title: Reflective grating interferometer in a noncollimated configuration.
abstract: 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.
authors.forename: P
authors.initials: P
authors.lastname: Ferraro
authors.forename: S
authors.initials: S
authors.lastname: De Nicola
authors.forename: A
authors.initials: A
authors.lastname: Finizio
authors.forename: G
authors.initials: G
authors.lastname: Pierattini