| abstract |
The color temperature of irradiation light from a metal halide lamp comprising an arc tube filled with metal halide, mercury and inert gas, electrodes at the opposite ends of the arc tube and a glass housing of housing said arc tube is lowered to 2000-6000 K by a selective transmission coating. The selective transmission coating which transmits irradiation light of longer wavelengths generated between said electrodes and reflects the irradiation light of shorter wavelengths is applied to the outer surface of said arc tube. The selective transmission coating transmits the irradiation light of wavelengths longer than nearly 600 nm and reflects the irradiation light of wavelengths shorter than nearly 600 nm. This coating is particularly effective for a metal halide lamp filled with metal halide which comprises dysprosium, neodymium and iode of cesium and the color temperature of the irradiation light inside the arc tube is 6000-7500 K. |