SU1714360A1 - Displacement transducer - Google Patents

Abstract

The invention relates to a control and measuring technique. The purpose of the invention is to improve accuracy by reducing the effect of fluctuations in the direction of the reference beam. The device consists of a source 1 of the reference light beam, an acousto-optic modulator 2, a photodetector 3, a retroreflector 4 and a photodetector 5i The phases of the signals on the photodetectors 3 and 5 depend on the position of the modulator 2 relative to the reference beam and on the angle of propagation of the reference beam. Measuring the phase delays of the signals from the photodetectors relative to each other and relative to the reference frequency signal, compensates for the effect of the fluctuations in the direction of the reference beam. 1 vl.VI ^ OJo about

Description

The invention relates to reference measurement technology and can be used to measure displacements, for example, in engineering geodesy, as well as in the creation of highly accurate systems for the automatic control of unique objects.

A device for measuring displacements is known, comprising a light source, a reference light beam forming system, an acousto-optic modulator (AOM), a carrier frequency generator connected to the AOM, a modulating oscillator, a photodetector, and a phase meter.

A disadvantage of the known device is the low accuracy due to the fluctuations of the direction of the reference light beam.

It is also known a device for measuring displacements comprising a sequentially mounted and optically coupled light source, a system for forming a reference light beam, an acousto-optic modulator, a carrier frequency generator connected to an AOM, a reference signal generator, the output of which is connected to a modulation input of a carrier frequency generator, photodetector and phase meter.

A disadvantage of the known device is that the measurement of displacements is carried out in conjunction with the fluctuations of the 1/1 directional light beam, which reduces the accuracy of the measurement of the displacement of the object being monitored.

The closest to the invention in technical essence and the achieved result is a device for measuring displacements containing their optically coupled source of the reference light beam, an acousto-optic modulator, retroreflector and photodetector, a carrier frequency generator, the output of which is connected to the output of the acousto-optic modulator, reference frequency generator, the output of which is connected to a modular input of a carrier frequency generator, and a phase meter, whose inputs are connected to the outputs of a photodetector and a generator of a reference hour Ota respectively.

A disadvantage of the known device is the low accuracy caused by the fact that it provides a measurement of the displacements in total with the fluctuations of the direction of the reference light beam.

In the known device, the AOM only works with the reference light beam incident on the retro-reflector, i.e. with the beam carrying simultaneously information about the object displacement and fluctuations of the reference light beam, which reduces the measurement accuracy.

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

This goal is achieved by the fact that a device for measuring displacements containing an optically coupled source of a reference light beam, an acousto-optic modulator, a retroreflector and a photoreceiver, a carrier frequency generator, the output of which is connected to the input of an acousto-optical module b, the reference frequency generator, the output of which is connected to The modulation input of the carrier generator, and the phase meter, the inputs of which are connected to the outputs of the photodetector and the reference frequency generator, respectively, are provided with a second photodetector and torym phase meter, whose inputs are connected to outputs of the first and second photodetectors, respectively, - wherein the acoustooptic .modul torus mounted for reacting x retrootrazhatel reflected from the beam and a second photodetector mounted downstream of the diffracted on the acoustooptic modulator retrootrazhatel reflected from the beam.

The establishment of an AOM in the region of both the reflected light from the retroreflector and the reference light beam directly incident on it with diffraction from both rays, and the introduction of an additional photodetector and phase meter allows measuring the fluctuations of the direction of the reference light beam and eliminating their influence on the measurement results of the actual displacement object, which increases the accuracy of these measurements.

The drawing shows a block diagram of a device for measuring displacements.

The device for measuring displacements (Fig. 1) contains a series-mounted and optically coupled source 1 of a reference light beam (for example, a helium-neon laser) an acousto-optic modulator (AOM) 2 installed on the object, a photodetector 3 located along the diffraction beam from the incident AOM reference light beam, retroreflector 4, made in the form of a mirror triple prism, photodetector 5, located along the diffraction beam from the reflected retroreflector 4 reference light beam, generator b carrier hour Oia, the output of which is connected to the input of the AOM 2, the generator 7 of the reference signal, the output of which is connected to the modulation input of the carrier frequency generator 6 and the input of the phase meter 8, another input of which is connected to the output of the photodetector 3, the phase meter 9, whose inputs are respectively connected to the outputs photodetectors 3 and 5.

