Modeling of Speckle Affected Laser Self-Mixing Interferometry Signals

Abstract

Self-mixing interferometry (SMI) has gained a lot of interest in sensing and measurements in past few decades. SMI system has better compactness, lower cost, and easier construction compared to other interferometric sys tems. Speckle, an optical phenomenon, causes amplitude modulation of self mixing interferometry Signals. Speckle is influenced by the target surface roughness, the laser spot size as well as the laser wavelength. For small displacements of the target, speckle may not affect the SM signals if the dis placement is much smaller than the typical longitudinal size of the speckle grain. For larger displacements, speckle can cause amplitude fading thereby hindering processing of signals. In this thesis, modelling of speckle affected laser self-mixing interferometry signals will be carried out by building upon the behavioral model currently in vogue for modelling laser self-Mixing in terferometry signals. Amplitude modulation of speckle affected SMI signals due to surface roughness will also be explored by using different models of surface roughness.