Title:
ZOOM LENS
Document Type and Number:
Japanese Patent JPH03180809
Kind Code:
A
Abstract:
PURPOSE:To obtain an about X3 - X8 zoom ratio with a small number of lenses and to make the zoom lens compact and reduce its cost by composing a lens system of lenses in four groups and satisfying specific conditions. CONSTITUTION:The lens system consists of a 1st group I composed of a negative meniscus lens which is convex to the object side and a positive lens which has a large-curvature surface on the object side, a 2nd group II composed of a negative lens which has a large-curvature surface on the image side and a positive meniscus lens, a 3rd group III with positive refracting power, and a 4th group IV with positive refracting power, and one aspherical surface each is provided in the 2nd group and 3rd group. Then inequalities I, II, and III are established, where phiI and phiII are the composite refracting power values of the 1st and 2nd groups, AII the on-axis gap of the lenses in the 2nd group, fW the focal length of the whole system at the wide-angle end, and ri the radius of curvature of an (i)th surface counted from the object side.
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Inventors:
HATA KAZUYOSHI
Application Number:
JP32016989A
Publication Date:
August 06, 1991
Filing Date:
December 08, 1989
Export Citation:
Assignee:
MINOLTA CAMERA KK
International Classes:
G02B13/18; G02B15/16; G02B15/173; (IPC1-7): G02B13/18; G02B15/16
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