US 11,703,661 B2
Optical system and optical apparatus
Kenji Shinohara, Utsunomiya (JP); and Takeo Mori, Utsunomiya (JP)
Assigned to CANON KABUSHIKI KAISHA, Tokyo (JP)
Filed by CANON KABUSHIKI KAISHA, Tokyo (JP)
Filed on Jun. 11, 2020, as Appl. No. 16/898,983.
Claims priority of application No. 2019-113311 (JP), filed on Jun. 19, 2019.
Prior Publication US 2020/0400919 A1, Dec. 24, 2020
Int. Cl. G02B 9/60 (2006.01); G02B 9/62 (2006.01)
CPC G02B 9/60 (2013.01) [G02B 9/62 (2013.01)] 11 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 second lens unit having a negative refractive power;
a third lens unit having a positive refractive power; and
a fourth lens unit having a negative refractive power,
wherein distances between adjacent lens units change during focusing,
wherein at least the second lens unit and the fourth lens unit move during focusing,
wherein the fourth lens unit consists of a negative partial unit having a negative refractive power and a positive partial unit having a positive refractive power,
wherein an air distance between the negative partial unit and the positive partial unit is the largest among air distances between adjacent lenses in the fourth lens unit, and
wherein the following conditional expression is satisfied
0.45<D4np/D4<0.95
−25.0<f4/f1<−3.0
where D4 is a distance on an optical axis from a lens surface closest to the object side to a lens surface closest to the image side in the fourth lens unit, D4 np is the air distance between the negative partial unit and the positive partial unit in the fourth lens unit, and f4 and f1 are focal lengths of the fourth lens unit and the first lens unit, respectively.