JPH0817018B2 - Tracking controller - Google Patents

Description

The present invention relates to a tracking control device suitable for use in an optical disc device.

[Outline of Invention]

In the present invention, the information detection point is jumped in synchronization with the sample hold operation for generating the tracking error signal.

[Conventional technology]

When jumping a predetermined number of tracks (for example, one) of a light spot as an information detection point in an optical disk device, first, a loop switch of a tracking servo loop is opened to supply a jump signal (kick pulse) to a tracking actuator (first). Fig. 4 (b)).
As a result, the light spot is moved toward the adjacent track in the predetermined direction. At this time, the level of the tracking error signal (FIG. 4 (a)) temporarily increases. When the information detection point reaches an intermediate position with the adjacent track, the level becomes zero again. When this zero cross point is detected, the kick pulse is terminated, and at the same time, the brake pulse is supplied for a predetermined time. As a result, the actuator slows down the light spot. At the end of the braking pulse, the loop switch is turned on again and the light spot follows the new track.

[Problems to be solved by the invention]

Incidentally, the tracking error signal may be generated by the sample hold operation.

FIG. 3 shows a servo byte pattern of a sample servo in such an optical disk device. Each sector of the optical disk is composed of 43 servo blocks, and one servo block is composed of 2 bytes of servo bytes and 16 bytes of data bytes following the servo bytes. The servo byte consists of two wobbled pits and one clock pit,
The wobbled pits are located on the left and right of the track center. When the pickup (light spot for information detection) traces the track center, the amount of decrease in the amount of light in the left and right wobbled pits becomes equal, and when the trace position shifts to the left and right, there are two The amount of decrease in the amount of light in the wobbled pit changes. Therefore, the difference in the amount of reduction at the two positions (the difference in the RF signal level)
A tracking error signal is generated from the tracking error signal, and the tracking error signal is held during the subsequent data byte.

Also, the two wobbled pits are transformed into a longer interval and a shorter interval every 16 tracks, and by detecting the change in this interval, the number of tracks can be accurately counted (16-track counting) even during high-speed search. You can do it.

Further, the distance D between the wobbled pit and the clock pit located later is set to a special length that does not appear in the data byte. Therefore, this distance D can be detected as a synchronization signal. Various timing signals are generated based on the detected synchronization signal. The clock is generated corresponding to the detection signal of the clock pit. The mirror surface portion of the distance D is used as a focus area, in which a focus error signal is detected and held in the section of the following data byte.

In the conventional optical disk device, when the light spot as the information detection point is jumped by a predetermined number of tracks (for example, one), when the input means is operated, the tracking servo loop is suddenly opened and the tracking actuator is kicked. It was supplying a pulse (jump signal).

Therefore, the start time of the jump signal (for example, the rising timing) is not synchronized with the sample hold signal,
It was supposed to start the jump at various timings.

When the tracking error signal is generated by the sample hold operation as described above, the period until the zero cross point of the tracking error signal is detected after the kick (jump) is started is a maximum of one sample section (servo block) depending on the jump start timing. There is a possibility that the jump operation becomes unstable because of the variation.

Therefore, the present invention is to realize a stable jump operation when the tracking error signal is generated by the sample hold operation.

[Means for solving problems]

In order to solve the above problems, the present invention provides a detection circuit for detecting a sync signal from a read signal read from a recording medium on which the sync signal is recorded, and a predetermined sample hold signal synchronized with the sync signal. One generation circuit,
A second generation circuit that samples and holds the read signal in synchronization with the sample and hold signal to generate a tracking error signal, an actuator that performs tracking control of the information detection point corresponding to the tracking error signal, and a jump of the information detection point. A first generation circuit that generates a kick pulse for performing the following, a second generation circuit that generates a brake pulse for ending the jump, and the generation timing of the kick pulse and the brake pulse are synchronized with the sample hold signal. And a control circuit.

[Action]

According to the present invention, the detection circuit detects the sync signal from the read signal read from the recording medium on which the sync signal is recorded. The first generation circuit generates a predetermined sample hold signal synchronized with the synchronization signal. The second generation circuit samples and holds the read signal in synchronization with the sample and hold signal to generate a tracking error signal. The actuator controls tracking of the information detection point in response to the tracking error signal. The first generation circuit generates a kick pulse for causing a jump of the information detection point under the control of the control circuit in synchronization with the sample hold signal. The second generation circuit generates a brake pulse for ending the jump under the control of the control circuit in synchronization with the sample hold signal.

