Laser diode Doppler velocimeter with 3-beams and Self-mixing effect enabling 3-dimensional velocity measurement

Laser Doppler Velocimeter (LDV) with a laser diode and Self-mixing effect is a new type of downsized and low cost LDV with high precision measurement. We propose a new LDV using a 3-beam fiber irradiation scheme. The sensor head consists of 3-fibers which are intersected perpendicularly each other. This new LDV enables three-dimensional velocity measurement. That is, the magnitude and direction of the velocity vector of the moving object can be measured independent on the relative position between the moving object and the 3-beam sensor head. We also study the case that these 3 beams are not right-angled each other. Operation principle and experimental results for both cases are reported.