Projection lens

Claim 2

A projection lens for a cathode ray tube consisting from the image side a first lens unit having two aspheric surfaces, said first lens unit consisting of a single element of generally positive meniscus form and providing correction for aperture dependent aberrations, a second lens unit consisting of a single positive lens element having at least one aspheric surface, said second lens unit providing the majority of the positive power of the overall lens, and a third lens unit having a strongly concave and aspheric image side surface and correcting for field curvature, said first element having an aspheric optical power changing from positive on axis to negative at the edge of the clear aperture of that element, and |Ky.sub.CA /Ky.sub.A |>2.5, where Ky CA is the aspheric optical power of the lens element of said first lens unit at the maximum clear aperture, and Ky A is the aspheric optical power of the lens at the optical axis thereof.

Claim 3

The lens of claim 1 where said third lens unit comprises a liquid optical coupling between said third lens unit and the cathode ray tube and said liquid coupling provides optical power to the overall lens.

Claim 4

The lens of claim 1 where 0.47>|D.sub.12 /F.sub.3 |>0.16 where D 12 is the axial spacing between said first and second lens units and F 3 is the equivalent focal length of the third lens unit.

Claim 5

The lens of claim 1 wherein said third lens unit comprises a housing member having a liquid therein in contact with the faceplate of the cathode ray tube and said housing member is closed on the image side by a meniscus element having both surfaces convex to the cathode ray tube.

Claim 6

The lens of claim 4 wherein the image side surface of said meniscus element is aspheric to provide correction for distortion.

Claim 7

The lens of claim 4 wherein said lens further includes a second meniscus element between said second and third lens units having surfaces convex to the object end and one of the surfaces is aspheric to provide correction for distortion.

Claim 8

The lens of claim 1 wherein the image side surface of said first lens element is generally convex to the image side but becomes concave to the image side as the height of the lens from the optical axis approaches the clear aperture of said lens element.

Claim 9

The lens of claim 1 where said aspheric surfaces are defined by the equation ##EQU7## where x is the surface sag at a semi-aperture distance y from the axis A of the lens, C is the curvature of a lens surface at the optical axis A equal to the reciprocal of the radius of the optical axis, K is a conic constant.

Claim 10

A lens according to claim 8 having a semi-field angle of approximately 35.8° defined substantially as follows: ______________________________________ AXIAL DISTANCE SURFACE BETWEEN SURFACES LENS RADII (mm) (mm) N.sub.d V.sub.d ______________________________________ S1 66.005 L1 8.000 1.491 57.2 S2 206.658 29.491 S3 80.214 L2 22.000 1.491 57.2 S4 -79.957 38.419 S5 -36.426 L3 2.000 1.491 57.2 S6 Plano ______________________________________ Aspheric Surfaces S1, S2, S3, S4, S5 S1 S2 S3 ______________________________________ D -0.4255 × 10.sup.-6 0.3151 × 10.sup.-6 0.2250 × 10.sup.-6 E -0.5708 × 10.sup.-9 -0.2865 × 10.sup.-9 -0.3646 × 10.sup.-10 F -0.7857 × 10.sup.-13 0.6562 × 10.sup.-13 0.3798 × 10.sup.-12 G -0.8750 × 10.sup.-16 0.1309 × 10.sup.-15 -0.2195 × 10.sup.-16 H 0.7139 × 10.sup.-19 -0.1229 × 10.sup.-18 -0.1481 × 10.sup.-18 I -0.1631 × 10.sup.-21 -0.6775 × 10.sup.-22 0.5067 × 10.sup.-22 -.01 ______________________________________ S4 S5 ______________________________________ D -0.1471 × 10.sup.-7 -0.3053 × 10.sup.-5 E 0.6774 × 10.sup.-10 0.2619 × 10.sup.-8 F 0.2866 × 10.sup.-12 -0.6689 × 10.sup.-13 G -0.5363 × 10.sup.-16 0.2209 × 10.sup.-14 H -0.1782 × 10.sup.-18 -0.5937 × 10.sup.-17 I 0.8195 × 10.sup.-22 0.3681 × 10.sup.-20 -.01 .01 ______________________________________ where L1-L3 are lens elements from the image end, N d is the index of refraction of the lens elements, V d is the dispersion of the lens elements measured by their Abbe number, S1-S6 are successive lens surfaces from the image end, the surfaces where positive are on radii struck from the right and where negative are on radii struck from the left, and surfaces S1, S2, S3, S4, and S5 are aspheric as shown.

