Abstract: A thermal imaging system is disclosed in which infrared radiation from the viewed scene is transmitted to a two-dimensional detector array carried on the focal plane of an optical/electronics module which has embedded in it amplifying, filtering and multiplexing circuitry utilizing MOSFET transistors. The module is located inside the cooling device. Cooling requirements depend on the alternatives (a) of using detectors responsive to wavelengths in the 3.0 to 5.0 micron range, which require less cooling, or (b) of using detectors responsive to wavelengths in the 8.0 to 12.0 micron range, which require liquid nitrogen cooling. The two-dimensional detector array may be combined with a limited scanning, called "nutation", which causes each detector to view a plurality of pixels in the incoming infrared radiation.

Abstract: A cryogenic cooler (10) includes a dewar (14) spaced from a cold finger (12). In the space (18) between the dewar and the cold finger, a trace amount of a noncondensable gas, preferably neon, is added to the air to maintain the thermal conductivity between the cold finger and the dewar and thereby to prevent temperature cycling in the cooler.

Abstract: An infrared radiation (IR) detector includes a cold shield consisting of (a) a light shielding portion having a substrate made of an infrared transmissive material, an infrared absorbing layer formed on one surface of the substrate, a dielectric layer formed on the infrared absorbing layer and an infrared reflecting layer formed on the dielectric layer, and (b) an opening portion consisting of a substrate made of an infrared transmissive material and a dielectric layer formed on the one surface of the substrate. The substrate and the dielectric layer are connected and generally continuous between the light shielding portion and the opening portion. The IR detector also includes an infrared detector array having a detective area arranged just below the opening portion of the cold shield.

Abstract: 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).

Abstract: A thermally insulating casing accommodates an infrared ray sensing element. The casing has a window which conducts infrared ray to the sensing element. The window is covered with heat absorption gas. An infrared ray emitting element may be accommodated within the casing. The casing may have a second window which passes infrared ray generated by the emitting element. The second window may be covered with the heat absorption gas.

Abstract: A preamplifier circuit provides a low noise, low power buffer preamplification stage for interfacing low output impedance, low noise sensors to a readout circuit at cryogenic temperatures. The preamplifier circuit may be formed of discrete components, or it may be formed as an integrated circuit that may have a plurality of channels. Each channel includes a germanium bipolar transistor exposed to a cryogenic environment for providing voltage gain and impedance matching to interface the sensor ouptut with a multiplexer.

Abstract: The invention relates to a high performance optical system for a wide angle IR imager requiring a cryogenic environment for the IR detector array. The wide angle requirement makes it necessary for one lens to be behind a "cold aperture" within the cryogenic environment where focusing is difficult and performance of the aperture reduced. These objectives are minimized by use of a telecentric lens pair, one member of which is within the cryogenic environment. The telecentric lens pair refocuses the primary image formed by an objective lens, permitting a high quality image to be formed on the IR detector array. The usual errors in positioning the internal lens, which might impair the quality of the focused image, are avoided by a compensatory repositioning of the externally accessible objective lens.

Abstract: In a double thermal coupled radiometer for preferable use with a centrifuge, an improved radiometer configuration is disclosed. The isothermal radiometic system improved is of the double junction variety (preferably copper-constantan-copper) and includes a black body housing defining a central concavity. The central concavity has a black body disk at the bottom thereof. The disk is preferably suspended by a copper and a constantan wire with one junction formed on the surface of the disk and the other junction formed on the surface of the housing. The improvement includes a plurality of and preferably three annular baffles defining central, circular and preferably concentric opening. These baffles are lodged in the opening of the housing above the mounted radiometer disk. The annular baffles on the side towards the radiation sources are coated as a black body so as to increase the thermal coupling of the black body housing to the ambient being radiometically observed.

Abstract: The invention uses a strip of infra-red detectors comprising a cold screen of the type that provides a constant viewing angle for all the directors in a direction that is prependicular to the axis of the strip. Two cylindrical mirrors are set at the ends of the strip and placed in the heated part of the cryostat containing the strip and the cold screen. The shape and dimensions of the mirrors as well as their positions are chosen so that the detector placed in the center of the strip detects, through reflection in two mirrors, only cold surfaces while the other detectors detect heated surfaces, through reflection in the two mirrors, in a proportion that increases with distance from the central detector of the strip, so that, along the axis of the strip, every detector has a substantially constant viewing angle. Applications: large-sized strips, for example in space applications.

