JPS63225976A - Tracking controller - Google Patents

Abstract

PURPOSE:To set the generating periods of a jump signal at almost the same length and to stabilize a jump operation, by jumping an information detecting point synchronizing with a sample/holding operation to generate a tracking error signal. CONSTITUTION:When a pause operation is inputted from an input means 11, a control circuit 10 repeats an operation to perform the jump back of an optical spot by one track at a prescribed position. The circuit 10 judges the prescribed position to ought to jump from an address inputted from a detection circuit 14, and also, monitors a timing signal from a production circuit 9, and after detecting a jump position, detects a timing by which a sample/hold signal is outputted to a production circuit 3, and controls a switch 5 and a generation circuit 12 synchronizing with the above timing. As a result, the jump signal is supplied to an actuator 7 via a switch 5, and the optical spot jumps to an adjacent track. At the time of detecting the zero-cross point of the tracking error signal by a detection circuit 15, the circuit 10 controls the generation circuits 12 and 13. Afterwards, the track of a jump destination is traced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tracking control device suitable for use in an optical disk device.

[Summary of the invention]

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

[Conventional technology]

When a light spot serving as an information detection point is made to jump by a predetermined number of tracks (for example, one track) in an optical disk device,
First, the loop switch of the tracking servo loop is opened and a jump signal (kick pulse) is supplied to the tracking actuator (FIG. 4(b)). As a result, the light spot is moved toward an adjacent track in a predetermined direction. At this time, the tracking error signal (Fig. 4 (a)
)) level increases once. Then, when the information detection point reaches a position halfway between 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 a brake pulse is supplied for a predetermined period of time. As a result, the actuator slows down the light spot. As soon as the brake pulse ends, the loop switch is turned on again and the light spot starts following the new track.

[Problem that the invention seeks to solve]

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

FIG. 3 shows a servo bite pattern of a sample servo in such an optical disk device.

Each sector of an optical disk consists of 43 servo blocks, and one servo block consists of 2 servo bytes followed by 16 data bytes. The servo byte consists of two wobbled bits and one clock pit, and the wobbled bits are arranged on the left and right sides of the track center. When the pickup (light spot for information detection) traces the track center, the amount of decrease in light intensity on the left and right wobbled bits becomes equal.

When the trace position shifts to the left or right, the amount of decrease in the amount of light in the two wobbled bits changes depending on the direction and amount of the shift. Therefore, the difference in the amount of decrease (R
A tracking error signal is generated from the F-fold signal level difference), and this tracking error signal is held for a period of subsequent data bytes.

In addition, the two wobbled bits are changed to a longer interval and a shorter interval every 16 tracks, and by detecting changes in this interval, the number of tracks can be accurately counted even during high-speed searches (16-track counting). It is now possible to do so.

The distance between the wobbled bit located further back and the clock bit is set to a special length that does not appear in the data byte. Therefore, this distance can be detected as a synchronization signal. Various timing signals are generated based on the detected synchronization signal. A clock is generated in response to a clock pit detection signal. The mirror surface at a distance is used as a focus area, where a focus error signal is detected and held for the following data byte.

When a tracking error signal is generated by sample and hold operation in this way, the period from the start of a kick (jump) until the zero-crossing point of the tracking error signal is detected depends on the timing of the start of the jump, and the maximum heaviest sample period (servo block) Because of the variation, there is a risk that the jumping motion will become unstable.

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

[Means for solving problems]

The present invention provides a tracking control device including a first generation circuit that generates a predetermined sample and hold signal, and a second generation circuit that samples and holds an output signal of a pickup in response to the sample and hold signal and generates a tracking error signal. an actuator that controls tracking of the information detection point in response to a tracking error signal; a generation circuit that generates a jump signal that causes the information detection point to jump; and a control circuit that synchronizes the generation timing of the jump signal with the sample hold signal. It is characterized by being prepared.

