Improved Infrared Fiberoptic Radiometer For Thermometry In Electromagnetic Induced Heating

Infrared fiberoptic radiometry of thermal surfaces offers several advantages over refractive optics radiometry. Besides eliminating the need for a direct line of sight to the measured surface, it combines high capability of resolving small areas with high efficiency of power coupling. Those aspects are treated theoretically in this paper. Undesired effects in fiberoptic radiometry are discussed and quantified by a factor termed the figure of merit. We also describe a novel infrared multi-channel fiberoptic radiometer, useful for thermometry in strong electromagnetic fields. With this system, thermometry is possible either in contact or non-contact mode, in the temperature regime 0-70°C, which is attractive for medical applications. The radiometer signal is linearly dependent on temperature, simplifying the calibration significantly. This system was used to monitor and control the temperature of samples heated by microwave and radio-frequency fields.