JPS59193550A - Track following device for optical disk system - Google Patents

Abstract

PURPOSE:To attain accurate follow-up to an information track as well as the stable track jump for a light spot by detecting the tracking direction of a condenser lens to the head base of an optical head and controlling the condenser lens at a fixed position. CONSTITUTION:The position of a lens mobile part 8 including a condenser lens is detected in the tracking direction to a head base 1 contained in an optical head 0 by a lens position detector 6 welded to the base 1. The head 0 is driven via a head position control circuit 16 and a head actuator 12 and then positioned with control so that a lens position signal, i.e., the output of the detector 6 is set at 0. When a track jump is carried out, a track jump instruction 11 is given from the outside to a tracking position control circuit 5. Then the part 8 is shifted by an amount equal to a track via a tracking actuator 7. A light spot 9 has a track jump and is positioned at the adjacent tracking guide groove.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical disk device that uses optical means to record information on a recording medium or reproduce information that has already been recorded, and particularly relates to a track following device for an hIJ recording device. It is something.

An optical disk device that uses a laser beam as a light source and modulates this laser beam with a pulsed signal from an external information source to record binary information on a recording medium on a disk surface, or to read information that has already been recorded. In order to accurately record or reproduce information, the position of the condenser lens is controlled by single focus control so that the surface of the recording medium is always at the focal point of the condenser lens. In addition, the tracking position control for the information track of the nine spots of the racer light during recording or reproduction of information is usually carried out in accordance with the optimal width of the light spot on the recording medium and the wavelength of the laser light used. A guide groove having a certain depth is provided, and tracking control is performed so that the small copying spot follows the guide groove. Furthermore, in the movement of the light spot between four tracks, that is, in the disk radial direction, the condenser lens is moved in the tracking direction (disk radius direction)
Inter-trunk movement is performed by track jumping of the optical spot, which moves one track at a time, and for long-distance inter-track movement, the entire optical head is moved in the tracking direction (disc, radial direction) by the head 7 cutter. The light spot is moved over long distances. That is, when moving over a long distance between tracks, the optical spot is first roughly positioned by the head 7 controller, and then the optical spot repeatedly jumps to the target track by moving the condensing lens relative to the optical head head base. Then, a two-stage a+1+ *Ii method for precise positioning on the target track is performed. However, in conventional two-stage control, the positioning of the optical head by the head actuator is not performed by an external position detector. i! The positioning of the optical spot is performed according to the I signal, and the positioning of the optical spot is performed via a tracking 7 cutuator that drives a condensing lens in the optical head.
This is performed according to the relative position if signal between the light spot and the tracking guide groove. In this way, the positioning of the optical head, the positioning of the light spot, that is, the converging lens, and the positioning of the optical head are performed in parallel, and since the positioning information of the light spot is not reflected in the positioning of the optical head, the tracking of the side light is difficult. Due to the condensing lens leaking in the center of the guide groove or inside the optical head due to trunk jump, the spring supporting the condensing lens is deflected, and a spring force proportional to the amount of deflection causes disturbance to the tracking control system. Form 9 is applied as Q. Specifically speaking, aspect 9 is a lack of stability in the track jump of the optical spot, an increase in position offset in tracking control, etc. To be extreme,
Due to the insufficient track jump amount, the target track may not be reached in some cases, and the positional offset increases, reducing the reliability of recording and reproducing information.

Furthermore, in an optical head that performs tracking control by moving only the prefectural light lens in the tracking direction, when the condenser lens moves, the optical axis of the reflected light from the recording medium deviates from that of the incident light, causing the tracking The optical axes for the position error detector and focus position error detector will shift, causing errors in track position error detection and focus position error detection, reducing the positioning accuracy of the two-wheel control system, and reducing the reliability of recording and playback of ↑l. decreases.

An object of the present invention is to detect the position of the condenser lens relative to the head base of the optical head in the tracking direction (disc radial direction), and to position the condenser lens at a certain position within the optical head, that is, on the head base. To provide a track following device that accurately follows a light spot to an information track while controlling the position of an optical head so that the light spot can move stably to a trunk jump due to the control of a condensing lens. be.

The present invention will be explained in detail below using the drawings.