Abstract: A heat radiation sensing device is provided, which comprises two receiver surfaces which are exposed to the radiation, one of which comprises a high absorption ability with respect to the heat radiation by means of a black coloring, while the other has a low absorption ability by means of a covering which reflects the heat radiation. These two receiver surfaces consist of NTC resistor material and are combined to form a bridge circuit with two cermet resistors which are independent of temperature. The four resistors are applied to a ceramic substrate and are connected with conductor path which, in turn, end in the four required connections. The ceramic substrate is fixed in a frame which carries a covering which is pervious to heat radiation to a great degree and which, in turn, carries a layer having a window over one of the two NTC resistors the layer is made of a material which reflects the heat radiation to a great degree.

Abstract: A miniature, evacuated and hermetically sealed detector refrigerator assembly for use in infrared imaging systems incorporates a miniature Joule-Thomson laminar refrigerator which serves as the substrate for the detector subassembly, electrical leads, as well as the primary structural element of the assembly. The detector subassembly is positioned on the cold region of the refrigerator, surrounded by a vacuum chamber and capped by an optical window or filter as required. As a result, the detector is cooled in a small and relatively inexpensive package that can operate intermittently or continuously, as desired.

Abstract: Calorimeter for measuring the energy transported by radiation. This calorimeter comprises an absorbing element able to absorb radiation and having an outer face exposed to the radiation and an inner face, said element undergoing a temperature rise during the interaction with the radiation. This temperature rise is measured by a thermopile. The calorimeter also comprises calibration means constituted by a strip-like resistive deposit in direct contact with the inner face of the absorbing element over at least 50% of the surface thereof. Application to the measurement of the energy transported by electromagnetic radiation or a particle flux.

Abstract: An infrared receiver for detecting a communications signal during a fixed reception period in a high noise environment that includes a sensor having a cooled detector mounted upon a substrate upon the end of a cold well tube that further includes a cooling gas tube having a fixed orifice to emit a cooling gas upon the interior surface of the substrate. The receiver further includes a signal processor that receives the detector signals and determines if the detector signals include prdetermined signal characteristics of the communications signal.

Abstract: An infrared detector has its sensor chip assembly (10,12,14) cooled to a relatively low temperature required for its operation, whereas a preamplifier (56) required to be positioned close to the sensor chip assembly and which generates considerably more heat than does the sensor chip assembly, is thermally isolated from the sensor chip assembly and its support (16) and is cooled to a higher temperature to thereby significantly reduce the power dissipated to the coldest refrigerator stage (90).

Abstract: A radiation detection apparatus, such as for the detection of infrared radiation, is formed of inner and outer cylindrical stainless steel vessels with the inner vessels supported from the top wall of the outer vessel by a thin, relatively long stainless steel tube. A heat transfer mounting member is attached to the bottom of the inner vessel and extends outwardly and then upwardly between and out of contact with the vessels to the position of a window opening within the outer vessel. A detector device is affixed in good thermal contact with the mounting member at the position of the window and thus is maintained substantially at the temperature of the bottom surface of the inner vessel. The surfaces of the inner and outer vessels may be highly polished to prevent heat transfer to the inner vessel by infrared radiation. The use of stainless steel for the outer vessel also allows utilization of a vacuum port window structure having a metal gasket to minimize potential gas infiltration.

Abstract: The inherent video noise and video-flashing encountered at the liquid nitrogen boiling point within a cryogenically cooled detector is substantially eliminated by filling any space which might entrap air with a flowable self-sealing silicone gel. The gel is sticky and maintains its adherence to both the cold finger and dewar as it is cooled to cryogenic temperatures without losing its internal self-cohesion. In the illustrated embodiment a two-part gel manufactured by Dow Corning under the trademark Sylgard 527 is employed. The gel is characterized by being self-sealing to at least a temperature within the range of -60 degrees C. to -100 degrees C. In addition, the gel is thermally stable at all temperatures from elevated ambient temperatures through cryogenic temperatures.

Abstract: An apparatus for mounting a device used for detecting infrared signals is disclosed. The apparatus includes a housing and an expander upon which the device is mounted. An insulating material comprising polymeric foam is disposed between the expander and the housing which allows the apparatus to be cooled without requiring evacuation of the apparatus.

