Objective lens and endoscope using the same
First Claim
1. An objective lens comprising a first negative lens, a second positive lens, an aperture stop, a third positive lens, and a joined lens arranged in order from an object side, the joined lens being formed of a fourth positive lens and a fifth negative lens that are joined together,wherein the joined lens satisfies conditional expressions (1) and (2), and the objective lens satisfies conditional expression (3):
-
nn≧
2.0
(1)
12<
(ν
p−
ν
n)<
34
(2)
1.52<
(f23/fl)<
1.75
(3)where nn denotes a refractive index with respect to a d-line of the fifth lens, ν
p denotes an Abbe number of the fourth lens, ν
n denotes an Abbe number of the fifth lens, f23 denotes a combined focal length of the second lens and the third lens, and fl denotes a focal length of the entire system.
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Abstract
Provided is a simple-structured endoscope objective lens suitable for a compact, high-resolution image acquisition element. Provided is an objective lens constituted of a first negative lens, a second positive lens, an aperture stop, a third positive lens, and a joined lens arranged in that order from an object side, the joined lens being formed of a fourth positive lens and a fifth negative lens and satisfying the expressions (1) and (2), and the objective lens satisfies the expression (3):
nn≧2.0 (1)
12<(νp−νn)<34 (2)
1.52<(f23/fl)<1.75 (3)
where nn, νp, νn, f23 and fl denote a refractive index at d-line of the fifth lens, an Abbe number of the fourth lens, an Abbe number of the fifth lens, a combined focal length of the second lens and the third lens, and a focal length of the entire, respectively.
114 Citations
8 Claims
-
1. An objective lens comprising a first negative lens, a second positive lens, an aperture stop, a third positive lens, and a joined lens arranged in order from an object side, the joined lens being formed of a fourth positive lens and a fifth negative lens that are joined together,
wherein the joined lens satisfies conditional expressions (1) and (2), and the objective lens satisfies conditional expression (3): -
nn≧
2.0
(1)
12<
(ν
p−
ν
n)<
34
(2)
1.52<
(f23/fl)<
1.75
(3)where nn denotes a refractive index with respect to a d-line of the fifth lens, ν
p denotes an Abbe number of the fourth lens, ν
n denotes an Abbe number of the fifth lens, f23 denotes a combined focal length of the second lens and the third lens, and fl denotes a focal length of the entire system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
Specification