Claim 11

A lens according to claim 8 having a semi-field angle of approximately 35.6° defined substantially as follows: ______________________________________ AXIAL DISTANCE SURFACE BETWEEN SURFACES LENS RADII (mm) (mm) N.sub.d V.sub.d ______________________________________ S1 59.083 L1 7.000 1.491 57.2 S2 124.029 22.605 S3 102.219 L2 27.000 1.491 57.2 S4 -64.593 42.779 S5 -38.637 L3 2.000 1.491 57.2 S6 Plano ______________________________________ Aspheric Surfaces S1, S2, S3, S4, S5 S1 S2 S3 ______________________________________ D -0.3568 × 10.sup.-6 0.7056 × 10.sup.-6 -0.4168 × 10.sup.-6 E -0.6422 × 10.sup.-9 -0.6771 × 10.sup.-10 0.8955 × 10.sup.-10 F 0.2063 × 10.sup.-12 0.1784 × 10.sup.-12 0.5212 × 10.sup.-13 G -0.1799 × 10.sup.-16 0.1469 × 10.sup.-15 0.5070 × 10.sup.-17 H -0.1073 × 10.sup.-18 -0.1012 × 10.sup.-18 -0.2303 × 10.sup.-20 I -0.5473 × 10.sup.-22 -0.3577 × 10.sup.-22 0.3823 × 10.sup.-22 K -.01 ______________________________________ S4 S5 ______________________________________ D -0.2980 × 10.sup.-6 -0.2465 × 10.sup.-5 E -0.8180 × 10.sup.-10 0.1867 × 10.sup.-8 F -0.6413 × 10.sup.-13 -0.1066 × 10.sup.-11 G 0.1105 × 10.sup.-16 0.2506 × 10.sup.-14 H 0.1728 × 10.sup.-19 -0.3208 × 10.sup.-17 I -0.3840 × 10.sup.-25 0.1547 × 10.sup.-20 K -.01 .01 ______________________________________ where L1-L3 are lens elements from the image end, N d is the index of refraction of the lens elements, V d is the dispersion of the lens elements measured by their Abbe number, S1-S6 are successive lens surfaces from the image end, the surfaces where positive are on radii struck from the right and where negative are on radii struck from the left, and surfaces S1, S2, S3, S4, and S5 are aspheric as shown.

Claim 12

A lens according to claim 8 having a semi-field angle of approximately 36.0° defined substantially as follows: ______________________________________ AXIAL DISTANCE SURFACE BETWEEN SURFACES LENS RADII (mm) (mm) N.sub.d V.sub.d ______________________________________ S1 66.255 L1 8.000 1.491 57.2 S2 191.051 31.649 S3 77.116 L2 19.000 1.491 75.2 S4 -82.903 40.248 S5 -36.972 L3 2.000 1.491 57.2 S6 Plano ______________________________________ Aspheric Surfaces S1, S2, S3, S4, S5 S1 S2 S3 ______________________________________ D -0.5104 × 10.sup.-6 0.2855 × 10.sup.-6 0.4013 × 10.sup.-6 E -0.4117 × 10.sup.-9 -0.1463 × 10.sup.-10 -0.8469 × 10.sup.-10 F 0.2031 × 10.sup.-13 0.1566 × 10.sup.-12 0.3911 × 10.sup.-12 G 0.5341 × 10.sup.-16 0.5370 × 10.sup.-16 -0.2213 × 10.sup.-16 H 0.1742 × 10.sup.-19 -0.1997 × 10.sup.-18 -0.1322 × 10.sup.-18 I -0.1700 × 10.sup.-21 -0.5610 × 10.sup.-22 0.5739 × 10.sup.-22 K -.01 ______________________________________ S4 S5 ______________________________________ D 0.3167 × 10.sup.-6 -0.2972 × 10.sup.-5 E -0.2928 × 10.sup.-9 0.2339 × 10.sup.-8 F 0.4604 × 10.sup.-12 -0.1192 × 10.sup.-11 G 0.1383 × 10.sup.-16 0.2717 × 10.sup.-14 H -0.2322 × 10.sup.-18 -0.4724 × 10.sup.-17 I 0.9630 × 10.sup.-22 0.2666 × 10.sup.-20 ______________________________________ where L1-L3 are lens elements from the image end, N d is the index of refraction of the lens elements, V d is the dispersion of the lens elements measured by their Abbe number, S1-S6 are successive lens surfaces from the image end, the surfaces where positive are on radii struck from the right and where negative are on radii struck from the left, and surfaces S1, S2, S3, S4, and S5 are aspheric as shown.

