Phase microscopy using the quadriwave lateral shearing interferometer with continuously variable shear ratio

Depending on the measured objects and the specific detection requirements, adjusting the shear ratio appropriately is crucial for optimizing the detection performance of quadriwave lateral shearing interferometric microscopy (QWLSIM). Hence, the shear ratio in QWLSIM should be continuously variable in practical applications. In this paper, phase microscopy using the quadriwave lateral shearing interferometer with continuously variable shear ratio is proposed. We use a globally random encoded hybrid grating (GREHG), which comprises an amplitude grating and a phase chessboard, as the beam splitter in the interferometer. The coding rule of GREHG approximates the ideal grating across the entire grating based on the optical flux constraint, effectively suppressing all higher-order diffraction orders except the necessary ±1 diffraction orders and pixel light, thus achieving a continuously variable shear ratio. As the pixel count of the grating period increases, the adjustment of the shear ratio approaches the ideal condition of continuous adjustment more closely. Simulation and experimental results demonstrate that this approach realizes continuously variable shear ratio without modifying the system, which is of great significance for QWLSIM with diverse measurement requirements.