1 August 2003 Optical filters to exclude non-Doppler-shifted light in fast velocimetry
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Proceedings Volume 4948, 25th International Congress on High-Speed Photography and Photonics; (2003) https://doi.org/10.1117/12.516818
Event: 25th international Congress on High-Speed photography and Photonics, 2002, Beaune, France
Abstract
We frequently measure velocity-time histories of dynamic experiments. In some, the Doppler-shifted light is often weak compared to non-shifted light reflected from stationary surfaces and imperfections in components. With our Fabry-Perot (FP) based systems which handle multiple frequencies, data is lost where the fringes coincide; if we had used an intensity-measuring VISAR system, it would probably fail. We designed a facility for doing experiments under such conditions by selectively eliminating most of the non-shifted light. Our first filter excluded non-shifted light by a factor of 300 when manually tuned, and by 150 when run in an auto-tuning mode. It used a single 50 mm diameter FP as the filter with a spacing of 1.65 mm and reflectivities of 77%, and filters five channels prior to use in one of our 5-beam velocimeters. One use of the filter system was to embed optical fibers in long sections of explosives to make continuous detonation velocity-time histories. We have carried out many such tests with this filter, and two without. A special single-beam filter was constructed with a 40% efficiency for shifted light that rejected non-shifted light by 4 million times, with a bandpass of a few GHz.
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David R. Goosman, David R. Goosman, George R. Avara, George R. Avara, James T. Wade, James T. Wade, Anthony T. Rivera, Anthony T. Rivera, "Optical filters to exclude non-Doppler-shifted light in fast velocimetry", Proc. SPIE 4948, 25th International Congress on High-Speed Photography and Photonics, (1 August 2003); doi: 10.1117/12.516818; https://doi.org/10.1117/12.516818
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