Objective optical system for endoscope and endoscope
First Claim
1. An objective optical system for an endoscope consisting of:
- a front group having negative refractive power as a whole, an aperture stop, and a rear group having positive refractive power as a whole, in order from an object side,wherein the front group consists of a first lens, having negative refractive power, in which an absolute value of a curvature radius of a lens surface on an image side is smaller than an absolute value of a curvature radius of a lens surface on an object side, and at least one parallel planar member of which an incidence surface and an emission surface are perpendicular to an optical axis, in order from the object side,wherein the rear group consists of a second lens having positive refractive power, a third lens having negative refractive power, and a fourth lens having positive refractive power, in order from the object side,wherein the third lens and the fourth lens are joined together to constitute a cemented lens, and a cemented surface of the cemented lens has a concave surface directed to the image side, andwherein the following Conditional Expression (1) is satisfied,
0.02<
f/fc<
0.10
(1)wheref;
Focal distance of entire system, andfc;
Focal distance of the cemented lens.
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Accused Products
Abstract
An objective optical system for an endoscope consists of a front group, an aperture stop, and a positive rear group in order from an object side. The front group consists of a negative first lens having a smaller absolute value of a curvature radius of a lens surface on an image side than that on an object side, and one or more parallel planar members of which an incidence surface and an emission surface are perpendicular to an optical axis, in order from the object side. The rear group consists of a positive second lens and a cemented lens in which a negative third lens, and a positive fourth lens are joined together in order from the object side and a cemented surface has a concave surface toward the image side. A predetermined conditional expression is satisfied.
10 Citations
20 Claims
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1. An objective optical system for an endoscope consisting of:
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a front group having negative refractive power as a whole, an aperture stop, and a rear group having positive refractive power as a whole, in order from an object side, wherein the front group consists of a first lens, having negative refractive power, in which an absolute value of a curvature radius of a lens surface on an image side is smaller than an absolute value of a curvature radius of a lens surface on an object side, and at least one parallel planar member of which an incidence surface and an emission surface are perpendicular to an optical axis, in order from the object side, wherein the rear group consists of a second lens having positive refractive power, a third lens having negative refractive power, and a fourth lens having positive refractive power, in order from the object side, wherein the third lens and the fourth lens are joined together to constitute a cemented lens, and a cemented surface of the cemented lens has a concave surface directed to the image side, and wherein the following Conditional Expression (1) is satisfied,
0.02<
f/fc<
0.10
(1)where f;
Focal distance of entire system, andfc;
Focal distance of the cemented lens. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification