A Fizeau interferometer combines the light of several telescopes to obtain panoramic images with an angular resolution equivalent to the longest edge-to-edge separation in the system. The overall performance of a Fizeau interferometer depends critically on the performance of the (MC)AO system and the efficiency of atmospheric piston correction, but also on other effects like alignment accuracies, filter bandwidths, tracking errors, atmospheric dispersion and field rotation. Due to the mutual dependence, Strehl ratio or fringe contrast like in conventional Adaptive Optics systems or pupil plane interferometers are not sufficient for a consice assessment of the performance of such an instrument. As a measure for the actual performance, we propose to use the ratio R23, which is the actual high-spatial frequency information in the images, divided by what could be measured in principal with a 23m telescope (as the LBT). We present the theoretical concept of this method and show the results of various simulations of the abovementioned effects as an application to LINC-NIRVANA, a Fizeau interferometer currently being built for the LBT.

Date Published: 28 July 2008
PDF: 12 pages
Proc. SPIE 7013, Optical and Infrared Interferometry, 70133C (28 July 2008); doi: 10.1117/12.787807

Published in SPIE Proceedings Vol. 7013:
Optical and Infrared Interferometry
Markus Schöller; William C. Danchi; Françoise Delplancke, Editor(s)