2-COLOR MIDINFRARED THERMOMETER WITH A HOLLOW GLASS OPTICAL-FIBER

We have developed a low-temperature optical-fiber-based two-color infr ared thermometer. A single 700-mu m-bore hollow glass optical fiber co llects and transmits radiation that is then modulated and split into t wo paths by a reflective optical chopper. Two different thermoelectric ally cooled mid-infrared HgCdZnTe photoconductors monitor the chopped signals that are recovered with lock-in amplification. With the two pr eviously obtained blackbody calibration equations, a computer algorith m calculates the true temperature and emissivity of a target in real t ime, taking into account reflection of the ambient radiation field fro m the target surface. The small numerical aperture of the hollow glass fiber and the fast response of the detectors, together with the two-c olor principle, permit high spatial and temporal resolution while allo wing the user to dynamically alter the fiber-to-target distance. (C) 1 998 Optical Society of America.