Laser self-mixing interference displacement measurement based on VMD and phase unwrapping

In order to measure displacement accurately and conveniently, the laser self-mixing interference measurement method based on variational mode decomposition (VMD) and phase unwrapping is proposed. The laser self-mixing interference technology has many advantages such as high sensitivity, ease of use and compactness. The VMD method can non-recursively decompose a self-mixing interference signal into a number of intrinsic mode functions and remove noise effectively. The linewidth enhancement factor and the optical feedback level factor are measured by the hysteresis phenomenon in the self-mixing interference. The reconstruction of displacement is implemented by phase unwrapping. The displacement measurement is carried out by the self-mixing interference experimental system. The experimental results show that the displacement measurement error is less than 80 nm, which verifies the correctness of the method.