Rotation velocity measurement based on self-mixing interference with a dual-external-cavity single-laser diode

A novel Doppler velocity measurement method based on laser self-mixing interference with two parallel optical external cavities is investigated. In this method, the target object rotation velocity can be measured by the sum of two Doppler frequency shifts, which can be extracted by fast Fourier transform without setting and measuring incident angles. This study highlights the validity of the proposed method through a theoretical model analysis. Experiments realized velocity measurement with a relative error of less than 0.6%.