U.S. Philips Corporation

David J Gowlett

William A Dunn

Robert J Barton

An infrared detector comprises an envelope in which a detector element (3) is mounted on an end of a cold finger (1). A chemically-active getter (30) is present in the space between the cold finger (1) and the envelope window (7) and outer wall (2). In accordance with the present invention the getter comprises a porous layer (30) of chemically-active getter material deposited on an inside surface area of the outer wall (2) at a location separated from both the cold finger (1) and the window (7). The getter (30) can be activated (or re-activated) by heating through the portion of the outer wall (2) on which the getter material (30) is deposited, e.g. using a heater coil (50). Preferably the getter material (30) on the outer wall (2) extends around heat reflector, e.g. a reflective surface area of the cold finger (1). The cold finger (1) may be operated to cool the detector element (3) while heating the layer ( 30) to activate the getter.

Infrared detector construction including a getter and method for

A device chamber (12) is evacuated by pumping via an evacuation tube (35) to produce a vacuum space in communication with a chemically-active getter (30) which is provided in the tube (35) to getter gases from the evacuated chamber (12). In accordance with the invention, the getter (30) in the form of one or more movable bodies of the getter material is activated by heating in the evacuation tube (35) at a safe location (36) distant from the chamber (12). It is then moved towards the chamber (12) and is retained in the sealed evacuation-tube outlet (31) of the device. A vacuum-permeable screen (12) in the evacuation-tube outlet (31) inhibits passage of the getter material (30) into the chamber (12) where it might, for example, otherwise damage or obscure an infrared detector element. This permits the inclusion of the getter (30) in an inexpensive manner which does not require the use of a getter unit with a support element and/or vacuum-sealed electrical connections, and is compatible with space limitations and standard device envelope requirements for infrared detectors. Furthermore, the getter (30) is activated by heating at a location which avoids damage to the device, and after moving towards the chamber (12) the evacuation tube (35) is shortened to provide a short (or even non-protruding) outlet (31) from the chamber (12).

Methods of producing vacuum devices and infrared detectors with a getter

An infrared detector has an infrared detector element (2) mounted at a first part (11) of a housing (1), a Joule-Thomson cooling element (3) accommodated in a second part (12), and an infrared transmissive window (15) at the front of the housing (1). A compact, space-saving and light weight structure with improved optical efficiency is obtained. The core of the Joule-Thomson cooling element (3) forms a third part (13) of the housing (1), and these second and third parts (12 and 13) of the housing extend towards the front of the detector. The cooler core (13) which may carry a cooled filter (25) has a hollow shape or is otherwise infrared transmissive in front of the detector element (2) and can direct incident radiation (50) towards the detector element (2). For this purpose the inner surface of the hollow core (13) may carry a reflective conductor pattern (18,19) which also provides electrical connections for the detector element (2). This core part (13) may seal a channel in a grooved intermediate member (48 in FIG. 3) between the second and third housing parts (12 and 13) so as to form the Joule-Thomson cooling element (3) without requiring conventional finned metal tubing (31 in FIG. 1).

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Hampshire, United Kingdom

David J Gowlett