Comparative Analysis of Single and Multistep Interferogram Processing Techniques

Digital processing of optical interferograms have been used for wide range of applications in engineering and scientific research. Some of the applications include measurement of step height, tilt angle, micro-displacement, deformation, etc. Two main interferogram processing techniques are phase shifting (PS) and Fourier Transform method (FTM). PS technique has been used to demodulate the phase information from multiple phase shifted interferograms; whereas FT is used to extract phase information from a single interferogram. In this paper, we perform a comparative analysis of PS and FTM technique using simulation analysis. The techniques are assessed based on two common problems, i.e. noise and non-sinusoidal waveforms (harmonics) that arise in the measurement system and reduce the accuracy. A new multi-step imaging technique is proposed by combining the advantages of PS and FTM and is also compared based on the same parameters. Advantages and drawbacks of each technique are also discussed.