Retrieving the relief of a low-roughness surface using a two-step interferometric method with blind phase shift of a reference wave

A two-step interferometric method with blind phase shift of a reference wave for surface relief retrieval is considered. The possibility of using this method to reconstruct a macrorelief and microrelief of low-roughness surfaces is studied. Computer simulations have testified to the possibility of obtaining a reliable low-noise reconstruction of a low-roughness surface macrorelief and microrelief with standard deviation of the roughness heights up to λ/10 by using the developed interferogram-processing algorithm. The simulations have shown that the correlation approach, which is used to determine the reference wave blind phase shift, is more suitable for a rough surface than for a smooth one and the increase of surface roughness leads to a sharp decrease of error in comparison with that for a smooth surface. The experiment-based verification of the performance of the proposed interferometric method has been done using an experiment setup based on a Twyman-Green interferometer. Peculiarities of choosing the sampling interval for a rough surface recording are discussed. The experimental results that were obtained virtually coincided with the computer simulation results, proving the feasibility of retrieving both smooth and low-roughness surfaces by the considered method.

► Two-step interferometric method is developed to retrieve a low-roughness surface. ► Blind phase shift is extracted from correlation coefficient between interferograms. ► Computer simulation has shown this method reliability. ► Twyman-Green interferometer is used to verify this method on a real object. ► Surface area of a gauge block measuring face is retrieved.