Optical EngineeringSurface profiling using phase shifting Talbot interferometric technique
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We implement a phase-shifting Talbot interferometric technique to measure step heights of a single-step and channel (dip) objects. Experimentally recorded interferograms include noise due to grating lines and speckles. To make the phase map, four interferograms are recorded with /2 phase shifts. To remove noise due to grating lines and speckle, interferogram data are first filtered using Fourier filtering. Height variations per profile of the objects is calculated from the phase map made using Fourier-filtered data. Results obtained from this technique are compared with the results acquired from a profile projector having a coordinate measurement facility with a resolution of 1 µm and an accuracy of ±1 µm. The results are in good agreement.