US Patent 7440115 System and methods for wavefront measurement

A method and apparatus for characterizing an object with a wavefront from the object is disclosed. In one embodiment, the apparatus includes: a reticle positioned in a path of the wavefront, the reticle comprising two superimposed linear grating patterns; at least one light detector positioned relative to the reticle to receive a self-image diffraction pattern of the reticle produced by the wavefront; and at least one processor receiving signals from the light detector representative of the self-image diffraction pattern and deriving derivatives associated therewith, the processor using the derivatives to characterize said object.