SU1571663A1 - Device for following information track of optical carrier - Google Patents

Abstract

The invention relates to an information storage technique, in particular, to devices for reproducing information from an optical disk medium, and makes it possible to increase the reliability of the device. In the fast track recording mode, the tracking system keeps the track until the deflection angle of the mirror becomes such that the focusing of the beam deteriorates and the tracking fails. To prevent the tracking from stalling, the angle of rotation of the mirror, i.e. the voltage at the output of the filter 5 is limited at a level where the accuracy of focusing and the quality of the reproduced signal are still satisfactory. 3 il.

Description

cn

Ze

OE

with

1

The invention relates to an information storage technique, in particular, to devices for reproducing information from an optical disk medium.

The purpose of the invention is to increase the reliability of the device.

Figure 1 shows the functional unit of the device; 2 and 3 are timing diagrams explaining the operation of the device.

The device contains a series-connected error signal sensor 1, a key 2, a control block 3, an executive Mechanism 4 with

movable mirror, connected to the output of control unit 3 are connected in series low-pass filter 5, single-phase rectifying bridge 6, first single-threshold comparator 7, waiting for multivibrator 8, the output of which is connected to the first input of the logic element OR 9, to bus 10 of the playback signal connected is a chain of amplitude detector 11, second single threshold comparator 12, and logic element HE 13, the output of which is connected to the control input of the key 4 2.

The device works as follows.

The error signal sensor 1 generates a signal indicating the magnitude and direction of the reproduction light offset relative to the center of the information medium of the disk. The received signal is fed through the key 2, which in the tracking mode conducts, to the control unit 3, in which the error signal is corrected and amplified in power. The signal from the control unit 3 is supplied to the actuator 4, which directs the reproduction light spot to the center of the track, thus enabling continuous tracking.

In the fast track recording mode, the tracking system keeps the track until the deflection angle of the mirror becomes such that the focusing of the beam deteriorates and the tracking fails. To prevent the tracking from stalling, the angle of rotation of the mirror, i.e. the voltage at the output of the filter 5 is limited at a level where the accuracy of focusing and the quality of the reproduced signal are still satisfactory. Single-phase rectifying bridge 6 with-

five

0

five

0 5

0 5

0

five

is used so that the signal of the filter 5 is fed to the input of the comparator 7 of the same polarity during an accelerated view forward and backward. The trigger level of the comparator 7 is set accordingly. When the output signal of filter 5 (fig. 2a) reaches a fixed value, a positive pulse is generated at the output of comparator 7 (fig.2b), the leading edge of which starts the waiting multivibrator 8, the output signal of which (figv) through the OR 9 element enters the control key 2 input. The latter breaks the system loop at a positive signal at its control input. The duration of the positive impulse is chosen in such a way that the mirror has time to return under the action of the returning moment to the neutral position or passes it a little. The circuit then closes and monitoring occurs until the mirror again reaches the set limit. As a result, the accelerated viewing occurs in equal sections without focus interruptions and without a significant deterioration in the quality of the reproduced signal.

To eliminate undesirable effects associated with the appearance of defects in a video disc or a zone without recording tracks, an amplitude detector 11 is inserted into the device, to which a reproducible high-frequency signal from the bus 10 is fed. As a result,

One of the reasons indicated, the magnitude of the reproduced signal (Fig. 3a) decreases to zero. Accordingly, the signal (Fig. 36) at the output of the amplitude detector is reduced to zero. The signal from the output of the second single-threshold comparator 12 (FIG. 3c) through the element NOT 13 enters the second input of the element OR 9. The duration of the positive pulse (Fig. 3g) depends on the trigger level of the comparator 12, which is set so that in normal playback mode, arriving from tire 10 has not decreased to this level. Consequently, only when these video disc defects appear, does the circuit of the tracking system open.

Claims (1)

Claims An optical information tracking track device comprising a sensor for a mass flow sensor, a control unit connected to an actuator that is optically coupled with a error signal sensor, characterized in that a key, an OR gate, a low-pass filter connected in series, a single-phase rectifying bridge, the first single-threshold computation control were introduced. rator and standby multivibrator and serially connected playback signal buses, amplitude detector, second single-threshold comparator, and NOT logic element, the key is connected between the output of the error signal sensor and the control unit input, the output of the multivibrator standby is connected to the first input of the OR element, the second input of which connected to the output of the logical element NOT, and the input of the low-pass filter is connected to the output of the block FIG. 2