JPS61283034A - Track access device in optical disk system - Google Patents

Abstract

PURPOSE:To attain a high speed track access by shifting an optical head at a high speed in a tracking direction in the state where a light condensing lens is positioned and fixed at the certain position of a head base. CONSTITUTION:A lens movable part 8 including the light condensing lens is fixed at the position where the output of a lens position detecting part 70 comes to zero. In a control circuit 23, a signal connecting a switch 20 to a side B is outputted until an optical head O approaches slightly before a target position. A reference speed signal generated by a reference speed generating circuit 22 in such a way is inputted to a power amplifier 21, and a head actuator 12 is driven according to the reference speed signal to drive the head O. Its speed is getting slower as the head O approaches the target position. When the head O approaches slightly before the target position, the switch 20 is connected to a side A, and the position of the head O is controlled so that a position signal can come to zero. In this case, there are no the dislocation of the movable part 8 and attenuation vibration, and accordingly the access time can be shortened.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an optical information recording and reproducing device fK that uses optical means to record information on a recording medium and to reproduce information that has already been recorded. In particular, the present invention relates to a tracking control system for the device.

(Prior art and its problems) A laser beam is used as a light source, and this laser beam is modulated with a pulse-like signal from an external information source, and is transmitted to a recording medium on a disk.
In optical information recording and reproducing devices that record numerically or read out information that has already been recorded, focus control is used to ensure that the surface of the recording medium is always aligned with the condenser lens in order to accurately record or reproduce information. The position of the condenser lens is controlled in a manner similar to the focal position. Tracking position control of the optical spot of the laser beam with respect to the information track during recording or reproduction of tt1 information is usually carried out by providing a guide groove on the recording medium with the optimal depth for the optical spot, and then inserting the microscopic guide groove into the guide groove. Tracking control is performed so that the spot follows the line.

Furthermore, when moving the light spot between information tracks, that is, in the disk radial direction, when moving the light spot over a relatively short distance (several tens of tracks), the condenser lens is moved in the tracking direction (disk radial direction). The optical head is moved one track at a time, and the optical spot is moved between tracks by track jumping. For long-distance inter-track movement, the optical head is moved in the tracking direction using a head actuator to change the length of the optical spot. They are moving a lot of distance. In other words, when moving over long distances between tracks, a two-stage control system is used in which the head actuator first performs rough positioning of the light spot, and then the condensing lens moves to precisely position the single light spot. will be held. However, when moving the entire optical head using the head actuator,
In order to achieve high-speed movement, it is necessary to generate acceleration and deceleration by the head actuator, and the optical head is also subjected to a force corresponding to the large acceleration and deceleration. When the optical head is subjected to such large forces due to acceleration and deceleration, the condenser lens in the optical head is usually supported by the head base with springs, etc., so the position of the condenser lens becomes large during acceleration and deceleration. Displace. Especially when decelerating,
That is, due to the damped vibration of the condenser lens in the tracking direction that occurs after the optical head is roughly positioned, the light spot also causes damped vibration in the tracking direction.

When damped oscillations occur in this manner, precise positioning of the optical spot cannot be performed until the damped oscillations have subsided to some extent, which slows down the positioning of the optical spot onto the target track. Furthermore, if the condensing lens is significantly displaced due to this acceleration/deceleration, it may adversely affect the optical system and cause focus control to be lost.

All of these problems occur because it is difficult to detect the position of the condenser lens relative to the optical head, and if a position signal of the condenser lens can be generated, that signal can be used to control the position of the condenser lens. The above-described large shift in the position of the condenser lens is likely to occur.

Regarding this problem, Japanese Patent Application Laid-Open No. 59-193 by the same applicant
Publication No. 553 (Specification of Japanese Patent Application No. 58-68626) Publication of Kokai No. 59-193550 (Specification of Patent Application No. 58-68627)
An optical head capable of detecting the position of a condenser lens is proposed in Japanese Patent Application Laid-Open No. 59-207439 (Japanese Patent Application No. 58-83080).

However, these optical heads require a special optical system for detecting the position of the condensing lens, resulting in disadvantages such as increased size of the optical head, high cost, and difficulty in adjustment.

(Object of the Invention) An object of the present invention is to eliminate the above-mentioned drawbacks, and to detect the position of the condenser lens with respect to the optical head, even in the conventional optical head, and to position the condenser lens at a fixed position on the hector base. 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 an optical head in a tracking direction at high speed in a fixed state.

