Lens systems for projection televisions
First Claim
1. A projection lens system for use in a projection television which has a screen and a first cathode ray tube which produces light of primarily a first color, a second cathode ray tube which produces light of primarily a second color, and a third cathode ray tube which produces light of primarily a third color, said projection lens system comprising three projection lenses, one projection lens being associated with each of the cathode ray tubes during use of the system for forming an image of the light produced by that tube on the screen, each projection lens consisting of:
- (A) a first lens unit on the long conjugate side of the lens, said first lens unit having a positive power; and
(B) a second lens unit which (i) is associated with a cathode ray tube during use of the lens, (ii) has a strong negative power when so associated, and (iii) provides most of the correction of the lens'"'"' field curvature;
wherein in addition to any difference based on satisfying the Scheimpflug condition or any difference in spectral transmission, the second lens unit of the second projection lens differs from the second lens unit of the first projection lens in at least one optical property, said difference being based on said first and second colors.
3 Assignments
0 Petitions
Accused Products
Abstract
Projection lens systems for use with cathode ray tube (CRT) projection televisions are provided which have positive first lens units (U1) and negative second lens units (U2) where the negative second lens units are customized in terms of at least one optical property for at least two of the colors of light produced by the CRTs with which the units are used. The at least one optical property is not spectral transmission, although the second lens units can also be customized for spectral transmission. As illustrated in FIGS. 1B-1F and FIGS. 8B-8F, such customization of a non-transmissive property provides an effective and cost effective approach for improving the color performance of CRT projection lens systems. Constructions for the positive first lens unit which improve image contrast and reduce manufacturing costs are also provided.
19 Citations
41 Claims
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1. A projection lens system for use in a projection television which has a screen and a first cathode ray tube which produces light of primarily a first color, a second cathode ray tube which produces light of primarily a second color, and a third cathode ray tube which produces light of primarily a third color, said projection lens system comprising three projection lenses, one projection lens being associated with each of the cathode ray tubes during use of the system for forming an image of the light produced by that tube on the screen, each projection lens consisting of:
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(A) a first lens unit on the long conjugate side of the lens, said first lens unit having a positive power; and
(B) a second lens unit which (i) is associated with a cathode ray tube during use of the lens, (ii) has a strong negative power when so associated, and (iii) provides most of the correction of the lens'"'"' field curvature;
wherein in addition to any difference based on satisfying the Scheimpflug condition or any difference in spectral transmission, the second lens unit of the second projection lens differs from the second lens unit of the first projection lens in at least one optical property, said difference being based on said first and second colors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 41)
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13. A projection lens system for use in a projection television which has a screen and a first cathode ray tube which produces light of primarily a first color, a second cathode ray tube which produces light of primarily a second color, and a third cathode ray tube which produces light of primarily a third color, said projection lens system comprising three projection lenses, one projection lens being associated with each of the cathode ray tubes during use of the system for forming an image of the light produced by that tube on the screen, each projection lens consisting of:
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(A) a first lens unit on the long conjugate side of the lens, said first lens unit having a positive power; and
(B) a second lens unit which (i) is associated with a cathode ray tube during use of the lens, (ii) has a strong negative power when so associated, and (iii) provides most of the correction of the lens'"'"' field curvature;
wherein in addition to any differences based on satisfying the Scheimpflug condition or any differences in spectral transmission, the second lens units of the first, second, and third projection lenses differ from one another in at least one optical property, said differences being based on said first, second, and third colors. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A projection lens for use in combination with a cathode ray tube and having a long conjugate side, a short conjugate side, and a focal length F0 when associated with the cathode ray tube, said lens consisting in order from its long conjugate side of:
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(A) a positive first lens unit which consists in order from the lens'"'"' long conjugate side of;
(i) a first lens subunit which consists of a first lens element which has at least one aspherical surface and a weak power;
(ii) a second lens subunit which provides most of the positive power of the projection lens and consists of a second lens element or a doublet; and
(iii) a third lens subunit which consists of a third lens element which has at least one aspherical surface and a positive paraxial power; and
(B) a second lens unit which (i) is associated with the cathode ray tube during use of the lens, (ii) has a strong negative power when so associated, and (iii) provides most of the correction of the lens'"'"' field curvature;
wherein;
(a) the second lens subunit has a radius R21 in the direction of the lens'"'"' long conjugate side and a radius R22 in the direction of the lens'"'"' short conjugate side;
(b) |R22|/R21≧
1.5;
(c) the third lens element has an axial thickness T3, a best-fit spherical radius R31 in the direction of the lens'"'"' long conjugate side, and a best-fit spherical radius R32 in the direction of the lens'"'"' short conjugate side;
(d) R31<
0;
(e) R32<
0;
|R31|>
|R32|; and
(g) T3/F0≦
0.13. - View Dependent Claims (28, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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24. A projection lens for use in combination with a cathode ray tube and having a long conjugate side, a short conjugate side, and a focal length F0 when associated with the cathode ray tube, said lens consisting in order from its long conjugate side of:
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(A) a positive first lens unit which consists in order from the lens'"'"' long conjugate side of;
(i) a first lens subunit which consists of a first lens element which has at least one aspherical surface and a weak power;
(ii) a second lens subunit which provides most of the positive power of the projection lens and consists of a second lens element or a doublet; and
(iii) a third lens subunit which consists of a third lens element which has at least one aspherical surface and a positive paraxial power; and
(B) a second lens unit which (i) is associated with the cathode ray tube during use of the lens, (ii) has a strong negative power when so associated, and (iii) provides most of the correction of the lens'"'"' field curvature;
wherein;
(a) the second lens subunit has a radius R21 in the direction of the lens'"'"' long conjugate side and a radius R22 in the direction of the lens'"'"' short conjugate side;
(b) |R22|/R21≧
1.5;
(c) the third lens element has a best-fit spherical radius R31 in the direction of the lens'"'"' long conjugate side and a best-fit spherical radius R32 in the direction of the lens'"'"' short conjugate side;
(d) R31<
0;
(e) R32<
0;
(f) |R31|>
|R32|; and
(g) the second lens unit comprises a meniscus element which is concave to the lens'"'"' long conjugate side. - View Dependent Claims (30)
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25. A projection lens for use in combination with a cathode ray tube and having a long conjugate side, a short conjugate side, and a focal length F0 when associated with the cathode ray tube, said lens consisting in order from its long conjugate side of:
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(A) a positive first lens unit which consists in order from the lens'"'"' long conjugate side of;
(i) a first lens subunit which consists of a first lens element which has at least one aspherical surface and a weak power;
(ii) a second lens subunit which provides most of the positive power of the projection lens and consists of a second lens element or a doublet; and
(iii) a third lens subunit which consists of a third lens element which has at least one aspherical surface and a positive paraxial power; and
(B) a second lens unit which (i) is associated with the cathode ray tube during use of the lens, (ii) has a strong negative power when so associated, and (iii) provides most of the correction of the lens'"'"' field curvature;
wherein;
(a) the second lens subunit is axially spaced from the third lens element by a distance T23;
(b) the third lens element has an axial thickness T3, a best-fit spherical radius R31 in the direction of the lens'"'"' long conjugate side, and a best-fit spherical radius R32 in the direction of the lens'"'"' short conjugate side;
(c) the third lens element is axially spaced from the second lens unit by a distance T34;
(d) R31<
0;
(e) R32<
0;
(f) |R31|>
|R32|;
(g) T23≦
T34; and
(h) T3/F0≦
0.13. - View Dependent Claims (29)
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26. A projection lens for use in combination with a cathode ray tube and having a long conjugate side, a short conjugate side, and a focal length F0 when associated with the cathode ray tube, said lens consisting in order from its long conjugate side of:
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(A) a positive first lens unit which consists in order from the lens'"'"' long conjugate side of;
(i) a first lens subunit which consists of a first lens element which has at least one aspherical surface and a weak power;
(ii) a second lens subunit which provides most of the positive power of the projection lens and consists of a second lens element or a doublet; and
(iii) a third lens subunit which consists of a third lens element which has at least one aspherical surface and a positive paraxial power; and
(B) a second lens unit which (i) is associated with the cathode ray tube during use of the lens, (ii) has a strong negative power when so associated, and (iii) provides most of the correction of the lens'"'"' field curvature;
wherein;
(a) the second lens subunit is axially spaced from the third lens element by a distance T23;
(b) the third lens element has a best-fit spherical radius R31 in the direction of the lens'"'"' long conjugate side and a best-fit spherical radius R32 in the direction of the lens'"'"' short conjugate side;
(c) the third lens element is axially spaced from the second lens unit by a distance T34;
(d) R31<
0;
(e) R32<
0;
(f) |R31|>
|R32|;
(g) T23≦
T34;
and(h) the second lens unit comprises a meniscus element which is concave to the lens'"'"' long conjugate side.
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27. A projection lens for use in combination with a cathode ray tube and having a long conjugate side, a short conjugate side, and a focal length F0 when associated with the cathode ray tube, said lens consisting in order from its long conjugate side of:
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(A) a positive first lens unit which consists in order from the lens'"'"' long conjugate side of;
(i) a first lens subunit which consists of a first lens element which has at least one aspherical surface and a weak power;
(ii) a second lens subunit which provides most of the positive power of the projection lens and consists of a second lens element or a doublet; and
(iii) a third lens subunit which consists of a third lens element which has at least one aspherical surface and a positive paraxial power; and
(B) a second lens unit which (i) is associated with the cathode ray tube during use of the lens, (ii) has a strong negative power when so associated, and (iii) provides most of the correction of the lens'"'"' field curvature;
wherein;
(a) the second lens subunit has a radius R21 in the direction of the lens'"'"' long conjugate side and a radius R22 in the direction of the lens'"'"' short conjugate side;
(b) |R22|/R21≧
1.5;
(c) the second lens subunit is axially spaced from the third lens element by a distance T23;
(d) the third lens element has an axial thickness T3, a best-fit spherical radius R31 in the direction of the lens'"'"' long conjugate side, and a best-fit spherical radius R32 in the direction of the lens'"'"' short conjugate side;
(e) R31<
0;
(f) R32<
0;
(g) |R31|>
|R32|;
(h) T3/F0≦
0.13;
(i) the third lens element is axially spaced from the second lens unit by a distance T34;
(j) T23≦
T34;
and(k) the second lens unit comprises a meniscus element which is concave to the lens'"'"' long conjugate side.
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Specification