FIG. 1 shows a block diagram of a trunk following device according to the invention. The track position 1M-error I, which is the relative position of the optical spot 9 with respect to the tracking guide groove provided on the recording medium surface of the disk 10, is detected by the track position error detector 34 and sent to the tracking position control circuit 5.
Input to. In the tracking position control circuit 5, when the trunk jump command 11 is not input, that is, in a mode in which the optical spot 9 follows the tracking guide groove, the tracking position control circuit 5 controls the tracking position based on the track position error signal.
The cut unit 7 is driven in the tracking direction shown by the arrow 31, and the positioning of the lens movable part 8 including the condensing lens is controlled so that the trunk position error becomes 0'', so that the light spot 9 is aligned with the tracking guide groove. Positioned.

At this time, the position of the lens movable part 8 including the condensing lens in the trunking direction (disk radial direction) with respect to the Herad base 1 in the optical head θ is detected by the lens position detector 6 fixed to the Herad base 1, and The optical head O is driven via the position control circuit 16 and the lens head 12, and the positioning of the optical head 0 is controlled so that the lens position signal, which is the output of the lens position detector 6, becomes θ''. By setting the position where the lens position signal becomes 0'' as the center position of the spring for supporting the lens movable part 8, the tracking guide groove is largely displaced due to eccentricity of the disk 10, etc. Even if the lens movable part 8 including the optical lens moves, the optical head O follows the movement of the lens movable part 8, so the lens movable part 8 is always located at the center position of the support spring, so the position offset due to the spring force is Does not occur.

Furthermore, when the light spot 9 tracks jumps to the adjacent tracking guide groove while following the tracking guide groove in which the light spot 9 is located, a track jump command 11 is inputted to the tracking position control circuit 5 from the outside. In the tracking position control circuit 5, the lens movable part 8 including the condensing lens is moved by one track via the tracking actuator 7, and the optical spot 9 is track-jumped, and the optical spot 9 is positioned in the adjacent tracking guide groove. do. At this time, the lens is also in position! Based on the signal, the optical head O follows the movement of the lens movable part 8, so even if many track jumps are repeated,
Since the lens movable portion 8 is always located at the center of the support spring, stable track jumping can be performed.

At this time, the position of the condensing lens 8 in the focal direction indicated by the arrow 32 is detected by the focal position error detector 3, and the focal point A7 cutter is driven via the focal position control circuit 2. Needless to say, focus control is performed so that the focus position is always the focus position of the condenser lens.

As mentioned above, it is possible to control the position of the optical head so that the optical head follows the lens movable part (1) to prevent the gain from decreasing in the low range of the tracking position control system due to the support spring, and to Not only can it have a high gain equivalent to that of a conventional control system, the track following characteristics are increased, and the position offset can be made very small, but also by moving only the conventional condensing lens in the trunking direction.
In optical heads that perform tracking position control, the position offset of tracking position control due to optical path deviation, which was often a problem, can be removed.
Furthermore, since the lens movable part is always located at the center position 11 of the support spring during one-light spot track jump,
You can perform stable track jumps repeatedly without applying unbalanced spring force.

FIG. 2 is a diagram showing operation waveforms of the track position error signal and lens position signal of the track following device of FIG.
Figure 2 shows operating waveforms when a conventional optical head is fixed, and Figure 2 shows operating waveforms when the position of the optical head is controlled by a lens position signal.

With the optical head fixed, when track jumps are repeated, the lens position 6'1 gradually shifts from the center of the support spring, and as shown in the second Ma, the lens position signal 41 gradually shifts. As the lens shifts, the force of the support spring, which is proportional to the shift in lens position, allows it to reach the track position! (An offset occurs in the 1ff. Also, due to the force of this support spring, the response during track jump becomes unstable. However, by controlling the positioning of the optical head with the lens position 1h, it is possible to The optical lens is always located at the center of the support spring, and even if one rack jump is repeated, the lens position number 43 will have a positional error during the 8th track jump as shown in Figure 2. As the head moves, it becomes "o" immediately. Also, no offset occurs in the trunk position error signal 42 due to force washing of the support spring, and the light spot is accurately positioned within the track, and the number of calls is responded to. is also stable.

