The fringe characteristics in four-beam cross-grating interferometers, illuminated by a source at finite distance, are analyzed. From the measurements of the fringe visibilities and the fringe shifts on discrete planes, the spatial irradiance distribution of the illuminating source which is separable in two orthogonal directions can be synthesized. When the line structures of the two cross gratings are not parallel, the fringe pattern has lower contrast which suggests that four line gratings should be used to replace the second cross grating in order to have high contrast fringes. The possibility of forming cross-gratinglike patterns using either a combination of one cross grating and two line gratings or a combination of two line-grating interferometers is discussed. Finally, moire interferometry using a cross-grating interferometer is suggested.
© 1989 Optical Society of AmericaFull Article | PDF Article
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