| 摘要 |
PURPOSE:To eliminate a magnification error due to the backlash of a gear, etc., by moving the backlash of a lens drive system toward the enlargement side during shifting a lens at the time of changing a magnification from a reduction magnification to an enlargement one, and moving a lens to a specified magnification position after said backlash is moved toward the reduction side at the time of changing from the enlargement to reduction. CONSTITUTION:A wire loop 14 wound on a pulley fixed on a spindle 45, which is rotated and driven through a gear, etc., from a lens drive source 40, moves a lens 27. A wire loop 51 wound on a pulley installed on a member, which is engaged with a rotary plate cam 42 fixed on the spindle 45 and executes a straight line motion, carries out the variable power shifting of a mirror. At the time of changing the reduction magnification to the enlargement one. the backlash of the lens drive system is moved toward the enlargement side, and the lens is shifted to the specified magnification position. On the other hand, when the enlargement magnification is changed to the reduction, said backlash is moved toward the reduction side, and the lens is sifted to said position.
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