Instantaneous laser Doppler velocimeter using a fast wavelength tracking Michelson interferometer.
A new species of laser Doppler velocimeter is presented based on wavelength detection with a two-beam interferometer. A finite optical path difference, Deltaphi, of the interferometer creates a sensitivity of the interference to wavelength changes. By means of a fast feedback system, the phase, Deltaphi/lambda is kept constant. Wavelength changes are immediately answered by changes of Deltaphi generated with a Pockels cell. The Pockels cell voltage represents a continuous signal proportional to the instantaneous velocity component of the scattering object. A time resolution of 1 micros or lower can be obtained. The field of applications includes velocity recordings in gas flows containing tracer particles as well as velocity recordings of moving surfaces. A number of experiments are described demonstrating the performance of the system.
Smeets
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German-French Research Institute of Saint-Louis, 68 Saint-Louis, France.
George
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