Acousto-optic modulator is installed between the source 1 of the reference light beam and the retro-reflector 4 in the area of both the reflected from the retro-reflector 4 and the direct light beam incident on it.

The device works as follows.

The light flux from source 1 is a thin beam with a flat wavelength. In this case, a helium-neon laser is used as the source 1. In the case of using a different light source (LED, semiconductor laser, etc.), it should include an optical system (collimator) that forms the reference light beam with the necessary parameters. In the event that an object is removed by a considerable distance, source 1 must also include such an optical system.

The reference light beam passes through AOM2.

As a result of the acousto-optic interaction, the incident reference light beam undergoes diffraction, the diffracted part of the beam falls on the photodetector 3. The reference light beam reflected from retroreflector 4 returns parallel to the incident beam and passes HOUSE 2 again. falls on the photodetector 5. The reference sinusoidal signal from the output of the generator 7 reference signal is fed to the modulation input of the generator torus 6 of the carrier frequency and one of the inputs of the phase meter 8. The carrier frequency generator b operates in an amplitude modulation mode. As a result, the generator 6 generates an AM signal converted to an AOM 2 into an ultrasonic wave, which, at intervals of time equal to its travel time the input end of the AOM 2 to the intersection of the incident reference light beam and the retroreflector 4 of the reference light beam reflected causes diffraction of these rays. - The diffracted rays generate signals at the outputs of photodetectors 3 and 5 at the frequency of the AM signal envelope generator 6, delayed in time. This time delay is proportional to the linear offset from the end of the AOM 2 of the incident reference light and the reflected reference light. A time delay leads to the appearance of a phase shift. The signal from the photodetector 3 is transmitted to the second input of the phase meter 8 and to one of the inputs of the phase meter

9, to another input of which a signal is fed from the photodetector 5. Thus, the phase meter 8 measures the end displacement. AOM 2 relative to the incident beam, which can be determined by the formula

XM3M. V -Q; (1)

where (p - readings of phase meter 8;

V is the velocity of ultrasonic waves in AOMZ;

Q is the frequency generator of the reference signal.

A phase meter 9 measures the distance between the incident and reflected light rays, which can be calculated using the formula

A. (2),

The starting point for measuring displacements is the optical axis passing through the center of radiation of the source of light 1 and the top of triplander prism 4. The angle a of the deflection of the direction of the reference beam from the optical axis can be calculated by the formula D

(3)

a-2Z

where Z is the distance between light source 1 and retro-reflector 4.

Object displacement hist. relative to the optical axis for any fluctuations and is

Heath. Hiz.-a1: (4)

where I is the distance from light source 1 to

AOM 2.

Substituting (1) - (3) into (4), we finally get

Heath. -Q (). (5)

Thus, the proposed device allows, in contrast to the known, to obtain an exact offset value, from which an error due to fluctuations in the direction of the reference light beam is excluded. ,

Calculations using formula (5) can be done manually by the operator or on a mini-computer in automatic mode. In this case, the computer can be connected to the outputs of phase meters 8 and 9.

An additional advantage of the proposed device is the ability to control the displacements of two objects simultaneously. At the same time on one of them

An AOM 2 must be installed, and a retro-reflector 4 on another.

Claims (1)

Claims An apparatus for measuring displacements containing optically coupled sources of a reference light beam acoustooptical modulator, retroreflector and first photodetector, carrier frequency generator, the output of which is connected to the input of an acousto-optic modulator, reference frequency generator, the output of which is connected to the modulation input of the carrier frequency generator, and the first phase meter, whose inputs are connected to the outputs of the photoreceiver and reference frequency generator accordingly, with the fact that, in order to increase accuracy, it is equipped with a second a photodetector and a second phase meter, the inputs of which are connected to the outputs of the first and Btoporo photodetectors, respectively, while the acousto-optic modulator is installed to interact with the beam reflected from the retroreflector, and the second photodetector is installed along the beam reflected from the retro-reflector beam reflected from the retroreflector.