FIELD: measurement technology. SUBSTANCE: beam of laser 1, being reflected from two semi-transparent plates 8 and 9, forms reference and registration beam for deforming unit 2. Reference and registration beams interfere and form registration and test interference patterns, which have to be transformed by photoconverters 12 and 16 into sequences of electric pulses. Movement of plunger 5 in some direction results to change in order of interference in both channels of refractometer 2. Shift of modulator 11 provides modulation according to law of triangle. Fractional part of order of interference is determined by measuring time interval Δt1 by means of phase meter 20; time intervals correspond to phase difference between two adjacent pulses. Entire part of order of interference is detected by means of application of circuits 25 and 24, which provide separation of trailing and leading edges of the pulses. Reversible counter counts number of pulse fronts. In this case, at the first half- period of modulation period, A leading edges are detected; B trailing edges are detected in the second half-period. Entire value of order of interference is determined from the relation Q= A-Б. In the last modulation period the values of fractional part of order interference δb and its entire part Qb. Values δ Qo are determined by comparing with values of fractional part ΔQ of order of interference in the beginning of the detection and with entire part Δδ of order of interference before the beginning of the first modulation period. Number is recorder in counter 28 at the moment of finishing detection, which corresponds to number of entire orders of interference, when modulation is absent at L disconnections. Result value is counted from determined values Dd, DQ and M. EFFECT: improved speed of operation due to reduced time of measurement. 6 dwg