Claim 13

A lens according to claim 8 having a semi-field angle of approximately 35.7° defined substantially as follows: ______________________________________ AXIAL DISTANCE SURFACE BETWEEN SURFACES LENS RADII (mm) (mm) N.sub.d V.sub.d ______________________________________ S1 58.718 L1 7.000 1.491 57.2 S2 121.874 22.889 S3 100.773 L2 27.000 1.491 57.2 S4 -65.053 42.766 S5 -38.670 L3 2.000 1.491 57.2 S6 Plano ______________________________________ Aspheric Surfaces S1, S2, S3, S4, S5 S1 S2 S3 ______________________________________ D -0.3228 × 10.sup.-6 0.7572 × 10.sup.-6 -0.4326 × 10.sup.-6 E -0.5975 × 10.sup.-9 -0.7962 × 10.sup.-10 0.6723 × 10.sup.-10 F 0.1621 × 10.sup.-12 0.1910 × 10.sup.-12 0.4057 × 10.sup.-13 G -0.1125 × 10.sup.-16 0.1329 × 10.sup.-15 -0.1047 × 10.sup.-17 H -0.9129 × 10.sup.-19 -0.1080 × 10.sup.-18 -0.3139 × 10.sup.-20 I -0.6032 × 10.sup.-22 -0.2983 × 10.sup.-22 0.4742 × 10.sup.-23 K -.01 ______________________________________ S4 S5 ______________________________________ D -0.3014 × 10.sup.-6 -0.2796 × 10.sup.-5 E -0.5533 × 10.sup.-10 0.2300 × 10.sup.-8 F -0.7621 × 10.sup.-13 -0.9769 × 10.sup.-12 G 0.7864 × 10.sup.-17 0.2174 × 10.sup.-14 H 0.1770 × 10.sup.-19 -0.3218 × 10.sup.-17 I 0.7948 × 10.sup.-26 0.1639 × 10.sup.-20 K -.01 .01 ______________________________________ where L1-L3 are lens elements from the image end, N d is the index of refraction of the lens elements V d is the dispersion of the lens elements measured by their Abbe number, S1-S6 are successive lens surfaces from the image end, the surfaces where positive are on radii struck from the right and where negative are on radii struck from the left, and surfaces S1, S2, S3, S4, and S5 are aspheric as shown.

Claim 14

A lens according to claim 8 having a semi-field angle of approximately 36.6° defined substantially as follows: ______________________________________ AXIAL DISTANCE SURFACE BETWEEN SURFACES LENS RADII (mm) (mm) N.sub.d V.sub.d ______________________________________ S1 52.647 L1 9.000 1.491 57.2 S2 117.896 17.002 S3 96.130 L2 26.000 1.491 57.2 S4 -61.351 35.699 S5 -42.571 L3 2.000 1.491 57.2 S6 Plano L4 8.200 1.460 50.0 S7 Plano L5 15.500 1.526 60.03 S8 -600.001 ______________________________________ Aspheric Surfaces S1, S2, S3, S4, S5 S1 S2 S3 ______________________________________ D -0.5097 × 10.sup.-6 0.8316 × 10.sup.-6 -0.5667 × 10.sup.-6 E -0.7730 × 10.sup.-9 0.1082 × 10.sup.-9 0.2059 × 10.sup.-9 F 0.1995 × 10.sup.-12 0.2556 × 10.sup.-12 0.5796 × 10.sup.-13 G -0.4524 × 10.sup.-17 0.2097 × 10.sup.-15 -0.1304 × 10.sup.-16 H -0.1880 × 10.sup.-18 -0.1774 × 10.sup.-18 -0.8578 × 10.sup.-20 I -0.1193 × 10.sup.-21 0.1267 × 10.sup.-23 0.1444 × 10.sup.-22 K -.01 ______________________________________ S4 S5 ______________________________________ D -0.4985 × 10.sup.-6 -0.7325 × 10.sup.-5 E -0.6420 × 10.sup.-10 0.7335 × 10.sup.-8 F -0.1663 × 10.sup.-12 -0.9409 × 10.sup.-11 G -0.4377 × 10.sup.-17 0.4257 × 10.sup.-14 H 0.4216 × 10.sup.-19 -0.1522 × 10.sup.-18 I 0.4502 × 10.sup.-23 -0.3500 × 10.sup.-21 K -.01 .01 ______________________________________ where L1-L5 are lens elements from the image end, N d is the index of refraction of the lens elements, V d is the dispersion of the lens elements measured by their Abbe number, S1-S8 are successive lens surfaces from the image end, the surfaces where positive are on radii struck from the right and where negative are on radii struck from the left, and surfaces S1, S2, S3, S4, and S5 are aspheric as shown.

