Direction detection in crossed-beam laser Doppler velocimetry using Brillouin frequency shift - using two or more laser beams with frequency shifts forming measurement volume with moving strip system

摘要

The method of direction detection involves using at least two laser beams with shifted light frequencies which form a measurement vol. with a moving strip system as a scale in their penetration region. A measurement signal is generated in the measurement volume (8) dependant on the Doppler shift in the instantaneous frequency of particle speeds in a flow. The Brillouin wave reflected and frequency shifted by exceeding the critical power in a length of optical fibre (5,6) is used to produce a light frequency shift between the illuminating beams. USE/ADVANTAGE - For sign-dependent, contactless photoelectric measurement of motion components of light scattering objects with scattering centres in form of surface elements of solid bodies or tracer particles in fluids. Conveniently adjusted.