US 11,796,777 B2
Zoom lens and imaging apparatus
Takahiro Mitsuhashi, Saitama (JP)
Assigned to TAMRON CO., LTD., Saitama (JP)
Filed by TAMRON CO., LTD., Saitama (JP)
Filed on Nov. 16, 2020, as Appl. No. 17/98,948.
Claims priority of application No. 2020-078385 (JP), filed on Apr. 27, 2020.
Prior Publication US 2021/0333525 A1, Oct. 28, 2021
Int. Cl. G02B 15/14 (2006.01); G02B 15/16 (2006.01)
CPC G02B 15/145121 (2019.08) [G02B 15/16 (2013.01)] 11 Claims
OG exemplary drawing
 
1. A zoom lens that includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a rear group having a positive refractive power as a whole in order from an object side, and performs a variable magnification operation by changing a distance between the lens groups adjacent to each other, wherein
the rear group includes at least a third lens group, a fourth lens group, and a fifth lens group in order from the object side,
any one lens group of the third lens group, the fourth lens group, or the fifth lens group is a focus group that performs focusing by moving on an optical axis, and
the zoom lens satisfies a following expression:
0.3≤|ff|/M<0.8  (1)
1.5≤βFW/βFT<7.0  (2)
where
M is a square root of a product of fw and ft,
ff is a focal length of the focus group,
fw is a focal length at a wide-angle end of the zoom lens at infinity focusing,
ft is a focal length at a telephoto end of the zoom lens at infinity focusing,
βFW is a lateral magnification at a wide-angle end of the focus group, and
βFT is a lateral magnification at a telephoto end of the focus group.