| 摘要 |
PURPOSE:To remove dew condensation speedily by driving a fan reversely when the dew condensation occurs in an original image projection optical system and blowing external air in the device. CONSTITUTION:Dew condensation sensors 14-1-14-6 and a temperature sensor 15 detect the dew condensation of the optical system and the temperature of the optical axis storage part and comparing circuits 16-1-16-6, and 17 compare their outputs with respective set signal levels. If the ambient temperature of the optical system is lower than a specific temperature and dew condensation occurs to at least one optical element, an AND gate 19 outputs ''1'' to turn on a transistor (TR)20, a relay 21 is excited to changeover switches K1 and K2, and a fan motor 12' reverses to take external air in the device. At the same time, a switch K3 is turned on to turn on a heater 13 and then hot air is sent in the device containing the optical system, thereby removing dew condensation from original platen glass 2, reflecting mirrors 5-7 and 9, and a lens 8. |
