Objective optical system for an endoscope
AssigneeOlympus Medical Systems Corp.
InventorTsutomu Igarashi
Life of this patent
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Abstract
An objective optical system is disclosed that is suitable for a high-precision endoscope that performs focusing by moving a single lens component. The objective optical system includes, in order from the object side, a front lens group, a middle lens group, and a rear lens group. The middle lens group is composed of two or more lens components, at least two of which have positive refractive power, and the lens component that is moved for focusing is in the middle lens group. Additionally, the objective optical system satisfies two specified conditions, and other conditions may apply.
Claims19
An objective optical system for an endoscope having an object side and an image side and comprising, arranged along an optical axis in order from the object side, as follows:
- a front lens group having negative refractive power and consisting of a first lens component;
- a middle lens group having positive refractive power and including at least two lens components, each of said at least two lens components having positive refractive power;
- and
- a rear lens group having positive refractive power and consisting of one lens component;
- wherein
- only one lens component of said middle lens group moves in the direction of the optical axis during focusing;
- a stop for controlling image brightness is positioned within said middle lens group or between said front lens group and said middle lens group;
- and
- the following conditions are satisfied:
- 2<|fUM/fTF|<10
- −1.25<fU1/fTF<−0.6
- where
- fUM is the focal length of said only one lens component;
- fTF is the focal length of the entire objective optical system for an endoscope focused at the far point on the object side;
- and
- fU1 is the focal length of said first lens component.
Dependencies are inferred from the claim text.