Lateral shearing interferometry with continuously variable shear ratio

Lateral shearing interferometry with different shear ratio has different measurement sensitivity, which corresponds to different measurement accuracy. To image the wavefront of an unknown system, high precision measurement accuracy is particularly important. Here a quadriwave lateral shearing interferometry (QWLSI) with continuous adjustable shear ratio is proposed, in which the light splitting grating is placed in the front of the first condenser lens rather than in late position for the traditional QWLSI. In this case, the shear ratio is proportional to the ratio of the defocusing amount to the focal length of the imaging lens. The newly developed QWLSI with continuously variable shear ratio, not only can measure the system aberration, but also calibrate the spatial resolution of the measured wavefront. Software GLAD simulation and experimental results on phase imaging show that the proposed scheme can not only realize variable-shear-ratio interferogram but also has a good robustness, which is well suitable for quantitative phase imaging.