Imaging optical system and image pickup apparatus including the same
AssigneeCanon Kabushiki Kaisha
InventorTakayoshi Yokoyama
Life of this patent
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Abstract
An imaging optical system includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, an aperture stop, and a third lens unit having a positive refractive power. The second lens unit moves toward the image side during focusing from a far object to a near object. The third lens unit includes, in order from the object side to the image side, two lenses having concave surfaces that face each other with a largest air gap in the third lens unit provided therebetween, and a positive lens. A focal length of the entire imaging optical system and a focal length of the second lens unit are appropriately set.
Claims11
An imaging optical system comprising, in order from an object side to an image side:
- a first lens unit having a positive refractive power;
- a second lens unit having a negative refractive power;
- an aperture stop;
- and
- a third lens unit having a positive refractive power,
- wherein the second lens unit moves toward the image side during focusing from a far object to a near object,
- wherein the third lens unit includes, in order from the object side to the image side, two lenses having concave surfaces that face each other with a largest air gap in the third lens unit provided therebetween, and a positive lens, and
- wherein, when f is a focal length of the entire imaging optical system and f2 is a focal length of the second lens unit, the following conditional expression is satisfied:
- 0.70<★f2/f|<2.50.
An imaging optical system comprising, in order from an object side to an image side:
- a first lens unit having a positive refractive power;
- a second lens unit having a negative refractive power;
- an aperture stop;
- and
- a third lens unit having a positive refractive power,
- wherein the second lens unit moves toward the image side during focusing from a far object to a near object,
- wherein the third lens unit includes, in order from the object side to the image side, a negative lens having a lens surface with a negative refractive power at the object side, and a positive lens, and
- wherein, when f is a focal length of the entire imaging optical system, f2 is a focal length of the second lens unit, f3 is a focal length of the third lens unit, and R3b is a radius of curvature of the object-side lens surface of the negative lens, the following conditional expression is satisfied:
- 0.70<|f2/f|<2.50
- 0.25<|R3b/f3|<0.60.
An image pickup apparatus comprising:
- an imaging optical system;
- and
- a photoelectric transducer that receives an image formed by the imaging optical system,
- wherein the imaging optical system includes, in order from an object side to an image side,
- a first lens unit having a positive refractive power,
- a second lens unit having a negative refractive power,
- an aperture stop, and
- a third lens unit having a positive refractive power,
- wherein the second lens unit moves toward the image side during focusing from a far object to a near object,
- wherein the third lens unit includes, in order from the object side to the image side, two lenses having concave surfaces that face each other with a largest air gap in the third lens unit provided therebetween, and a positive lens, and
- wherein, when f is a focal length of the entire imaging optical system and f2 is a focal length of the second lens unit, the following conditional expression is satisfied:
- 0.70<|f2/f|<2.50.
Dependencies are inferred from the claim text.