Multiple aperture exit plate for field-widening a Fabry-Perot interferometer

Replacement of the central exit aperture of a conventional Fabry-Perot (F.P.) photoelectric interferometer with a multiple annulus exit plate provides a substantial gain in luminosity while maintaining resolving power in the study of extended sources of radiation. The design, fabrication, assembly, and testing of multiple aperture exit plates (MAEPs) which pass 6 interference orders via a central aperture and five concentric annular openings are described. The measured luminosity gains and inferred aperture finesses of MAEPs used with 150- and 100-mm aperture F.P.s are quite close to the design values of 6 and 14.5, respectively.