Zoom lens and projector employing zoom lens
First Claim
1. A zoom lens comprising an optical system made up of a plurality of lens elements or a plurality of lens groups, wherein the following conditional expression (1) is satisfied with respect to a maximum effective aperture and a size of an image circle, and the following conditional expressions (2), (3) are satisfied with respect to an angle of view and brightness, respectively:
-
1.00<
φ
L/φ
I<
1.60
(1)
55<
BW<
70
(2)
1.8<
FN<
2.9
(3) where, φ
L;
maximum effective aperture of a lens system;
φ
I;
diameter of a minimum-sized circle which encapsulates a whole image display unit on a reducing side image plane about an optical axis;
BW;
total angle of view relative to an image point with in φ
I (focused to an object distance of 1700 mm from an enlarging side first surface when a focusing operation is available, at a wide-angle end in the case of a zoom lens);
FN;
full-aperture, F value of a whole lens system (focused to the object distance of 1700 mm from the enlarging side first surface when the focusing operation is available, at a minimum value in the case of the zoom lens).
1 Assignment
0 Petitions
Accused Products
Abstract
To provide a thin projector for projecting an image from a light bulb such as a DMD for forming an image by changing reflecting directions of light on to a screen or the like in an enlarged fashion and a compact zoom lens with high performance and which has a small lens aperture. There is provided a zoom lens made up of, in order from an enlarging size thereof, a first lens group having a negative refractive power as a whole, a second lens group having a positive refractive power as a whole, a third lens-group having a negative refractive power as a whole, and a fourth lens group having a positive refractive power as a whole, wherein the fourth lens group is fixed while the focal length is being changed, the first lens group and the second lens group are made to move on an optical axis in a direction from the enlarging side towards the reducing side over a range from a wide angle end to an intermediate range and are made to move on the optical axis in a direction from the reducing side towards the enlarging side over a range from the intermediate range to a telephoto end, and the third lens group is made to move on the optical axis in a direction from the reducing side to the enlarging side over a range from the wide angle end to the telephoto end, whereby the focal length of the whole lens system of the zoom lens is changed.
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Citations
8 Claims
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1. A zoom lens comprising an optical system made up of a plurality of lens elements or a plurality of lens groups, wherein the following conditional expression (1) is satisfied with respect to a maximum effective aperture and a size of an image circle, and the following conditional expressions (2), (3) are satisfied with respect to an angle of view and brightness, respectively:
-
1.00<
φ
L/φ
I<
1.60
(1)
55<
BW<
70
(2)
1.8<
FN<
2.9
(3)where, φ
L;
maximum effective aperture of a lens system;
φ
I;
diameter of a minimum-sized circle which encapsulates a whole image display unit on a reducing side image plane about an optical axis;
BW;
total angle of view relative to an image point with in φ
I (focused to an object distance of 1700 mm from an enlarging side first surface when a focusing operation is available, at a wide-angle end in the case of a zoom lens);
FN;
full-aperture, F value of a whole lens system (focused to the object distance of 1700 mm from the enlarging side first surface when the focusing operation is available, at a minimum value in the case of the zoom lens).- View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
0.90<
(φ
L/2)/SP<
1.50
(4)
50<
VG<
70
(5)where, SP;
difference in dimension between from the center of the image display device to the upper edge portion of the image display area and to the upper end portion of the package;
VG;
marginal lumination or quantity of marginal light ratio (focused to the object distance of 1700 mm from the enlarging side first surface when the focusing operation is available, at the wide-angle end in the case of the zoom lens).
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3. A zoom lens as set forth in claim 1, wherein the focal lens of the zoom lens can be changed as a result of a plurality of lens groups moving in directions along an optical axis thereof.
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4. A zoom lens as set forth in claim 2, wherein the focal lens of the zoom lens can be changed as a result of a plurality of lens groups moving in directions along an optical axis thereof.
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5. A projector which installs therein a zoom lens as set forth in claim 1.
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6. A projector which installs therein a zoom lens as set forth in claim 2.
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7. A projector which installs therein a zoom lens as set forth in claim 3.
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8. A projector which installs therein a zoom lens as set forth in claim 4.
Specification