A self-mixing displacement sensor compensating parasitic vibration with a MEMs accelerometer

A self-mixing (SM) laser diode displacement sensor coupled with a microelectromechanical system (MEMS) accelerometer with improved resolution is presented that allows reliable displacement measurements even in the presence of parasitic vibrations acting on the laser head. This sensing system presents a six-fold improvement in the measurement resolution (40nm rms) as compared to a previously published accelerometer coupled SM sensor (267nm rms). The present system resolution of 40nm rms is dictated by (1) the noise characteristics of present accelerometer and (2) the λ/16 resolution of present SM displacement reconstruction algorithm, where λ=laser wavelength. This technique thus paves the way for the use of high-resolution SM-based sensors for embedded applications in industrial conditions.