Zoom lens and image display apparatus using the same
AssigneeCanon Kabushiki Kaisha
InventorKen Wada
Life of this patent
Estimating the term…
Abstract
It is an object of this invention to provide a zoom lens capable of projecting an original projection image displayed by a liquid crystal display element onto a screen surface with high optical performance, and an image projection apparatus using the zoom lens. A zoom lens includes a first lens unit having negative refractive power, a second lens unit having positive refractive power, a stop, a third lens unit having negative refractive power, a fourth lens unit having negative refractive power, and a fifth lens unit having positive refractive power, which are sequentially arranged from the enlargement side and having one or a plurality of lenses. When the magnification is to be changed from the wide angle end to the telephoto end, the second, third, and fourth lens units and the stop move.
Claims38
A zoom lens comprising:
- a first lens unit having negative refractive power;
- a second lens unit having positive refractive power;
- a third lens unit having negative refractive power;
- a fourth lens unit having negative refractive power;
- a fifth lens unit having positive refractive power, said first to fifth lens units being sequentially arranged from an enlargement side, each of said lens units having one or a plurality of lenses, and
- a stop provided between lenses included within said second and third lens units,
- wherein when magnification is changed from wide angle end to telephoto end, intervals between said first to fifth lens units are changed, and
- wherein both refractive power on the enlargement side from said stop and refractive power on a reduction side from said stop are positive.
A zoom lens comprising:
- a first lens unit having negative refractive power;
- a second lens unit having positive refractive power;
- a third lens unit having negative refractive power;
- a fourth lens unit having negative refractive power;
- and
- a fifth lens unit having positive refractive power, said first to fifth lens units being sequentially arranged from an enlargement side, each of said lens units having one or a plurality of lenses,
- wherein when a magnification is changed from a wide angle end to a telephoto end, said first and fifth lens units are fixed, all said second, third, and fourth lens units move from a reduction side to the enlargement side, and letting β2w and β3w be imaging magnifications of said second and third lens units at the wide angle end, f5 be a focal length of said fifth lens unit, and fw be a focal length of an overall system at the wide angle end,
- 0.25<−β2w<1.0
- 1.0<β3w<5.0
- 1.2<f5/fw<2.2
- are satisfied.
A zoom lens comprising:
- a first lens unit having negative refractive power;
- a second lens unit having positive refractive power;
- a third lens unit having negative refractive power;
- a fourth lens unit having negative refractive power;
- and
- a fifth lens unit having positive refractive power, said first to fifth lens units being sequentially arranged from an enlargement side, each of said lens units having one or a plurality of lenses,
- wherein when magnification is changed from wide angle end to telephoto end, intervals between said first to fifth lens units are changed, and
- wherein letting f5 be a focal length of said fifth lens unit at the wide angle end, and fw be a focal length of an overall system at the wide angle end, a conditional expression, 1.2<f5/fw<2.2 is satisfied.
Dependencies are inferred from the claim text.