SU1413422A1 - Acoustooptical displacement-measuring device - Google Patents

Abstract

The invention relates to optoelectronics and can be used to measure linear displacement of the scales relative to the light beam. The purpose of the invention is to expand the field of use by measuring the coordinate of the point of incidence of the light beam relative to a given scale by using and modulating a surface acoustic wave (SAW). In the acoustic duct 3, a surfactant is excited, modulated by harmonic oscillations of frequency K. As a result of passing through the diffraction grating 2 and interacting with the traveling surfactant, the light beam generated by the source of optical radiation 1 acquires spatial modulation. Using a photodetector 9 and detector 11, a signal is selected with a phase that depends on the position of the light beam relative to a predetermined point of the sound duct 3. Phase meter 13 compares it with the phase of the modulation signal and performs the registration of the positional offset of the light beam. 1 il. Ф С /)

Description

{1GGL11

with k

 YU

one

The invention relates to optoelectronics and can be used to measure linear displacement of a scale relative to a light beam.

The purpose of the invention is to expand the use of measuring the coordinate of the point of incidence of the light beam relative to a given scale, using the modulation of the surface acoustic wave.

The drawing shows a block diagram of the device.

The device contains an optical radiation source 1, a diffraction grating 2, an optical conductor 3, a surface acoustic wave (SAW) exciter 4, a carrier frequency F electrical oscillator 5, a frequency harmonic oscillator 6 F, a modulator 7, a spatial filter 8 serving to highlight the zero order of the diffracted radiation, the photodetector 9, the amplifier 10 oscillation frequency F / |, the detector 1 filter 12 frequency F, the phase meter 13,

The device works as follows.

A surface acoustic wave exciter 4 from modulator 7 is supplied with an amplitude-modulated signal at carrier frequency T with modulation frequency F. As a result of passing through diffraction grating 2 and interacting with a traveling surface acoustic wave, the light beam generated by the optical radiation source 1 receives spatial phase modulation from both the phase grating and the traveling acoustic wave. The zero diffraction order is extracted by the spatial filter 8 and focused on the photodetector 9. The variable component of the optical radiation intensity at the frequency F in the zero diffraction order is modulated in amplitude with the modulation frequency F. From the output of the photodetector 9, the amplitude-modulated signal is fed to the amplifier 10 , an amplitude modulated signal detector 11 and a Lilter 12 for extracting a signal at a frequency F., Phasol

The meter 13 serves to measure the phase difference of the signals at frequency F, from the output of the filter 12 and the reference signal from the 6 harmonic oscillations of the frequency Fyv.

The initial phase of the output signal from the filter F depends on the position of the point of incidence of the optical beam on the acoustic duct 3 with respect to the causative agent of the acoustic wave.

When changing the position of the point of incidence of the optical beam on the junction of scales by the value of x in the direction of propagation of the acoustic wave, the phase of the output signal changes by 2.1

  - 4, where

L ff-- spatial period of the amplitude-modulated acoustic wave envelope.

Based on the indications of the phase meter 13, it is possible to determine the magnitude of the displacement of the optical beam relative to the initial state or the magnitude of the displacement of the conjugation of the scales relative to the fixed optical beam by recalculating

x 5 0

g

five

0

The phase meter can be calibrated directly in units of displacement.

Materials for the manufacture of a sound core may be lithium niobate, lithium tantalate or crystalline quartz. The causative agent of a surface acoustic wave can be of an interdigital type. The diffraction grating is made on a plate of fused quartz 810-2 by etching on its surface a relief in

A v

form of a meander with a period- / -, where

 And V is the surfactant velocity in the sound duct material. Optimum relief depth on a substrate of fused quartz with a refractive index, 46, using a laser with an A-wavelength of 0.6328 µm NTDT

A helium-neon laser with a radiation power of 5–15 mW can be used as an optical radiation source.

The distance between the diffraction grating and the sound duct is chosen

of condition or I. ---.

L d

The device can be used high-frequency p-i-p-photoliod with a resonant LC circuit in the load

t h h

 . 1 with gain

“Amplifier / -50 dB.

For measuring the phase difference of two signals, the phase meter F 5126 can be used with an accuracy of measuring a phase difference of 0.3 ° and a resolution of 0.1.

Claims (1)

Invention Formula Acousto-optic device for measuring displacements containing optically coupled source of optical radiation, diffraction grating, sound conduit kinematically associated with the object of measurement, space filter from the diaphragm and lens, the generator GD, the causative agent of the surface acoustic wave, input which is connected to the output of the generator of electrical oscillations of the carrier frequency, and the output is connected to the suction duct, the amplifier of the oscillation frequency F, whose input connected to a photodetector, and a phase meter, characterized in that, in order to broaden the field of use by measuring the coordinate of the point of incidence of the light beam, it is equipped with a harmonic oscillator of the frequency Rd, modulator, detector and frequency filter F, the diffraction grating and the acoustic conductor The output of the frequency oscillating amplifier F is connected to the input of the detector, whose output is through the frequency filter Gd, connected to the first input of the phase meter 5, the second input of which is connected to the output of the harmonic generator frigged frequency F, which is also connected to the first input of the modulator, a second input of the modulator connected to the output of the generator electrical fluctuations of the carrier frequency, the modulator output is connected to a surface acoustic wave exciter.