Cross-sectional laser Doppler velocimetry with nonmechanical scanning of points spatially encoded by multichannel serrodyne frequency shifting.

A laser Doppler velocimeter (LDV) using nonmechanical scanning of multiple points spatially encoded by multichannel serrodyne frequency shifting is proposed for cross-sectional velocity distribution measurement. In the proposed LDV, nonmechanical scanning using wavelength change and simultaneous multipoint measurement using spatial encoding are combined. The use of a LiNbO3 phase-shifter array for multichannel serrodyne modulation makes it possible to simplify the generation of a spatially encoded beam array. An experiment was performed using a sensor probe setup with a six-channel beam array. The results indicate that two-dimensional velocity distribution measurement was successfully demonstrated.