〔Example〕

FIG. 1 is a block diagram of a tracking control device according to the present invention. The pickup has a photodetector 1 that receives light reflected by the optical disk. The output of the photodetector 1 is current-voltage converted by the conversion circuit 2 and output as an RF signal. The RF signal is input to the detection circuit 8. The detection circuit 8 detects the synchronization signal between the wobbled pit and the clock pit described above, and supplies the detection signal to the generation circuit 9. The generation circuit 9 generates various timing signals in synchronization with the reproduction synchronization signal. The sample hold signal generated by the generation circuit 9 is supplied to the generation circuit 3.
The generation circuit 3 samples the level of the RF signal at the positions of the two wobbled pits, as described above, corresponding to the input sample and hold signal, and generates a tracking error signal from the difference. The tracking error signal sampled in one servo block is held until sampling in the next servo block. As a result, the tracking error signal output by the generation circuit 3 changes stepwise in the cycle of the servo block corresponding to the sample hold operation. This tracking error signal is input to the servo circuit 4 and further supplied to the actuator 7 via the switch 5 and the driver 6. Therefore, the light spot is tracking-controlled so as to follow the track in accordance with the tracking error signal.

When the input means 11 is operated and, for example, a pause operation is input, the control circuit 10 composed of a microcomputer or the like controls each circuit and means so as to repeat the operation in which the light spot jumps back one track at a predetermined position.

The detection circuit 14 decodes the input RF signal and detects a predetermined address. The control circuit 10 determines a predetermined position to jump from the address input from the detection circuit 14. Of course, it is also possible to determine the jump position from the pulse output by the servo circuit 4 in synchronization with one rotation of the optical disc. The control circuit 10 also monitors the timing signal output from the generation circuit 9, and determines the timing at which the sample hold signal is output to the generation circuit 3 after the jump position is detected from the output of the detection circuit 14 or the servo circuit 4. To detect. Then, the switch 5 and the generation circuit 12 are controlled in synchronization with this timing. As a result, a kick pulse (jump signal) output by the generation circuit 12 in synchronization with the sample hold operation of the tracking error signal (FIG. 2A) is supplied to the actuator 7 via the switch 5 and the driver 6. As a result, the light spot starts moving (jumping) toward the adjacent track in the predetermined direction.

When the detection circuit 15 detects the zero-cross point of the tracking error signal, it outputs the detection signal to the control circuit 10. At this time, the control circuit 10 controls the generation circuits 12 and 13 to terminate the kick pulse and simultaneously generate the brake pulse. This brake pulse is supplied to the actuator 7 via the switch 5 and the driver 6. Therefore, the light spot is decelerated by the brake pulse when it moves to the intermediate position between the adjacent tracks. When a predetermined time (which can also be synchronized with the sample hold operation) elapses after the generation of the brake pulse, the control circuit 10 controls the generation circuit 13 to stop the generation of the brake pulse. At the same time, control switch 5,
Turn on the tracking servo loop again. As a result, the light spot comes to trace the jump destination track.

The mass of the movable portion of the actuator 7 and the driving force of the kick pulse are set to predetermined values in advance. Therefore, the kick pulse generation period has a substantially constant length that is an integral multiple of the sample hold period.

〔effect〕

As described above, according to the present invention, the detection circuit detects the sync signal from the read signal read from the recording medium on which the sync signal is recorded. The first generation circuit generates a predetermined sample hold signal synchronized with the synchronization signal. The second generation circuit samples and holds the read signal in synchronization with the sample and hold signal to generate a tracking error signal. The actuator controls tracking of the information detection point in response to the tracking error signal. The first generation circuit, under the control of the control circuit, generates a kick pulse for jumping the information detection point in synchronization with the sample hold signal. The second generation circuit generates a brake pulse for ending the jump under the control of the control circuit in synchronization with the sample hold signal.

As a result, since the generation of the jump signal is synchronized with the sample hold signal, the generation period of the jump signal is kept substantially constant and the jump operation is stabilized.

[Brief description of drawings]

FIG. 1 is a block diagram of a tracking control device of the present invention,
FIG. 2 is a timing chart of the jump operation, and FIG.
FIG. 4 is an explanatory diagram of the servo byte pattern, and FIG. 4 is a timing chart of the jump operation in the conventional tracking control device. 1 ... Photodetector 2 ... Conversion circuit 3 ... Generation circuit 4 ... Servo circuit 5 ... Switch 6 ... Driver 7 ... Actuator 8 ... Detection circuit 9 ... Generation circuit 10 ... Control circuit 11 ... … Input means 12,13 …… Generation circuit 14,15 …… Detection circuit

Claims (1)

[Claims] 1. A detection circuit for detecting the synchronization signal from a read signal read from a recording medium on which the synchronization signal is recorded, and a first generation circuit for generating a predetermined sample hold signal in synchronization with the synchronization signal. A second generation circuit that samples and holds the read signal in synchronization with the sample and hold signal to generate a tracking error signal; an actuator that performs tracking control of an information detection point corresponding to the tracking error signal; A first generation circuit that generates a kick pulse for causing a jump at an information detection point, a second generation circuit that generates a brake pulse for ending the jump, and a generation of the kick pulse and the brake pulse A control circuit for synchronizing the timing with the sample-and-hold signal, And tracking control device.