Extender optical system
AssigneeFuji Photo Optical Co., Ltd.
InventorKatsuhisa Tsutsumi
Life of this patent
Estimating the term…
Abstract
An extender optical system, for insertion between a photographic main lens and a camera body for changing the focal length of the lens system as a whole to the long focus side, is formed of, in order from the object side, a first lens group having negative refractive power, a second lens group formed of a single negative lens, and a third lens group having positive refractive power. The negative lens that constitutes the second lens group is made to move in directions that are normal to the optical axis so as to correct for what would otherwise be blurred images due to vibrations. Various conditions are preferably satisfied so as to ensure high image quality over the entire field of view.
Claims8
An extender optical system, for attachment between a photographic main lens and a main body of a photo apparatus in order to increase the focal length of the lens system as a whole as compared to that of the photographic main lens without the extender optical system attached, said extender optical system comprising, in order from the object side:
- a first lens group having an overall negative refractive power and that includes a cemented lens which is formed of, in order from the object side, a negative lens that is cemented to a positive lens element;
- a second lens group that consists of a negative lens;
- and
- a third lens group having an overall positive refractive power and that includes a cemented lens which is formed of, in order from the object side, a positive lens element that is cemented to a negative lens element;
- wherein the following Conditions (1) and (2) are satisfied
- ν1p≦30 Condition (1) ν3p−ν3n≧38 Condition (2)
- where
- ν1p is the Abbe number of the positive lens element of the first lens group,
- ν3p is the Abbe number of the positive lens element of the cemented component in the third lens group, and
- ν3n is the Abbe number of the negative lens element of the cemented component in the third lens group.
An extender optical system, which is a lens optical system to be inserted between a photographic main lens and a camera body for changing the focal length of the lens system as a whole to the long focus side, comprising, in order from the object side:
- a first lens group having negative refractive power;
- a second lens group that consists of a negative lens;
- and
- a third lens group having positive refraction power;
- wherein
- the negative lens that constitutes the second lens group is made to move in directions that are normal to the optical axis so as to correct for what would otherwise be blurred images due to vibrations.
Dependencies are inferred from the claim text.