US 12,393,014 B2
Objective optical system, imaging unit, endoscope and endoscope apparatus
Yoshihito Iguchi, Hino (JP)
Assigned to OLYMPUS CORPORATION, Tokyo (JP)
Filed by OLYMPUS CORPORATION, Hachioji (JP)
Filed on Feb. 12, 2024, as Appl. No. 18/438,521.
Application 18/438,521 is a continuation of application No. PCT/JP2021/034548, filed on Sep. 21, 2021.
Prior Publication US 2024/0192479 A1, Jun. 13, 2024
Int. Cl. G02B 23/24 (2006.01); G02B 5/30 (2006.01); G02B 27/28 (2006.01); H04N 23/50 (2023.01)
CPC G02B 23/243 (2013.01) [G02B 5/3083 (2013.01); G02B 27/283 (2013.01); H04N 23/555 (2023.01)] 7 Claims
OG exemplary drawing
 
1. An objective optical system comprising:
a lens group that forms an object image;
a polarizing beam splitter having an optical path dividing surface that divides an optical path into a first optical path that intersects the optical axis of the lens group and a second optical path that extends straight on the optical axis;
a first reflection surface provided in the first optical path;
a second reflection surface provided in the second optical path; and
a quarter wave plate provided between the polarizing beam splitter and the first reflection surface,
wherein the objective optical system satisfies the following conditional expression (1):
(Tp+Ts)/(100−Ts)≥1.25  (1)
where Tp (%) is the transmittance of the optical path dividing surface for p-polarized light, and Ts (%) is the transmittance of the optical path dividing surface for s-polarized light.