Patent ID: 9587927
Date: 2017-03-07
CPC Classifications: G01B,G01J,G02B

Claim:
1. A high speed high resolution heterodyne interferometric method comprising following steps: (a) providing two parallel laser beams which are linear polarized laser beam having a 45° angle from the horizontal direction and with different frequencies f (b) detecting a portion of each laser beam by a photodiode and the detected result is then converted to a reference signal having a frequency (f (c) dividing a rest portion of the each laser beam into a reference beam and a measurement beam by a polarizing beam splitter; (d) directing the two reference beams with different frequencies f (e) directing the two measurement beams with different frequencies f (f) adjusting the reference reflector and the measurement reflector to realize that the measurement beam with frequency f (g) detecting the first and second measurement signals at two photodiodes respectively and the respective results are then transferred to a first phasemeter for processing the first measurement signal I (h) selecting between the first phasemeter and the second phasemeter by a switching circuit according to a direction and speed of a movement of a plane mirror; (i) calculating a displacement of a subject measured according to an output of the selected phasemeter.