SU1580166A1 - Apparatus for measuring shifts - Google Patents

Abstract

This invention relates to a control measurement technique. The purpose of the invention is to extend the measurement range by measuring the time delays of the acoustic signal by values exceeding the oscillation period of the reference signal. The device contains an optically coupled light beam source 1, an acousto-optic cell 2 and a photodetector 3, a carrier frequency generator 5, the output of which is connected to the input of cell 2, and a sweep generator 6. The signal phase from the photodetector 3 depends on the displacement of the beam from source 1 relative to the end face of cell 2 1 hp f-ly, 1 ill.

Description

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SL

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The invention relates to the instrumentation technology and can be used to measure object displacements.

The purpose of the invention is to extend the measurement range by measuring the time delays of the acoustic signal by values exceeding the oscillation period of the reference signal.

The drawing shows the block diagram of the device.

The device consists of optically coupled light beam source 1, an acousto-optic cell 2 and a photodetector 3, a phase meter 4, the first output of which is connected to the output of the photoreceiver 3, a carrier frequency generator 5, the output of which is connected to the input of the cell 2, sweep generator 6, the output of which is connected to the modulating input of the generator 5, the phase comparison unit 7, the inputs of which are connected to the output of the photodetector 3 and to the output of the sweeper 6, respectively, of the recording unit 8, the information input of which is connected to the output of the phase meter 4, and the input of the write command is to the output signal of the frequency tuning end of the sweep generator 6, and counter 9, whose information input is connected to the output of block 7, and the reset input to the output of the signal of the beginning of the frequency tuning of the sweep generator 6.

The device works as follows.

The generator 5 generates sinusoidal oscillations with the frequency SI, modulated in amplitude by the frequency of the SG signal from the sweep generator 6, varying within I, SI ®-

As a result, an amplitude-modulated signal arrives at cell 2, and cell 2 excites an ultrasonic wave of the form

ten

15

x - coordinate

along with the propagation of ultrasound howl.

When the distance from the input end of cell 2 to the light beam from source 1 is equal to x0, the wave acquires a time delay and interacts with the light beam. As a result, a part of the light beam deviates into the diffraction maximum and enters the photodetector 3, which detects the light signal and sends a time delayed signal from the frequency sweep generator 6 to the first input of the phase meter 4.

20

25

U

out

 cos (nt - Kx).

The second input of the phase meter 4 is supplied with a reference signal from the generator 6.

U

on

 cos fit.

thirty

The phase shift between these signals is

l v

f Kx x0 ---,

linearly related to distance xc,

When operating in a wide range of measurements of x 0, the phase shift may contain several integer periods of a phase equal to 21Г

f 21TN + C,

40

45

where N is an integer number of periods;

If is a fractional part. Phase meter 4 measures only the fractional part of if. In the process of tuning the frequency of the generator 6 from SI to 51, the total phase shift changes by

 how-

During the time of frequency tuning of Generator 6 from SI, TO Z4 phase shift

f (x, t) - 1 4-cos () cos (wt-Kx), 50 signals at the inputs of phase meter 4 passes N periods 2 and. At the same time, block 7 outputs N pulses to the counter 9. V

where k

I.

V

to -and. to v

V wavenumbers envelope and carrying oscillations; ultrasonic wave speed;

55

as a result, a number is recorded in counter 9.

At the time of the end of the tuning, when the frequency of the generator 6 takes the value of $ 1, the fractional part of the phase shift at the frequency Ј1 is input from the phase meter 4 to the recording unit 8

x - coordinate

along with the propagation of ultrasound howl.

When the distance from the input end of cell 2 to the light beam from source 1 is equal to x0, the wave acquires a time delay and interacts with the light beam. As a result, a part of the light beam deviates into the diffraction maximum and enters the photodetector 3, which detects the light signal and sends a time delayed signal from the frequency sweep generator 6 to the first input of the phase meter 4.

20

U

out

 cos (nt - Kx).

The second input of the phase meter 4 is supplied with a reference signal from the generator 6.

25

U

on

 cos fit.

The phase shift between these signals is

l v

f Kx x0 ---,

linearly related to distance xc,

When operating in a wide range of measurements of x 0, the phase shift may contain several whole periods of a phase equal to 21Г

f 21TN + C,

signals at the inputs of phase meter 4 passes N periods 2 and. At the same time, block 7 outputs N pulses to the counter 9. V

as a result, a number is recorded in counter 9.

At the time of the end of the tuning, when the frequency of the generator 6 takes the value of $ 1, the fractional part of the phase shift at the frequency Ј1 is input from the phase meter 4 to the recording unit 8

Claims (2)

1. An apparatus for measuring displacements containing an optically coupled light beam source, an acousto-optic cell and a photodetector, a carrier wave generator, the output of which is connected to the input of the acousto optic cell, a reference wave generator, the output of which is connected to the modulation input of the carrier wave, a phase meter The inputs of which are connected to the outputs of the photodetector and the generator of the reference oscillations, respectively, and the recording unit, the input of which is connected to the output of the phase meter, characterized in that range broadening measurements, it is equipped with a cpra-20 sweep generator. phase, the inputs of which are connected to the outputs of the photodetector and the generator of the reference oscillations, respectively, and a counter, the input of which f is connected to the output of the phase comparison unit, and the generator of the reference oscillations made tunable. i 2. The device according to claim 1, is molded so that the reference oscillator is made in the form of a sweep generator, the counter is made with a reset input connected to the clock output of the beginning of the change in the frequency of the oscillator, and the recording unit is executed with the write command input connected to the output of clock pulses of the end of frequency change