Grating-based laser self-mixing interferometry for simultaneous measurement of two-dimensional displacement

A laser self-mixing interferometer (SMI) is proposed for simultaneous measurement of two-dimensional (2D) displacement. It consists of only two laser diodes and a reflective grating, with each laser operating in a moderate feedback regime. Based on the unique characteristics of SMI signals under moderate feedback, high-precision 2D displacement reconstruction has been achieved by pre-estimating the optical feedback coupling factor and the linewidth enhancement factor. Experimental results indicate that the maximum relative error in the 2D displacement reconstruction is less than 0.84%. This system features a compact and cost-effective design, maintaining high measurement accuracy while demonstrating good resistance to environmental interference.