Abstract
We have tried to improve the spectral radiant characteristics of the metal halide lamps by controlling the arc temperature by means of an additional metal halide which emits almost no spectral lines in the visible range. This technique has been applied to two kinds of metal halide lamps, the red-colored lithium iodide lamp and the high color rendering thorium iodide lamp. The former has been improved in the purity of red color and the latter has been improved in color rendering property by the addition of aluminum iodide or lead iodide. In both lamps, the arc temperature is lowered, decreasing selectively the visible mercury atomic lines.
