Anti-condensation device for infra-red detector

Abstract

Abstract An infra-red (IR) detector operating in ambient temperatures in the range of 4* to 200* Kelvin, and pressures in the range of 10 2 to 10 12 mm Hg is provided with a trap for preventing condensation and thus icing of water molecules in the infra-red (IR) optical path that may be present in or near the detector or icing of water molecules which may emerge from the surface of the components adjacent to the detector owing to the ambient low pressures. The detector is mounted within a two-piece cylindrical shield around the IR-path arranged in coaxial spaced relation. The clearance space between the shield pieces defined by the overlapping open ends of the cylinders is less than the mean free path of water molecules at the ambient pressure which is less than 10 microns for orbiting satellites. The outer shield is kept at a temperature that is greater than the vapor condensation or crystallization temperature while the inner shield, insulated from the outer shield, is kept at a temperature that is less than the vapor condensation or crystallization temperature. Water vapor or other vaporizable contaminants that would tend to leak into the portion of the inner shield adjacent to the detector surface are condensed or crystallized at the surface of the inlet portion of the space and thus precludes such vapors from being deposited on the operating portions of the detector disposed within the inner shield. Although water vapor is the more troublesome volatile vapor that is removed from the sensor chamber, oils, alcohols, and various synthetic polymers are also removed precluding contaminant deposition in the sensor chamber.

Inventors

• 👤 R Williams

Bibliographic Details