Abstract: A cryogenic device for radiation detectors is provided comprising an enclosure situated between a cryogenic cold finger supporting a detector and an external wall. After a brief degasification under vacuum of said enclosure, at least one gas is therein introduced, whose liquefaction or solidification temperature is higher than the temperature reached by said cold finger.

Abstract: A turret system providing access to the interior of a vacuum vessel integral to a cryostat used for super conducting magnets in MRI systems. The system enabling the movable connection of a neck tube that provides access to the interior of the vacuum vessel when that tube is fixedly attached to the liquified gas container of the cryostat and moves with the liquified gas container, said moveable connection being affected by a supple member attaching said neck tube to said vacuum member, so that relative movement between said liquified gas container and said vacuum vessel does not over-stress said neck tube.

Abstract: The cooled infrared detector of an infrared microscope is scanned over a target specimen at ambient temperature, the signal is stored, inverted and added to subsequent radiance signals derived from subsequent scans of the target to provide a continuous correction for the "Narcissus Effect".

Abstract: The present invention is directed to a method and apparatus for reducing temperature variation in an infrared detector. The apparatus comprises a coldfinger for receiving thermal energy from an infrared detector. A thermal damper is also provided for conducting thermal energy from said detector to the coldfinger by one or more thermally conductive paths. A detector mount is used for combining the thermal energy flowing through the paths, thereby reducing the temperature variation in the detector.

Abstract: A gas-sample collection device provides for the matrix isolation of increased amounts of a sample material for spectrographic analysis from a gas chromatographic separation. The device includes an evacuated sample collection chamber containing a disc-like specular carousel having a generally circular lateral surface upon which the sample is deposited in an inert gas matrix for infrared (IR) spectral analysis. The evacuated sample chamber is mounted in a fixed manner and is coupled to and supports a rotating cryostatic coupler which, in turn, supports the specular carousel within the collection chamber. A rotational drive system connected to the cryostatic coupler provides for its rotational displacement as well as that of the sample collecting carousel. In addition, rotation of the cryostatic coupler effects vertical displacement of the carousel to permit the collection of an extended sample band in a helical configuration on the entire lateral surface of the carousel.

Abstract: A bolometer which is adapted for a wide-band of radiation including soft adiation, and in which the sensitivity of the time constant (the heat flow from the absorber layer to the dissipator layer) can be exactly preselected without regard to the wave length of the radiation. The bolometer includes an electrically insulating carrier foil which has mounted thereon an absorber layer on one side thereof and a resistance layer on the opposite side of the foil, the resistance layer being part of a resistance measuring bridge. A thermally conductive layer is placed between the absorber layer and the carrier foil. The thermally conductive layer has portions protruding beyond the absorber layer. A heat dissipator is in thermally conductive contact with the protruding portions of the thermally conductive layer to dissipate the heat of the absorber layer. The laterally protruding portions of the thermally conductive layer in contact with the heat dissipator are shielded against the radiation to be measured.

Abstract: An infrared photodetector is disclosed which is deposited directly onto a Joule-Thomson cryostat. The cryostat includes an elongated body having gas-carrying channels contained therein. The photodetector is deposited directly onto one end of the elongated body to form a direct thermal path between the detector and cryostat, thereby eliminating the need for any intermediate thermal bridge such as a mechanical bond, thermal conductive paste or epoxy. The direct contact between the photodetector material and the cryostat reduces the thermal mass of the structure to be cooled by the cryostat, thereby decreasing both the time and the quantity of gas required to cool the detector.

Abstract: A digital IR gas analyzer comprises a sample cell having a conical shaped interior wall and a filter wheel provided with HC, CO and CO2 interference filters. The filter wheel and IR detector are temperature stabilized. The HC, CO and CO2 gas samples are normalized to a precision reference voltage. The normalized samples are digitized and processed, i.e., for linearization, cross-talk correction and zero drift temperature compensation, by a digital processor. The processed samples are then converted to analog to drive HC, CO and CO2 meters. HC, CO and CO2 gas channels are zeroed simultaneously and calibrated automatically in response to control panel switches.

