A third-order aberration analysis for a reflective grating interferometer (RGI) is developed for a noncollimated configuration. In such a configuration the RGI is still a folded and reversing interferometer that is sensitive only to coma aberration, as it is in the collimated configuration. However, for an unaberrated input beam converging on a plane grating, the reflective grating of the interferometer introduces self-aberrations. Consequently, a nonnull fringe pattern is obtained. Nevertheless, a RGI in the noncollimated configuration has the potential to be applied for isolating and measuring coma, and a possible configuration for this application is proposed. As an example of the application, the coma of a large mirror could be isolated and measured by use of a converged configuration to avoid the main limitation in using the RGI in a configuration with a nearly collimated beam.
© 2000 Optical Society of America
(090.1000) Holography : Aberration compensation
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(220.0220) Optical design and fabrication : Optical design and fabrication
(220.4840) Optical design and fabrication : Testing
(230.4040) Optical devices : Mirrors
Pietro Ferraro, Sergio De Nicola, Andrea Finizio, and Giovanni Pierattini, "Reflective Grating Interferometer in a Noncollimated Configuration," Appl. Opt. 39, 2116-2121 (2000)