SU1280335A1 - Device for measuring acoustic vibrations - Google Patents

Abstract

This invention relates to a measurement technique. The aim of the invention is to increase the accuracy and expand the measurement range by obtaining complete information about the vector of acoustic oscillations. The device contains an acoustic wave receiving membrane and a three-sided pyramid, the mirror faces of which are normal to the optical axis of interferometers 2-4, optically coupled to the acoustic transducer 1. Interference patterns change as the membrane oscillates, changes are recorded by photodetectors 5-7. The electrical signal at the output of each measuring circuit is proportional to the amplitude of oscillations in the direction corresponding to the optical axis of the laser interferometer. Information about the phase difference of oscillations between the measuring circuits is obtained using phase meters 14 and 15. According to the data obtained in the calculator 16 (L, the acoustic wave vector is constructed. 2 or tc 00 o 00

Description

The invention relates to measurement technology and can be used to measure acoustic waves in objects of control in mechanical engineering, defectometry, applied acoustics.

The aim of the invention is to improve the accuracy and expand the measurement range by obtaining complete information about the vector of acoustic oscillations.

Fig. 1 shows a functional diagram of the device for measuring acoustic oscillations in Fig. 2 — an acoustic transducer and an arrangement of the acoustic axes of laser interferometers.

The device consists of an acoustic transducer 1, three measuring circuits from series-connected laser interferometers 2-4 optically coupled to an acoustic transducer 1, photodetectors 5-7, broadband amplifiers and filters 11-13, phase meters 14 and 15, and a calculator 16, with the outputs filters 11-13 and phase meters 14 and 15 are connected to inputs of calculator 16, and inputs of phase meters 14 and 15 are connected respectively to the outputs of filters 11, 13 and 11, 12.

Acoustic transducer 1 consists of a receiving membrane 17 and a three-sided pyramid 18, the mirror-reflecting faces of which are normal to the optical axis X, Y, Z of interferometers 2-4, and the optical axes X, Y, Z are normally located relative to each other and at the point of their intersection on the receiving membrane 17 a three-sided pyramid 18 is installed (FIG. 2).

The device works as follows.

When the acoustic wave falls on the surface of the receiving membrane 17, the membrane 17 and the triangular pyramid 18 oscillate. To improve the matching with the medium, the membrane is made in the form of a thin colloidal film. When the pyramid moves along any of the axes, the interference pattern changes, which is recorded by the photodetectors 5-7. The signal from the photodetectors is amplified by wideband amplifiers 8-10 and fed to the inputs

filters 11-13, tuned to the frequency of the acoustic wave.

The electrical signal from each filter is proportional to the amplitude of the oscillations in the direction corresponding to the optical axis of the laser interferometer. Information about the phase difference of the oscillations, for example q, - Cfj. and Cp -F, -tfs between channels are obtained using phase meters 14 and 15, installed between the outputs of the three filters. The information about the phase and amplitude of the projection of the acoustic wave vector is used in the calculator 16 to calculate the modules I o j, I, / QZ / amplitudes of the acoustic wave along the X, Y, Z axes, which are used to construct vectors

15

about x, /) ay bu / oy / cosqiij, oh g.j / az / co5Cf ,, j,

where g

X,

y

 - unit vectors in the direction of the axes X, Y, Z;

Then the acoustic wave vector is constructed in the calculator. For example, if the optical axes of laser interferometers are mutually orthogonal, then the magnitude of this vector is

thirty

/ a / l

 ,

and the direction cosines of the angles to the axes X, Y, Z are respectively equal to

C05 8x

but.

coe Q.

but-.

cos wc

ai

Ta

fQ + a

toy + a

Claims (1)

The invention relates to a measurement technique and can be used to measure acoustic waves in objects of control in mechanical engineering, defectometry, applied acoustics. The aim of the invention is to improve the accuracy and expand the range of measurements by obtaining full information about the acoustic vector. Figure 1 shows the functional design of the device for measuring acoustic oscillations in Figure 2, the acoustic transducer and the acoustic axis arrangements of laser interferometers. The device consists of an acoustic transducer 1, three measuring circuits from successively connected laser interferometers 2–4, optically coupled to the acoustic transducer 1, photodetectors 5–7, broadband amplifiers and filters 11–13, phase meters 14 and 15, and a computer 16, with the outputs of the filters 11-13 and phase meters 14 and 15 connected to the inputs of the calculator 16, and the inputs of the phase meters 14 and 15 respectively connected to the outputs of the filters 11, 13 and 11, 12. The acoustic transducer 1 consists of a receiving membrane 17 and a three-sided pyramids 18 mirrors But the reflecting faces of which are normal to the optical axis X, Y, Z of interferometers 2-4, the optical axes X, Y, Z being normally located relative to each other and at the intersection point on the receiving membrane 1 a three-sided pyramid 18 is installed (Fig. 2) . The device works as follows. When an acoustic wave falls on the surface of the receiving membrane 17, the membrane 17 and the triangular pyramid 18 oscillate. To improve the matching with the medium, the membrane is made in the form of a thin colloidal film. When moving the pyramid n any of the axes, the interference pattern changes, which is recorded by the photodetectors 5-7. The signal from the photodetectors is amplified by wideband amplifiers 8-10 and fed to the inputs of filters 11-13 tuned to the frequency of the acoustic wave. The electrical signal from each filter is proportional to the amplitude of the oscillations in the direction corresponding to the optical axis of the laser interferometer. Information about the phase difference of the oscillations, for example, q, -Cfj and Cp -CH, -tfs between channels, is obtained using phase meters 14 and 15, installed between the outputs of the three filters. The information on the phase and amplitude of the projection of the acoustic wave vector is used in the calculator 16 to calculate the modules I o j, I, / QZ / amplitudes of the acoustic wave along the x, y, z axes, which are used to build the x, y) cosqiij, og .j / az / co5Cf ,, j, where,. g - unit vectors in the direction of the axes X, Y, Z; Then the acoustic wave vector is constructed in the calculator. For example, if the optical axes of laser interferometers are mutually orthogonal, then the magnitude of this vector is equal to / a / l, and the direction cosines of the angles to the axes X, Y, Z are respectively cos Bc fQ + a a-. , toy + a Formula of the Invention A device for measuring acoustic oscillations, comprising a receiving membrane and a measuring circuit including a laser interferometer optically coupled to the membrane, and a photodetector mounted at the output of the interferometer, a wide-pole amplifier and a filter, characterized in that in order to increase the accuracy and expansion of the measurement range, it is equipped with two additional identical measuring circuits, two phase meters, a calculator and a three-sided pyramid, a mirror of reflecting faces which are normal to the axes of the optical interferometers, the measuring filter circuits outputs coupled to input and calculator phase meters, exits phase meters are coupled to inputs of the calculator, the optical axis interferometers arranged normally relative each other, and the triangular pyramid is installed at the point of their intersection on the receiving membrane and forms an acoustic transducer with the receiving membrane. Acoustache Direction HOpfiQ u n pl. / iefiffpa tji g Figure 2