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 being a single lens having a negative refractive power,an aperture stop,a second lens component being a single lens having a positive refractive power disposed adjacent to said aperture stop, anda third lens component being a single lens having a positive refractive power;
wherein an image side surface of said second lens component is an aspherical surface having a shape expressed by the formula shown below when the direction of the optical axis is taken as the x axis and the direction perpendicular to the optical axis is taken as the y axis, and wherein said objective lens system satisfies the following conditions (1) through (3);
##EQU3## wherein the reference symbol f23 represents a total focal length of the second lens component and the third lens component, the reference symbols f1, f2 and f3 designate focal lengths of the first lens component, the second lens component and the third lens component, respectively, the reference symbol ri, denotes a radius of curvature on a reference sphere of the aspherical surface, the reference symbols Ei '"'"', Fi '"'"', Gi '"'"', . . . represent aspherical surface coefficients of the fourth, sixth, eighth, . . . orders respectively, and the reference symbols ni-1 and ni designate refractive indices of media located on the object side and the image side respectively of the aspherical surface.
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Abstract
An objective lens system for endoscopes comprising, in order from the object side, a first lens unit having a negative refractive power, an aperture stop, a second lens unit having a positive refractive power and a third lens unit having a positive refractive power, and using an aspherical surface adopted as an image side surface of the second lens unit or an object side surface of the third lens unit. The objective lens system is of a nearly telecentric retrofocus type, composed of a small number of lens elements and compact.
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Citations
10 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 being a single lens having a negative refractive power, an aperture stop, a second lens component being a single lens having a positive refractive power disposed adjacent to said aperture stop, and a third lens component being a single lens having a positive refractive power; wherein an image side surface of said second lens component is an aspherical surface having a shape expressed by the formula shown below when the direction of the optical axis is taken as the x axis and the direction perpendicular to the optical axis is taken as the y axis, and wherein said objective lens system satisfies the following conditions (1) through (3);
##EQU3## wherein the reference symbol f23 represents a total focal length of the second lens component and the third lens component, the reference symbols f1, f2 and f3 designate focal lengths of the first lens component, the second lens component and the third lens component, respectively, the reference symbol ri, denotes a radius of curvature on a reference sphere of the aspherical surface, the reference symbols Ei '"'"', Fi '"'"', Gi '"'"', . . . represent aspherical surface coefficients of the fourth, sixth, eighth, . . . orders respectively, and the reference symbols ni-1 and ni designate refractive indices of media located on the object side and the image side respectively of the aspherical surface. - View Dependent Claims (7, 10)
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2. An objective lens system comprising, in order from the object side:
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a first lens component being a single lens having a negative refractive power, an aperture stop, a second lens component being a single lens having a positive refractive power disposed adjacent to said aperture stop, and a third lens component being a single lens having a positive refractive power; wherein an image side surface of said second lens component is an aspherical surface, and wherein said objective lens system satisfies the following conditions (1) , (2) and (7);
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3. 4<
- |f23 /f1 |<
2 (1)
space="preserve" listing-type="equation">0.8<
f.sub.3 /f.sub.2 <
4 (2)
space="preserve" listing-type="equation">.sup.Δ
x (h.sub.M)·
(n.sub.i-1 -n.sub.i)>
0 (3)wherein the reference symbol f23 represents a total focal length of the second lens component and the third lens component, the reference symbols f1, f2 and f3 designate focal lengths of the first lens component, the second lens component, and the third lens component, respectively, the reference symbol .sup.Δ
x (hM) denotes a departure of the aspherical surface from a reference sphere at a height of a marginal ray on said aspherical surface, and the reference symbols ni-1 and ni represent refractive indices of media located on the object side and the image side respectively of said aspherical surface.
- |f23 /f1 |<
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4. An objective lens system for endoscopes comprising, in order from the object side:
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a first lens component being a plano-concave lens, an aperture stop, a second lens component being a biconvex lens disposed adjacent to said aperture stop, and a third lens component being a positive single lens, having an objective side being a convex surface; wherein an image side surface of said second lens component is an aspherical surface having a shape expressed by the formula shown below when the direction of the optical axis is taken as the x axis and the direction perpendicular to the optical axis is taken as the y axis, and wherein said objective lens system satisfies the following conditions (1) through (3);
##EQU4##
space="preserve" listing-type="equation">0.4<
|f.sub.23 /f.sub.1 |<
2 (1)
-
-
5. 8<
- f3 /f2 <
4 (2)
space="preserve" listing-type="equation">E.sub.i '"'"', (n.sub.i-1 -n.sub.i)>
0 (3)wherein the reference symbol f23 represents a total focal length of the second lens component and the third lens component, the reference symbols f1, f2 and f3 designate focal lengths of the first lens component, the second lens component and the third lens component, respectively, the reference symbol ri denotes a radius of curvature on a reference sphere of the aspherical surface, the reference symbols Ei '"'"', Fi '"'"', Gi '"'"'. . . represent aspherical surface coefficients of the fourth, sixth, eighth . . . orders respectively, and the reference symbols ni-1 and ni designate refractive indices of media located on the object side and the image side, respectively, of the aspherical surface. - View Dependent Claims (8)
- f3 /f2 <
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6. An objective lens system comprising, in order from the object side:
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a first lens component being a plano-concave lens, an aperture stop, a second lens component being a biconvex lens disposed adjacent to said aperture stop and a third lens component being a positive single lens, having an object side being a convex surface; wherein an image side surface of said second lens component is an aspherical surface, and wherein said objective lens system satisfies the following conditions (1), (2) and (7);
space="preserve" listing-type="equation">0.4<
|f.sup.23 /f.sub.1 |<
2 (1)
space="preserve" listing-type="equation">0.8<
f.sub.3 /f.sub.2 <
4 (2)
space="preserve" listing-type="equation">.sup.Δ
x (h.sub.M)·
(n.sub.i-1 -n.sub.i)>
0 (3)wherein the reference symbol f23 represents a total focal length of the second lens component and the third lens component, the reference symbols f1, f2 and f3 designate focal lengths of the first lens component, the second lens component, and the third lens component, respectively, the reference symbol .sup.Δ
x (hM) denotes a departure of the aspherical surface from a reference sphere at a height of hM of a marginal ray on said aspherical surface, and the reference symbols ni-1 and ni represent refractive indices of media located on the object side and the image side respectively of said aspherical surface. - View Dependent Claims (9)
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Specification