Measurement of the second-order degree of coherence by means of a wavefront shearing interferometer.

A method of measuring the second-order degree of coherence in an arbitrary plane by means of a compact wavefront shearing interferometer is described. The prism interferometer previously described by Saunders produces two sheared images that interfere, allowing measurement of the degree of spatial coherence. If the degree of coherence is a function of coordinate differences only, the visibility is constant; otherwise it varies over the field. Experimental results are given.