Macro lens
AssigneeFuji Photo Optical Co., Ltd.
InventorHitoshi Miyano
Life of this patent
Estimating the term…
Abstract
A macro lens comprises first to third lens groups having positive powers and an aperture stop disposed the first and second lens groups. The first lens group, aperture stop and second lens group remain fixed with respect to one another and movable as one unit relative to the third lens group for focusing. The third lens group is stationary with respect to an image plane of the macro lens.
Claims6
A macro lens comprising, from a subject end to an image end, a first lens group having a positive power, an aperture stop, a second lens group having a positive power and a third lens group having a positive power, said first lens group, said aperture stop and said second lens group remaining fixed with respect to one another and movable as one unit relative to said third lens group, which is stationary with respect to an image plane of the macro lens, along an optical axis of said macro lens for focusing, said macro lens satisfying the following conditions:
- F.sub.12 <0.5.times.f/M
- Ff.sub.a <d<[fd.sub.d ]Ff.sub.b <o
- where f is an overall focal length of said macro lens;
- M is a magnification for a closest focusing distance;
- F.sub.12 is a composed focal length of said first and second lens groups;
- Ff.sub.a is a composed focal length of said second and third lens groups for an infinite focusing distance;
- Ff.sub.b is a composed focal length of said second and third lens groups for the closest focusing distance;
- and
- d is the distance between a foremost lens element of the second lens group and the aperture stop.
Dependencies are inferred from the claim text.