Abstract

Interference patterns formed by two light beams that are split and redirected by two or three line gratings, with grating lines oriented in the same direction, were analyzed. Either localized or nonlocalized fringes can be formed in the symmetric (with respect to the optical axis) achromatic grating interferometer, depending on the degree of spatial coherence of the illuminating light. For an asymmetric achromatic grating interferometer, only localized white light fringes can be produced. An incident light beam is split by the first grating into two beams in different directions. Each light beam is guided by a set of plane gratings with grating lines not necessarily parallel to one another. Ray tracing is used to obtain the expression of the interference pattern. White light fringes can be formed for equal-path arrangement. The illuminating source can be broadened in a direction if the projection of the interferometer from the orthogonal direction has equal length for all the parallel line segments. The fringe depth is inversely proportional to the angle between two arms, the spectral bandwidth, and the illuminating angle of the source.

© 1992 Optical Society of America