Patent ID: 9157806
Filing Date: 2015-10-13
Classification: G01J

Abstract:
1. An optical system comprising: (a) an infra-red detector disposed within a cryogenically cooled cold shield; (b) a spectral filter for allowing transfer to said infra-red detector of incoming radiation at a desired spectral range while preventing transfer thereof at an undesired spectral range; (c) said spectral filter being disposable into and removable from a position outside the cold shield, the disposing and removing of said spectral filter facilitating respective changes of the operational spectral range; (d) a surface of said spectral filter having high reflectance at said undesired spectral range while having high transmittance at said desired spectral range; and (e) the position of said spectral filter and said high reflectance of its surface being adapted for providing at the detector a reflected field of view at said undesired spectral range directed towards at least one cold blackened surface.