| 摘要 |
PURPOSE:To vary the size of the image formation area while maintaining a constant longitudinal/lateral ratio through one driving means by varying the size of the area while holding the moving speed ratio of both light shield members at the constant longitudinal/lateral ratio of the image formation area. CONSTITUTION:Drums 22 and 23 are used to take up the orthogonal light shield members 20 and 21, and timer gears 24 and 25 which have a 1:1 gear ratio are used as a transmission means between both drums. One-side edges of the light shield members 20 and 21 are fixed to the drums 22 and 23 and one-side terminals of ropes 27 and 28, and 29 and 30 are bound to both ends of the other-side edges; and the other-side ends of the ropes are coupled with pulleys 31-34 which incorporates a spiral spring to draw the light shield members with a weak force. In this constitution, the diameter ratio of the drums 22 and 23 is set to 1:2<1/2>, and then the light shield member 20 is moved by a driving motor 26 and the drum 23 is rotated through the timer gears 24 and 25 to move the light shield member 21 and also sets its moving speed to 1:2<1/2>.
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