High-intensity-discharge lamp of the mercury-metal halide type which efficiently illuminates objects with excellent color appearance

摘要

High-intensity-discharge lamp of the mercury-metal halide type efficiently illuminates objects with excellent color appearance. The arc tube filling comprises the usual inert, ionizable starting gas and mercury in predetermined amount as required to provide a predetermined operating voltage drop between the lamp electrodes. The metal halide filling substantially comprises a predetermined limited amount of thallous iodide, a predetermined limited amount of stannous iodide and a predetermined limited amount of calcium iodide. The stannous iodide is used in such amount that it serves primarily to enhance the emission of the calcium iodiode and the amount of stannous iodide is sufficiently limited to curtail the generation of the characteristic continuous tin emission. The calcium iodide is present in greater gram amount than the tin iodide so that the effects of the calcium iodide emission are predominant. The resulting discharge has its emission concentrated in three selected wavelength portions of the visible spectrum, namely, blue violet which is due primarily to the calcium iodide emission, green which is due to the thallium iodide emission, and red which is due to the tin-iodide-enhanced calcium iodide emission. The efficiency of the composite discharge is good and the color appearance of illuminated objects is excellent.