Design parameters for a two-mirror telescope for stray-light sensitive infrared applications

Established telescope designs used in the infrared-wavelength region are not responsive to the specific imaging requirements of this wavelength interval. A Gregorian telescope using off-axis mirror segments, and a real focus for the cold stop placement is proposed for the detection of faint IR sources. Exact ray trace equations are given for a general ray propagating through two coupled confocal spheroids. Relationships between the spheroid mirror parameters and object, and image distances are presented in a graphical form to facilitate the first order telescope design.