Objective optical system

Patent metadata

Field	Value
Publication number	US-9846295-B2
Application number	US-201615251327-A
Country	US
Kind code	B2
Filing date	Aug 30, 2016
Priority date	Jul 11, 2014
Publication date	Dec 19, 2017
Grant date	Dec 19, 2017

Abstract

The objective optical system includes in order from an object side, a first unit having a positive refractive power, a second unit having a negative refractive power, and a third unit having a positive refractive power, and focusing is carried out by moving the second unit, the first unit and the third unit are fixed at the time of focusing, and the first unit G 1 includes in order from the object side, a negative lens L 1 , one of a positive lens and a cemented lens, and a positive lens, and the third unit includes a positive lens, and a cemented lens of a positive lens and a negative lens, and the objective optical system satisfies the following conditional expression (3)

−20< f 2 /f <−5  (3)
where, f 2 denotes a focal length of the second unit, and f denotes a focal length of the overall objective optical system in a normal observation state.

First claim

What is claimed is:

1. An objective optical system, comprising in order from an object side:
a first unit having a positive refractive power;
a second unit having a negative refractive power; and
a third unit having a positive refractive power, wherein:
focusing is carried out by moving the second unit,
the first unit and the third unit are fixed at a time of the focusing,
the first unit includes, in order from the object side, a negative lens, one of a positive lens and a cemented lens, and a positive single lens,
the third unit includes a positive lens, and a cemented lens of a positive lens and a negative lens, and
the objective optical system satisfies the following conditional expression (3)
−20< f 2 /f<− 5  (3)

where:
f 2 denotes a focal length of the second unit, and
f denotes a focal length of the overall objective optical system in a normal observation state.

2. An objective optical system, comprising in order from an object side:
a first unit having a positive refractive power;
a second unit having a negative refractive power; and
a third unit having a positive refractive power, wherein:
the second unit includes a meniscus lens having a convex surface directed toward the object side,
focusing is carried out by moving the second unit on an optical axis,
the first unit and the third unit are fixed at a time of the focusing, and
the objective optical system satisfies the following conditional expressions (1), (2), and (3)
0.12< d 2g /f< 1.02  (1)

1.8< f 1 /f< 4.2  (2)

−20< f 2 /f<− 5  (3)

where:
d 2g denotes an amount of movement of the second unit,
f denotes a focal length of the overall objective optical system in a normal observation state,
f1 denotes a focal length of the first unit, and
f2 denotes a focal length of the second unit.

3. An objective optical system, comprising in order from an object side:
a first unit having a positive refractive power;
a second unit having a negative refractive power; and
a third unit having a positive refractive power, wherein:
focusing is carried out by moving the second unit,
the first unit and the third unit are fixed at a time of the focusing,
the first unit includes, in order from the object side, a negative lens, one of a positive lens and a cemented lens, and a positive single lens,
the third unit includes a positive lens, and a cemented lens of a positive lens and a negative lens, and
the objective optical system satisfies the following conditional expression (3′)
−20< f 2 /f≦− 6.39  (3′)

where:
f 2 denotes a focal length of the second unit, and
f denotes a focal length of the overall objective optical system in a normal observation state.

Assignees

• Olympus Corp

Inventors

• Takato Hideyasu

Classifications

• G02B9/26

  the front and rear components having compound lenses · CPC title

• G02B23/243

  Objectives for endoscopes · CPC title

• G02B27/0025

  for optical correction, e.g. distorsion, aberration · CPC title

• G02B9/14 Primary

  arranged + - + · CPC title

• G02B13/04 Primary

  Reversed telephoto objectives · CPC title