Patent ID: 11860347
Assignee: CANON KABUSHIKI KAISHA
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A zoom lens comprising in order from an object side to an image side:
a first lens unit configured not to move for zooming;
a plurality of zooming lens units configured to move in zooming;
a front relay lens unit configured not to move for zooming;
an extender lens unit insertable into and removable from an optical path for changing a focal length range of the zoom lens; and
a rear relay lens unit configured not to move for zooming,
wherein a part of the first lens unit moves at focusing,
a combined focal length of the front relay lens unit, the extender lens unit and the rear relay lens unit is a positive value,
wherein following conditional expressions are satisfied:

1.00<(Def/Der)/βe+(1−few/feF)<1.75,

0.50<(le/Der)/βe<1.22, and

0.10<few/feF<1.00,

where few is a focal length at a wide-angle end and in a state where the extender lens unit is inserted, feF is a combined focal length from the first lens unit to the front relay lens unit, Def is an effective diameter of a lens surface in a lens included in the extender lens unit and closest to the object side, Der is an effective diameter of a lens surface in a lens included in the extender lens unit and closest to the image side, βe is a lateral magnification of the extender lens unit, and le is a distance on an optical axis from a surface included in the extender lens unit and closest to the object side to a surface included in the extender lens unit and closest to the image side.