JPS54157620A - Photographic telephoto lens - Google Patents

Abstract

PURPOSE: To achieve the balance of aberration correction and prevent the degradation in the positive coma aberration and distortion aberration produced from the refracting power of the front group by making the combined thickness of the 5 group type through combination of positive and negative single lenses smaller under the specified conditions.

CONSTITUTION: The front group disposed with a biconvex single lens L₁ whose convex face of a larger curvature is opposed to the object side as the 1st group subsequently from the object side, a plane-concave or negative meniscus single lens L₂ whose object side is a concave lens as the 2nd group and a positive meniscus single lens L₃ whose convex face of a larger curvature is faced to the object side as well as the rear group disposed with a megative neniscus single lens L₄ whose convex face is faced to the image side as the 4th group and a positive single lens L₅ on the image side as the 5th group are disposed on the optical axis by leaving a specified distance. The formulas (1) thru (7) are satisfied in respective specifications. (f is focal length, d is axial air spacing, r is radius of curvature and υ is Abbe number).

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