| 摘要 |
PURPOSE:To eliminate the need to very the slit width of a slit specifying plate for light quantity adjustment with copy magnification by arranging the slit specifying plate near the position obtained from a specific equation based upon the focal length and F value of an image forming lens. CONSTITUTION:The slit specifying member for light quantity adjustment is arranged near at distance (x), expressed by the equation, from an image plane along the optical axis. In the equation, (f) and F are the focal length and F value of the image forming lens 2, ma and mb are maximum in-use enlargement magnification and minimum in-use reduction magnification, and L is the slit width of an original. Consequently, the slit of exposure luminous flux is specified by the slit specifying plate fixed at the constant position from the maximum enlargement magnification to the minimum reduction magnification, so the quantity of light is adjusted at the constant ratio regardless of magnification variation. |
