| 摘要 |
A Gauss type objective lens system with a high speed of F1.2 for 35 mm SLR cameras is provided. The lens system consists of seven lenses, the object side surface of the second lens being aspheric, and fulfills the following conditions: 0.65<Da/Db<1.1 B<0 and C<0 0.55f<R<f wherein: Da represents the sum of axial distance from the object side surface of the second lens to the image side surface of the third lens; Db represents the sum of axial distance from the object side surface of the fourth lens to the image side surface of the fifth lens; B and C represent the aspheric surface coefficients of the fourth degree and of the sixth degree, respectively; f represents the focal length of the whole lens system; and R represents the paraxial radius of curvature of the object side surface of the second lens.
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