US 12,392,991 B2
Optical system and image pickup apparatus having the same
Takeharu Nakada, Tochigi (JP); and Takahiro Hatada, Tochigi (JP)
Assigned to CANON KABUSHIKI KAISHA, Tokyo (JP)
Filed by CANON KABUSHIKI KAISHA, Tokyo (JP)
Filed on Jul. 6, 2022, as Appl. No. 17/858,250.
Claims priority of application No. 2021-113299 (JP), filed on Jul. 8, 2021.
Prior Publication US 2023/0020736 A1, Jan. 19, 2023
Int. Cl. G02B 9/26 (2006.01); G02B 7/04 (2021.01)
CPC G02B 9/26 (2013.01) [G02B 7/04 (2013.01)] 9 Claims
OG exemplary drawing
 
1. An optical system comprising, in order from an object side to an image side, a first lens unit having a positive refractive power, a diaphragm, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power,
wherein each distance between adjacent lens units is changed during focusing,
wherein the second lens unit is moved to the image side during focusing from an object at infinity to a short-distance object,
wherein the first lens unit includes a positive lens closest to the object and two or more negative lenses,
wherein the second lens unit consists of a single negative lens, and
wherein the following conditional expressions are satisfied:
0.2<LD1/LD<0.4,
BF/f<0.25, and
15<vdG1<26
where LD1 is a distance on an optical axis from a lens surface closest to the object of the first lens unit to a lens surface closest to an image plane of the first lens unit, LD is a distance on the optical axis from the lens surface closest to the object of the first lens unit to the image plane, f is a focal length of the optical system, BF is a back focus of the optical system during focusing on the object at infinity, and vdG1 is an Abbe number of the positive lens.