| CPC G02B 23/243 (2013.01) [G02B 9/60 (2013.01); G02B 9/62 (2013.01); G02B 9/64 (2013.01); G02B 13/18 (2013.01)] | 16 Claims |
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1. An objective lens for an endoscope comprising:
a stop;
at least one lens which is disposed closer to an object side than the stop and of which an image-side lens surface is a concave surface; and
at least one set of cemented lenses that is disposed closer to an image side than the stop,
wherein focusing on an object positioned at a nearest point from an object positioned at a farthest point is performed by integral movement of a lens group, which includes a lens of the objective lens for an endoscope closest to the image side, along the optical axis,
the objective lens for an endoscope has a total angle of view of 120° or more in a state where focusing on the object positioned at the farthest point is performed and in a state where focusing on the object positioned at the nearest point is performed,
in a case where a focal length of the objective lens for an endoscope in a state where focusing on the object positioned at the nearest point is performed is denoted by fn, a half angle of view in a state where focusing on the object positioned at the nearest point is performed is denoted by θn, and a maximum image height in a state where focusing on the object positioned at the nearest point is performed is denoted by Hn, Conditional expression (1) is satisfied,
1.4<fn×(tan θn)/Hn<2 (1),
in a case where an interval on the optical axis between a lens, which is disposed on an object side of the stop in succession to the stop, and the stop in a state where focusing on the object positioned at the nearest point is performed is denoted by Dsn, Conditional expression (5) is satisfied,
0.3<fn/Dsn<2.5 (5).
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