(Structure of the Invention) According to the present invention, the first peak hold circuit holds and outputs the positive peak value of the tracking error signal indicating the position in the tracking direction of the light spot focused on the recording medium; a second peak hold circuit that holds and outputs the negative peak value of the tracking error signal;
a lens position detection circuit that receives the two outputs of the first and second peak hold circuits and outputs a lens position signal indicating the position of the condenser lens in the disk radial direction with respect to the head base; a lens position control circuit that controls the position of the condensing lens by a fixed tracking actuator that drives the condensing lens in the disk radial direction; a head actuator that drives the entire optical head in the disk radial direction; It is comprised of a head position detector that generates a head position signal indicating the position of the optical head in the disk radial direction, and a head position control circuit that receives the head position signal as input and controls the position of the optical head, In response to the signal, the optical head is moved at high speed in the disk radial direction by the head position control circuit while the condenser lens is positioned and fixed on the head base through the lens position control circuit and the tracking actuator. A track access device in an optical disk system having the above characteristics is obtained.

(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.

The figure shows a stroke signal 2 indicating the movement stroke of the head base 1 of the optical head 0 from an external control circuit.
5 is preset in the counter 17, and the counter 17
The output signal is input to the reference speed generation circuit 22 and the control circuit 23. In the control circuit 23,
At the same time as receiving the output signal of the counter 17, the head position signal 30 is received, and the optical head reaches the target position until the counter output signal is "O" and the head position signal 30 is 10". Until the switch 28 is connected to the A side, a signal is output to the switch 28 to connect the switch to the A side.When the switch 28 is connected to the A side, it is detected by the lens position detection section 70, which will be described in detail later, and the lens movement relative to the head base 1 is detected. A lens position signal in the tracking direction (disc radial direction) indicated by an arrow 31 in the section 8 is fed back to the tracking actuator 7 via a switch 28 and a power amplifier 29, and the lens movable section 8 receives the lens position signal as O''. It is positioned and fixed at the desired position. 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 aligned with the focus position of the focusing lens. Focus control is performed to make the image appear lighter.

On the other hand, in the control circuit 23, the counter output is 0''
In addition, until the head position signal 30 becomes less than a certain value, that is, until the optical head O reaches a certain distance before the target position, the switch 20 is set to B.
Output the signal connected to the side. 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 the head actuator is operated according to the reference speed signal. 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, and the movement of the head is detected by the head position detector 13. The head position signal is input to a speed detector 18 via an amplifier 14 . Speed detector 18
Then, the speed of Rad0 is optically detected based on the head position signal 30, and the head speed signal is fed back to the differential amplifier 19. In this manner, the speed of the optical helad O is controlled so that its speed follows the speed indicated by the reference speed signal. On the other hand, the head position signal 30 is also input to the direction pulse generation circuit 15, which generates a direction pulse in the direction of movement every time the optical head O moves a certain distance. This direction pulse is fed back to the counter 17, subtracts the preset stroke signal, and the counter 17
The reference speed generated by the reference speed generating circuit 22 which receives the output of the optical head 0 also becomes smaller as the optical head 0 approaches the target position.

In this way, the optical helad O 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 flj is at a high speed. In order to achieve track access, it is set to be as large as when accelerating.

However, as described above, the lens movable section 8 including the condensing lens is positioned and fixed at a position where the output of the lens position detection section 70 is 10'', so it is not affected by large accelerations and decelerations due to speed control of the optical head O. In contrast, the lens movable portion 8 hardly moves, and the lens position error can be kept very small.

In this manner, when the optical heald 0 is controlled in speed and reaches a certain distance before the target position, the control circuit 23 outputs a signal to the switch 20 to connect the switch to the A side. In this way, the position signal of the optical head O detected by the head position detector 13 is inputted to the power amplifier 21 via the amplifier 14, the filter circuit 16 for phase compensation, and the switch 20i, and the head actuator is activated based on this position signal. The optical radar 12 is driven, and the position of the optical radar 0 is controlled so that the position signal becomes 0", and the optical radar 0 is positioned at the target position. At this time, the lens including the condenser lens As in the case of speed control, the movable part 8 is positioned and fixed at the position where the output of the lens position detection part 70 reaches 0", so the optical head O is fixed at the target position of about 1tK due to large deceleration. However, the positional displacement of the lens movable section 8 rarely occurs, and the damped vibration of the lens movable section 8 due to the positional displacement after the optical head O is positioned does not occur, and the track access time is reduced accordingly. Can be shortened. Furthermore, the adverse effects on the optical system due to large displacement of the condensing lens within the optical head can also be eliminated.

In this way, after the optical head O is positioned at the target position, the control circuit 23 outputs a signal to the switch 28 to connect the switch to the B side, and this signal connects the switch 28 to the B side, and the tracking A tracking position signal for the data track of the beam spot 9 detected by the position detector 34 is transmitted to the amplification circuit 32,
Filter amplifier 33 for phase compensation, and switch 28
The signal is input to the power amplifier 29 via the power amplifier 29 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 the beam spot 9 is moved and positioned to the target data track by a series of track jump controls shown in the figure. .

