Patent ID: 8488237

Claim:
A Cassegrain-like telescope, comprising: a primary mirror; a secondary mirror spaced apart from the primary mirror, the primary mirror and the secondary mirror configured to form a focal surface; and an optical aberrations corrector consisting of a plurality of lenses, the optical aberrations corrector being disposed between the secondary mirror and the focal surface, the optical aberrations corrector being configured to correct optical aberrations of the primary mirror and the secondary mirror, wherein a material of the plurality of lenses is barium fluoride (BaF 2 ) selected to transmit radiation in a wavelength range between approximately 0.4 μm and approximately 12 μm, and having variations in refractive index below about 0.05 so as to reduce chromatic aberration to a level such that an average root mean square of wave front error (RMS WFE) is less than approximately 0.08.