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

Claim 27:
28. 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

−400.00<ff1/ff1gt<−5.00, 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, ff1gt is a distance on an optical axis from a surface closest to an object of the first focus lens unit to a surface closest to an image of the first focus lens unit, and ff1 is a focal length of the first focus lens unit.