Wave-front sensing by optical phase differentiation

A wave-front sensor consisting of a coherent processing system with a rotating filter in its Fourier-transform plane and an array of detectors in its image plane is described. The phase gradient at any point in the object plane of such a system may be calculated from the output of a detector located at the image of that point. The output from an array of detectors in the image plane allows the phase distribution in the object plane to be calculated in real time.