LINEAR DISPLACEMENT METERING DEVICE Russian patent published in 1994 - IPC

FIELD: measurement technology. SUBSTANCE: laser 1 shapes light beam. Metering interferometer 2 and reference interferometer 6 generate measurement and reference interference patterns. Generator 11 shapes triangular signals coming to beam trace length modulator 12 that sets corner reflector 4 in reciprocating motion. Number of pulse picked off photodetectors 13 and 14 during forward and backward travel of corner reflector 4 is counted in differential-signal computing unit 15 by means of reversing counters 21 and 22. Difference in readings of counters 21 and 22 shows degree of displacement of object 34. After object 34 has stopped displacing, reference interference pattern phase is adjusted to metering interference pattern phase by means of phase-error detecting unit 24, drive 29, and optical compensator 10. Fine value of displacement of object 34 is determined by means of phasemeter 25. EFFECT: improved measurement accuracy due to reduced probability of the effect of destabilizing factors in interferometer optical path on measurement results. 3 dwg