Improvements in the design of thermal-infrared radiation thermometers and sensors

A new design for thermal-infrared radiation thermometer and sensors is described. Critical optical elements. such as the field stop, Lyot stop collimating lens. and detector are placed inside a thermally stabilized assembly that is controlled using thermo-electric coolers and thermistors. The assembled radiation thermometer is calibrated using both variable-temperature fluid-bath and heat-pipe blackbodies from -45 degrees C to -75 degrees C and the use of a modified-Planck function and these blackbodies. The size-of-source effect both with and without the Lyot stop has been measured. This new design. during operations without the need for cryogenic cooling, demonstrates sub millikelvin temperature measurement resolution with few millikelvin, week-long stable operations while measuring room-temperature objects.