Iterative algorithm for phase shifting interferometry with finitebandwidth illumination

摘要

While phase shifting interferometry (PSI) has clearly established itself as a powerful tool for surface profiling, two mainexperimental drawbacks still exist, namely phase-shift errors and non-sinusoidal interferometric signals. These problemscause a fringe print-through pattern in measured phase having a frequency typically double the original fringe frequency.The main tool used to compensate for non-linear phase-shift errors is the least-square phase-stepping method, which iscapable of accurately determining the phase separation between consecutive frames as well as phase distribution for eachframe. Our work here extends the capabilities of this algorithm so as to account for the effects of a wide bandwidth lightsource and a higher numerical aperture, which make the interference signal deviate from the ideal sinusoidal signal. Wepresent a simple variable change mechanism that overcomes the coupling that occurs between the planar and depthcoordinates and allows for a seamless integration with the standard least-square procedure.