SU1260682A1 - Device for measuring fractional part of interference band - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure displacements. deformations and vibrations. The increase in measurement accuracy is achieved due to the fact that each channel is equipped with a series-connected rectifier, whose input is connected to the amplifier output, and an analog-to-digital converter, and the device is equipped with a dividing unit, whose information inputs are connected to the outputs of the analog-to-digital converters, and trigonometric functions and three two-input elements EXTRACT. OR. The effect of changes in the intensity of the radiation and the effect of interference is reduced due to the use of division of the input signals, followed by the calculation of the inverse trigonometric functions. 1 il.

Description

The invention relates to a measurement technique and can be used to measure displacements, deformations and vibrations.

The purpose of the invention is to increase the measurement accuracy by increasing the number of sampling pulses and by increasing the stability with a change in the radiation intensity and the effect of interference.

The drawing shows a block diagram of an apparatus for measuring the fractional part of an interference fringe.

The device contains two channels, each of which consists of successively connected photodetectors 1; 1, 1.2, amplifier 2.1, 2.2, and a former 3.1, 3.2, a rectifier 4.1, 4.2, and an analog-to-digital converter 5.1, 5.2, a summation and a subtractor unit 6, the inputs of which are connected to the outputs of the amplifiers, 2.1 and 2.2

first 7 and second 8 signal conditioning units, combinational logic circuit 9, reversible counter 10 connected at the output of circuit 9, first 11, second 12 and third 13 elements EXCLUSIVE OR, division block 14, whose information inputs are connected to the outputs of analog-to-digital converters 5.1 and 5.2, and block 15 for calculating inverse trigonometric functions, the information input of which is connected to the output of division block 14, and the control input to the output of the third element 13, FATHER OR.

The device works as follows.

The photodetectors 1 are located at such points in the interference pattern that their output signals are phase-shifted by ir / 2. The amplified signals in amplifiers 2 are converted by the formers of the 3 channels into square pulses. The summation and subtraction unit 6 generates the sum and difference signals, which are converted by the first 7 and second 8 formation units into square pulses, which are fed to the inputs of the combinational logic circuit 9, which generates eight reference pulses in one period of the signal from the photodetectors. the pulses are fed to the summing or subtracting inputs of the reversible counter 10, containing 26682 g

my A is equal to the whole part of the interference band.

At the same time, signals from photo detectors 1 through rectifiers 4 are fed to the inputs of analog-to-digital converters 5. By dividing the digital codes of the input signal modules in dividing unit 14, the tangent or cotangent is determined from the current phase

 About input signal. The control of dividing unit 14 is carried out in such a way that it always divides a smaller number into a larger one in order to eliminate overflow of the 5-bit grid of the block. The control signal of dividing unit 14 is generated by the first element EXCLUSIVE OR 11. The digital code of the private from the block 14 division enters the information

The 20th input of arctg and arcctg inverse trigonometric functions calculation unit 15, at the output of which a digital code of the current phase of photodetector signals T is formed, equal to the fraction of the 25th part of the interference band B. happened in two

30 times more often than the change of the dividend by the divisor or vice versa in block 14 of the division, which is necessary so that the current phase of the signals grows in the intervals between the reference

35 pulses of the integer part of the interference band. When changing the direction of movement, the change in the form of the calculated function does not occur, which corresponds in this case

40 a decrease in the current phase, and consequently, a decrease in the magnitude of the absolute displacement. The control signal for block 15 for calculating inverse trigonometric functions is formed by the second and third elements

EXCLUSIVE SHSh 12 and 13.. Thus, the magnitude of the measured displacement L is L A - B,

Where A is the whole part of the interference band, is equal to A

il; TB

 - wavelength of the radiation source received by photomultipliers;

B is the fractional part of the interference band, defined in the interval from O to or from.

The device allows you to measure movement with accuracy

Ji

) pte

where n is the analog-to-digital size

converters. In this case, the described signal processing algorithm, based on dividing the input signals and then calculating the functions of arctg and arcctg, provides a higher stability of the measurement accuracy of the fractional part of the interference band when the radiation intensity at the input of photodetectors changes, as well as under the influence of noise and interference on the measuring circuits, in comparison with the prototype.

Claims (1)

Invention Formula A device for measuring the fractional part of the interference band, containing two channels, each of which consists of sequentially connected photoreceiver, amplifier and shaper, the summation-subtraction unit whose inputs are connected to the outputs of the channel amplifiers, the first and second signal-shaping units, whose inputs connected to the outputs of the summing-subtracting unit, com0 five 0 0 binational logic circuit, the inputs of which are connected to the outputs of the formers and signal conditioning blocks, and a reversible counter, the inputs of which are connected to the outputs of the combinational logic circuit, which is designed to increase the accuracy of measurements connected by rectifier ,. the input of which is connected to the output of the amplifier, and the analog-digital converter, and the device is equipped with a dividing unit, the information inputs of which are connected to the outputs of the analog-ts1-1phonic converters, the calculating unit of the inverse trigonometric functions arctg and arcctg, whose information input is connected to the output of the first two-code element EXCLUSIVE OR, whose inputs are connected to the outputs of the signal conditioning units, and the output to the control input of the division unit, the second two-input element EXCLUSIVE IL And, the inputs of which are connected to the outputs of the formers, and the third two-input element EXCLUSIVE OR, the inputs of which are connected to the outputs of the first and second elements EXCLUSIVE OR, and the output - to the control input of the block of delineation of inverse trigonometric functions. Editor N.Gorvat Order .5214 / 36 Circulation 670 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4 Compiled by V.Nikolaev Tehred L.Oleynik Proofreader S.Cherni