Abstract: The invention is an adjustable mount for positioning an electro-optic transducer in an evacuated cryogenic environment. Electro-optic transducers are used in this manner as high sensitivity detectors of gas emission lives of spectroscopic analysis. The mount is made-up of an adjusting mechanism 10 and a transducer mount 20. The adjusting mechanism provided five degrees of freedom, 3 linear adjustments and 2 angular adjustments. The mount allows the use of an internal lens 66 to focus energy on the transducer element thereby improving the efficiency of the detection device. Further, the transducer mount 20, although attached to the adjusting mechanism 10, is isolated thermally such that a cryogenic environment can be maintained at the transducer while the adjusting mechanism 10 remains at room temperature. Radiation shields 68 also are incorporated to further reduce heat flow to the transducer location.

Abstract: A sample gas is introduced into a sample cell housed in a cell block. A self-operated temperature-controlling type heater is disposed within the hollow place of the cell block and said sample cell is indirectly heated by the heat from said heater.

Abstract: A miniature, nonevacuated, detector refrigerator assembly for use in infrared imaging systems is described. The assembly incorporates a miniature Joule-Thomson laminar refrigerator which serves as the substrate for the detector subassembly, electrical leads, as well as the primary structural element of the assembly. The detector subassembly is positioned on the cold region of the refrigerator, surrounded by two prefabricated vacuum chambers and capped by an optical window or filter as required. As a result, the detector is easily built and is cooled in an efficient manner.

Abstract: A cryogenic cell comprises a sealed external annular chamber, adapted to be maintained under vacuum which chamber surrounds a heat shield. A section of the shield is exposed and is adapted to make contact with a closed cycle cooler. The shield encloses a sealed inner chamber adapted for the storage of a solid/liquid refrigerant. The shield has a relatively thin base and sidewall and the section which is exposed is a relatively thick upper collar which has a well leading to the top of the inner chamber immediately above and in contact with the top of the inner chamber. The inner chamber is connected at its lower end to a section containing an absorbent and the latter section is connected at its lower end to a further chamber suitable for the reception of a gamma radiation detector. The cryogenic cell is suitable for keeping the semi-conductor detector of a neutron borehole logging tool at the required low temperature.

Abstract: The method and apparatus permit analyses, by optical means, of properties of gaseous suspensions of particles, by measuring radiation that is emitted, transmitted or scattered by the particles. Determinations of composition, size, temperature and spectral emittance can be performed either in-situ or by sampling, and Fourier-transform infrared spectrometric techniques are most effectively used. Apparatus specifically adapted for performing radiation scattering analyses, and for collecting radiation from different sources, are provided.

Abstract: A cooling apparatus for an infrared up-convertor incorporates a transparent heat sink in a conductive heat exchange relationship with a surface of the up-convertor and a Joule-Thomson effect cryostat located outside of the incoming and emitted image paths for cooling the heat sink. In this manner, the cooling apparatus does not obscure the path of the image to or from the up-convertor.

Abstract: An improved detector dewar assembly in which the flange supporting the upper cap of the dewar assembly comprises a disc ceramic matrix, including buried electrical leads. This disc serves several purposes. First, it provides a vacuum tight electric feedthrough which connects a tape cable from the detector assembly to a pin assembly imbedded in the exterior portion of the disc feedthrough. Second, it includes metalizations on its top and lower surface in order to provide a surface for connecting (by brazing or soldering) the upper cap assembly and the major vessel wall. A tape cable comprising wires embedded in a flexible nonconductive matrix connects the detector element leadout wires with the electrical connectors of the feedthrough disc. The cable forms a collar which substantially surrounds the coldwell and has tabs at its basal portion which fold up to attach to pin or pad connectors on the lower surface of the disc.

Abstract: A training device is provided to test the skill of a worker assembling cors with cold fingers to dewars containing infrared detectors. The latter are very expensive and fragile. Dummy units are employed and undesirable contacts between these units are recorded electrically.

Abstract: The invention relates to an arrangement for an electronic component operable at low temperatures, in particular, to a radiation sensitive semiconductor component. The arrangement consists of a housing for the component and of a cooler which is in communication with the housing and operates in accordance with the Joule-Thomson effect. The invention consists in that there is arranged between the cooler and the adjacent housing wall a super-insulation comprised of a single- or multi-layered foil with low thermal conductivity and capacity and high thermal-transfer resistance.

