Optical system and imaging apparatus having the same
AssigneeCanon Kabushiki Kaisha
InventorShuichi Mogi
Life of this patent
Estimating the term…
Abstract
An optical system includes, 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. The first lens unit is fixed during focusing. 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. The first lens unit includes a single lens which is disposed closest to an object and has a negative refractive power. A predetermined condition is satisfied.
Claims20
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 conditional expressions are satisfied:
- −0.78<ff2/ff1<−0.20
- 2.20<ff2/bf<12.00
- where ff1 is a focal length of the first focus lens unit, ff2 is a focal length of the second focus lens unit, and bf is a back focus of the optical system.
An imaging apparatus comprising:
- an optical system;
- and
- an image sensor configured to receive an image formed by the optical system,
- wherein the optical system includes, 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 conditional expressions are satisfied:
- −0.78<ff2/ff1<−0.20
- 2.20<ff2/bf<12.00
- where ff1 is a focal length of the first focus lens unit, ff2 is a focal length of the second focus lens unit, and bf is a back focus of the optical system.
Dependencies are inferred from the claim text.