SU1275533A1 - Device for automatic focusing of optical system for recording-reproducing information - Google Patents

Abstract

The invention relates to a technique of recording and reproducing information and allows to improve the accuracy of focusing by reducing the static error. The device has two control loops: analog, eliminating dynamic errors, and digital, eliminating static errors. The total error is eliminated, since in the common control loop, the control factor at low frequencies is significant. To eliminate the mutual influence of analog and digital-analog loops at the output of digital-to-analog converter 16, a low-pass filter 17 is included that integrates all high-frequency components (LL signals received at its input. 1 sig.

Description

The invention relates to the accumulation of information by optical means, in particular, to the technique of recording and reproducing information, and can be used in audio video players.

The purpose of the invention is to improve the accuracy of focusing by reducing the static error.

The drawing shows a block diagram of the device.

The device contains a photodetector unit 1, a first differential 2 and a summing 3 amplifiers, a controlled switch A, a second differential amplifier 5, an executive element 6, a comparator 7. Level, the first matching circuit 8, a comparator of lower 9 and upper 10 levels, generator 11 U-shaped pulses, a vtoru 12 and a third 13 coincidence circuit, a reversible counter 14, a start block 15, a D / A converter 16 and

17 low pass filter. I

The device works as follows.

The start block 15, which is started at the operator's command from the console, generates a signal Log, 1, at the output (Stop command), when it is received at the reversible counter 14, the counter content is reset to zero. This state is transmitted to a digital-to-analog converter 16. At its output, a voltage is produced, under the action of which, for example, the linear motor of the actuating element 6 shifts the lens (not shown) to the extreme position. When appearing at the output of block 15 of the start of the Log.O (Start command), the generator starts with 11 U-shaped pulses. The pulses from the generator arrive at the second coincidence circuit 12, which is opened by the signal received from the start-up unit 15 (Log.1). These pulses then go to a reversible counter 14, which increases its digital content, which is transmitted to a digital-analog converter 16, the output voltage of which decreases and, accordingly, the lens starts moving towards the surface of the information carrier (not shown).

As the lens moves to the surface of the carrier, the voltage at the output of the first differential amplifier 2 begins to change due to a change in the illumination of the photodetector unit 1, until the moment when the voltage at its output lies in the zone near zero. Then the low level comparator 9 is triggered, by a signal to the second matching circuit 12, the access of the U-shaped pulses from the generator 11 to the reversible counter 14 is stopped. If the external position of the lens and the carrier is violated during any external actions, the comparator 10 of the upper level, therefore, the lens is too close to the surface of the carrier (out of the focus area), the static error increases. When the upper level comparator 10 is triggered, the pulses from the generator 11 begin to flow to the reversible counter 14 through the third matching circuit 13.

The digital content of the reversible counter 14 decreases, and the voltage at the output of the D / A converter 16 increases, causing the actuating element 6 to return the lens to an area close to optimal focusing, the signal at the output of summing amplifier 3 reaches such a magnitude that the comparator 7 level works. Under the condition that the signals from the outputs of the comparators 9, 10 and 7 coincide, the first coincidence circuit 8 is triggered, which by its output signal closes the control switch 4, as a result of which the control signal from the first differential amplifier 2 passes through the second differential amplifier 5 to the actuator 6,

Thus, the analog feedback loop closes and the operating point is in the zone of optimal focus, i.e. There is no static error in the device. If for any reason a static error suddenly appears, then

either a low level comparator 9 or a high level comparator 10, depending on the sign of the error signal. The operation of the comparator is triggered by the corresponding circuit.

match, which is why the digital content of the reversible counter. 13 decreases or increases. The actuator 6 reacts to this change, putting the lens into the focus area.

Thus, there are two adjustment loops in the device: an analog, eliminating dynamic errors, and digital, eliminating static errors, which is why the total error is significantly eliminated, because in a common adjustment loop, the adjustment coefficient at lower frequencies is much higher. The analog and digital-analog loops at the output of the digital-to-analog converter 16 include a low-pass filter 17 that integrates all high-frequency components of the input to its input.

Claims (1)

Invention Formula A device for automatically focusing the optical information recording system, containing a start-up unit, a photoreceiver unit, the outputs of which are connected to the inputs of the first differential and summing amplifiers, the output of the first differential amplifier is controlled by a control switch to the non-inverting input of the second differential amplifier, the output of which is connected the input of the actuator. the output of the summing amplifier is connected via a level comparator to the first input of the first coincidence circuit, the output of which is connected to the control input Controlled switch, characterized in that, for the purpose of To increase focusing accuracy by reducing the static error, low and high level comparators, second and third coincidence circuits, a U-shaped pulse generator, a reversible counter, a digital-to-analog converter and a low-pass filter, and upper and lower comparator inputs are introduced to it. the amplifier, and the outputs, respectively, with the second and third inputs of the first matching circuit and with the first inputs of the second and third matching circuits, the second inputs of which are connected to the output By the generator of the U-shaped pulses, the control input of which is connected to the output of the start-up unit, with which the control inputs of the second coincidence circuit and the reversible counter are also connected, the outputs of the second and third coincidence circuits are connected respectively to the forward and reverse count inputs of the reversible counter, output which through a digital-to-analog converter and a low-pass filter is connected to the inverting input of the second differential amplifier.