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:''Metal-halide lamp should not be confused with Halogen lamp'' A metal-halide lamp is an electric lamp that produces light by an electric arc through a gaseous mixture of vaporized mercury and metal halides (compounds of metals with bromine or iodine). It is a type of high-intensity discharge (HID) gas discharge lamp.〔 Developed in the 1960s, they are similar to mercury vapor lamps,〔 but contain additional metal halide compounds in the quartz arc tube, which improve the efficiency and color rendition of the light. The most common metal halide compound used is sodium iodide. Once the arc tube reaches its running temperature, the sodium dissociates from the iodine, adding orange and reds to the lamp's spectrum from the sodium D line as the metal ionizes. As a result, metal-halide lamps have high luminous efficiency of around 75 - 100 lumens per watt,〔 which is about twice that of mercury vapor lights and 3 to 5 times that of incandescent lights〔 and produce an intense white light. Lamp life is 6,000 to 15,000 hours.〔 As one of the most efficient sources of high CRI white light, metal halides were the fastest growing segment of the lighting industry.〔 They are used for wide area overhead lighting〔 of commercial, industrial, and public spaces, such as parking lots, sports arenas, factories, and retail stores,〔 as well as residential security lighting and automotive headlamps (xenon headlights). The lamps consist of a small fused quartz or ceramic arc tube which contains the gases and the arc, enclosed inside a larger glass bulb which has a coating to filter out the ultraviolet light produced.〔〔 They operate at a pressure between 4 to 20 atmospheres, and require special fixtures to operate safely, as well as an electrical ballast. Metal atoms produce most of the light output.〔 They require a warm-up period of several minutes to reach full light output.〔 ==Uses== Metal-halide lamps are used both for general lighting purposes both indoors and outdoors, automotive and specialty applications. Because of their wide spectrum,〔(【引用サイトリンク】title=Metal Halide )〕 they are used for indoor growing applications, in athletic facilities and are quite popular with reef aquarists, who need a high intensity light source for their corals. Metal-halide lamps are used in automobile headlights, where they are commonly known as "xenon headlamps" due to the use of xenon gas in the bulb instead of the argon typically used in other halide lamps. They produce a more intense light than incandescent headlights. Another widespread use for such lamps is in photographic lighting and stage lighting fixtures, where they are commonly known as MSD lamps and are generally used in 150, 250, 400, 575 and 1,200 watt ratings, especially intelligent lighting. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Metal-halide lamp」の詳細全文を読む スポンサード リンク
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