[Effect]

A first generation circuit generates a sample and hold signal. Corresponding to this sample and hold signal, the second generation circuit samples and holds the output signal of the pickup and generates a tracking error signal. The actuator performs tracking control on the information detection point in response to the tracking error signal. The generating circuit generates a jump signal, and the information detection point is jumped in response to this jump signal. The control circuit synchronizes the timing of generation of this jump signal with the sample and 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 irradiated onto the optical disc and reflected. The output of the photodetector 1 is converted into current and voltage by a conversion circuit 2, and outputted as an RF multiplied signal.

The signal is input to the RF multiplied signal detection circuit 8. The detection circuit 8 detects the synchronization signal between the wobbled bit and the clock bit 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 generates two signals as described above in response to the input sample and hold signal.
The RF multiplied signal levels at the positions of the two wobbled pits are sampled, and a tracking error signal is generated from the difference. A tracking error signal sampled in one servo block is held until sampling in the next servo block. As a result, the tracking error signal outputted by the generation circuit 3 changes stepwise at the cycle of the servo block in response to the sample and hold operation. This tracking error signal is input to the servo circuit 4, and further supplied to the actuator tough via a switch 5 and a driver 6. Therefore, the optical spot is tracking-controlled to follow the track in response to the tracking error signal.

When the input means 11 is operated to input, for example, a pause motion, the control circuit 10 comprising a microcomputer or the like controls each circuit 1 means so that the light spot repeats an operation in which the light spot jumps back by one track at a predetermined position.

The detection circuit 14 decodes the input RF multiplied signal and detects a predetermined address. The control circuit 10 determines the 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 pulses output by the servo circuit 4 in synchronization with one rotation of the optical disk. The control circuit 10 also monitors the timing signal output by 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, the generation circuit 12 generates a tracking error signal (FIG. 2(a)).
A kick pulse (jump signal) output in synchronization with the sample and hold operation is supplied to the actuator 7 via the switch 5 and the driver 6. As a result, the light spot starts moving (jumping) toward an adjacent track in a predetermined direction.

When the detection circuit 15 detects a zero-crossing 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,
At the same time as ending the kick pulse, a brake pulse is generated. This brake pulse is applied to switch 5. It is supplied to the actuator 7 via the driver 6. Therefore, when the light spot moves to an intermediate position between adjacent tracks, it will be decelerated by the brake pulse. When a predetermined time (this time can also be synchronized with the sample and hold operation) has elapsed after the brake pulse is generated, the control circuit 1° controls the generation circuit 13,
At the same time as stopping the generation of brake pulses, the switch 5 is controlled to turn on the tracking servo loop again. As a result, the light spot will trace the track to which it jumps.

The mass of the movable part 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 and hold period.

〔effect〕

As described above, the present invention provides a tracking control device including a first generation circuit that generates a predetermined sample and hold signal, and a second generation circuit that samples and holds an output signal of a pickup in response to the sample and hold signal and generates a tracking error signal. a generation circuit, an actuator that performs tracking control of the information detection point in response to the tracking error signal, a generation circuit that generates a jump signal that causes the information detection point to jump, and a control that synchronizes the generation timing of the jump signal with the sample and hold signal. Since the jump signal generation period can be made to have approximately the same length, the jump operation can be performed stably.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a tracking control device of the present invention.
Figure 2 is a timing chart of the jumping action, Figure 3 is a timing chart of the jumping operation.
The figure is an explanatory diagram of the servo bite pattern, and FIG. 4 is a timing chart of a jump operation in a 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 or higher

Claims (1)

[Claims] a first generation circuit that generates a predetermined sample and hold signal; a second generation circuit that samples and holds the output signal of the pickup in response to the sample and hold signal and generates a tracking error signal; Correspondingly, the present invention includes an actuator that performs tracking control of the information detection point, a generation circuit that generates a jump signal that causes the information detection point to jump, and a control circuit that synchronizes the generation timing of the jump signal with the sample and hold signal. Features tracking control device.