SU1388731A1 - Sonic detector - Google Patents

Abstract

The invention relates to acoustic engineering and can be used to detect and record acoustic wave parameters. The purpose of the invention, an increase in accuracy, is achieved by reducing the level of interference by narrowing the receiving acoustic antenna pattern. When a plane acoustic wave is incident on the surface of membranes 1 and 7, oscillations are excited in them with a phase shift determined by the angle ei of the wave incidence. The signal from laser interferometer 2 (membrane 1 is mechanically connected to one of the interferometer mirrors) enters the positive feedback circuit of the second receiver (formed by membrane 7 and additional interferometer 8), which records the signal, which allows narrowing the effective radiation pattern of the device. 2 Il. (L 00 OO 00: o Outgoing signal

Description

// t /

1

The invention relates to acoustic engineering and can be used to detect and record acoustic wave parameters.

The purpose of the invention, an increase in accuracy, is achieved by reducing the interference level by narrowing the receiving acoustic antenna pattern.

FIG. 1 shows a block diagram of an acoustic receiver; FIG. 2 shows the characteristic characteristics of the device.

Acoustic receiver contains a modified receiving membrane 1, laser interferometer 2, photodetector 3, amplifier 4, frequency doubler 5, piezoceramic rod 6, additional membrane 7, additional laser: interferometer 8, additional photo receiver 9 and additional amplifier 10.

The device works as follows. When a plane acoustic wave is incident on the surface of the receiving membranes 1 and 7, they begin to oscillate with a phase shift if, the value of which is determined by the angle

wavelength and distance d by membrane centers:

between

2 ir

fd-sinci

V.

(one)

36

Where

star

(f is the frequency of the acoustic wave;

- the wave propagation velocity in the phase. Oscillations of the membrane 1 lead to a change in the intensity of the optical beam at the output of the laser interferometer 2, which is recorded using a photodetector 3 connected to the amplifier 4. From the signal of the amplifier 4, the signal is sent to the frequency doubler 5. The doubled voltage is applied to the metallized plates of the piezoceramic rod 6, which carries out the in-phase alternating tension of the membranes 1 and 7. Due to the alternating tension with the doubled frequency, the oscillation energy in the feedback circuit is converted into transverse oscillations of the membrane 1 with the frequency and the phase of the incoming acoustic wave.

.-

The amplification factor of the oscillations of the membrane 7 is determined by the phase shift between the transverse oscillations excited by the feedback circuit and the acoustic wave. The resulting vibrations of the membrane 7 are recorded using a laser interferometer 8, the optical signal on the code of which is converted into an electrical one by means of a photodetector 9 and amplified by an amplifier 10. The output direction of the device is defined as

Ub .. l.

2k „cos

xZirdf sino6.

V

5B

-t (a

+ k.

(2)

where k

- feedback loop transfer ratio. The scaling characteristic Ug, j ((6) of the device (Fig. 2) is determined by the positive feedback coefficient k, and the width (by angle) is determined by the instability of the device. Fig. 2 shows Ug, (i) for three values kq О (curve 1); 0.7 (curve 2), 095 (curve 3).

five

0 j.

0

five

Claims (1)

Invention Formula Acoustic receiver containing optically coupled acousto-optic sensor, laser interferometer and photodetector,. An amplifier connected to the input, characterized in that, in order to improve accuracy, it is equipped with a frequency doubler, an additional laser interferometer, a photo-receiver and an amplifier, the acousto-optical sensor being made in the form of two membranes arranged in one plane, the optical axes of the interferometers are perpendicular to this plane and a piezoceramic rod, at the ends of which one of the edges of the membranes are fixed, the other edges of which are rigidly fixed, the output of the amplifier is connected to the piezoceramic rod through a frequency doubler it, one of the membranes is optically coupled to a laser interferometer, and further additional photodetector, connected to the input of an additional amplifier, another membrane optically coupled to a laser interferometer. 15 Yu mm lg 50 510 W 15 20 about Ф14г, 2