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US 7,397,610 B2Granted
Zoom lens and image projection apparatus having the same
AssigneeCanon Kabushiki Kaisha
InventorKen Wada
Life of this patent
Estimating the term…
Abstract
A zoom lens of the invention has three lens groups. In the zoom lens, magnification change is performed by moving only one lens group among the three lens groups, and focus adjustments is performed by moving one of a first lens group and a second lens group counted from an enlargement conjugate side among the three lens groups. In addition, the zoom lens is approximately telecentric on reduction conjugate side thereof.
Claims12
A zoom lens comprising:
- three lens units including a first lens unit having negative refractive power, a second lens unit having positive refractive power, and a third lens unit having positive refractive power in this order from an enlargement conjugate side,
- wherein a magnification change is performed by moving only the second lens unit in an optical axis direction of the zoom lens, focus adjustments of the zoom lens is performed by moving the first lens unit on the optical axis, and the zoom lens is approximately telecentric on reduction conjugate side of the zoom lens,
- wherein when a focal distance of the second lens unit is referred to as “fv” and a lateral magnification, a magnification changing ratio, an F-value in an intermediate region at a time of the magnification changing, and a minimum diameter of a circle of confusion of the third lens unit are respectively referred to as “βr”,“Z”, “Fm”, and “ε”, a following expression is satisfied:
- 2Fm·ε−|−fv·(1−√Z)2|·βr2/√Z>0.
1 more element
A zoom lens comprising:
- a first lens unit having negative refractive power;
- a second lens unit having positive refractive power;
- and
- a third lens unit having positive refractive power,
- wherein the first lens unit, the second lens unit, and the third lens unit are located in this order from an enlargement conjugate side,
- wherein magnification changing is performed by moving only the second lens unit and focus adjustment is performed by moving only the first lens unit, and
- wherein when a focal distance of the second lens unit is referred to as “fv” and a lateral magnification, a magnification changing ratio, an F-value in an intermediate region at a time of the magnification changing, and a minimum diameter of a circle of confusion of the third lens unit are respectively referred to as “βr”, “Z”, “Fm”, and “ε”, a following expression is satisfied:
- 2Fm·ε−|−fv·(1−√Z)2|·βr2/√Z>0.
5 more elements
An image projection apparatus comprising:
- an image display element;
- and
- a zoom lens for projecting light from the image display element,
- wherein zoom lens comprises a first lens unit having negative refractive power, a second lens unit having positive refractive power, and a third lens unit having positive refractive power, which are located in this order from an enlargement conjugate side,
- wherein magnification changing is performed by moving only the second lens unit and focus adjustment is performed by moving only the first lens unit, and
- wherein when a focal distance of the second lens unit is referred to as “fv” and a lateral magnification, a magnification changing ratio, an F-value in an intermediate region at a time of the magnification changing, and a minimum diameter of a circle of confusion of the third lens unit are respectively referred to as “βr”, “Z”, “Fm”, and “ε”, a following expression is satisfied:
- 2Fm·ε−|−fv·(1−√Z)2|·βr2/√Z>0.
4 more elements
Dependencies are inferred from the claim text.