Quadriwave lateral shearing interferometry (QLSI) is well established phase imaging technique. Information about phase distribution within this method is encoded into complex pattern of intensity distribution. So called difference fronts are then extracted via fast Fourier transform (FFT) technique and optimally merged with various integration algorithms, depending on character of measured phase distribution. QLSI experiment is typically build with the use of dedicated shearing device, based on combination of special amplitude grating with phase chessboard. In our experiment, we perform the diffractive shear through phase spatial light modulator (SLM), which also serves as known in advance phase test. In this context, we present a comparison of measurement results with the use of different illumination sources.
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