Objective lens system for endoscopes
First Claim
Patent Images
1. An objective lens system for endoscopes comprising, in order from the object side:
- a first lens component having a negative refractive power;
a second lens component having a positive refractive power;
an aperture stop;
a rear lens unit including a positive cemented lens component consisting of a positive lens element and a negative lens element, said rear lens unit having a positive refractive power as a whole;
said aperture stop being disposed substantially at a location of a front focal point of said rear lens unit; and
said objective lens system satisfying the following conditions (1), (2) and (3);
(1) |f1 /f|<
5(2) |f2 /f|<
10(3) |rb /ra |<
0.7wherein the reference symbol f represents the focal length of the objective lens system as a whole, the reference symbols f1 and f2 designate the focal lengths of the first lens component and the second lens component, respectively, and the reference symbol ra represents a radius of curvature on the most object side surface of said second lens component and the reference symbol rb denotes a radius of curvature on the most image side surface of said second lens component.
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Accused Products
Abstract
An objective lens system for endoscopes comprising, in the order from the object side, a first lens component having a negative refractive power, a second lens component having a positive refractive power, an aperture stop arranged right after the second lens component, and a rear lens unit comprising a third lens component designed as a cemented doublet consisting of a lens element having a positive refractive power and a lens element having a negative refractive power. Said objective lens system for endoscopes has a wide field angle, a compact design, a small number of lens elements and favorably corrected aberrations.
52 Citations
13 Claims
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1. An objective lens system for endoscopes comprising, in order from the object side:
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a first lens component having a negative refractive power; a second lens component having a positive refractive power; an aperture stop; a rear lens unit including a positive cemented lens component consisting of a positive lens element and a negative lens element, said rear lens unit having a positive refractive power as a whole; said aperture stop being disposed substantially at a location of a front focal point of said rear lens unit; and said objective lens system satisfying the following conditions (1), (2) and (3); (1) |f1 /f|<
5(2) |f2 /f|<
10(3) |rb /ra |<
0.7wherein the reference symbol f represents the focal length of the objective lens system as a whole, the reference symbols f1 and f2 designate the focal lengths of the first lens component and the second lens component, respectively, and the reference symbol ra represents a radius of curvature on the most object side surface of said second lens component and the reference symbol rb denotes a radius of curvature on the most image side surface of said second lens component. - View Dependent Claims (2, 3, 4, 5, 6, 12, 13)
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7. An objective lens system for endoscopes comprising, in order from the object side:
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a first lens component having a negative refractive power; a second lens component having a positive refractive power; an aperture stop; and a rear lens unit comprising a third lens component being a cemented doublet consisting of a positive lens element and a negative lens element, and a fourth lens component having a positive refractive power; wherein said rear lens unit has a positive refractive power as a whole; wherein said aperture stop is disposed substantially at a location of a front focal point of said rear lens unit; and wherein the first lens component and the second lens component satisfy the following conditions (5) and (6) respectively; (5) 0.5f<
|f1 |+|f2 |<
5f(6) 0.1<
|f1 |/|f2 |<
1.5wherein the reference symbol f represents a focal length of said objective lens system as a whole, the reference symbol f, designates focal length of said first lens component and the reference symbol f, denotes focal length of said second lens component.
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8. An objective lens system for endoscopes comprising, in order from the object side:
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a first lens component having a negative refractive power; a second lens component having a positive refractive power; an aperture stop; and a rear lens unit including a third lens component being a cemented doublet consisting of a positive lens element and a negative lens element, and a fourth lens component having a positive refractive power, said rear lens unit having a positive refractive power as a whole; said aperture stop being disposed substantially at a location of a front focal point of said rear lens unit; wherein the rear lens unit satisfies the following condition (7); (7) 1.5f<
f1 <
6fwherein the reference symbol f1 represents the focal length of the rear lens unit, and the reference symbol f represents a focal length of said objective lens system as a whole.
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9. An objective lens system for endoscopes comprising, in order from the object side:
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a first lens component having a negative refractive power; a second lens component having a positive refractive power; an aperture stop; and a rear lens unit including a third lens component being a cemented doublet consisting of a positive lens element and a negative lens element, and a fourth lens component having a positive refractive power, said rear lens unit having a positive refractive power as a whole; said aperture stop being disposed substantially at a location of a front focal point of said rear lens unit; wherein a plane parallel plate is disposed between the aperture stop and the rear lens unit, and said rear lens unit satisfies the following condition (8); (8) 1.2<
fR /Iwherein the reference symbol fR represents the focal length of the rear lens unit and the reference symbol I designates the maximum image height.
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10. An objective lens system for endoscopes comprising, in order from the object side:
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a first lens component having a negative refractive power; a second lens component having a positive refractive power; an aperture stop; and a rear lens unit comprising a third lens component being a cemented doublet consisting of a positive lens element and a negative lens element, and a fourth plano-convex lens component having a planar surface on the image side; wherein said rear lens unit has a positive refractive power as a whole; wherein said aperture stop is disposed substantially at a location of a front focal point of said rear lens unit; and wherein said fourth lens component satisfies the following condition (10); (10) 1.1×
nD<
r, <
1.9×
nD orr, <
0.9×
nD and r, >
2.1×
nDwherein the reference symbol r, represents the radius of curvature on the image side surface of the fourth lens components, the reference symbol n designates the refractive index of the medium located on the image side of said surface and the reference symbol D denotes the optical path length as measured from said surface to the image surface.
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11. An objective lens system for endoscopes comprising, in order from the object side:
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a first lens component having a negative refractive power; a second lens component having a positive refractive power; an aperture stop; and a rear lens unit including a third lens component being a cemented doublet consisting of a positive lens element and a negative lens element, and a fourth lens component having a positive refractive power, said rear lens unit having a positive refractive power as a whole; said aperture stop being disposed substantially at a location of a front focal point of said rear lens unit; said objective lens system satisfying the following conditions (1), (2) and (3); (1) |f1 /f|<
5(2) |f2 /f|<
10(3) |rb /ra |<
0.7wherein the reference symbol f represents the focal length of the objective lens system as a whole, the reference symbols f1 and f2 designate the focal lengths of the first lens component and the second lens component, respectively, and the reference symbol ra represents a radius of curvature on the most object side surface of said second lens component and the reference symbol rb denotes a radius of curvature on the most image side surface of said second lens component.
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Specification