Visible Light Source Temperature Estimation Using Digital Camera Photography

Light source temperature measurement has been an important aspect in many industrial applications. The aim of this study is to determine the temperature of different sources like flames, incandescent lamps. The sensor installation is difficult in these sources. Imaging these sources to correlate with the temperature is attempted. A digital still camera is used to capture the source images. The optical characteristics of CCD sensor are not mentioned in the camera specifications. It is desired that the device bandwidth should be greater than the source bandwidth. Hence, the optical characteristics of the camera are also obtained. As Incandescent lamp is the most familiar light source its photographs are taken. The images are taken at known excitation voltages in a dark room with camera settings unaltered. Filament temperature is a function of intensity. Intensity difference of two consecutive images is found out by image subtraction. Unwanted part of image, like reflection from the shell is removed by thresholding and segmentation. The colour temperature of the filament can be found out with reference to black body radiations. If these values are compared with standard temperatures, source temperature values can be predicted.