Wide angle optical system

Patent metadata

Field	Value
Publication number	US-9810886-B2
Application number	US-201715582633-A
Country	US
Kind code	B2
Filing date	Apr 29, 2017
Priority date	Jun 16, 2015
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

Abstract

The wide angle optical system includes in order from a side of an object in front, a first lens group having a negative refractive power, a second lens group having a catadioptric optical element, an aperture stop, and a third lens group having a positive refractive power, and the catadioptric optical element has a first surface, a second surface, and a third surface, and the first surface has a first transmitting surface and a first reflecting surface, the second surface has a second transmitting surface and a second reflecting surface, and the third surface has a third transmitting surface, and the third transmitting surface is a side surface of a circular truncated cone, and the following conditional expressions (1), (2), and (3) are satisfied:

υ p<υn   (1),

|φ p|<|φn|   (2), and

90°−θ k <α/2  (3).

First claim

What is claimed is:

1. A wide angle optical system, comprising:
a first optical path along which light from an object in front of the wide angle optical system passes;
a second optical path along which light from an object on a side of the wide angle optical system passes; and
a common optical path along which the light from the object in front and the light from the object on a side pass, wherein
the wide angle optical system includes in order from a side of the object in front, a first lens group having a negative refractive power, a second lens group having a catadioptric optical element, an aperture stop, and a third lens group having a positive refractive power, and
the first lens group includes a positive lens and a negative lens, and
the catadioptric optical element has a first surface, a second surface, and a third surface that is formed between the first surface and the second surface, and
the first surface has a first transmitting surface and a first reflecting surface, and
the first transmitting surface is formed to include an optical axis of the first optical path, and
the first reflecting surface is an annular reflecting surface, and is formed around the first transmitting surface, and
the second surface has a second transmitting surface and a second reflecting surface, and
the second transmitting surface is formed to include the optical axis of the first optical path, and
the second reflecting surface is an annular reflecting surface, and is formed around the second transmitting surface, and
the third surface has a third transmitting surface, and
the third transmitting surface is a side surface of a circular truncated cone, and
an apex of the circular truncated cone is positioned on the side of the object in front of the first lens group, and
in the first optical path, the first lens group, the first transmitting surface, and the second transmitting surface are positioned in order from the side of the object in front, and
in the second optical path, the third transmitting surface, the second reflecting surface, the first reflecting surface, and the second transmitting surface are positioned in order from the side of the object on a side, and
the aperture stop and the third lens group are positioned in the common optical path, and
the following conditional expressions (1), (2), and (3) are satisfied:
υ p<υn   (1),

|φ p|<|φn|   (2), and

90 °−θk <α/2  (3)

where,
υp denotes Abbe number for the positive lens,
υn denotes Abbe number for the negative lens,
φp denotes a refractive power of the positive lens,
φn denotes a refractive power of the negative lens,
θk denotes the minimum half angle of view for the second optical path, and 0°<θk<90°, and
α denotes an apex angle of the circular truncated cone.

2. The wide angle optical system according to claim 1 , wherein the following conditional expression (4) is satisfied:
0.7<(|φ n|/υn )/(φ p/υp )<1.5  (4)

where,
υp denotes Abbe number for the positive lens
υn denotes Abbe number for the negative lens,
φp denotes the refractive power of the positive lens, and
φn denotes the refractive power of the negative lens.

3. The wide angle optical system according to claim 1 , wherein the following conditional expressions (5) and (6) are satisfied:
35 <υn   (5)

υ p <35  (6)

where,
υp denotes Abbe number for the positive lens, and
υn denotes Abbe number for the negative lens.

4. The wide angle optical system according to claim 1 , wherein the third lens group includes a lens that moves in an optical axial direction.

5. The wide angle optical system according to claim 4 , wherein a lens nearest to image in the third lens group is fixed.

6. The wide angle optical system according to claim 4 , wherein the wide angle optical system is a zoom lens system having a wide angle end and a telephoto end, wherein the following conditional expression (7) is satisfied:
0.7 <|f 3/ fi |<1.2  (7)

where,
f 3 denotes a focal length of the third lens group at the wide angle end, and
fi denotes a focal length of the lens that moves in the optical axial direction.

7. The wide angle optical system according to claim 4 , wherein by the lens which moves in the optical axial direction, it is possible to switch to an observation of the object in front and the object on a side and to an observation of only the object in front.

Assignees

• Olympus Corp

Inventors

• Mizusawa Masayuki

Classifications

• G02B17/086

  wherein the system is made of a single block of optical material, e.g. solid catadioptric systems · CPC title

• G02B9/64

  having more than six components · CPC title

• G02B13/0055

  employing a special optical element · CPC title

• G02B13/06

  Panoramic objectives; So-called "sky lenses" {including panoramic objectives having reflecting surfaces} · CPC title

• G02B27/0081

  with means for altering, e.g. enlarging, the entrance or exit pupil · CPC title