SU1631600A2 - Device for following the data track on optical recording medium - Google Patents

Abstract

The invention relates to the accumulation of information by optical means, in particular, to devices for reproducing information from disc-shaped recording media. The invention allows to increase the accuracy and reliability of tracking the information track in special modes. In special modes, the common control input 37 receives a logical zero signal. In this case, the scanning amplitude of the alternating voltage generator 30 increases and more accurately determines the moment when the reproduction spot is located in the middle between the information tracks, which improves the accuracy and reliability of tracking the information track in special modes. 1 il.

Description

The invention relates to a technique for accumulating information by optical means, in particular, to devices for reproducing information from disc-shaped recording media.

The purpose of the invention is to improve the accuracy and reliability of tracking the information track in special modes.

The drawing shows the scheme of the proposed device.

The device contains a laser 1, a first mirror 2 with a 3 turn actuator, a second mirror 4 with a 5 turn actuator, a shaper 6 of three beams, a photoreceiver unit 7 with a multi-element photodetector 8 and single-element photoreceivers 9 and 10, the first and second subtraction units 11 and 12 , the first and second differential amplifiers 13 and 14, the first and second filters 15 and 16 low frequencies, the first, second and third electronic switches 17, 18 and 19, the first, second and third summing amplifiers 20, 21 and 22, the first, the second, third and fourth differentiating units 23, 24, 25 and 26, according to moose filter 27, phase shifter 28, synchronous switch 29, alternating voltage generator 30, integrating unit 31, power amplifier 32, amplitude detector 33. The first and second differentiating units 23 and 24 constitute the first frequency response 34, and the integrating unit 31 and the fourth differentiating unit 26 is the second shaper 35 of the amplitude-frequency characteristic. The alternating voltage generator 30 is provided with a control input 36 connected to a common control input 37 of the electronic keys 17 and 18.

The device works as follows.

Laser 1 emits a beam of radiation that is directed to the second mirror 4, which is rotated around its axis by a rotation drive and performs angular oscillations of the radiation beam with a small amplitude at one fixed frequency. The amplitude of the oscillations is about 2 GD4 rad., And the frequency is about 70 kHz. The radiation beam reflected from mirror 4 is converted in the former of three beams 6 into a main reproducing and two additional tracking beams that are directed to the first mirror 2, the drive 3 of which turns it into angular oscillations. Mirror 2 with drive 3 is a tracking actuator that rotates the reproduction beam in accordance with the radial deviations of the information track of the recording medium. The radiation beams are directed by the mirror 2 to the information track of the optical recording medium (not shown), after which they are projected onto the photoreceiver unit 7, consisting of a multi-element photoreceiver 8 for reproduction and two single-element photoreceivers 9 and 10 for tracking. When the reproduction beam is located at the center of the information track, the tracking beams are located symmetrically on both sides of the track, the signals from the single-element photodetectors are the same and the signal at the output of the first subtraction unit 11 is zero. When the center of the track is shifted relative to the reproduction beam, the luminance of the photodetectors changes, as a result of which the output of the first subtraction unit 11 appears as an error signal, the value of which is proportional to the amount of displacement and the phase to the direction of displacement.

This signal is amplified by the second differential amplifier 14 and passes through the first low-pass filter 15 to the input of the first electronic switch 17.

In the tracking mode, the common control input 37 provides the control inputs of the electronic switches 17 and 18 and the alternating voltage generator 30 with a logical unit signal. From the output of the electronic key 17, the mismatch signal passes to the first input of the second summing amplifier 21, the second input of which is not monitored in the information track mode. The error signal is corrected by the first shaper 34 of the amplitude-frequency characteristic consisting of the first 23 and second 24 differentiating units, and through the third summing amplifier 22 and the power amplifier 32 enters the input of the turn actuator 3, which controls the mirror 2 in such a way that the reproduction beam centered on the information track.

The outputs of the four-element photo-receiver 8 of the photo-receiving unit 7 are connected to the inputs of the first summing amplifier 20, the output of which is amplified by the second differential amplifier 13. The band-pass filter 27 selects a scanning signal, which is formed as a result of the angular oscillations of the second mirror 4, which is scanned by the drive 5 connected to the output of the alternating voltage generator 30. A reproduction patch displaces across the information track with a generator frequency of 30 and with a small amplitude, e.g. 0.1 µm, which gives approximately 10% amplitude modulation of the reproduction signal. The selected scan signal passes the phase shifter 28, which sets the phase of this signal in accordance with the phase of the reference signal that comes from the second output of the alternating voltage generator 30 to the control input of the synchronous switch 29 (the phase shifter 28 can also be connected to the second output of the generator 30 and rotate phase reference signal). The scan signal is supplied by the synchronous switch 29 to the negative, then to the positive input of the second subtractor 12 in synchronization with the reference signal at the control input.

Since the control input 36 receives a logical unit signal, the scan amplitude in tracking mode remains unchanged.

In special modes, the common control input 37 receives a logical zero signal. In this case, the scan amplitude of the alternating generator 30

the voltage increases and more accurately determines the moment of finding the reproducing spot in the middle between the information tracks, which provides increased accuracy and reliability

tracking information track in special modes.

Claims (1)

Claims of the Invention A device for tracking an information track of an optical recording medium according to the author. No. 1265843, characterized in that, in order to increase the accuracy and reliability of tracking the information track in special modes, the alternating voltage generator is equipped control input that is connected to a common control input of electronic keys.