Zoom lens and camera using the same
AssigneeCanon Kabushiki Kaisha
InventorAkihisa Horiuchi
Life of this patent
Estimating the term…
Abstract
A zoom lens includes, in order from the object side to the image side, a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit which has positive optical power and which does not move for zooming, and a fourth lens unit having positive optical power. In zooming from a wide-angle end to a telephoto end, the first lens unit is moved toward the object side and the second lens unit is moved toward the image side, whereby the distance between the first and second lens units is increased. By constructing each lens unit such that the focal length, the distance between the principal points, etc., satisfy predetermined conditions, a small zoom lens having a high zooming ratio and high optical quality can be obtained.
Claims23
A zoom lens comprising, in order from an object side to an image side of said zoom lens:
- a first lens unit having positive optical power;
- a second lens unit having negative optical power;
- a third lens unit which has positive optical power and which does not move for zooming;
- and
- a fourth lens unit having positive optical power,
- wherein when zooming from a wide-angle end to a telephoto end, the first lens unit is moved toward the object side and the second lens unit is moved toward the image side, whereby the distance between the first and second lens units is increased, and
- wherein, when fW and fT are focal lengths of the overall system at the wide-angle end and the telephoto end, respectively, f2 is a focal length of the second lens unit, e3T is the distance between principal points of the third and fourth lens units at the telephoto end when an object located at infinity is in focus, f3 and f4 are focal lengths of the third and fourth lens units, respectively, and fA is defined as fA={square root over (fw·fT)}, the following expressions are satisfied:
- 0.17<|f2/fA|<0.30,
- 2.05<e3T/fW<2.96, and
- 0.6<f3/f4<0.92.
A camera comprising:
- a zoom lens, said zoom lens comprising, in order from an object side to an image side of said zoom lens:
- a first lens unit having positive optical power;
- a second lens unit having negative optical power;
- a third lens unit which has positive optical power and which does not move for zooming;
- and
- a fourth lens unit having positive optical power,
- wherein when zooming from a wide-angle end to a telephoto end, the first lens unit is moved toward the object side and the second lens unit is moved toward the image side, whereby the distance between the first and second lens units is increased, and
- wherein, when fW and fT are focal lengths of the overall system at the wide-angle end and the telephoto end, respectively, f2 is a focal length of the second lens unit, e3T is the distance between principal points of the third and fourth lens units at the telephoto end when an object located at infinity is in focus, f3 and f4 are focal lengths of the third and fourth lens units, respectively, and fA is defined as fA={square root over (fw·fT)}, the following expressions are satisfied:
- 0.17<|f2/fA|<0.30,
- 2.05<e3T/fW<2.96,
- and
- 0.6<f3/f4<0.92;
- and
- a photoelectric transducer that receives an image formed by said zoom lens.
A zoom lens comprising, in order from an object side to an image side of said zoom lens:
- a first lens unit having positive optical power;
- a second lens unit having negative optical power;
- a third lens unit which has positive optical power and which does not move for zooming;
- and
- a fourth lens unit having positive optical power,
- wherein when zooming from a wide-angle end to a telephoto end, the first lens unit is moved toward the object side and the second lens unit is moved toward the images side, whereby the distance between the first and second lens units is increased,
- wherein said zoom lens further comprising an aperture stop which does not move during zooming, and
- wherein, when fW is focal length of the overall system at the wide-angle end, e3T is the distance between principal points of the third and fourth lens units at the telephoto end when an object located at infinity is in focus, the following expression is satisfied:
- 2.05<e3T/fW<2.96.
A camera comprising:
- a zoom lens comprising, in order from an object side to an image side of said zoom lens:
- a first lens unit having positive optical power;
- a second lens unit having negative optical power;
- a third lens unit which has positive optical power and which does not move for zooming;
- and
- a fourth lens unit having positive optical power,
- wherein when zooming from a wide-angle end to a telephoto end, the first lens unit is moved toward the object side and the second lens unit is moved toward the image side, whereby the distance between the first and second lens units is increased,
- wherein said zoom lens further comprising an aperture stop which does not move during zooming, and
- wherein, when fW is focal length of the overall system at the wide-angle end, e3T is the distance between principal points of the third and fourth lens units at the telephoto end when an object located at infinity is in focus, the following expression is satisfied:
- 2.05<e3T/fW<2.96;
- and
- a photoelectric transducer that receives an image formed by said zoom lens.
Dependencies are inferred from the claim text.