| 摘要 |
A high intensity discharge lamp is provided with an arc tube having an improved heat insulator. The heat insulator is formed proximate to at least one end of the arc tube but absent around an outer middle portion of the arc tube. In addition, the heat insulator is made of a material transmissive of visible light but not transmissive of thermal radiation. By adding a heat insulator to the cold spot area of the arc tube, radiation heat lose from that area will be significantly reduced and the temperature of that area will be increased. Moreover, by choosing a material that will not get oxidized and will not block the visible light, higher lamp efficacy can be achieved.
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