US 11,940,623 B2
Observation optical system and display apparatus
Kazutaka Inoguchi, Tokyo (JP)
Assigned to CANON KABUSHIKI KAISHA, Tokyo (JP)
Filed by CANON KABUSHIKI KAISHA, Tokyo (JP)
Filed on Jul. 21, 2020, as Appl. No. 16/934,411.
Claims priority of application No. 2019-138509 (JP), filed on Jul. 29, 2019.
Prior Publication US 2021/0033868 A1, Feb. 4, 2021
Int. Cl. G02B 27/01 (2006.01); G02B 9/14 (2006.01); G02B 17/08 (2006.01)
CPC G02B 27/0172 (2013.01) [G02B 9/14 (2013.01); G02B 17/0816 (2013.01); G02B 17/0852 (2013.01); G02B 17/0856 (2013.01); G02B 2027/011 (2013.01); G02B 2027/0116 (2013.01)] 8 Claims
OG exemplary drawing
 
1. An optical system configured to guide a light beam from a display element, the optical system comprising:
a positive lens;
a negative lens; and
an optical element having a transmission surface, an optical surface, and a reflection and transmission surface,
wherein the light beam from the display element;
passes through the positive lens, the negative lens, and then the transmission surface;
then reflects on the reflection and transmission surface and then on the optical surface;
then passes through the reflection and transmission surface; and
then travels to an exit pupil, and
wherein the following inequalities are satisfied:
0.28<nn-np<0.60
50.26≤vp-vn<80
where np and nn are refractive indices of the positive lens and the negative lens for the d-line, respectively, and vp and vn are Abbe numbers of the positive lens and the negative lens for the d-line, respectively.