Wavefront sensor using a surface acoustic wave diffraction grating

Claim 1

An arrangement for detecting the slope of an input wavefront, comprising: a. means for focusing an input wavefront to a focal point; b. a surface acoustic wave reflective diffraction grating positioned substantially at said focal point and generating acoustic surface waves at two primary frequencies f 1 and f 2 to produce a first AC shearing interferogram, sheared in a first direction, between two like diffraction orders generated by the f 1 and f 2 surface acoustic waves; c. photodetector means positioned to detect the first AC shearing interferogram at a two dimensional array of zones and for producing an output signal for each zone, such that the phase of each output signal is representative of the local slope of the wavefront in said first direction in that zone; d. a beam splitter means in the input wavefront for directing a first portion thereof to said surface acoustic wave reflective diffraction grating, and for directing a second portion of the input wavefront to a second surface acoustic wave reflective diffraction grating positioned substantially at the focal point of said second portion of the input wavefront, said second surface acoustic wave reflective diffraction grating generating acoustic surface waves at two primary frequencies f 1 and f 2 to produce a second AC shearing interferogram, sheared in a second direction substantially orthogonal to said first direction, between two like diffraction orders generated by the f 1 and f 2 surface acoustic waves; and e. a second photodetector means positioned to detect the second AC shearing interferogram at a two dimensional array of zones and for producing an output signal for each zone, such that the phase of each output signal is representative of the local slope of the wavefront in said second direction in that zone.