Abstract
The infrared radiation thermometer with an InSb detector operated dc-mode has been developed in the NMIJ for establishing a traceability of the infrared radiation thermometry in the middle-temperature range, 100°C-400°C. To remove chromatic aberration, it has an infrared doublet lens as an objective. Optical components except the objective lens are mounted in the cold radiation shield and are cooled by the liquid nitrogen. The radiation thermometer is calibrated against the blackbodies in the range from 0°C to 450°C. The responsibility of the thermometer is good enough to be used in the middle-temperature range.