US 5,633,757 AGranted

Projection lens

AssigneeGoldstar Co., Ltd.

InventorSung C. Park

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Abstract

An improved projection lens capable of substantially and advantageously implementing a distinct picture by compensating for a chromatic aberration and a residue aberration, which includes a first lens group, including a lens element convex to a screen and having a relatively weak optical power, for eliminating a spherical surface aberration; a second lens group having positive optical power and cemented with a two side lens element having a positive optical element and a lens element having a negative optical element, which have a different dispersion from each other; a third lens group having a positive optical power on an optical axis and a radius code of a curvature surface toward an upper surface of which has the same radius code as the radius curvature surface of a cathode ray tube; and a fourth lens group having a high optical power toward an upper surface of the screen for compensating for a field dependent aberration.

Claims25

Dependent claims

A projection lens, comprising:

a first lens group, including a single lens convex to a screen, said first lens group having a positive optical power for eliminating a spherical aberration;
a second lens group having a positive optical power and including a positive element and a negative element having a dispersion different from that of the positive element;
a third lens group having a positive optical power on an optical axis thereof and having a meniscus shape concave to the screen at the optical axis and convex to the screen adjacent an outer extent of a clear aperture thereof;
and
a fourth lens group having a negative optical power and being concave to the screen for compensating for field dependent aberrations, wherein said projection lens satisfies the condition:
0.32<D.sub.12 /f.sub.0 <0.42
where D.sub.12 denotes the distance between the first lens group and the second lens group and f.sub.0 denotes the focal length of the entire projection lens, and wherein
0.11<f.sub.0 /f.sub.1 <0.14
0.91<f.sub.0 /f.sub.2 <0.95
0.21<f.sub.0 /f.sub.3 <0.25
-0.68<f.sub.0 /f.sub.4 <-0.62
where f.sub.0 is the overall focal length of the projection lens, f.sub.1 is the focal length of the first lens group, f.sub.2 is the focal length of the second lens group, f.sub.3 is the focal length of the third lens group, and f.sub.4 is the focal length of the fourth lens group.

9 more elements

A projection lens, comprising:

a first lens group, including a single lens convex to a screen, the first lens group having a positive optical power for eliminating a spherical aberration;
a second lens group having a positive optical power and including a positive element and a negative element having a dispersion different from that of the positive element;
a third lens group having a positive optical power on an optical axis thereof and having a meniscus shape concave to the screen at the optical axis and convex to the screen adjacent an outer extent of a clear aperture thereof;
and
a fourth lens group having a negative optical power and being concave to the screen for compensating for field dependent aberrations, wherein said projection lens satisfies the condition:
0.32<D.sub.12 /f.sub.0 <0.42
where D.sub.12 denotes the distance between the first lens group and the second lens group and f.sub.0 denotes the focal length of the entire projection lens, and
wherein the distance between said third lens group and said fourth lens group satisfies the condition:
0.40D.sub.34 /f.sub.0 <0.43
where D.sub.34 is the distance between the third lens group and the fourth lens group and f.sub.0 is the focal length of the entire projection lens.

7 more elements

Dependencies are inferred from the claim text.