result, the acceleration command means outputs an acceleration profile signal that is synchronized with the speed profile signal and has no time delay, and the responsiveness of the actuator is improved by feedforward control using this acceleration profile signal, so that the seek operation of the optical head is improved. Stability can be improved.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 shows a first access control device for an optical head according to the present invention.
FIG. 2 is a diagram showing the configuration of an embodiment, in which only the speed control system is shown. This device is compared with the device shown in Fig. 5.
The difference is that the control system for the coarse actuator is constructed without using a filter (the control system for the fine actuator is almost the same). That is, speed command means lO1 speed detector 11
, an error amplifier 12, a precision actuator 13, and a track counter 14 constitute a precision actuator control system, an acceleration command means 15, and a precision actuator position detector 1.
6, a phase compensator 17, a summing amplifier 18, a coarse actuator 19 (for example, a voice coil motor), and a track counter 14 constitute a coarse actuator control system. The fine actuator 13 includes a pair of permanent magnets 13a,
13b, a support member 13c that elastically supports the objective lens 20, and a coil (not shown) wound around the objective lens 20. The fine actuator 1 is placed on the permanent magnet 13b side.
A precision actuator position detector 16 is incorporated to detect the amount of displacement of the movable part that supports the objective lens 20 of No. 3 from the neutral position.

The speed command means 1O outputs a preset speed profile signal according to the output of the track counter 14. This speed profile signal instructs the speed at which the light spot should move, and the error amplifier 12 to which this signal is input
is an objective lens 2 that condenses a luminous flux and irradiates a light spot.
0 and a track on the disk 22 as an information recording medium in a direction perpendicular to the track, the output signal of the speed detector 11 is subtracted from the speed profile signal and amplified, and the obtained speed error signal is Precision actuator 1
Enter 3. When a current flows through a coil (not shown), the precision actuator 13 moves the objective lens 20 from the neutral position in a direction perpendicular to the track against the spring force of the support member 13c, thereby moving the objective lens and, by extension, the position of the light spot in the direction perpendicular to the track. Can be fine-tuned.

The speed detector 11 detects the relative speed of the optical spot and the track in a direction perpendicular to the track based on a signal representing a positional deviation between the target track and the actual optical spot inputted from the optical head 21, for example, a tracking error signal. The track counter 14 counts the number of tracks crossed by the optical spot based on this tracking error signal, subtracts this count value from the target number of tracks inputted from an external device, and sends the feedback to the error amplifier 12. and feedback to the acceleration command means 15.

On the other hand, the acceleration command means 15 outputs an acceleration profile signal preset according to the output of the track counter 14 in synchronization with the output of the speed profile signal. This acceleration profile signal commands the acceleration that the coarse actuator 19 should apply to the optical head 21, and this acceleration profile signal is obtained by adding the output signal of the fine actuator position detector 16 to a signal whose phase is compensated by the phase compensator 17. The signals are added by the amplifier 18, and the signal after the addition becomes the drive signal for the coarse actuator 19.

Next, the operation of this example will be explained. When moving the light spot from one track to another (target track), the track following control system (not shown) is switched to the speed control system shown in FIG. 1, and the external device 2
It is assumed that the setting of the number of tracks to be traversed from 3 to the track counter 14 has been completed.

The speed command means IO first receives the number of tracks set by the external device 23 into the track counter 14, and
A speed profile with the shape shown in Figure 2 (a) according to the number of tracks, that is, a speed control pattern until the number of remaining tracks becomes zero, is set, and the light spot crosses the tracks based on this speed profile. Every time the count value of the track counter 14, which is updated (decreased) at the time, is input, a speed profile signal corresponding to the number of remaining tracks is sequentially output as a speed command signal. For example, if there are A tracks from the current position to the target track, this output will follow a speed profile starting from the number of remaining tracks A, as shown by the arrow on the solid line in Figure 2 (a). If there are fewer B tracks, the velocity profile will follow a speed profile starting from the number of remaining tracks B, as indicated by the dotted line arrow in the figure. Although the velocity profile in the figure is drawn as a continuous curve, it actually becomes a step-like signal as in the case of the device shown in FIG. This speed profile signal is subtracted by the relative speed in the direction perpendicular to the track between the light spot and the track detected by the speed detector 11 (the speed at which the light spot crosses the track) in the error amplifier 12, and becomes a speed error signal, which is output to the precision actuator. 13, and a speed control system is configured to reduce the speed error to zero.

On the other hand, like the speed command means 1O, the acceleration command means 15 receives the number of tracks set in the track counter 14, and generates a step-like pattern according to the number of tracks as shown in FIG. 2(b). An acceleration profile, that is, an acceleration control pattern until the number of remaining tracks becomes zero, is set, and based on this acceleration profile, the track counter 14
Every time a count value is input, an acceleration profile signal corresponding to the number of remaining tracks is sequentially output as an acceleration command signal. For example, if there are A tracks from the current position to the target track, this output will follow the acceleration profile starting from the number of remaining tracks A, as shown by the arrow on the solid line in Figure 2(b), and from A to A. When there are a small number of B tracks, the acceleration profile starts from the number B of remaining tracks as indicated by the dotted line arrow in the figure. At this time, the acceleration profile signal is output in synchronization with the speed profile signal as shown in the figure, so
Unlike the device shown in FIG. 5, the acceleration command signal does not lag behind the speed command signal.

