High-aperture-ratio inner-focus telephoto lens
AssigneeNikon Corporation
InventorFumio Suzuki
Life of this patent
Estimating the term…
Abstract
A high-aperture-ratio inner-focus telephoto lens comprises a first lens group of positive refracting power, a second lens group of negative refracting power and a third lens group of positive refracting power arranged in the named order from the object side, in which the first lens group and the second lens group form a substantially afocal system, focusing is effected by moving the second lens group along the optical axis, and the first lens group has a front group of positive refracting power and a rear group of weak positive refracting power arranged in the named order from the object side.
Claims13
A high-aperture-ratio inner-focus telephoto lens comprising a first lens group of positive refracting power, a second lens group of negative refracting power and a third lens group of positive refracting power arranged in the named order from the object side;
- wherein said first lens group and said second lens group form a substantially afocal system;
- wherein focusing is effected by moving said second lens group along the optical axis;
- wherein said first lens group has a front group of positive refracting power and a rear group of weak positive refracting power arranged in the named order from the object side;
- wherein said third lens group comprises a front group of weak positive refracting power and a rear group of positive refracting power arranged in the named order from the object side;
- and
- wherein the following conditions are satisfied:
- 0. 60<.PHI./f.sub.1 <0.77
- 0.10<D.sub.1 /Bf.sub.11 <0.26
- where .PHI. is an effective diameter of an object-side lens surface of a positive lens element closest to an object in said first lens group, f.sub.1 is a focal length of said first lens group, Bf.sub.11 is a back focus of said front group in said first lens group and D.sub.1 is an air gap between said front group and said rear group in said first lens group.
A high-aperture-ratio inner-focus telephoto lens comprising a first lens group of positive refracting power, a second lens group of negative refracting power and a third lens group of positive refracting power arranged in the named order from the object side;
- wherein said first lens group and said second lens group form a substantially afocal system;
- wherein focusing is effected by moving said second lens group along the optical axis;
- wherein said first lens group has a front group of positive refracting power and a rear group of weak positive refracting power arranged in the named order from the object side;
- and
- wherein said third lens group is arranged movable across the optical axis to deflect the image thereby.
Dependencies are inferred from the claim text.