SU1580434A1 - Device for following information track of disc optical information carrier - Google Patents

Abstract

The invention relates to an information storage technique and can be used in devices for reproducing information from optical disk media. The invention makes it possible to improve the accuracy of tracking the information track. As a result of synchronous detection, an output signal S R is generated at the output of the amplifier 5, which indicates the magnitude and direction of the displacement of the reproduction beam relative to the center of the information track. This signal is fed to the summing input of the adder 8. The constant component S ** 0 of the signal of the photoreceiver unit 1 is fed through the low-pass filter 3 to the first input of the multiplier 9, the second input of which receives the signal S from the input of the adder 8. The same signal goes to the second summing input of the adder 8. From the output of the multiplier 9, the signal S 0 .S is fed to the third (subtractive) input of the adder 8. As a result, the signal at the output of the adder will be S = SR / S 0. Thus, the signal S at the output of the adder 8 does not depend from change in laser power to change and the reflection coefficient of the optical disc medium. 1 il.

Description

3-1

The invention relates to an information storage technique and can be used in devices for reproducing information from optical disk media.

The purpose of the invention is to improve the tracking accuracy.

The drawing shows a functional diagram of the device.

A device for tracking information track of a disk optical information carrier contains a photoreceiver unit 1, filters 2 and 3 (low frequencies, synchronous switch 4, a differential amplifier

5, generator 6, adders 7 and 8, multiplier 9, power amplifier 10 and tracking actuator 11

The input of the photodetector unit 1 is optically coupled to the tracking actuator 11, and the output is connected to the inputs of filters 2 and 3 of the lower frequencies. The signal input of the switch 4 is connected to the output of the filter 2 of low frequencies, the control input is connected to the first output of the generator 6, and the outputs with the inputs of the amplifier 5 connected to the output of the first input of the adder 8. The first input of the adder 7 is connected to the second output of the generator

6, the second with the second input and with the output of the adder 8, and the output with the input of the amplifier 10, the output of which is connected to the input of the actuator 11. The first input of the multiplier 9 is connected to the output of the filter 3 second to the output of the adder 8, and the output to the third the input of the adder 8.

The device works as follows.

The generator 6 generates a signal of a fixed frequency, fed through the adder 7 and the power amplifier 10 to the input of the tracking actuator 11, which scans the reproduction light beam across the information track with an amplitude on the order of 0.1 of the diameter of the light beam. The photodetector unit 1 generates a signal proportional to the modulated light flux. Using a low-pass filter 2, a scanning signal is extracted, which is fed to the signal input of the switch 4 "The generator 6 also generates a reference

0

five

0

a signal that is phase aligned, for example, using a phase shifter (not shown) with a dedicated lowpass filter 2 signal. The reference signal is fed to the control input of the switch. As a result of synchronous detection at the output of the amplifier 5, the error signal 3 is generated, which indicates the magnitude and direction of the reproduction beam relative to the center of the information track. This signal is fed to the first (summing) input of the adder 8.

The low-pass filter 3 allocates a constant component S0 of the signal of block 1, which is fed to the first input of the multiplier 9. The second input of the multiplier 9 receives the signal S from the output of the adder 8. The same signal goes to the second (summing) inputs of the adders 7 and 8 At the output of the multiplier 9, a signal is generated, 5 equal to the product of S0-S signals at the peow and second inputs, which goes to the third (subtractive) input of the sum-thtor 8. The signal S at the output of the adder b will be equal to

ABOUT -

SR +

S s0 s.

five

0

The resulting expression can be recorded.

 S in the form of S

yo

Thus, the signal S at the output of the adder 8 is equal to the ratio of the error signal SR to the constant component SQ. Since the signals SR and S0 are equally dependent on such parameters.

0

five

As the laser power and reflection coefficient of the optical disk carrier, the received signal S is independent of them. The error signal amplified by the power amplifier 10 controls the tracking actuator 11, which biases the reproduction light beam in accordance with the care of the information track by performing continuous tracking.

Claims (1)

Apparatus of the Invention A device for tracking an information track of a disk optical information carrier, comprising an actuator optically coupled to a photo-receiving unit, the first and second low-pass filters whose inputs are connected to the output 51 a photodetector unit, a synchronous switch, a signal hitch which is connected to the output of the first low-pass filter, a generator, the first output of which is connected to the control input of the synchronous switch, the first adder, the first input of which is connected to the second output of the generator, a power amplifier, which is connected with the output of the first adder, and the output with the input of the actuator, a differential amplifier, the inputs of which are connected to the outputs of the synchronous switch and the second adder, I distinguish 6 So that, in order to improve the tracking accuracy, a multiplier is inserted into it, and the second adder is made with an additional summing input, the first input of the multiplier is connected to the output of the second low-pass filter, the second input of the multiplier is connected to the output of the second adder, the second input of the first adder and an additional summing input of the second adder, and the output of the differential amplifier is connected to the first input of the second adder.