Estimation of ambient radiation temperature for emissivity-corrected thermography

A non-contact method for the measurement of emissivity, and emissivity-corrected temperatures has been developed, where the ambient radiation-temperature is changed in a discontinuous way. When the ambient radiation-temperature is changed quickly, so that the surface temperature of the object can be assumed to be unchanged, the radiometer output before, and immediately after that change can be expressed as two simultaneous equations. The temperature and emissivity of the surface can be derived by solving these equations when the ambient radiation-temperatures are known. In previous studies, one or two hoods were used to provide the ambient radiation-temperature. However, there was a problem in controlling the ambient radiation-temperature. A new method is introduced where two reference plates coated with paints of different emissivities are placed in the field of view of the infrared camera. Eight simultaneous equations were derived from regions of the plates, and the ambient radiation-temperatures before and after the change were obtained by solving these equations. The validity of this method was confirmed by experiment. This method will eliminate the need to use hoods as in the previous report, and will simplify the equipment needed.