Measurements of surface temperature and emissivity by two-dimensional four-color thermometry with narrow bandwidth

To study characteristics of heated material surface over 600 K, non-contact measurements of two-dimensional (2D) distributions of temperature and emissivity are very useful for process monitoring in engineerings, because of remote sensing in a short time. The 2D temperature distributions enable us to monitor the surface temperature quantitatively with high spatial resolution. The 2D emissivity distributions give us a capability to judge thermal degradations or defects of the surface. The 2D distributions of temperature and emissivity determined by two-color method using a CCD camera and two optical filters have been already reported by many authors. In this study, a four-color method is proposed to improve accuracy and precision of the temperature and emissivity. Four optical filters with narrow bandpass of 10 nm were used for our measurements, because the thermometry using narrow band is advantageous over that using wide one in terms of accuracy of temperature determination. Distributions of temperature and emissivity were also determined by two-color method for comparison. The results obtained by the four-color method have higher accuracy and precision than two-color method and we can recognize that several conditions of the material surface are clearly illustrated by the resultant 2D emissivity distribution.