Rear conversion lens
AssigneeNikon Corporation
InventorKoichi Ohshita
Life of this patent
Estimating the term…
Abstract
A rear conversion lens which is to be mounted between a main lens and a predetermined image plane for attaining a larger resultant focal distance than a focal distance of the main lens basically comprises, in the order taken from an object, a first lens unit having a positive refractive power and a second lens unit having a negative refractive power, and has a negative refractive power as a whole. The structure meets the following conditional formulas. 0.5<f.sub.1 /.vertline.f.sub.RCL .vertline.<0.6, f.sub.RCL <0 (1) 1.2<r.sub.2 /r.sub.3 <1.4 (2) where f.sub.RCL is a focal distance of the rear conversion lens, f.sub.1 is a focal distance of the first lens unit, r.sub.2 is a radius of curvature of the first lens unit facing an image, and r.sub.3 is a radius of curvature of the second lens unit facing an object.
Claims8
A rear conversion lens to be mounted in rear of a main lens for expanding a resultant focal distance to a longer one than a focal distance of the main lens, comprising:
- a first lens unit having a positive refractive power;
- and
- a second lens unit having a negative refractive power;
- said first lens unit and said second lens unit being arranged in this order when viewed from an object;
- said first lens unit and said second lens unit meeting condition of:
- 0.5<f.sub.1 /.vertline.f.sub.RCL .vertline.<0.6, f.sub.RCL<
- 0
- 1.2<r.sub.2 /r.sub.3 <1.4
- where f.sub.RCL is a focal distance of said rear conversion lens, f.sub.1 is a focal distance of said first lens unit, r.sub.2 is a radius of curvature of a plane of said first lens unit facing an image, and r.sub.3 is a radius of curvature of a plane of said second lens unit facing an object.
Dependencies are inferred from the claim text.