JPS61177641A - Track access device in optical disk - Google Patents

Abstract

PURPOSE:To minimize the position dislocation of a converging lens and an optical head by controlling the speed so that the speed to the track of the optical spot can follow the first reference speed at the time of accelerating the speed and the second reference speed at the time of reducing the speed. CONSTITUTION:When an optical spot is shifted from the track of the present position to another goal track, a stroke signal equivalent to the stroke from an external control circuit to a goal track is preset to a counter 15, and the output is inputted to the first reference speed generating circuit 16 and a control circuit 17. The circuit 16 generates the first reference speed signal up to the goal track. On the other hand, the second reference speed generating circuit controlled by the circuit 17 generates the second reference speed signal which goes to be large in proportion to the time. Here, at the time of accelerating the optical spot, the speed is controlled so that the speed of the optical spot can follow the first reference speed which increases constantly for the time, and at the time of reducing the speed, so that the speed of the optical spot can follow the second reference speed as the function of the distance up to the goal.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an optical information recording and reproducing device that uses optical means to record information on a recording medium or to reproduce information that has already been recorded. , particularly regarding track access devices.

(Prior art and its problems) A laser beam is used as a light source, and this laser beam is modulated with a pulsed signal from an external information source to record binary information on a recording medium on a disk, or to record information that has already been recorded. In an optical information reproducing device that reads out information, in order to accurately record or reproduce information, the position of the condenser lens is controlled by focus control so that the surface of the recording medium is always at the position of the condenser lens. In addition, tracking position control of the optical spot of the laser beam with respect to the information track during recording or reproduction of information usually involves setting the optimal width for the optical spot on the recording medium and the optimal depth for the wavelength of the laser beam used. A guide groove is provided, and tracking control is performed so that the minute spot follows the guide groove. Furthermore, in the movement of the light spot between information tracks, when the light spot is moved over a relatively short distance (several tens of tracks), the light spot is moved by moving the condensing lens in the tracking direction, and the light spot is moved over a long distance. When moving between tracks,
The optical spot is moved by moving the entire optical head in the tracking direction using a head actuator. That is, for long-distance inter-track movement, a two-stage control method is used in which the light spot is first roughly positioned by the head actuator, and then the light spot is precisely positioned by moving the condenser lens. However, when the entire optical head is moved by a head actuator, in order to achieve high-speed movement, it is necessary to generate a large acceleration/deceleration using an external actuator, and the optical head is also subjected to the large acceleration/deceleration. When the optical head is subjected to such large accelerations and decelerations, the condensing lens inside the optical head is usually supported by a spring, etc., so the condensing lens position changes greatly during acceleration and deceleration, causing damped vibration. . In particular, due to the damped vibration of the condenser lens in the tracking direction that occurs during deceleration, that is, when the optical head is roughly positioned, the light spot also causes damped vibration in the tracking direction. When such damped vibrations occur, precise positioning of the light spot cannot be performed until the damped vibrations have subsided to some extent, which slows down the positioning of the light spot to the target track.

Therefore, in order to solve the above-mentioned drawbacks, Japanese Patent Application Nos. 101912 and 1802 filed by the same applicant as the present application were filed.
No. 48, Japanese Patent Application No. 68626, No. 68627, and No. 83080 of 1981 propose a track access device that detects the position of a condensing lens with respect to an optical head and suppresses the damped vibration.

However, in the track access device of the above specification, when moving between tracks over a long distance, the optical head is moved by a head actuator that drives the optical head based on a position signal from an external position sensor.
The light spot is roughly positioned at a position largely deviated from the target track due to the eccentricity of the track, and then the light spot is positioned on the target track by precise positioning. As described above, if there is a large deviation from the target track during rough positioning, it will take time for precise positioning, and the overall access time will become longer.

Furthermore, the control mode differs depending on rough positioning or fine positioning, and a complicated mode switching operation is required. As described above, although the track access method described in the above specification can eliminate the damped vibration caused by the spring described above, there remains a drawback in shortening the access time.

SUMMARY OF THE INVENTION An object of the present invention is to provide a track access device that eliminates the above-mentioned drawbacks, has a short access time, and is capable of high-speed and stable track access.

According to the present invention, the lens position of the condensing lens in the tracking direction with respect to the optical head is detected, and the lens actuator moves to the target track while controlling the position of the optical head so that the lens position is always zero by the head actuator. The speed of the focusing lens, i.e. the speed of the light spot relative to the track, is so that when accelerating it follows the first reference speed, and when decelerating it follows the second reference speed.

A track access device is obtained which is characterized in that it performs control and moves a light spot at high speed to a target track.

(Example) The present invention will be described in detail below using the drawings. FIG. 1 shows a block diagram of a track access device according to the invention.

Focus control of the light spot 9 focused on the surface of the recording medium 10 is performed by the focus error detector 3, and the focusing lens 8 is controlled in the focal direction via the focus control circuit 2 and the focus actuator 4. The focus is controlled so that the focal position of the condenser lens 8 is always on the surface of the recording medium. Also, the condenser lens 8 for the optical head housing 5
The position of is detected by the lens position detector 24, and the head actuator 21 is
is driven, and the position of the optical head 1 is controlled so that the lens position signal is zero. At this time, the position control of the light spot 9 in the direction perpendicular to the track (arrow 24) is performed by detecting the relative position of the guide groove and the light spot 9 by the track error detector 6 and the track error detection circuit 11, and by using a filter. The lens actuator is driven via the circuit 14, the switch 19, and the lens actuator drive circuit 20, and the optical spot 9 is positioned on the guide groove, ie, the track, where it is currently located. By doing this, the optical spot 9 is positioned on the currently located track, and the optical head 1 is controlled in position so as to follow the position of the condenser lens 8 so that the lens position error becomes zero.

