Athermalization design in the big-aperture IR zoom telescope

摘要

How to solve effectively the athermalization of IR zoom lenses is an important problem. We have designed and described an IR zoom lens with a mechanical passive athermalization to compensate for the focus deviation caused by germanium refractive index variation with working temperature in the past research phase. After that, in the other design of an IR zoom telescope, (with aperture 160 mm, magnification 4$MUL - 12$MUL@, five-element lenses made of germanium used in the 8 - 12 micrometer range of the wavelength and at a working temperature of $MIN@10$DGR@C to $PLU@40$DGR@C), we adopt a mechanical active athermalization in the front element used for focusing and the rear element for collimating. In this paper we stress the rear collimating element realizing the thermal compensation.