Real time multispectral high temperature measurement: Application to control in the industry

Many devices are used to realize non-contact temperature measurements. Whenever the body to be controlled behaves as a black body, all the devices inferring the true temperature from the body radiation are accurate and reliable. On the other hand, when it exhibits a behavior different from the black body, emissivity compensations need to be done. In case of a known emissivity, the spectral system (single wavelength) is used whereas, for gray body (unknown but constant emissivity in a narrow bandwidth) a bicolor system is more likely to be utilized. For all other cases, assumptions about the emissivity variations as a function of the wavelength and the temperature have to be ascertained and multispectral system or “hybrid-systems” which are a mix between spectral and multispectral systems have been built and used in particular cases. In this paper, a real time multispectral imaging system based on two CCD cameras is presented. The system is herein carefully characterized and applications such as vision control system are presented. An extension of the system with three cameras is also exposed in the perspectives.