<title>Optical design for interferometry with the Large Binocular Telescope</title>

Abstract

Designs for the large binocular telescope (LBT) beam combiner optics, collimators, and reimaging cameras for the visible and infrared over a range from 0.5 to 13 microns are presented and discussed. To achieve good images at the combined focus of the LBT, an adaptive correction will be made independently for each of the two telescopes prior to beam combination. For interferometry the image planes of each telescope are first collimated. The two beams then pass to two flats. The two flats will be shifted to remove the remaining piston differences between the two telescope beams, using an error signal derived from a fringe tracker further down the optical path. The flats output a pair of parallel collimated beams with the collimator exit pupils and separation scaled to the original LBT entrance pupil geometry. Because the pixel matching, diffraction limits and isoplanatic fields are different in the different wavelength bands, a series of cameras have been designed covering the different bands from the visible through 12 microns. Both refractive and reflective optical designs are considered.