US 12,292,621 B2
Optical system and image pickup apparatus
Takahiro Hatada, Tochigi (JP)
Assigned to CANON KABUSHIKI KAISHA, Tokyo (JP)
Filed by CANON KABUSHIKI KAISHA, Tokyo (JP)
Filed on Mar. 1, 2024, as Appl. No. 18/592,657.
Application 18/592,657 is a continuation of application No. 17/097,108, filed on Nov. 13, 2020, granted, now 11,971,607.
Claims priority of application No. 2019-223914 (JP), filed on Dec. 11, 2019.
Prior Publication US 2024/0201470 A1, Jun. 20, 2024
Int. Cl. G02B 9/12 (2006.01); G02B 27/00 (2006.01)
CPC G02B 9/12 (2013.01) [G02B 27/0025 (2013.01)] 16 Claims
OG exemplary drawing
 
1. An optical system with a fixed focal length comprising:
a front lens unit closest to an object;
a rear lens unit having a negative refractive power closest to an image plane; and
a middle group having a positive refractive power as a whole, including one or more lens units, and disposed between the front lens unit and the rear lens unit,
wherein a distance between adjacent lens units changes during focusing,
wherein the front lens unit includes four or more lenses,
wherein the middle group includes three or more positive lenses and one or more negative lenses,
wherein the rear lens unit consists of two positive lenses and two negative lenses, and
wherein the following inequality is satisfied:

OG Complex Work Unit Math
where f is a focal length of the optical system, and fr is a focal length of the rear lens unit.