Abstract: An optical system in which an aggressively compact reflective front end is combined with beam splitting elements and refractive relay optics to allow several imaging systems working in widely different wavelength bands to share a common aperture. The aggressively compact design results in significant field curvature at the uncorrected intermediate or virtual focus, which is corrected in the refractive relay optics for each band's imaging path.

Abstract: An optical system in which an aggressively compact reflective front end is combined with beam splitting elements and refractive relay optics to allow several imaging systems working in widely different wavelength bands to share a common aperture. The aggressively compact design results in significant field curvature at the uncorrected intermediate or virtual focus, which is corrected in the refractive relay optics for each band's imaging path.

Abstract: A method of aligning a lens assembly to a focal plane array is provided. The method may comprise the steps of providing an upper cold shield which holds the lens assembly, providing a lower cold shield for holding the focal plane array, mounting the upper cold shield onto the lower cold shield, lowering the temperature of the upper and lower cold shield to a cryogenic level, translating the upper cold shield with respect to the lower cold shield until the lens assembly is aligned to the focal plane array while the upper and lower cold shields are at the cryogenic temperature levels, and fixing the upper cold shield to the lower cold shield while the upper and lower cold shields are maintained at cryogenic levels.