Laser self-mixing based on peak–valley point detection algorithm for displacement reconstruction

The peak–valley point serves as the intersection for the derivative of both the self-mixing interference signal and its anti-cosine transform. In this study, a peak–valley point detection algorithm based on the phase unwrapping method for self-mixing interference was proposed, The proposed method had the advantage of identifying the peak–valley point without setting a threshold. In addition, the relative error of the algorithm did not exceed 1% of the simulation signal, when the optical feedback factor is within the range from 0.1 to 4. Further, the experimental results were found to be in accordance with the theoretical analysis, with a relative error of 4.9%.