ABSTRACT
This chapter describes method to obtain the wavefront by measuring local curvatures using diffraction images. It presents the most important techniques for testing optical wavefronts by estimating the slope and curvature changes as the wavefront propagates along the experimental setup. Wavefront slopes can be measured by using testing methods that measure the transverse ray aberrations in the x and y directions, which are directly related to the partial derivatives of the wavefront under analysis. Curvature sensing consists of taking the difference between the illuminations observed in two planes located symmetrically with respect to the diffracting stop. The two planes on which the irradiance has to be measured are symmetrically located with respect to the diffracting pupil. C. F. Roddier reported a method for obtaining the wavefront deformations, W(x, y), from a knowledge of the Laplacian operator by solving the Poisson equation using iterative Fourier transforms.
