Abstract

Experiments are described for producing low-noise diffraction gratings by the interference of multiple light beams from an extended source. Noise levels of the interfering beams are measured in varying conditions of coherence and compared with the noise levels of coherent beams. We note that, although for any given beam-generating system, incoherent light produces lower spatial noise than does coherent light, it is also true that a system for producing incoherent illumination fringes necessarily has more elements than does a system for producing fringes with coherent illumination and thus has more noise generating sources. The incoherent light system must thus overcome the handicap of being the inherently noisier system. A certain level of incoherence is thus needed simply to bring the incoherent system noise down to the level of the simpler coherent system. An additional degree of incoherence tilts the balance in favor of the incoherent system.

© 1987 Optical Society of America