Impact of High Coupling Factor in Absolute Distance Measurement with Self-Mixing Interferometry

Absolute distance measurement by means of a self-mixing interferometer (SMI) can be obtained by modulating the laser frequency. This modulation is typically achieved through the modulation of the laser injection current with a triangle waveform. Various strategies have been proposed to increase the performances and recent researches have shown real-time performance of SMI with resolution reaching 100 μm for distances up to 2 m. In the present paper, we demonstrate for the first time, both experimentally and by modeling, that with high coupling factors between the laser and the target, disappearance of interferometric fringes occurs that can strongly affect the measurement reliability.