Metal halide discharge lamp suitable for an optical light source.

摘要

A metal halide discharge lamp operated from a D.C. power source, which is suitable for an optical light source, has a quartz arc tube. Anode and cathode electrodes are disposed in the arc tube. A gap length between electrodes is so short that the metal halide discharge lamp is capable to function as a point light source. The arc tube contains an inert gas, mercury and metal halide additives including metal bromine. By utilizing the catephoresis effects, the transformation of silica (SiO2) of the arc tube to be the cystbalite or the formation of an opaque substance on the arc tube is prevented. Atomic percent of bromine to halogen contained in the arc tube is about 60% to 90% and a wall load developed in the arc tube is substantially greater than 40 W/cm<2>.