Patent ID: 8466964

Claim:
An apparatus to analyze an object or a scene, comprising: an uncooled housing having a first window and a second window to pass incoming infrared radiation from the object or the scene through the uncooled housing; a lens placed in front of the first window to receive the incoming infrared radiation; a cooled housing placed inside, and being thermally isolated from, the uncooled housing, the cooled housing being cooled below a temperature of the uncooled housing and having a first aperture and a second aperture positioned between the first and second windows of the uncooled housing; a cooled filter disposed in a tilted position, inside the cooled housing and substantially centered about an optical axis defined by the lens to filter radiation directed between the first window and the second window, the cooled filter being cooled below the temperature of the uncooled housing; and an uncooled infrared detector placed outside the uncooled housing and located behind the second window in the uncooled housing to receive a spectral range of the incoming infrared radiation from the scene through the lens and the cooled filter wherein the uncooled infrared detector is substantially centered about the optical axis defined by the lens; wherein the tilted position of the cooled filter relative to the optical axis is selected to deflect parasitic radiation received at the cooled filter, including emitted thermal radiation by the uncooled infrared detector, away from and without returning back to, the uncooled infrared detector and to direct the deflected parasitic radiation to a cooled surface of the cooled housing to be absorbed; and wherein the cooled housing and the cooled filter in the tilted position collectively minimize a level of parasitic radiation in the apparatus including emitted thermal radiation and thus improve detection by the uncooled infrared detector.