Visibility retrieval in Michelson wide-field stellar interferometry
  Wide field interferometry has become a subject of increasing interest in the recent years. New methods have been suggested in order to avoid the drawbacks of the standard wide-field method (homothetic mapping) which is not applicable when the aperture is highly diluted; for this reason imaging with non-homothetic arrays is being extensively studied [1], [2]. The field of view of a pupil plane interferometer or a densified array consists only of a few resolution elements; in order to improve these systems, we developed a new method consisting of a Michelson pupil-plane combination scheme where a wide field of view can be achieved in one shot. This technique, called "staircase mirror" approach, has been described in a previous paper [3] and uses a stair-shaped mirror in the intermediate image plane of each telescope in the array, allowing for simultaneous correction of the differential delay for both the on- and off-axis image positions. Experimental results have been obtained showing the simultaneous recovering of the fringes of off-axis stars with an appreciable angular separation, and with a contrast similar to that of the on-axis reference star. With this example, we demonstrate an increase of the field of view by a factor of five, with no need of extra observation time. In this article, we present a further analysis of the method. We investigate how to retrieve the visibility when a star is focused on the edge of a step of the stair-shaped mirror. Even though the Optical Pathlength Difference (OPD) correction is discontinuous, we show both numerically and analytically that the visibility can be completely recovered, so that no information is lost. Our experimental results demonstrate that the visibility can be retrieved to within a 1% error. 
I. Montilla, J. Sellos, S. F. Pereira, and J. J. M. Braat