| 摘要 |
PURPOSE:To reduce weight and size by consisting a titled lens, successively from an object side, of 4-group 6 lenses of positive biconvex and negative biconcave combined meniscus, positive single meniscus, positive single meniscus and negative biconcave and positive biconvex combined meniscus lenses and forming these lenses so as to satisfy specific conditions. CONSTITUTION:A titled lens is formed of an orthometa type lens of 4-group 6 lenses consisting, successively from an object side, of the 1st group lens of the meniscus combined with positive biconvex and negative biconcave lenses and directing the convex face to the object side, the 2nd group lens of the positive single meniscus directing the convex face to the object side, the 3rd group lens of the positive single meniscus directing its convex face to the object side and the 4th group lens of the meniscus combined with negative biconcave and positive biconvex lenses and directing its convex face to the object side. The conditions specified by the equations I -IV are satisfied where f is designated as the combined focal length of the entire lens system, f3 as the focal length from the object side to the 3rd face, f5 is the focal length from the object side to the 5th face, ni as the refractive index of the i-th lens from the object side, and gammai as the Abbe number of the i-th lens from the object side. The lens having a small size and lightness and high contrast is thus obtd. by using plastic materials. |
