Projection variable focusing lens and projection display device
First Claim
1. A projection variable focusing lens comprising:
- a first lens group having a negative refractive power;
a second lens group having a positive refractive power;
a third lens group, wherein the third lens group includes a first negative lens, a second positive lens having a convex surface facing the reduction side, and a third positive lens having a convex surface facing the reduction side arranged in this order from the magnification side; and
a fourth lens group having a positive refractive power,wherein the first to fourth lens groups are arranged in this order from a magnification side, andwhen a focal length varies, the second lens group is moved in an optical axis direction,during focusing, the third lens group is moved in the optical axis direction, anda reduction side is substantially telecentric.
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Accused Products
Abstract
A projection variable focusing lens and a projection display device that has a reduction side which is telecentric, a high magnifying power, a small size, a light weight, and a low manufacturing cost and is capable of correcting all aberrations occurring when power varies with good balance. A projection variable focusing lens that moves only one lens group when power varies includes a first negative lens group G1, a second positive lens group G2, a third lens group G3, and a fourth positive lens group G4 arranged in this order from a magnification side. When a focal length varies, only the second lens group G2 is moved along an optical axis X. During focusing, the third lens group G3 is moved along the optical axis X. A reduction side is substantially telecentric.
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Citations
15 Claims
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1. A projection variable focusing lens comprising:
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a first lens group having a negative refractive power; a second lens group having a positive refractive power; a third lens group, wherein the third lens group includes a first negative lens, a second positive lens having a convex surface facing the reduction side, and a third positive lens having a convex surface facing the reduction side arranged in this order from the magnification side; and a fourth lens group having a positive refractive power, wherein the first to fourth lens groups are arranged in this order from a magnification side, and when a focal length varies, the second lens group is moved in an optical axis direction, during focusing, the third lens group is moved in the optical axis direction, and a reduction side is substantially telecentric. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification