Injected current reshaping in distance measurement by laser self-mixing interferometry

Abstract

Self-mixing interferometry (SMI), as an extremely simple and compact laser range finding technique, is especially appropriate to develop minitype sensors for narrow space and small precision parts. In order to enhance the distance resolution performance of this technique, we described the mechanism of nonlinearity in laser frequency under injected current tuning, and proposed a current reshaping method to linearize the laser frequency to attain higher resolution in the scheme of SMI. The proof of nonlinearity was obtained through numerical simulation by considering the change of temperature and carrier concentration and experiment by complex wavelet analysis. The current reshaping method, based on the experimental data of wavelength versus injected current, was proposed to suppress the nonlinearity and improve the distance resolution to better than 20 μm over the range of 2.4-20.4 cm. The influence of tuning parameters and other sources of error was discussed additionally.