| 摘要 |
PURPOSE: To prevent the fluctuation in the image-forming position of an optical system caused by shrinkage at the time of a low temperature and expansion at the time of a high temperature by controlling an exposure optical system to be at a suitable temperature. CONSTITUTION: The axial center part of a supporting member 20 supporting the exposure optical system 12 is made to be a hollow part 20A, and an electric heater H and a heat pipe P are arranged on the inner peripheral surface of it, and also an intake air hole provided with a dust-proof filter (f) is provided at one aperture part of the hollow part 20A and a discharge hole provided with a propeller fan F is provided at the other aperture part, and in the case that the temperature of the supporting member 20 detected by a temperature sensor S is equal to or below normal temperature, the air heater H is only actuated, and in the case that it reaches a temperature equal to or above the normal temperature, the electric heater H is stopped and the propeller fan F is actuated and the temperature of the supporting member 20 is controlled by working together with the heat pipe P, so that the exposure optical system 12 is maintained at a suitable temperature. |
