The Accurate Measurement Of Small Rotations By Modulating Polarization

William L. Robinson; Calvin H. Gillespie

doi:10.1117/12.976197

12 May 1986 The Accurate Measurement Of Small Rotations By Modulating Polarization

William L. Robinson, Calvin H. Gillespie

Proceedings Volume 0608, Optical Alignment III; (1986) https://doi.org/10.1117/12.976197
Event: O-E/LASE'86 Symposium, 1986, Los Angeles, CA, United States

Abstract

An instrument developed to accurately measure small rotations (twist about an optical axis) uses a Faraday rotator to modulate the polarization of a HeNe laser beam. Twist sensors located in the beam path consist of a calcite polarizer (analyzer), a silicon detector and associated electronics. The sensors measure relative changes of the sensor analyzer and the null position of the modulated source beam. Reference measurements of the laser intensity and beam modulation are made to avoid accurately characterizing the modulation amplitude. This instrument has a sensitivity of 0.2 microradians at 5 Hz bandwidths over a 17.5 milliradians measuring range. This is accomplished by controlling the beam wander, reducing the laser divergence, and utilizing synchronous detection.

Citation Download Citation

William L. Robinson and Calvin H. Gillespie "The Accurate Measurement Of Small Rotations By Modulating Polarization", Proc. SPIE 0608, Optical Alignment III, (12 May 1986); https://doi.org/10.1117/12.976197

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