FIELD: measurement technology. SUBSTANCE: method consists in performance of interference modulation with isolation of one measurement interval, in formation of one interference picture with its conversion into one sequence of electric pulses, in registration of fronts of this sequence, in determination of three time intervals per each modulation period and in fixing of changes of order of interference at end of last modulation period by results of registration of fronts and determination of time intervals. In this case second interference picture shifted through quarter of interference period is formed in addition and is converted into second sequence of electric pulses. Fronts in first sequence are registered with due account of presence of pulses in second sequence. Second measurement interval in each modulation period. Four time intervals are determined for each measurement interval, with allowance for number of registered fronts and determined time intervals resulting change of interference is calculated. EFFECT: expanded application field. 3 dwg
