sudden prevention device null of the glass lens in the magnification change

摘要

PURPOSE:To prevent the collision of lenses by providing a means for detecting the position of the lenses to a copying machine for varying powers by the combination of a main lens which moves to several points in the optical axis direction and stops and additive lenses to be inserted into the optical axis in the respective positions thereof. CONSTITUTION:The image of an original 6 is projected via mirrors 7-10 and a main lens 10 to a photosensitive drum 11. The main lens 1 is movable to several stages along the optical axis and additive lenses 2-5 are inserted to the optical axis in the respective positions thereof. The magnification is changed to several stages by the combination of the main lens 1 and the additive lenses 2-5. The lens 1 is movable only when a means for detecting the additive lenses detects the evacuation of the lenses 2-5. The movement of the additive lens corresponding to the position where the lens stops is made possible only when the stop of the lens 1 at a certain point is checked by a detecting means.