Abstract: The invention relates to a housing for opto-electronic components, with the semiconductor component being cooled by a cooler which operates in accordance with the Joule-Thomson effect and is in communication with the housing. The gist of the invention is that the non-evacuation housing comprises several sections, with the first section of the housing which is in direct communication with the cooler having a low thermal conductivity and a low thermal capacity, whereas the end section of the housing containing a radiation transmitting window has a high thermal conductivity and a high thermal capacity.

Abstract: An apparatus for measuring bath temperature of metallurgical furnaces through a tuyere is disclosed. The apparatus comprises a periscope adapted to be inserted into a tuyere, a fiber optic cable having one end connected to the periscope for receiving radiation entering the tuyere from the bath of a furnace, and a two wavelength pyrometer connected to the other end of the fiber optic cable for analysing the radiations transmitted through the fiber optic cable to provide an indication of the temperature of the bath.

Abstract: Infrared radiation source arrangement, in particular for use in infrared spectral analysis. To an electrically insulating substrate (2) there is applied one and preferably at least two separate electrically conductive films (2a, 2b) adapted to be heated by application of a time dependent electric current thereto. Tow or more films may form a radiation group (array) in which each film (2a, 2b) is adapted to be energized separately with electric current from an electric drive circuit (1) for applying a time dependent, preferably pulse shaped electric current to the film or films, so that infrared radiation pulses are emitted. The electric current is time controlled in order that the radiation pulses from the respective films may be distinguished from each other in a detector (6). The thickness of the substrate and the thermal conductivity, specific heat and density of the substrate material are so chosen that the thermal time constant is adapted to the pulse frequency range of the drive circuit.

Abstract: An image sensing device is improved by an optical shield having a multi-aperture to provide high signal to noise ratio. The improved optical shield is provided with a plurality of shield elements forming a grid-like or cellular structure. With such a structure, the solid angle of the field of view for each sensing element becomes almost the same, resulting in the reduction of "shading". The distance between the heat shield and the array can be reduced, resulting in miniaturization of the device. Each sensing element is not shielded individually, so the pitch of the shield elements can be larger than that of the sensing elements, which allows easier and less costly fabrication of the shield.

Abstract: A rugged Fabry-Perot interferometer comprises a solid etalon (15) made of single-crystal silicon with precisely parallel stacks (13) and (14) of dielectric materials coated on opposite sides thereof. The stacks (13) and (14) are identical to each other, and each stack comprises a plurality of layers of different materials having alternately high and low indices of refraction. A dielectric ring (30) made of the same material as the etalon (15) is bonded to a peripheral portion of one side of the etalon (15) by an epoxy material having the same coefficient of thermal expansion as the ring (30) and the etalon (15). The ring (30) with the etalon (15) bonded thereto is kinematically mounted on Teflon contact members (34) within an annular receiving structure (31) made of a metal (such as copper) of high thermal conductivity.

Abstract: Military mechanical field equipment, such as an electrical generator, is camouflaged from airborne IR detection by enclosing the equipment in a double-walled enclosure having hollow walls through which air is forced to flow. By adjusting the air flow in the enclosure, the radiance from the enclosure can be made the same as its immediate surroundings. A dual temperature sensor senses temperature differences between the enclosure surface and the surroundings and varies the air cooling accordingly until thermal balance is achieved.

Abstract: An unfocused optical input signal is applied to an optically absorbent wall portion of an interaction region 30 in a fluidic device to effect flow impedance modulation thereat. The flow impedance modulation adjusts the velocity profile of the flow to achieve a desired output from the device.

Abstract: An infrared fluid analyzer with an improved sensitivity and signal to noise ratio is provided. The device includes a capacitor microphone for detecting absorption by the sample of characteristic infrared wavelength lines, and utilizes an electret material to electrically polarize the capacitive element. Also included are means for controlling the temperature of the infrared radiation source in order to stabilize the output thereof and increase the reliability of the instrument, and means for controlling the temperature of the fluid sample. In a double-beam embodiment of the invention, a gas-free reference cell is provided to further stabilize the instrument.

