| 摘要 |
PURPOSE:To prevent a deficiency in the quantity of light, a decrease in resolving power, etc., from occurring owing to the contamination of an optical system by releasing the mirror of an optical device by a dust protection plate in an exposure process and covering it in a return process. CONSTITUTION:An arm 28 with a roller 30 which contacts the slanting surface of an operating cam 31 under an original platen 11 is energized counterclockwise by a spring 28 and a lever 24 is also energized by a spring 26, so that the mirror 3 on a scanning optical path is covered with the dust protection plate 21 when not in operation. The leftward movement of the original platen 31 presses down the arm 28 and the clockwise rotation of the lever 24 and the counterclockwise rotation of a sector gear 23 allows the dust protection plate 21 to release the mirror 3 during exposure; and the roller 30 returns along the right-side slanting surface of the cam 31 and the dust protection plate covers the mirror. Therefore, the mirror is covered with the dust protection plate except during the exposure and prevented from being contaminated to prevent a deficiency in the quantity of light, a decrease in resolving power, etc., thereby obtaining images of high quality.
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