Objective lens for endoscope
AssigneeFuji Photo Optical Co., Ltd.
InventorChikara Yamamoto
Life of this patent
Estimating the term…
Abstract
An objective lens for endoscope comprises, successively from an object side, a first lens group having a negative refracting power, a second lens group having a positive refracting power, a third lens group having a negative refracting power, and a fourth lens group having a positive refracting power; wherein the third lens group and one of the second and fourth lens groups are movable along an optical axis. The objective lens further satisfies the following conditional expressions: 2.0<β1T/β1W<10.0 1.2<fT/fw where β1T is the magnification of the first lens group at the telephoto end; β1W is the magnification of the first lens group at the wide end; fT is the focal length of the whole lens at the telephoto end; and fW is the focal length of the whole lens at the wide end.
Claims9
An endoscope objective lens comprising, successively from an object side, a first lens group having a negative refracting power, a second lens group having a positive refracting power, a third lens group having a negative refracting power, and a fourth lens group having a positive refracting power;
- wherein two lens groups consisting of said third lens group and one of said second and fourth lens groups are moved along an optical axis so as to change magnification and carry out focusing;
- said endoscope objective lens further satisfying the following conditional expressions (1) and (2):
- 2.0<β1T/β1W<10.0 (1)
- 1.2<fT/fW (2)
- where
- β1T is the magnification of the first lens group at the telephoto end;
- β1W is the magnification of the first lens group at the wide end;
- fT is the focal length of the whole lens at the telephoto end;
- and
- fW is the focal length of the whole lens at the wide end.
Dependencies are inferred from the claim text.