Wavefront sensor using a surface acoustic wave diffraction grating

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A wavefront sensor for detecting the slope of an input wavefront. A surface acoustic wave reflective diffraction grating is positioned at a focal point of the wavefront, and generates surface acoustic waves at two primary frequencies f1 and f2. The reflective diffraction grating produces a first AC shearing interferogram between two like diffraction orders generated by the f1 and f2 surface acoustic waves. A photodetector array is positioned to detect the shearing interferogram at a two dimensional array of zones, and the phase of the output signal for each zone is representative of the local slope of the wavefront in the direction of shearing, thus producing the slope in one direction. Complete two dimensional wavefront slope information is obtained by shearing the wavefront in a second orthogonal direction in substantially the same manner utilizing a second surface acoustic wave diffraction grating and a second photodetector array.