METHOD AND DEVICE FOR AUTOMATIC INTERPOLATION OF PHASE-SHIFT IN LASER INTERFEROMETERS Russian patent published in 1994 - IPC

FIELD: measurement technology. SUBSTANCE: method involves converting a measured displacement into an electric signal at a harmonic modulation frequency a phase-shift of which relative to a modulation signal is proportional to a measured displacement with the aid of an interference converter using harmonic modulation, obtaining n synchronous signals shifted by Π/n in phase from the harmonic modulation signal, multiplying an initial electric signal by n synchronous signals in n balanced mixers, respectively, a frequency of n harmonic signals being K times the harmonic modulation frequency in the interference converter (K is an odd integral number), forming 2 nK pulses from n electric signals obtained as a result of multiplication for each period of phase shift of light waves. Device for effecting the method has a laser, a light-dividing cube, reference and measuring reflectors, modulator 2, stable frequency generator 3, photodetector 4, two balance mixers coupled with the photodetector. Signals from the generator shifted by Π/2 in phase are applied to the second inputs of balance mixers the outputs of which are coupled through rectangular pulse shapers with a digital indication device. The stable frequency generator is coupled through an odd-ratio frequency divider with the optic modulator. EFFECT: enhanced accuracy and resolution, simplified electric circuit. 2 cl, 2 dwg