Abstract: A gas-sample collection device provides matrix isolation of individual gas bands from a gas chromatographic separation and for the spectroscopic analysis of the individual sample bands. The device includes a vacuum chamber containing a rotatably supported, specular carousel having at least one reflecting surface for holding a sample deposited thereon. A gas inlet is provided for depositing a mixture of sample and matrix material on the reflecting surface which is maintained at a sufficiently low temperature to cause solidification. A first parabolic mirror directs an incident beam of electromagnetic radiation, such as in the infrared (IR) spectrum, from a source onto the sample/matrix mixture while a second parabolic mirror directs a second beam of electromagnetic radiation reflected by the specular surface to an IR spectrometer for determining the absorption spectra of the sample material deposited on the reflecting surface.

Abstract: The degree of cure of a traveling carbonaceous polymeric material (on 48), formed (at 34) from a plurality of chemical reactants (32) and subjected to a curing process (at 42 and 44) is determined by directing (with 86 and 88) into the traveling material radiations including a first infrared radiation (A1) from the group thereof adapted to selectively interact with molecular resonance vibrations at frequencies that are characteristic of respective terminal functional groups of atoms involved in reactions that take place in the material during the curing process. Also directed into the material is a second infrared radiation that is either of the kind (R) that does not exhibit substantial selective interaction with molecular resonance vibrations in the material or of the kind (A2) that is adapted to selectively interact with molecular resonance vibrations at a frequency that is characteristic of groups of atoms forming the backbones of the polymeric molecules in the material.

Abstract: Apparatus for converting weak light, or light of low intensity, to electrical signals descriptive of such light. The apparatus is capable of sensing differences in photon flux over an area of detection, that is, sensing a pattern of lighter and darker areas. An important application of the apparatus is in spectroscopy and spectroscopic anaylsis, where it is desired to record a spectrum in other than visual form.

Abstract: A vacuum dewar for infrared detectors is disclosed, in which unitary Kovar leads are used to reduce heat load and improve reliability and ruggedness. The Kovar leads are encapsulated in the glass walls of the hollow stem which carries the sensor array and supplies cryogenic fluid for cooling the array. The Kovar leads extend throughout the entire length of the stem to form both the electrical feed-through and the contact points at each end of the stem for the attachment of wire leads or cables, and to form a reinforcing structure for the stem. A fabrication method is also disclosed, in which a unitary Kovar leadframe is held under tension while two concentric glass tubes, between which the leadframe is vacuum-sandwiched, are fused together to form a stem encapsulating continuous Kovar leads throughout its length, while preventing excessive oxidation of the Kovar leads.

Abstract: A radiation shield in a light detector and/or sensor assembly generally comprises a horizontally oriented buffer on which the detector is disposed, a vertically oriented radiation shield surrounding the detector, and a horizontally oriented collimating buffer disposed on the vertically oriented radiation shield above the detector. Advantages of the invention include minimization of the effect of radiation emitted from the hot junctions of a thermoelectric cooler employed in the detection assembly, and the provision of an electromagnetic shield when the arrangement is connected to the low-impedance side of the amplifying circuitry associated with the detector. The buffer preferably comprises a highly emissive material, while the collimating buffer is preferably of an electrically conductive material. Electromagnetic shielding can be provided by the use of high permeability material.

Abstract: A cooled infrared detector post includes a detector post formed of a stack of wafer disks with a detector substrate wafer forming one end of the post and a cooling chamber adjacent to the detector substrate with coolant supply and return passages formed in the series of wafers with a supply passage contained to a supply port with a supply passage forming a plurality of serpentine passages at various planes within the post and a return passage including a plurality of precooling chambers with the wafer stacked in a predetermined arrangement and fused together to form a monolithic post structure.

Abstract: The leads for an infrared detector unit are arranged to pass through bores in a cooled detector housing with intimate contact with the cooled detector housing for precooling the leads extending from the detector elements to the respective preamp leads.

Abstract: A Fourier transform infrared spectrometer utilizes a selectable area infrared detector to optimize performance of the instrument depending upon the nature of the sample being analyzed. The detector includes an inner detecting segment and one or more outer detecting segments which extend at least partially around the inner segment and are electrically isolated therefrom. In those cases where a small area detector provides optimal sensitivity and performance, only the inner detecting segment is enabled to contribute to the output of the detector. In those cases where a larger area detector provides optimal sensitivity and performance, one or more of the outer detecting segments are enabled to contribute to the output of the detector, either alone or in combination with the inner segment. Thus, a single detector in the instrument provides optimal sensitivity and performance for a wide range of applications.