FIG. 3 is a diagram showing in detail one embodiment of the optical head of the track following device according to the present invention. Semiconductor L/-f'-5
The laser beam emitted from 0 passes through the frimate lens 51.
, s;+1″jrS Be J\7. Passes through the splitter 52, enters the Beano splitter 53, and its reflecting surface
9, the incident light is divided into two, and of the two lights, the light reflected in the right angle direction at the reflecting surface 59 is 1/4.
The light passes through a wavelength plate 54 and a condensing lens 55 and is focused on a beam spot 9 on the recording medium surface of the disk 10, where information is recorded or output. - the reflected light from the recording medium passes through a condensing lens 55 and a 1/4 wavelength plate 54;
It enters the beam splitter 53, and the anti! ! , one surface 59, and the seventh reflected light is reflected by the polarizing beam splitter 52.
The light is incident on the semiconductor laser 50, reflected at -60, and separated from the incident light from the semiconductor laser 50. The reflected light separated from the incident light enters the half mirror 56, where it is further divided into two parts.
divided into. One of the divided lights passes through a convex lens 57,
The light passes through the knife 58 and enters the two-split optical sensor 3, where a focus error is detected. This focus error detection method is a well-known technique known as the Knifezi method, and the focus actuator 4 is driven by this focus error detection, and the condenser lens 55 in the lens movable part 8 is driven.
Positioning control is performed only in the direction shown by arrow 62.

The other reflected light split by the half mirror 56 enters the tracking position detector 3, and detects the tracking position of the beam spot 9 with respect to a tracking guide groove provided on the surface of the disk 100 (not shown). ah
Difference detection is performed.

This tracking position error detecting power method is a method that has been well known as the Nossyburka method, and the detected tracking position kh difference signal is transmitted to the amplification circuit 32, filter 7 amplifier 33, and It is fed back to the tracking actuator 7 via the power amplifier 29, and the lens movable part 8 is driven in the direction shown by the arrow 31 so that the beam spot 9 is located at the center of the tracking guide groove. Splitter 53, prism 6
1. Since the 174 wavelength plate and the condenser lens 55 are fixed in the direction not shown by arrow 31, the lens movable part 8 is moved in the direction shown by arrow 3.
When moving in the direction indicated by 1 (disc radial direction), the condensing lens 55 also moves in the same direction, and the Heems Bonoto 9
can be moved in the direction shown by arrow 31.

On the other hand, the incident light from the semiconductor laser 50 that passes through the beam brick 53 is reflected by the prism 61 in the right angle direction and enters the lens position detector 6 fixed to the head base 1 . By doing this, the amount of light incident on the two optical sensors in the lens position detector differs depending on the position of the prism 61 in the direction shown by the arrow 31, and a signal proportional to the position of the prism 61, that is, the position of the condenser lens 550, is generated. can be obtained. In other words, the position of the condenser lens 55 in the direction indicated by the arrow 31 with respect to the head base 1 of the optical head can be detected, and as described above, this lens position signal can be used to position the optical head. can.

In addition to the optical head shown in Figure 3,
Even if the optical helad shown in Specification No. 1, Japanese Patent Application No. 57-187704, and Japanese Patent Application No. 57-187705 is used, the effect of the same material is not good. .

[Brief explanation of drawings]

FIG. 3 is a diagram showing the details of the optical head of the track following device of the optical disk system. In the figure, 0...,...optical head, 1...
・Head base, 2... Focus position control circuit, 3
. . . Focus position error detector, 4- . . . Focus 7 unit, 5- . . . Tracking position control circuit, 6.
... Lens position detector, 7 ... Tracking 7 cut unit, 8 ... Lens movable part, 9 ...
...Light spot, 10...Disc, 11
...Track jump command, 12...Head 7 controller, 16...Head position control path, 34...Track position error detector, respectively. . O 1 Figure O 2 Figure

Claims (1)

[Claims] Light emitted from a semiconductor laser fixed to the head base of an optical head is focused by a condensing lens into a minute light spot on the surface of a disk-shaped recording medium to record information or read information that has already been recorded. At the same time, a lens actuator inside the optical head drives the condensing lens, so that the light spot follows a tracking guide groove provided on the surface of the recording medium and moves. In optical disk systems,
a lens position detector that detects a lens position signal of the condensing lens in the disk radial direction with respect to the herad base, a head actuator that drives the optical head in the disk radial direction, and based on the lens position signal,
and a head position control circuit that controls the head actuator, and when the light spot follows the tracking guide groove and performs an S movement, the position of the optical head is controlled by the lens position signal. A track following device in an optical disk system characterized by controlling the condenser lens to always maintain a constant position of the optical head.