US 6,856,467 B2Granted

Image pickup system

AssigneeOlympus Corporation

InventorNoriyuki Iyama

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Abstract

The invention has for its object to use a zoom system that comprises a reduced number of lens elements, is compact and simplified, and has high image-formation capability, thereby achieving thorough size reductions in video cameras or digital cameras. A zoom lens for use on an image pickup system comprises a first lens group G1 negative power comprising an aspheric negative lens element and a positive lens element, a second lens group G2 comprising a positive single lens element, a positive doublet wherein a positive and a negative lens element are cemented together in this order and which is in a meniscus form convex toward an object side of the zoom lens and a positive single lens element, wherein two or more surfaces except the cementing surface of the doublet are each defined by an aspheric surface, and a third lens group G3 comprising one positive lens component. For zooming from the wide-angle end to the telephoto end of the zoom lens, the second lens group G2 moves only toward the object side of the zoom lens, and the third lens group G3 moves in a locus different from that of the second lens group G2. For focusing, the third lens group G3 moves. Condition (1) for the shape factor of the object side-positive lens element in the second lens group G2 and condition (2) for the magnification of the second lens group G2 are satisfied.

Claims19

Dependent claims

An image pickup system comprising a zoom lens and an image pickup plane located on an image side of the zoom lens, wherein:

said zoom lens comprises, in order from an object side of said zoom lens, a first lens group of negative refracting power comprising a negative lens element having an aspheric surface and a positive lens element, a second lens group comprising, in order from an object side thereof, a positive single lens element L21, a doublet component of positive refracting power wherein a positive lens element L22 and a negative lens element L23 are cemented together in this order and which is in a meniscus form convex toward the object side and a positive single lens element L24, wherein two or more surfaces except a cementing surface in said doublet component are each defined by an aspheric surface, and a third lens group composed of one positive lens component, wherein:
for zooming from a wide-angle end to a telephoto end of said zoom lens focused on an object point at infinity, said second lens group moves only toward the object side, said third lens group moves in a locus different from that of said second lens group, said third lens moves for focusing, and the following conditions (1) and (2) are satisfied:
−0.4<(R21F+R21R)/(R21F−R21R)<0.3 (1)
1.4<−β2T<2.1 (2)
where R21F is an axial radius of curvature of an object side-surface of the single lens element L21 in the second lens group, R21R is an axial radius of curvature of an image side-surface of the single lens element L21 in the second lens group, and β2T is a magnification of the second lens group at the telephoto end focused on an object point at infinity.

2 more elements

An image pickup system comprising a zoom lens and an image pickup plane located on an image side of the zoom lens, wherein:

said zoom lens comprises, in order from an object side of said zoom lens, a first lens group of negative refracting power comprising a negative lens component having an aspheric surface and a positive lens component, a second lens group composed of, in order from an object side thereof, a positive single lens element L21, a doublet component of positive refracting power wherein a positive lens element L22 and a negative lens element L23 are cemented together in this order and which is in a meniscus form convex toward the object side and a positive single lens element L24, wherein two or more surfaces except a cementing surface in said doublet component are each defined by an aspheric surface, and a third lens group comprising a positive lens component, wherein:
for zooming from a wide-angle end to a telephoto end of said zoom lens focused on an object point at infinity, said second lens group moves only toward the object side, said third lens group moves in a locus different from that of said second lens group, said third lens moves for focusing, and the following conditions (1) and (2) are satisfied:
−0.4<(R21F+R21R)/(R21F−R21R)<0.3 (1)
1.4<−β2T<2.1 (2)
where R21F is an axial radius of curvature of an object side-surface of the single lens element L21 in the second lens group, R21R is an axial radius of curvature of an image side-surface of the single lens element L21 in the second lens group, and β2T is a magnification of the second lens group at the telephoto end focused on an object point at infinity.

2 more elements

Dependencies are inferred from the claim text.