Variable-magnification optical system and imaging apparatus

A variable magnification optical system connected to an observation optical system, the variable magnification optical system comprising:

• a first lens group arranged closest to an observation optical system side, a final lens group arranged closest to an image side, and a plurality of movable lens groups arranged between the first lens group and the final lens group and movable in an optical axis direction, wherein
• the first lens group and the final lens group are fixed in the optical axis direction, and the plurality of movable lens groups are moved in the optical axis direction, to perform zooming, and
• at least one of the plurality of movable lens groups is moved in the optical axis direction to perform focusing on a nearest point object from a farthest point object,
• wherein a following condition is satisfied:
• 1.10≤bit≤3.00 (2)
• where
• bit:
• a lateral magnification of the final lens group at a time of focusing on the farthest point object at a telephoto end,
• wherein a following condition is satisfied:
• 0.20≤|fi|/√(fw×ft)≤1.20 (4)
• where
• fi:
• a focal length of the final lens group,
• fw:
• a focal length of the variable magnification optical system at a time of focusing on the farthest point object at the wide angle end, and
• ft:
• a focal length of the variable magnification optical system at a time of focusing on the farthest point object at the telephoto end.