SU1374103A1 - Optical method of determining ultrasound wave velocity - Google Patents

Abstract

The invention relates to a measurement technique and can be used to determine the speed of a sound wave in transparent media. The purpose of the invention — an increase in the accuracy of measuring the velocity of an ultrasonic wave in optically transparent media — is achieved by measuring the intensity of a diffracted light beam in a given direction. The accuracy of the sum of the light intensity in a given direction is greater than the accuracy of measuring the angle corresponding to a given light intensity. In the optically transparent medium 2, a traveling ultrasonic wave is excited by the ultrasound exciter 3 and the sound absorber 4. The light wave of laser 1 is directed to the sound beam, and the magnitude of the first diffraction component is measured using a light intensity meter. By varying the frequency of the ultrasonic vibrations with the aid of the generator 6, two maximum values of the diffraction component are achieved. The frequencies corresponding to these values are fixed. 1 Il. from the next

Description

with

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The invention relates to a measurement technique and can be used to determine the speed of a sound wave in transparent media.

The purpose of the invention is to improve the accuracy of measuring the speed of an ultrasonic wave in optically transparent media by measuring the intensity of a diffracted light beam in a given direction.

The drawing shows a device for carrying out the proposed method.

The device consists of a laser 1, whose light passes through a medium 2, in which it is required to determine the speed of sound, the exciter 3 sound vibrations, the sound absorber 4, the light intensity meter 5 and the tunable ultrasonic oscillator 6.

The device works as follows.

To realize the Raman Nath diffraction, it is necessary to ensure the normal incidence of light on the sound beam.

In the optically transparent medium 2, excitation of the traveling ultrasonic wave is induced by the exciter 3 and the sound absorber 4. The light wave of laser 1 is directed to the sound beam, and using the light intensity meter 5, the value of the first diffraction component is measured. At the same time, the frequency of the sound vibrations is changed, to achieve two maximum values of the diffraction component at frequencies f,

and

2.5 then calculate

the speed of sound is as follows.

The ratio of the intensity of the first L / and zero IP diffraction components is determined by the expression

K and K are the wave vectors of light and

sound respectively-, q 01-03.

As follows from the expression (1), the ratio 1, / is a periodic function of a number of parameters, including the frequency of the sound wave.

If fd and f01 are the frequencies of ultrasonic vibrations at which the ratio (1) takes the maximum values:

K 01 ij 4K

G / 2 and 1 3 / F / 2,

that of equality

iT L (f 01 - f 01). -G

can determine the speed of the medium:

and

TO

50

five

Claims (1)

Invention Formula An optical method for determining the speed of an ultrasonic wave, consisting in choosing the angle of interaction, ultrasound frequency and interaction length in such a way as to ensure Raman-Nata diffraction, in that, in order to improve the measurement accuracy, the intensity of the first diffraction component is measured , change the frequency of the ultrasonic vibrations, determine the values of the frequencies at which the intensity of the component twice reaches its maximum values with a change in the frequency of the sound, and then calculate the speed of sound in the environment.