SU408145A1 - DESCRIPTION OF THE INVENTION - Google Patents

Description

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The invention relates to the field of measurement technology, in particular, to methods for constructing photoelectric interferometers, designed to measure the magnitude of the linear and angular displacements of moving bodies of precision metal cutting machines, measuring instruments and machines, systems and devices for automatic control.

An interference method for measuring the magnitude of linear and angular displacements is known, in which monochromatic radiation transforms an optoacoustic node into two KoreipeHTHbix monochromatic streams, connects an optical node with the object being measured, and checks the results of the flux interference.

However, the measurement accuracy of the known methods is insufficient due to the instability of the ratio of the channel parameters.

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

To do this, the monochromatic radiation is directed to the ultrasonic mode module, one of the streams after the light modulator is directed to the photo receiver, and the other through the semi-transparent mirror to the reflecting element and the photodetector.

Thus, in the proposed method, one single frequency stabilized laser is used. This makes it possible to obtain an initial optical frequency with maximum attainable stability. The formation of interfering nooses with different optical frequencies is accomplished by diffraction of laser radiation on an acousto-optical modulator located outside the laser resonator. An acoustic-optical modulator is an optically transparent body, for example, from a photoelastic crystal (fused silica, niobate line, and others), in which a traveling ultrasonic wave is excited. As a result of ultrasonic light diffraction, diffracted light beams appear at the output of an acousto-optic modulator — orders of the diffraction spectrum, whose optical frequencies differ from the frequency of a direct non-diffracted beam by an amount multiple of the ultrasonic frequency.

the waves. .

FIG. Figure 1 is a diagram explaining the diffraction of light by ultrasound; in fig. 2-- single-channel scheme for the implementation of an interference method for measuring the magnitude of displacements; in fig. 3 - the same two-channel scheme.

The essence of the proposed method is the following.

When illuminated by traveling ultrasonic

Volpa propagating in an elastic transparent medium parallel to a beam of monochromatic light flux, a diffraction phenomenon appears, schematically represented in FIG. 1. Light wave 0 - amplitude, v - frequency, in the form of a parallel beam 1 of the aperture L illuminates a traveling harmonic ultrasonic wave 2 with frequency 1, propagating in an optically transparent elastic medium along the Y axis. As a result of phase modulation of the light wave on indicator variations refraction of the medium (caused by elastic wave 2, several parallel light beams occur at the exit 43 of it, propagating at different angles to the original direction of the light (X axis). These beams are orders of the spectrum of the | If the intensity of the ultrasonic wave is small enough, it can be limited to zero plus or minus first orders. The zero order preserves the original direction of beam 1, beams plus first and minus first orders are angled at one angle, XX Pg + Y -1 - T is to the X axis, respectively, where I is the light wavelength, L is the ultrasonic wavelength. One of the diffraction orders is used as a signal beam (interferomer), the optical path is changed in accordance with the controlled movement: goy - as a reference beam, the optical path length of which is non-dimensional. As interfering, it is possible to use “rat-any n-beam of diffractional beams (c & kr .. At the same time, you should take a signal with a“ most intensive ”signal, i.e., zero order. In Fig. 2 and Fig. 3 shows the various Earnaats of the method. Fig. 2 IlD1Oct; It is a single-channel version of the way in which interferes with a zero and - 1 - order handle. Light source - a stabilized laser 1 illuminates a forging modulator in which traveling ultrasound a wave of excitement is expected in modulator 2 by a neutral emitter 3 from the electronic generator 4 and is absorbed by the absorber 5. If the illuminating -thun 6 is tilted to the front of the ultrasonic wave, at an angle fy-AND VYPOL2 ln bts condition 1 - then due to the same and -Gov diffraction of light by ultrasound and the diffraction spectrum of only zero nucy plus plus first wave solids.The zero order, being the signal beam 7, passes through the semi-transparent mirror 8 and is directed to the movable reflector 9 moving in the course of the measurement. Having reflected from the reflector 9, the signal beam 7 returns back after reflection from the mirror 8, falls on the receiving surface of the photodetector 10. Plus the first diffraction order, which is the reference beam 11, on the surface of the photodetector 10 interferes with the signal one. The signal from the photodetector 10 is fed to the input of the amplifier 12. The phase of the signal, proportional to the movement of the movable mirror 9, is measured, and the number of phase cycles corresponding to a phase change of 180 ° is measured using known phase-matching methods. The reference electrical signal when measuring the phase of the signal can be a signal from the output of the generator 4 ultrasonic vibrations. For the case when the ultrasound light diffraction spectrum is symmetric, there are both positive and negative diffraction orders, a two-channel scheme of the method is realized (Fig. 3). Such a case occurs when Raman diffraction of light by ultrasound, when the illuminating beam is directed strictly normal to the direction of the traveling ultrasonic wave, and FIG. 3 positions 1 to 12 completely repeat the elements shown in FIG. 2. As in the previous case, the signal beam 7 is a zero order beam, which is separated on a translucent mirror 8. A part of the beam 7, passing through mirror 8, is directed to a movable mirror 9 and, reflected from it, and then from mirrors 8, falls on the photodetector 10, where it interferes with the beam plus the first order of diffraction. The latter is the reference beam 11 and its interference with the signal beam 7 allows the measurement signal to be extracted in the manner described above. The presence of the first-order minus in the diffraction spectrum, whose optical frequency is (v - /), i.e. also shifted by the ultrasonic frequency, makes it possible to obtain a reference signal also by photoelectric. This is achieved by the fact that a part of the zero-order beam reflected from the translucent mirror 8 interferes with the minus first diffraction order — the beam 13 at the photodetector 14. Since the difference of the optical frequencies of the interfering beams is equal to /, the output of the selective amplifier 15 tuned to this frequency is allocated a reference harmonic signal. Measurement of the phase of the signal proportional to the displacement is carried out by phase metering methods by equating it with the reference signal.

Subject invention

Interference method for measuring linear linear angular displacements, which implies that monochromatic radiation is converted by an opto-acoustic node into coherent monochromatic streams of various frequencies, one of which is directed to a moving reflective element of an optical node that is connected to a moving object, and according to H1 IIO The phases of the ciphers identified in the zero of interference of coherent flows are judged on the measurement results, characterized in that, for the purpose of new measurement accuracy, chromatic radiation is directed to the ultrasonic svetomodul torus one monolayer svetomodul torus flow - on the photoreceiver nick and the other through a semitransparent mirror - on element otrazhayuoschy n fotopr1 smnik.

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