Two-dimensional laser Doppler velocimeter using polarized beams and 90° phase shift for discrimination of velocity direction

A laser Doppler velocimeter (LDV) for two-dimensional velocity measurement using a simple optical configuration without any optical modulator is proposed. The structure using polarized beams and the 90° phase shift of the reference beam is used to discriminate the direction of velocity. The analytical relation among beat frequencies and velocity components is derived and the characteristics of the proposed LDV are simulated. The simulation results indicate that the direction of velocity can be discriminated by the proposed LDV as well as the magnitudes of the components of the velocity.