| 摘要 |
PURPOSE:To prevent fogging from being caused even when the device is used for a long period by providing an overcooling preventing means which heats or keeps the reflecting surface of a reflective optical member warm almost uniformly. CONSTITUTION:When a lamp 1 which generates much heat like a mercury vapor discharge lamp and the reflective optical member 2 which surrounds the periphery of the lamp 1 are put in a lamp case and the lamp 1 is cooled forcibly with air, the overcooling preventing means (heater) 30 which heats or keeps the reflecting surface of the reflective optical member 2 warm almost uniformly is provided so as to prevent the reflective optical member 2 from being overcooled. Namely, a heating wire (heater) 30 is wound around the outer periphery of an elliptic mirror 2 to forcibly heat the reflecting surface. Consequently, the reflective optical member 2 or glass member such as a lens is prevented from fogging. |
