Optical wavefront measurement using phase retrieval with subaperture stitching method

We present a method for optical wavefront measurement using phase retrieval with subaperture stitching method in situations where detected intensity patterns are undersampled or where the limit of aberrations is determined by the largest spot size overfilling the detector array. In this technique we use a smaller moving subaperture to produce a number of adequately sampled intensity patterns captured by the detector located near the focus plane. These patterns are then used to retrieve the full-aperture wavefront through an optimization phase retrieval algorithm. The relationship between the optimization parameters of moving subaperture and the support information is given. Then expressions for the gradient of an error metric with respect to the optimization parameters are presented. An experimental setup used to measure the reflected wavefront of a concave mirror by employing this method is arranged. The experimental results indicate that the phase retrieval results are in excellent agreement with that obtained with interferometer, which confirms the validity of this method.