| 摘要 |
PURPOSE:To obtain a bright and broad view angle, by constituting the system from the front and rear groups in the order of magnification side, constituting the front group with at least two different lenses which are a positive lens at the magnification side and a negative lens at the projected side and satisfying specified conditions. CONSTITUTION:The system consists of the front groupIand the rear group II in the order of magnification side, and the front gruopIconsists of at least two different lenses such as a positive lens L1 at the magnification side and a negative lens P at the projected side. On the other hand, the rear group II consists of, in the order of the magnification side, a positive lens L4, a negative combined meniscus lens L5 having the concave surface toward the magnification side, a positive lens L6, and a positive combined meniscus lens L7 having the convex surface toward the magnification side. The conditions of equationsI-IV are satisfied, where (f) is the focus of the total system, f1 is the synthesized focus of the front groupI, D4 is the interval of air between the front groupI and the rear group II, DB is the thickness of the axis of the lens L3, RA is the radius of curvature of a plane of the lens L3 toward the projected side, and RB and RC are the radiiof curvatures of the lenses L5 and L7 at the magnification and projected sides respectively. |