On the other hand, when moving the optical spot 9 from the currently located track to another target track, a stroke signal corresponding to the stroke to the target track is sent from an external control circuit (not shown) to the counter 15. The output of the counter is input to the first reference speed generation circuit 16 and the control circuit 17. 1st
A reference speed generation circuit 16 generates a first reference speed signal that is a function of the stroke to the target track.

Generally, the function used is such that as the stroke becomes smaller, the first reference speed signal also becomes smaller.

On the other hand, the second reference speed generation circuit controlled by the control circuit 17 generates two second reference speed signals that increase in proportion to time immediately after the stroke to the target is set in the counter 15. 1st and 2nd
The reference speed signals are input to the comparator 26, and the respective magnitudes are compared. If the first reference speed signal is larger, the second reference speed signal is selected. is large, the switch 25 is controlled to select the first reference speed signal.

By doing this, the reference speed signal that is the output of the switch 25 starts from zero, increases monotonically with respect to time until the first and second reference speed signals become equal, and then increases to the target. decreases with respect to the stroke. Furthermore, the control circuit 17 detects whether or not the target track is a certain distance ahead of the target track, and switches the switch 1.
Switch 9. That is, the switch 19 selects B until the current track is a certain distance before the target track, and the switch 19 selects A after the current track reaches a certain distance before the target track. In this way, the reference speed signal which is the output of the switch 25 is input to the differential amplifier, and the light spot 9 (
The difference from the speed signal of the condenser lens 8) is calculated, and a speed error signal is output. The speed error signal drives the lens actuator 7 via the switch 19 and the drive circuit 20, and speed control is performed so that the speed of the light spot 9 follows the reference speed corresponding to the reference speed signal. In this way, the speed of the light spot 9 initially rises from zero in accordance with the second reference speed, and after the switch 25 is switched, it follows the first reference speed and as it approaches the target track. The speed of the light spot 9 is decreasing.

At this time, the track cross pulse generation circuit 13 receives the track error signal, generates a track cross pulse every time the optical spot moves by one track, and outputs a track cross pulse to the counter 1.
The stroke signal preset to 5 is subtracted.

At this time, the optical head follows the position of the condenser lens 8 as described above. In this way, when the light spot 9 reaches a certain distance before the target track, the control circuit 17 switches the switch 19 to A, and the position of the light spot 9 is controlled and determined on the target track. At this time, the optical head 1 also follows the condenser lens 8 in the same control mode as described above.

In this way, when the light spot 9 accelerates, the speed is increased at a predetermined acceleration, and then decelerated by the standard speed expressed as a function of the distance to the target, which is normally used, so that the focusing lens The positional deviation between the optical head and the optical head can be reduced, allowing more stable access between tracks.

FIG. 2 is a diagram showing the reference speed, the speed of the light spot, and the number of types of lens position errors in FIG. 1. 1st and 2nd
A first reference speed signal 32 and a second reference speed signal 31 are generated from the reference speed generation circuit, respectively, and the speed 32 of the light spot follows the second reference signal up to point 34, and after point 34 it follows the first reference speed signal 31. according to the reference signal 30 of

By doing this, the lens position error 35, which indicates the positional deviation between the condenser lens and the optical head, can be kept very small, and the focus servo can be applied stably during track access, making it even more stable. Track error signals can be detected, allowing reliable and stable track access.

Note that the optical head 1 can detect the position of the condenser lens 8 with respect to the head housing 5 as described above, and the details are as follows.
It is described in Japanese Patent Application Nos. 180250 and 180251 of 1982, Japanese Patent Application No. 6825 of 1982, and Japanese Patent Application No. 199504 of 1981.

(Effects of the Invention) As explained above, according to the present invention, when moving from the current track to the target track, the positional deviation between the condenser lens and the optical head can be suppressed to a small extent, and the movement can be performed at high speed, with reliability and stability. This enables highly efficient track access.

[Brief explanation of drawings]

The first part is a block diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram showing operating waveforms of each part of FIG. 1. In the figure, 1... Optical head 2... Track error detector 7... Lens actuator 11... Track error detection circuit 12... Speed detection circuit 13... Track cross pulse generation circuit 15... -Counter -6...first reference speed generation circuit 21
. . . Head actuator 27 . . . Second reference speed generation circuit is shown, respectively.

Claims (1)

[Claims] It has a head actuator that drives an optical head and a lens actuator located inside the optical head that drives a condensing lens, and when moving a light spot from a current track to a target track, the tracking direction of the condensing lens with respect to the optical head is controlled. While controlling the position of the optical head so that the lens position is always zero by the head actuator, the lens actuator moves the condensing lens, that is, the light spot, to the target track. A track access device for an optical disc that moves a light spot at high speed to a target track by controlling the speed of the light spot to follow a preset reference speed, and when accelerating the light spot, the speed of the light spot is constant with respect to time. Speed control is performed so that the speed of the light spot follows a first reference speed that increases, and then, when decelerating, a second reference speed that is expressed as a function of the distance to the target is controlled. A track access device characterized in that speed control is performed so that the speed of the light spot follows.