SU624157A1 - Method of determining velocity of propagation of surface acoustic waves - Google Patents

Description

one

This invention relates to the field of ultrasound measurements.

There is a known method for determining the speed of surface waves, which includes the measurement of acoustic 1 probe electrostatically connected with the surface under study, the amplitude of the surface wave.

The disadvantage of this method is the low measurement accuracy since the acoustic probe introduces a disturbance into the test medium.

The closest technical solution to the invention is a method based on the diffraction of a coherent light beam on surface waves, which consists in that the sample excites surface acoustic waves and illuminates the surface of the sample at some angle with a coherent light beam. The light beam diffracts on the phase diffraction grating, which is formed as a result of the deformation of the surface and a change in the refractive index of the medium. Measuring the angular dependence of the diffraction of light on surface waves, determine the speed of wave propagation ...

2

The disadvantage of this method is the difficulty of accurately measuring the angles of incidence and diffraction and, therefore, low accuracy in determining the surface wave velocity.

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

This is achieved by the fact that the proposed method simultaneously excites in the second sample, the material of which is identical to the first, surface acoustic waves, whose frequency is different from the excitation frequency of the waves in the first sample, illuminate the surface of the SECOND sample with a coherent light beam, reflecting rays on both samples, and a beat signal is recorded, and the speed of propagation of the surface wave is calculated by the formula

V

Sithk -kjh

Claims (1)

 where e2 is the beating signal; K-IR, wave numbers-, t measurements. The drawing shows the implementation of the proposed method. 3 6 The scheme contains a source of light 1, samples 2 and 3, a receiver 4 of light radiation, an optical system of 5p. Surface waves with a frequency f and i2 respectively are excited to and repetitively, and these frequencies are synchronized. Surfaces over which they are propagated from a wave are illuminated by coherent light beams. The light rays are diffracted by the phase diffraction grating formed by the surface wave. Optical diffraction beams are combined with an optical system and fed to a light source that detects a beating signal. The variable component of the photocurrent, which carries information) about the speed of propagation of the surface wave, is calculated by the formula, n (-in-5ir (. Where K and Kg are wave numbers; V is the speed of propagation of the wave. Thus, due to the absence Angular Measurements Accuracy of Speed Measurement. 74 Claim Method The method for determining the speed of propagation of surface acoustic waves in a material is that the sample excites surface acoustic waves and illuminates the surface of the sample with a coherent light beam. m and register a diffraction pattern, the parameters of which are judged on the speed of the waves, characterized in that, in order to improve the measurement accuracy, the second sample, the material of which is identical to the first, is simultaneously excited, surface acoustic waves, whose frequency is different from the frequency of excitation of the waves in the first sample, illuminate the surface of the second sample with a coherent light beam, combine the rays diffracting on both samples, and record the beating signal, and the velocity of the surface wave is calculated as about the formula. v-where sin (K,, 0 beating signal wave numbers t is the Measurement time.