| 摘要 |
PURPOSE:To decrease the number of lenses and at the same time to eliminate a control mechanism for the length of an optical path, by adding a mirror to a lens system in an attachable and detachable way to make it function as an in-mirror lens or a through-lens according to the attachement or detachment of the mirror. CONSTITUTION:A mirror is added in an attachable and detachable way to an exposure lens system of a copying machine which leads the image of an original illuminated by a light source onto a photoreceptor for the image formation and exposure. The lens system includes a lens 1 or plural lenses 1, 1', etc. For instance, in the case of an in-mirror lens combining the lens 1 and a mirror 2, a through-lens is obtained by unsetting the mirror 2. In this case, the beam passes just once through the lens 1. While an in-mirror lens is obtained by setting the lenses 1 and 1' at both sides of the mirror 2. In this case, the lens 1' is not used. When the mirror 2 is excluded, a through-lens system is obtained with a focal distance which is optimum to the variable copy magnification ratio. |
