US 9,810,886 B2
Wide angle optical system
Masayuki Mizusawa, Hachioji (JP)
Assigned to OLYMPUS CORPORATION, Tokyo (JP)
Filed by OLYMPUS CORPORATION, Hachioji-shi, Tokyo (JP)
Filed on Apr. 29, 2017, as Appl. No. 15/582,633.
Application 15/582,633 is a continuation of application No. PCT/JP2016/067388, filed on Jun. 10, 2016.
Claims priority of application No. 2015-121166 (JP), filed on Jun. 16, 2015.
Prior Publication US 2017/0235132 A1, Aug. 17, 2017
This patent is subject to a terminal disclaimer.
Int. Cl. G02B 13/04 (2006.01); G02B 13/06 (2006.01); G02B 9/64 (2006.01); G02B 17/08 (2006.01); G02B 27/00 (2006.01); G02B 13/00 (2006.01)
CPC G02B 13/04 (2013.01) [G02B 9/64 (2013.01); G02B 13/0055 (2013.01); G02B 13/06 (2013.01); G02B 17/086 (2013.01); G02B 27/0081 (2013.01)] 7 Claims
OG exemplary drawing
 
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:
υp<υn  (1),
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.