Abstract
We propose and demonstrate multiple shearing interferometry for measuring two-dimensional phase object. Multi-shear interference can effectively eliminate the problem of spectral leakage that results from the single-shear interference. The Fourier coefficients of a two-dimensional wavefront are computed from phase differences obtained from multiple shearing interferograms, which are acquired by a shearing interferometer, and the desired phase is then reconstructed. Numerical and optical tests have confirmed that the multiple shearing interferometry has a higher recovery accuracy than single-shear interferometry and the reconstruction precision increases as the number of shear steps increases.
Highlights
Lateral shearing interferometry is a useful technique for evaluating optical wavefronts and is a promising measurement tool for many applications [1,2,3,4,5,6,7]
An improved algorithm is proposed based on Fourier modal expansion for reconstructing a two-dimensional wavefront from phase differences with large shear [9]
Numerical and optical tests have confirmed that this multiple shearing interferometry method results in higher recovery accuracy than single-shear interference, especially for objects with discontinuous phase profiles
Summary
Lateral shearing interferometry is a useful technique for evaluating optical wavefronts and is a promising measurement tool for many applications [1,2,3,4,5,6,7]. An improved algorithm is proposed based on Fourier modal expansion for reconstructing a two-dimensional wavefront from phase differences with large shear [9]. This algorithm has a disadvantage, i.e., the signal’s Fourier spectra at frequency periods corresponding to multiples of the shear amount are lost, and the reconstruction accuracy is impaired. Elster and Weingärtner proposed a two-shear algorithm to combine the information of two sheared phase differences to avoid spectral leaking [16, 17] Their method requires that the product of two shear parameters must equal the number of sampling points, which means that one or both of the two shears must be relatively large. Numerical and optical tests have confirmed that this multiple shearing interferometry method results in higher recovery accuracy than single-shear interference, especially for objects with discontinuous phase profiles (e.g., step-like optic surface)
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