Laser Doppler Velocimeter for Vehicle Inertial Navigation System

Direction discrimination of laser Doppler velocimetry system based on acousto-optic frequency shifter

“…Although there are many mature products available both domestically and internationally, these systems possess the common deficiency of 180°direction ambiguity. This is because particles of the same size moving in opposite directions produce the same Doppler shift [5][6] , and the detector cannot directly discriminate the sign of the signal frequency. When the velocity is negative, the LDV without direction discrimination provides a positive velocity value, which is irrelevant for certain measurements where the direction of motion is known.…”

Laser Doppler velocimeter using phase shift method for discrimination of the motion direction

“…Laser Doppler velocimetry (LDV) has the advantages of non-contact measurement, fast dynamic response and high measurement accuracy, and has been widely used in scientific research and industry [1,2]. However conventional LDVs can only give the absolute value of the frequency difference and cannot indicate whether the Doppler shift is up or down [3] .…”