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 φ
I, when focused to an object distance of 1700 mm from an enlarging side first surface when a focusing operation is available, and at a wide-angle end in the case of a zoom lens;
FN;
full-aperture F value of a whole lens system, when 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
In a thin projector for projecting an image from a light valve such as a DMD, a compact zoom lens comprises, in order, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens-group having a negative refractive power, and a fourth lens group having a positive refractive power. The fourth lens group is fixed while the focal length is being changed. The first and second lens group are movable 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 movable 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. The third lens group moves 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.
6 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 φ
I, when focused to an object distance of 1700 mm from an enlarging side first surface when a focusing operation is available, and at a wide-angle end in the case of a zoom lens;FN;
full-aperture F value of a whole lens system, when 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)
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Specification