Patent ID: 9207434
Filing Date: 2015-12-08
Classification: G01J,G02B

Abstract:
1. An optical system comprising: at least one beam of infrared light including both mid-wave infrared light and long-wave infrared light; an external entrance pupil, for infrared light to be shown through, being located in front of the optical system; a transparent formed material through which the at least one beam of infrared light, including both mid-wave infrared light and long-wave infrared light, travels; a series of optical materials spaced at varying distances from one another by a series of spacers, a respective spacer, of the series of spacers, separating each adjacent pair of optical materials from one another during operation of the optical system; a Dewar window, and a filter being located between the last optical material and a focal plane; the series of optical materials and spacers being selected and arranged so as to simultaneously focus both the mid-wave infrared light and the long-wave infrared light of the at least one beam of infrared light on the focal plane; and the series of spacers varying the spacing of the optical materials from one another, during operation of the optical system, so that the optical system is passively athermal over an operating temperature range from about −40° C. to about 60° C.