Patent ID: 11966030
Assignee: FUJIFILM CORPORATION
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 25:
26. A zoom lens consisting of, in order from an object side to an image side, a first lens group that has a negative refractive power, a middle group, and a final group,
wherein during zooming, a spacing between the first lens group and the middle group changes, and a spacing between the middle group and the final group changes,
during focusing, at least a part of the middle group moves along an optical axis as a focus group, and the first lens group and the final group remain stationary with respect to an image plane,
a back focal length of the zoom lens at an air conversion distance at a wide angle end in a state where an infinite distance object is in focus is Bfw,
a focal length of the zoom lens at the wide angle end in the state where the infinite distance object is in focus is fw,
a maximum half angle of view at the wide angle end in the state where the infinite distance object is in focus is ωw,
Conditional Expression (1) is satisfied, which is represented by

0.35<Bfw/(fw×tan|ωw|)<1.5  (1),

the middle group includes, in order from the object side to the image side, a front subgroup having a positive refractive power and a rear subgroup having a negative refractive power,
a height of a principal ray from the optical axis at a maximum image height on a lens surface closest to the image side in the front subgroup at the wide angle end in the state where the infinite distance object is in focus is HMfb,
a height of an on-axis marginal ray from the optical axis on the lens surface closest to the image side in the front subgroup at the wide angle end in the state where the infinite distance object is in focus is HMfa,
a height of a principal ray from the optical axis at a maximum image height on a lens surface closest to the image side in the rear subgroup at the wide angle end in the state where the infinite distance object is in focus is HMrb,
a height of an on-axis marginal ray from the optical axis on the lens surface closest to the image side in the rear subgroup at the wide angle end in the state where the infinite distance object is in focus is HMra, and
Conditional Expression (7) is satisfied, which is represented by

0.08<(HMfb/HMfa)/(HMrb/HMra)<0.8  (7).