The cold light source is characterized by converting almost all other energy into visible light. The other wavelengths have little light, and the heat source is different. In addition to visible light, there is a large amount of infrared light, and a considerable part of the energy is converted into no contribution to the illumination. Infrared light. The light coming out of the heat source and the infrared filter should be similar to the light from the cold source, because the infrared light has been filtered out.