SU1221502A1 - Laser vibration meter - Google Patents

Description

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The invention relates to measurement technology and can be used to measure the amplitude and hour TtjTbi of a diffusely reflecting vibration surface.

The object of the invention is to improve noise immunity.

The drawing shows a block diagram of a laser vibration meter.

The laser vibration meter contains a laser 1 5 which emits a linearly polarized beam 2, a beam splitter 3 s, during which beam 2 is converted into beam 4s by a polarization rotator 5, a high-frequency generator 6, one of the outputs of which is connected to the polarizer 5 input of a polar plane shade, quarter-wave plate 7. mirror 8, set at 45 ° to beam 4, frequency shift element 9, second mirror 10 with two openings, located at 45 ° angle to beams 2 and 4, lens G, directing rays 2 and 4 to measurement object 12 with diffuser scatter light surface of the second lens 13j photodetector 14, bandpass filters 15, 16, mixer 17 frequency discriminators 18; 19, differential amplifier 20, frequency detector 210 peak detector 22e amplifiers 23 and 24. voltage ratio meter 25; digital voltmeter 2-6 and purely tomer 27,

The meter works as follows.

Laser 1 emits a linearly polarized beam 2 with a frequency Q,., Which the beam splitter 3 converts into beam 4. Beam 2- enters the input of the polarizer 5 of the polarization plane, which is sparse, for example, 5 of successively installed quarter-wave plate and electro-optical a crystal (not shown) s placed in a rotating electric field. A rotating electric field is created by applying to two pairs of mutually orthogonal plates (not shown) arranged symmetrically with respect to the axis of the third order of the voltage crystal corresponding to a quarter-wave delay in quadrature at a frequency of, for example, 3 o from one output of the generator 6. At the output the rotator 5 of the polarization plane is installed a quarter-wave plate 7 a conversion beam 2 S two mutually orthogonal: linearly polarized

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a beam with different frequencies from, and co + - - Z), with Beam 4, reflected from mirror 8, is directed to the input of frequency element 9, which consists, for example, of a series-mounted quarter-wave plate to a rotating half-wave plate. If an electro-optical crystal with a third-order symmetry axis, oriented in the direction of propagation of beam 4, is placed in a rotating electric field corresponding to a half-wave lag, a rotating plate is formed. Moreover, the rotating electric field is created by applying two pairs of mutually orthogonal electrodes sprayed on the face of a cristags. Dvzgh voltage in quadrature at a frequency j for example, co. from another output of the generator 6. At the output of the frequency shift element 9, a beam is formed, which has a circular polarization state and the frequency MO + MI providing a frequency shift of the value of, and the Bragg's acousto-optical frequency shifting at its output a quarter-wave plate, designed to produce a beam with a polarization polarization. Then parallel rays 2 and 4, having passed through holes in the mirror 10, are focused by a 1f lens in a local area of a diffusely scattering object 12 along the axis, Erpandi1: the optical optical OHSD of the lens according to the harmonic law A Af sinfotc A swarm of 13 on the photo is taken. 14. As a result of the optical heterodyning at the output of the photocurrent 14, a variable component of the photocurrent e is formed representing the add}: eny mixture of two equal amplitudes of signals, j .Everything is different stot,

0), - GJg (.ShSh, &) .; о о,): 2 a, - W; i

(or 2 cOj -; - WB). 3 TV. Digital: -: - r, are bandpass filters, one of which 15 is tuned to the frequency CO, and the other 16 is set to 2 co, (and, v “), the signal from the code of the bandpass filter 15 is at the first inlet is 17

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the second input of which is supplied with a signal having the frequency W,, from the output of the generator 6. At the output of the mixer 17, a signal with the frequency CO, - WQ, is extracted. The signals from the output of the mixer 17 and bandpass filter 16 are fed to the inputs of frequency discriminators 18, 19 and further to differential amplifier 20, where the signal doubles while reducing laser noise, since the useful signals at the output of frequency discriminators 18 and 19 have the same amplitude and frequency, but are in antiphase. The signal from the output of the differential amplifier 20 is fed to the input of the frequency detector 21 with amplifier 23 at the output of which the signal is propagated to the oscillation frequency of the object 12 and to the input of the peak detector 22 with the amplifier 24. At the output of the latter, the signal is proportional to the amplitude and frequency of vibration of the object 12. Next The signals from the amplifiers are fed to the voltage ratio meter 25, the output of which produces a signal proportional to the amplitude of the object 12, recorded by a digital voltmeter 26. The signal at the output is differential cial amplifier 20 has a frequency equal to the vibration frequency Q, which is measured by a digital frequency counter 27.

Claims (3)

Formula invented ., 1. A laser vibration meter containing a laser, a polarizer plane rotator, a quarter-wave plate and a photodetector, a generator, a generator, one of the outputs connected to the polarizer plane input, a frequency meter, a voltage ratio meter, a voltmeter . . Compiled by V. Lopukhin Editor M. Kelemesh Tehred O. Gortvay Corrector A. Ferenc Order 1603/47 Circulation 507 VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Branch PPP Patent 5 Uggorod, st. Project, 4 0 1S02 connected to its output, a differential amplifier {amplifier, two frequency discriminators, outputs connected to the corresponding inputs of a differential amplifier S whose output is connected to a voltage ratio meter through frequency-related and peak detectors and corresponding whether amplified, connected to their outputs, about the t and h and with the fact that, with the purpose of povpen and noise immunity, it is equipped with a beam splitter installed between the laser and the rotator 5 polarization planes forming a beam, successively installed along the second beam by a mirror and a frequency shift element, a second mirror with two openings for passing the laser and second beams, a lens installed after the second mirror, a second lens installed along the path the second mirror of the rays and in front of the photodetector, 5 mixers and two field filters, inputs connected to the photo receiver and outputs to the inputs of frequency discriminators, one through the mixer, the other directly, and the other generator output connected to the second input of the mixer and the frequency shift element. 2. The meter according to claim 1, wherein the frequency shift element is designed as a series-installed quarter-wave plate and an electro-optical crystal placed in a rotating half-wave electric field. 3. The meter according to claim 1, wherein the frequency shift element is implemented in the form of a Bragg cell and a quarter-wave plate. 0 five  P single entry