Measurement of the degree of coherence in nonmonochromatic light.

A method is described for measuring the degree of coherence, gamma(12)(tau), of two points in a plane illuminated, directly or through an optical system, by a nonmonochromatic source. The vibrations from the two points are superposed by means of a birefringent system. The degree of coherence can be determined from the measurements of intensity in the region of superposition. The positions of the two points for which gamma(12)(tau) is to be measured and the time delay tau between the interfering vibrations can be varied easily by suitably displacing the birefringent element. Experimental results are compared with the theoretical values.