Study On Analysis And Correction Algorithms Of Nonlinear Errors In Phase-shifting Interferometry

Phase shifting interferometry(PSI)has been widely studied as a fast and non-contact metrology accurate technology in recent years,and several new methods of phase-shifting and computing are proposed.As the characteristics of high precision,fast rate and real-time measure,it can define the phase of any point in the square accurately,which can perform the whole-field testing with high precision.Therefore PSI has been one of the effective methods in the interferometry and widely used in several fields,such as the measurement of 3-D shape,the technology of digital micro holography,Fuzzy Recognition,the detection of coarseness,the encryption images and the technology of water marked.The accurate of phase-shifting in phase-shift interference has the very tremendous influence to precision of the measurement result.This will limit the precision of phase-shifting interferometry.For the impact of various error sources for interference system,there has been a lot of efficient algorithms which can restrain the influence of the error on the measurement results.However,these methods are more or less defective.So it is certain difficult to eliminate the phase-shifting error effectively during the phase-shifting process,especially for the problem in calibrating nonlinear errors for phase shifter.This paper presents some typical phase extracting algorithms,and studies deeply the Least-squares iterative algorithm.Finally,an effective iterative least-squares algorithm is proposed to calibrate nonlinear errors for phase-shifting interferometry,which estimate the high-order coefficients of nonlinear errors of phase shift from those derived residuals based on least-squares iterative algorithm.Then the correction computation formula and iterative steps of the algorithm is also given.Experiment results demonstrated that this algorithm has been play a significant part to restrict the nonlinear errors of phase shift system.