Patent ID: 11940606
Assignee: CANON KABUSHIKI KAISHA
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 24:
25. An optical system comprising, in order from an object side to an image side:
a first lens unit having a positive refractive power;
a first focus lens unit having a negative refractive power; and
a second focus lens unit having a positive refractive power,
wherein the first lens unit is fixed during focusing,
wherein the first focus lens unit and the second focus lens unit move so that a distance between the first focus lens unit and the second focus lens unit changes during focusing,
wherein the first lens unit includes a single lens which is disposed closest to an object and has a negative refractive power, and
wherein the following inequalities are satisfied:

2.20<ff2/bf<12.00

0.50<βff1/βff2<400.0, where ff2 is a focal length of the second focus lens unit, bf is a back focus of the optical system, f is a focal length of the optical system, βff1 is a lateral magnification of the first focus lens unit when focused on an object at infinity, and βff2 is a lateral magnification of the second focus lens unit when focused on an object at infinity.