This acceleration profile signal is sent to the summing amplifier 18 to detect the amount of displacement from the neutral position of the objective lens 20 that is moved by the speed control system (becomes zero at the neutral position and takes positive and negative values). The detected output signal is added to the signal whose phase has been compensated by the phase compensator 17, and is input to the coarse actuator 19.

As a result, the coarse actuator 19 keeps the objective lens 20 at a constant position relative to the optical head 21 (here, the neutral position).
The optical head 21 is controlled so as to be positioned at . In addition, since the coarse actuator 19 is driven by the acceleration profile signal without delay with respect to the speed profile signal, the effect of feedforward control is fully exhibited and the response is extremely good, so that even when the acceleration suddenly changes, the coarse actuator 19 can sufficiently follow the objective lens 20 and suppress the amount of displacement of the objective lens 20 with respect to the optical head to a sufficiently small value, making it possible to improve control stability both during seek and at the completion of seek. Furthermore, in this example, the filter used in the apparatus of FIG. 5 can be eliminated.

Note that when the light spot finally reaches the target track and the number of remaining tracks, which is the output of the track counter 14, becomes zero, the control is switched to a track following control system (not shown) again, and the light spot follows the target track. control.

FIG. 3 shows a second view of the access control device for an optical head according to the present invention.
It is a diagram showing the configuration of an embodiment, and the same parts as in the first embodiment are given the same reference numerals.

The difference between this example and the first example is that the speed control system controls the coarse actuator 19, and the fine actuator 13 performs position control by feeding back the amount of displacement from its own reference position (neutral position). This is what I did. That is, the speed command means 10 inputs the speed profile signal generated based on the output signal of the track counter 14 to the error amplifier 12 in the same manner as in the first embodiment, and the error amplifier 12 uses the speed profile signal to determine the speed detector 11. A speed error signal obtained by subtracting a signal related to the relative speed of the detected optical spot and the track in a direction perpendicular to the track is input to the summing amplifier 18, and the acceleration command means 15
The similarly generated acceleration profile signal is input to the summing amplifier 18, and the coarse actuator 19 is driven by the output signal of the summing amplifier 18 to form a speed control system. A position control system is constructed by inverting a signal representing the amount of displacement of the actuator 13 from the neutral position by an inverting amplifier 24, performing phase compensation by a phase compensator 17, and feeding it back to the fine actuator 13.

In this example, during the seek operation, the coarse actuator is used so that the relative velocity of the optical spot and the track in the direction orthogonal to the track, which is fed back from the velocity detector 11, changes along the velocity profile signal as the velocity command of the velocity command means. 19 is speed-controlled, and at this time, the precision actuator 13 prevents the objective lens 20 elastically supported on the optical head 21 from vibrating about the neutral position by the action of the position control system. The objective lens 20 is controlled so as to be always positioned at the neutral position, and feedforward control similar to that in the first embodiment is performed using the acceleration profile signal from the acceleration command means 15.

As a result, the rough actuator 19 receives an acceleration profile signal without delay with respect to the speed profile signal, so the response becomes extremely good, and the occurrence of speed errors can be suppressed even when the acceleration suddenly changes. Even in a short-distance seek operation in which the switching time between acceleration and deceleration is short, the speed deviation when reaching the target track can be made extremely small, and a stable seek operation can be performed.

〔Effect of the invention〕

As explained above, according to the present invention, the acceleration signal used for feedforward control is not generated from the speed profile signal via a filter having a smoothing function, but is outputted by the acceleration command means in synchronization with the speed profile signal. Since the acceleration profile signal is used, the effect of feedforward control is fully exhibited, the responsiveness of the actuator is improved, and the stability of the seek operation of the optical head is improved.

[Brief explanation of the drawing]

FIG. 1 shows a first access control device for an optical head according to the present invention.
2(a) and 2(b) are diagrams illustrating the velocity profile signal and acceleration profile signal on the same side, respectively. FIG. 3 is a diagram illustrating the configuration of the optical head access control device of the present invention. 2
FIGS. 4 to 7 are diagrams illustrating the configuration of an embodiment, and are diagrams for explaining the prior art. 10...Speed command means 11...Speed detector 12
...Error amplifier 13...Precision actuator 1
4...Track counter 15...Acceleration command means 16...Fine actuator position detector 17...Phase compensator 18...Summing amplifier 19...Coarse actuator 20...Objective lens 21...・Optical head 22
... Disk (information recording medium) 23 ... External device

Claims (1)

[Claims] 1. In an access control device for an optical head that records and/or reproduces information using a light spot along a track on an information recording medium, a speed detection means for detecting the relative speed of the light spot and the track in a direction perpendicular to the track; a first actuator capable of moving a light spot over the entire range of tracks on the information recording medium; and a first actuator capable of moving the light spot within a minute range while moving in conjunction with the operation of the first actuator. 2, a speed command means for outputting a speed profile signal preset according to the distance to which the light spot is to be moved, and an acceleration command means for outputting an acceleration profile signal preset according to the distance, The optical head is characterized in that the drive control of the first actuator and/or the second actuator is performed based on the comparison result of the velocity profile signal and the signal related to the relative velocity and the acceleration profile signal. Access control device.