JPH0150973B2 - - Google Patents

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 to reproduce information that has already been recorded, and particularly to a track access device for the device. It is.

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 the 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 focus control so that the surface of the recording medium is always at the focal point of the condenser lens. Furthermore, tracking position control of the optical spot of the laser beam with respect to the information track when recording or reproducing information is usually performed by determining the optimal width for the optical spot on the recording medium and the optimal depth for the waveform of the laser beam used. With a guide groove,
Tracking control is performed so that the minute spot follows the guide groove. Furthermore, when moving the spot between information tracks, that is, in the disk radial direction, when moving the spot over a relatively short distance (several tens of tracks), the condenser lens is moved in the tracking direction (disk radial direction).
The light spot moves one track at a time, and moves between tracks by track jumps of the light spot.
For long-distance inter-track movement, the optical spot is moved over long distances by moving the entire optical head in the tracking direction by a head actuator. In other words, when moving over long distances between tracks, a two-stage control method is used in which the head actuator is used to first roughly position the light spot, and then the light spot is precisely positioned by moving the condensing lens. It will be done. However, when moving the entire optical head using a head actuator, in order to achieve high-speed movement, the head actuator must generate large accelerations and decelerations, and the optical head also needs to generate large accelerations and decelerations. Subject to 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 the head base by a spring or the like, so the position of the condensing lens changes greatly during acceleration and deceleration. . Particularly during deceleration, that is, due to the damped vibration of the condenser lens in the tracking direction that occurs after the optical head has been roughly positioned, the optical spot also undergoes damped vibration in the tracking direction. When such damped oscillations occur, the optical spot cannot be accurately positioned until the damped oscillations have subsided to a certain extent, which slows down the positioning of the optical spot onto the target track. Furthermore, if the condensing lens is largely displaced due to this acceleration/deceleration, it may adversely affect the optical system and cause focus control to be lost.

An object of the present invention, in order to eliminate the above-mentioned drawbacks, is to detect the tracking direction of the condensing lens relative to the head base of the optical head, that is, the position in the radial direction of the disk, and to detect the position of the condensing lens in the disk radial direction with respect to the head base. It is an object of the present invention to provide a track access device which suppresses the occurrence of damped vibration of a condensing lens and enables high-speed track access by moving a head in a tracking direction at high speed.

The present invention will be explained in detail below using the drawings. FIG. 1 shows a block diagram of a track access device according to the invention. A stroke signal 25 indicating the movement stroke of the head base 1 of the optical head 0 is preset in the counter 17 from an external control circuit (not shown), and the output of the counter is input to the reference speed generation circuit 25 and the control circuit 23. . The control circuit 23 receives the output of the counter 17 and simultaneously receives the head position signal 3.
0, until the counter output is "0" and the head position signal 30 is "0", that is, until the optical head reaches the target position, the signal connected to the A side is not connected to the switch 28. Output. In this way, when the switch 28 is connected to the A side, the tracking direction (disk radial direction) of the lens movable part 8 relative to the head base 1 detected by the lens position detector 6 fixed to the head base 1 as shown by the arrow 31 is detected. The lens position signal is fed back to the tracking actuator via the amplification circuit 26, filter circuit 27, switch 28 and power amplifier 29, and the lens movable section 8
is positioned and fixed at a position where the lens position signal is "0". At this time, the position of the lens movable part 8 in the focus direction is detected by the focus error detector 3 and fed back to the focus actuator 4 via the focus control circuit 2, so that the recording surface of the disk 10 is the focus of the condensing lens. Focus control is performed to ensure the correct position.

