SU1404812A1 - Method of measuring distance sections - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure distances. The goal — an increase in productivity, a simplified process, and an extension of the measurement range — is achieved by reducing the influence on the measurement process of the ratios of modulation frequencies and information signal. The radiation beam is divided into reference and measuring beams and, reflected from the mirrors, is brought together. In the measuring beam, the frequency of the radiation phase is modulated, the modulation frequency is changed to a value at which the amplitude of the variable component of the interference signal is zero, the modulation frequency is measured, and the value of the segment is determined by the calculated formula. 1 il. with SS (L

Description

four

OS

The invention relates to a measurement technique and can be used to measure distance segments.

The purpose of the invention is to simplify the measurement process, increase the productivity and extend the measurement range - by reducing the influence on the measurement process of the ratios of modulation frequencies and information signal.

The drawing shows an optical diagram of a device implementing the proposed method.

The method is carried out as follows.

The laser beam 1 is split by a dividing mirror 2 into measuring and reference beams. In the measuring beam, the phase modulation of the radiation is carried out by passing it through the modulator 3, which is controlled by the variable signal source 4 with frequency adjustment. The modulation frequency is measured by meter 5. The measuring beam is reflected from mirror 6, passes through the modulator 3 again, and interferes with the reference beam reflected from mirror 7. The resulting interfering beam is detected by the photodetector 8.

When the beam phase is modulated with a frequency v according to a harmonic law, the intensity 1 (1} of the output signal is equal to

/(;)/,+/2+2VyW2COs2.(.-TvX

X (/ + | -)

(one)

measuring and

reference beams;

the order of interference in the absence of modulation; radiation wavelength; phase modulation amplitude; measured distance; the speed of light.

By changing the modulation frequency, one chooses its value v, at which a half-integer number (m is an integer) of modulation periods passes during the double passage of radiation by the measured segment.

Since the radiation in the measuring beam is subjected to phase modulation twice, its phase shift at frequency v of modulation is zero. It is also seen from formula (1) that when the frequency value v satisfies the condition --- (t + - | -) - t ;, the quantity I (t)

is constant, i.e. there is no variable component of the interference signal at frequency v of modulation. The measured distance is from the ratio

.). With t- (m-t) j

20

Claims (1)

Invention Formula The method of measuring the distance segments, which consists in that the beam of coherent monochromatic radiation is divided into reference and measurement, is modulated phase of the measuring beam according to a periodic law, combine the measuring and reference beams, record the interference signal and determine the length of the segment, characterized in that, in order to increase productivity, simplify the process measuring and extending the limits of measurement, changing the modulation frequency from zero to a value at which the amplitude A of the variable component of the interference signal is zero, the frequency V of the modulation is measured at, and the length / length determined by the formula 1 (+ {) where c is the speed of light; m is the number of integer half-periods of modulation during the passage of radiation by the measured segment. L " ij