As described above, when the head actuator 12 performs high-speed movement of Rad0 to the optical system, the movement of the lens movable section 8 including the condensing lens in the tracking direction is determined by positioning and fixing it to the head base 1. Even with large acceleration/deceleration speeds, the lens movable portion 8 hardly shifts its position, and tracking control of the beam spot 9 on the data track is possible immediately after the optical head 1 is positioned at the target position. Access time can be greatly reduced.

FIG. 2 is a block diagram for explaining the lens position detection section 70 of FIG. 1 in detail. Tracking position detector 3
4, the north track error signal is input to a positive peak hold circuit 71 and a negative peak hold circuit 72, respectively, and the positive peak hold circuit 71 holds the positive peak of the track error signal, and the north track error signal The circuit 72 holds the negative peak of the track error signal. At this time, the positive and negative peak hold circuits usually have some leakage characteristics, so
The outputs of the positive and negative peak hold circuits represent the positive and negative envelopes of the track error signal amplitude, respectively, and indicate the DC voltage along with the change in the track error signal amplitude.

On the other hand, a push-pull method is used to detect the track error signal, which is a method of detecting the diffraction of light by the guide groove as described above based on the difference between two split light processors arranged on the far field. In this case, when the condenser lens misaligns in the tracking direction with respect to the optical head, a DC offset occurs in the tracking error signal in proportion to the misalignment. Therefore, the midpoint output circuit 7 receives the output cuff 4 of the positive peak hold circuit and the output cuff 5 of the negative peak hold circuit and outputs the midpoint of both signals.
The output cuff 6 of No. 3 represents a lens position signal proportional to the relative positional deviation between the optical head and the condensing lens.

FIG. 3 is a diagram showing a companion operation waveform that clearly explains the operation of the lens position detection section of FIG. 2. When the condensing lens is misaligned with respect to the optical head, a negative or positive DC offset is superimposed on the tracking error signal 77 as shown in the figure.

At this time, the output of the positive peak hold circuit 71 shows a positive envelope 74, and the output of the negative peak hold circuit 72
The output of shows a negative envelope 75. In this way, the center point output circuit 73 outputs the center values of the positive and negative envelopes, but for the reason mentioned above, the center values are
The lens position signal 78ft is proportional to the positional deviation of the collective lens with respect to the optical head.

(Effects of the Invention) As explained above, according to the present invention, it is possible to detect the relative fishing force position shift between the optical head and the condensing lens with a simple force circuit without using any special optical system. Furthermore, by positioning and fixing the condensing lens at a constant value of the optical head using the lens position signal during track access, it is possible to suppress the vibration of the condensing lens due to the acceleration/deceleration of the optical head. can be achieved stably and in a shorter time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
This figure is a block diagram explaining in detail the lens position detection section of FIG. 1, and FIG. 3 is a waveform diagram showing operating waveforms of each section of FIG. 2. In the figure, 0... optical head, 1... head base, 2... focus control circuit, 3... focus error detector, 4... focus actuator, 7... tracking actiniator, 8... Lens movable part, 9... Beam spot, 10... Disk, 12... Head actuator, 13... Head position detector, 14.3
2... Amplifier, 15... Directional pulse generation circuit, 16
．． 33... Filter circuit, 17... Counter, 18
...Speed detector, 19...Differential amplifier, 20.28
...Switch, 21.29...Power amplifier, 22
... Reference speed generation circuit, 23 ... Control circuit, 34 ... Tracking position detector, 70 ... Lens position detection section, 71 ... Positive peak hold circuit, 7
2 shows a negative peak hold circuit, and 73 shows a midpoint output circuit. Figure 1

Claims (1)

[Claims] The light is focused onto the surface of a rotating disk-shaped recording medium by an optical head having a semiconductor laser, a head base to which the semiconductor laser is fixed, and a condensing lens that focuses the light emitted from the semiconductor laser. In a track access device in an optical disk system that records or reads information by using a hold circuit; a second peak hold circuit that holds and outputs the negative peak value of the tracking error signal; and a second peak hold circuit that receives two output signals from the first and second peak hold circuits, The light is focused by a lens position detection circuit that outputs a lens position signal indicating the position of the optical lens in the disk radial direction, and a tracking actuator that is fixed within the head base and that drives the focusing lens in the disk radial direction. a lens position control circuit that controls the position of the lens; a head actuator that drives the entire optical head in the disk radial direction; and a head position detector that generates a head position signal that indicates the position of the optical head in the disk radial direction. and,
and a head position control circuit that controls the position of the optical head by inputting the head position signal, and controls the condenser lens to the head base via the lens position control circuit and a tracking actuator according to the lens position signal. A track access device characterized in that the optical head is moved in the radial direction of the disk by the head position control circuit while the optical head is positioned and fixed at.