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Patent Searching and Data


Title:
【発明の名称】中望遠レンズ
Document Type and Number:
Japanese Patent JP2717560
Kind Code:
B2
Abstract:
A telephoto lens system which composed of a front group comprising, in order from the object side, a positive first lens having a convex surface of large curvature directed toward the object, a positive meniscus second lens having a convex surface of large curvature directed toward the object and a negative third lens having a concave surface of large curvature directed toward the image, and a rear group comprising, in order from the object side, a biconvex fourth lens, a biconcave fifth lens, a positive sixth lens and a seventh lens having a weak positive refractive power, all lenses except the seventh lens being moved in unison to effect focusing. The lens system satisfies conditions which result in a light weight lens system having a focal length of about 100 mm and a large effective aperture ratio of 1:2.0, and which is capable of satisfactory compensation for spherical aberration and astigmatism over a shooting range from infinity to close-up at a magnification of about -0.1x.

Inventors:
Yoneyama Shuji
Application Number:
JP27840188A
Publication Date:
February 18, 1998
Filing Date:
November 02, 1988
Export Citation:
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Assignee:
Asahi Optical Co., Ltd.
International Classes:
G02B9/64; G02B13/02; (IPC1-7): G02B13/02; G02B9/64
Attorney, Agent or Firm:
Itami Tatsuo