On the other hand, in the control circuit 23, until the counter output is "0" and the head position signal 30 is below a certain value, that is, the optical head is 0.
The means outputs a signal for connecting to the B side to the switch 20 until it reaches a certain distance before the target position. In this way, the reference speed signal generated by the reference speed generation circuit 22 corresponding to the counter output 17 is inputted to the power amplifier 21 via the differential amplifier 19 and the switch 20, and is inputted to the power amplifier 21 according to the reference speed signal. The head actuator 12 is driven. In this way, when the head actuator 12 is driven, the optical head 0 mechanically connected to the head actuator 12 is also driven.
Head movement is detected by a head position detector 13, and the head position signal is inputted to a speed detector 18 via an amplifier 14. The speed detector 18 detects the speed of the optical head 0 based on the head position signal 30 and feeds back the head speed signal to the differential amplifier 19. In this manner, the speed of optical head 0 is controlled so that its speed follows the speed indicated by the reference speed signal. on the other hand,
The head position signal is also input to a direction pulse generation circuit 15, which generates a direction pulse in the direction of movement each time the optical head 0 moves a certain distance. This direction pulse is fed back to the counter 17, and the preset stroke signal is subtracted.The reference speed generated by the reference speed generation circuit 22 receiving the output of the counter 17 is also changed as the optical head 0 approaches the target position. Therefore, it becomes smaller. In this way, the optical head 0 is initially accelerated by a large acceleration, and when its speed reaches the reference speed, the speed is controlled to follow the reference speed, but generally the deceleration from the reference speed to the target position is at a high speed. In order to realize track access, it is set to be as large as when accelerating.

However, as mentioned above, the lens movable part 8 including the condensing lens has an output of "0" from the lens position detector 6.
Since the lens movable portion 8 is fixedly positioned at a position where the lens movable portion 8 is fixed, the lens movable portion 8 hardly moves even in response to large accelerations and decelerations caused by speed control of the optical head 0, and lens position errors can be kept very small.

In this way, when the speed of the optical head 0 is controlled and it reaches a certain distance before the target position, the control circuit 23 causes the switch 20 to switch to A.
Output the signal connected to the side. In this way, the position signal of the optical head 0 detected by the head position detector 13 is inputted to the power amplifier 21 via the amplifier 14, the phase compensation filter circuit 16, and the switch 20. The head actuator 12 is driven, and the position of the optical head 0 is controlled so that the position signal becomes "0", and the optical head 0 is positioned at the target position. At this time as well, the lens movable section 8 including the condensing lens is positioned and fixed at the position where the output of the lens position detector 6 is "0" as in the case of speed control, so the optical head 0 has a large deceleration. Even if the lens is positioned at the target position by
There is almost no misalignment of the optical head.
Damped vibration of the lens movable portion 8 due to positional deviation after the lens is positioned does not occur, and the track access time can be shortened accordingly. Furthermore, it is possible to eliminate the adverse effect on the optical system caused by the large displacement of the condenser lens within the optical head.

After the optical head 0 is positioned at the target position in this way, the control circuit 23 switches the switch 28
The switch outputs a signal to connect to the B side, and this signal connects the switch 28 to the B side, and outputs a tracking position signal for the data track of the beam spot 9 detected by the tracking position detector 34. However, the amplifier circuit 32, the filter amplifier 33 for phase compensation, and the switch 2
The signal is input to the power amplifier 29 via the power amplifier 8 to drive the tracking actuator. Then, the lens movable part 8 is positioned so that the beam spot 9 is located on the data track, and by a series of track jump controls (not shown), the beam spot 9 is moved to and positioned on the target data track.

As described above, when the optical head 0 is moved at high speed by the head actuator 12, the movement of the lens movable part 8 including the condensing lens in the tracking direction can be greatly adjusted by positioning and fixing it to the head base 1. Regarding the speed, there is almost no positional deviation of the lens movable part 8, and tracking control of the data track of the beam spot 9 can be performed immediately after the optical head 1 is positioned at the target position, and the track access time can be greatly shortened.

FIG. 2 is a diagram showing each operation waveform of the track access device of FIG. 1. FIG. 2a is a diagram showing the reference speed and the speed of the optical head 1 in speed control, FIG. 2b is a diagram showing the current flowing through the head actuator during track access, and FIG. It is a figure showing the position signal of the lens movable part 8 when the movable part 8 is not fixed in position, and is a second
FIG. d is a diagram showing a position signal of the lens movable portion 8 when the lens movable portion 8 is positioned and fixed.

During speed control, control is performed so that the speed 41 of the optical head 1 follows the reference speed 40. At this time, a large acceleration/deceleration current 42 shown in FIG. 2b flows through the head actuator 12, and this current causes As a result, the lens movable section 8 receives a large force, and when the lens movable section 8 is not fixed in position, a large positional shift occurs as shown by the lens position signal 43 in FIG. Even after positioning, the damped vibration indicated by reference numeral 44 remains, and the track access time cannot be shortened.
However, when the lens movable part 8 is positioned and fixed, the lens position signal can be suppressed to a very low level as shown in Figure 2 d, and furthermore, the damped vibration after positioning the optical head does not occur, and as shown in Figure 2 c. Access can be shortened by the time during which the damped vibration 44 occurs as shown.

