A self-mixing interferometer using an external dual cavity

Abstract

A novel self-mixing interferometer with a double external cavity was proposed to measure absolute distance and microscopic displacement. The technique developed uses an additional reference reflector to form an external dual cavity between the laser diode and the target. A fast Fourier transform phase detection technique was applied to analyse the self-mixing interferometry signal and a reference external cavity was used to compensate the error due to optical frequency fluctuation. Using these techniques, a distance resolution of 1 mm and displacement resolution down to 10 nm can be obtained.