15 May 2001 Divided mirror technique for measuring Doppler shifts with a Michelson interferometer
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Abstract
Upper atmospheric winds have been measured for many year by the detection of the Doppler shifts of airglow emission lines using both Fabry-Perot and Michelson interferometers. The Michelson is usually used in a field-widened configuration with the path difference set at a large value. Filters isolate a single emission line and the Doppler shifts are manifested as phase shifts of the interferometric fringes. The phase shifts are measured by sampling the fringe at four points separated by about one-quarter wavelength in path difference. One problem with the technique is that the phase is subject to error if the source intensity varies while the four exposures are made. A solution is to divide one Michelson mirror into four quadrants, with a different coating on each quadrant, in order to provide the four fringe samples simultaneously. This method is proposed for WAMI, the Michelson instrument in the WAVES proposal. The technique of sampling a fringe at four points simultaneously while imaging is discussed and demonstrated. A laser source is Doppler shifted using a spinning disk and the velocities measured interferometrically agree with the known speed of the disk within statistical error.
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William A. Gault, Stoyan I. Sargoytchev, Stephen Brown, "Divided mirror technique for measuring Doppler shifts with a Michelson interferometer", Proc. SPIE 4306, Sensors and Camera Systems for Scientific, Industrial, and Digital Photography Applications II, (15 May 2001); doi: 10.1117/12.426964; https://doi.org/10.1117/12.426964
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KEYWORDS
Doppler effect

Mirrors

Michelson interferometers

Visibility

Calibration

Phase shifts

Sensors

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