FIG. 3 shows in detail one embodiment of the optical head of the track access device according to the invention. Laser light emitted from the semiconductor laser 50 on the head base passes through a collimating lens 51 and a polarizing beam splitter 52, and enters a beam splitter 53, where its reflection surface 59 splits the incident light into two. . Of the two divided lights,
The light reflected in the right angle direction on the reflecting surface 59 is 1/
The light passes through a four-wavelength plate 54 and a condensing lens 55 and is focused on a beam spot 9 on the recording medium of the disk 10, where information is recorded or read. on the other hand,
The reflected light from the recording medium passes through the condensing lens 55 and the quarter-wave plate 54, enters the beam splitter 53, is reflected by the reflective surface 59, and the reflected light enters the polarizing beam splitter 52. and reflective surface 60
At this point, it is separated from the incident light from the semiconductor laser 50. The reflected light separated from the incident light is reflected on 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 and a knife edge 58, and enters the two-split optical sensor 3, where a focus error is detected. This focus error detection method is called a knife edge method.
This is a conventionally well-known technique, and the focus actuator 4 is driven by this focus error signal to control the positioning of only the condenser lens 55 within the lens movable section 8 in the direction shown by the arrow 62.

The other reflected light split by the half mirror 56 is incident on the tracking position detector 3, and is detected at the tracking position of the beam spot 9 with respect to a tracking guide groove (not shown) provided on the surface of the disk 10. Error detection is performed. This tracking position error detection method is a conventionally well-known push-pull method, and the detected tracking position error signal is transmitted to the amplification circuit 32 and filter amplifier 3 in FIG.
3. The beam 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.
On this movable lens, the beam splitter 53, prism 61, 1/4 wavelength plate, and condensing lens 55 are fixed in the direction shown by the arrow 31. When the beam spot 9 is moved in the direction shown by the arrow 31, the condensing lens 55 also moves in the same direction, and the beam spot 9 can be moved in the direction shown by the arrow 31.

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

In addition to the optical head shown in Figure 3,
It goes without saying that similar effects can be obtained by using the optical heads shown in Japanese Patent Application No. 180251, Japanese Patent Application No. 57-187704, and Japanese Patent Application No. 57-187705.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a track access device for an optical disk system according to the present invention, and FIG.
FIG. 3 is a block diagram showing in detail the optical head of the track access device of the optical disk system. In the figure, 0: optical head, 1: head base, 2: focus control circuit, 3: focus error detector, 4: focus actuator, 6: lens position detector, 7: tracking actuator. 8... Lens movable part, 9... Beam spot, 10... Disk, 12... Head actuator, 13... Head position detector, 14, 26,
32... Amplifier, 14... Directional pulse generation circuit,
16, 27, 33... Filter circuit, 17... Counter, 18... Speed detector, 19... Differential amplifier, 20, 28... Switch, 21, 29... Power amplifier, 22... Standard Speed generation circuit, 23...
. . . control circuit, 34 . . . tracking position detector, respectively.

Claims (1)

[Claims] 1. The light is focused onto the surface of a rotating disk-shaped recording medium by an optical head that includes a semiconductor laser, a head base to which the semiconductor laser is fixed, and a condenser lens that focuses the light emitted from the semiconductor laser. An optical disk system that records or reads information using light includes a lens position detector that generates a lens position signal indicating the position of the condenser lens in the disk radial direction with respect to the head base; a tracking actuator that drives the optical lens in the disk radial direction; a lens position control circuit that receives the lens position signal as input and controls the position of the condensing lens by the tracking actuator; a head actuator that drives the entire head in the disk radial direction;
a head position detector that generates a head position signal indicating the position of the optical head in the disk radial direction;
a head position control circuit that controls the position of the optical head by receiving the head position signal as input; 1. A track access device for an optical disk system, wherein the optical head is moved at high speed in a disk radial direction by the head control circuit while a lens is positioned and fixed on the head base.