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Patent Searching and Data


Title:
REAR FOCUS TYPE ZOOM LENS
Document Type and Number:
Japanese Patent JPH0593861
Kind Code:
A
Abstract:
PURPOSE:To provide the rear focus type zoom lens which has an X8 power variation ratio and an about 1.8 F number by providing four lens groups on the whole, putting the lens in focus through a lens group behind a power variation system, and reducing the overall size of the lens system. CONSTITUTION:This zoom lens consists of the 1st, 2nd, 3rd, and 4th groups with a positive, a negative, a positive, and a positive refracting power in order from an object side; and the power is varied by moving the 2nd group, and the 4th group is moved to correct image plane variation accompanying the power variation and to put the lens in focus. The 2nd group consists of three separate lenses which are a negative lens 21, a negative lens 22, and a positive lens 23, and a condition is satisfied, where DA is the air interval between the lenses 22 and 23, RA and RB are the radii of curvature of the image-plane side surface of the lens 22 and the object-side lens surface of the lens 23, and f2 is the focal length of the 2nd group.

Inventors:
MURATA YASUNORI
Application Number:
JP27879391A
Publication Date:
April 16, 1993
Filing Date:
September 30, 1991
Export Citation:
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Assignee:
CANON INC
International Classes:
G02B13/18; G02B15/16; (IPC1-7): G02B13/18; G02B15/16
Domestic Patent References:
JPH04171411A
Attorney, Agent or Firm:
高梨 幸雄