21 September 1999 Signal-to-noise ratio of differential interferometer and reference beam interferometer: a comparative study
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Proceedings Volume 3824, Optical Measurement Systems for Industrial Inspection; (1999) https://doi.org/10.1117/12.364250
Event: Industrial Lasers and Inspection (EUROPTO Series), 1999, Munich, Germany
Abstract
A differential interferometer is used to measure the difference in motion of two points of the diffuse surface. The disadvantage of a differential interferometer is a very small amplitude of the interference signal. The heterodyning with a strong reference beam can be used for optical amplification of weak backscattered light to overcome this disadvantage. In that case the system of two separate reference beam interferometers is used instead of a differential interferometer. In this paper the comparative study of the signal-to-noise ratio of a differential interferometer and of a system of two reference beam Michelson type interferometers is carried out. The investigation is carried out on the assumption that the laser of the same power is used in both interferometers. It is found that when the shot noise is dominant the signal-to-noise ratio of a differential interferometer is practically the same as the signal-to-noise ratio of a reference beam Michelson type interferometer. When the thermal noise is dominant the signal-to-noise ratio of the reference beam interferometer greatly exceeds the signal-to- noise ratio of the differential interferometer for a typically rough surface.
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Vyacheslav Aranchuk, Vyacheslav Aranchuk, } "Signal-to-noise ratio of differential interferometer and reference beam interferometer: a comparative study", Proc. SPIE 3824, Optical Measurement Systems for Industrial Inspection, (21 September 1999); doi: 10.1117/12.364250; https://doi.org/10.1117/12.364250
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