Claim 15

A lens according to claim 8 having a semi-field angle of approximately 35.7° defined substantially as follows: ______________________________________ AXIAL DISTANCE SURFACE BETWEEN SURFACES LENS RADII (mm) (mm) N.sub.d V.sub.d ______________________________________ S1 59.250 L1 8.000 1.491 57.2 S2 126.142 19.841 S3 106.127 L2 29.000 1.491 57.2 S4 -62.052 40.517 S5 -38.078 L3 5.000 1.586 34.0 S6 -46.433 3.000 S7 -44.000 L4 6.000 1.526 60.0 S8 -50.000 L5 7.000 1.460 50.0 S9 Plano L6 6.000 1.526 60.0 S10 Plano ______________________________________ Aspheric Surfaces S1, S2, S3, S4, S5 S1 S2 S3 ______________________________________ D -0.5275 × 10.sup.-6 0.5259 × 10.sup.-6 -0.4787 × 10.sup.-6 E -0.7562 × 10.sup.-9 -0.7944 × 10.sup.-10 0.8750 × 10.sup.-10 F 0.3016 × 10.sup. -12 0.2725 × 10.sup.-12 0.6063 × 10.sup.-13 G 0.2747 × 10.sup.-16 0.2377 × 10.sup.-15 0.2880 × 10.sup.-17 H -0.9126 × 10.sup.-19 -0.7377 × 10.sup.-19 -0.2519 × 10.sup.-20 I -0.6548 × 10.sup.-22 -0.4335 × 10.sup.-22 0.1101 × 10.sup.-23 K -1.00 ______________________________________ S4 S5 ______________________________________ D -0.3346 × 10.sup.-6 0.1236 × 10.sup.-5 E -0.1260 × 10.sup.-9 -0.4714 × 10.sup.-9 F -0.5560 × 10.sup.-13 -0.9912 × 10.sup.-12 G 0.9904 × 10.sup.-17 0.3271 × 10.sup.-15 H 0.1253 × 10.sup.-19 0.5399 × 10.sup.-18 I -0.1543 × 10.sup.-24 -0.3744 × 10.sup.-21 K -1.00 ______________________________________ where L1-L6 are lens elements from the image end, N d is the index of refraction of the lens elements, V d is the dispersion of the lens elements measured by their Abbe number, S1-S10 are successive lens surfaces from the image end, the surfaces where positive are on radii struck from the right and where negative are on radii struck from the left, and surfaces S1, S2, S3, S4, and S5 are aspheric as shown.

Claim 16

A lens according to claim 8 having a semi-field angle of approximately 35.5° defined substantially as follows: ______________________________________ AXIAL DISTANCE SURFACE BETWEEN RADII LENS RADII (mm) (mm) N.sub.d V.sub.d ______________________________________ S1 59.859 L1 8.000 1.491 57.2 S2 126.597 20.019 S3 104.999 L2 29.000 1.491 57.2 S4 -62.298 40.731 S5 -38.320 L3 5.000 1.586 34.0 S6 -44.605 3.000 S7 -42.000 L4 6.000 1.526 60.03 S8 -48.000 L5 7.000 1.460 50.0 S9 Plano ______________________________________ Aspheric Surfaces S1, S2, S3, S4, S5 S1 S2 S3 ______________________________________ D -0.5394 × 10.sup.-6 0.5062 × 10.sup.-6 -0.4653 × 10.sup.-6 E -0.7509 × 10.sup.-9 -0.1028 × 10.sup.-9 0.7778 × 10.sup.-10 F 0.2980 × 10.sup.-12 0.2579 × 10.sup.-12 0.5899 × 10.sup.-13 G 0.2197 × 10.sup.-16 0.2388 × 10.sup.-15 0.3768 × 10.sup.-17 H -0.9188 × 10.sup.-19 -0.6914 × 10.sup.-19 -0.2063 × 10.sup.-20 I -0.5645 × 10.sup.-22 -0.4258 × 10.sup.-22 0.1237 × 10.sup.-23 K -1.0 ______________________________________ S4 S5 ______________________________________ D -0.3364 × 10.sup.-6 0.1580 × 10.sup.-5 E -0.1158 × 10.sup.-9 -0.1122 × 10.sup.-8 F -0.5415 × 10.sup.-13 -0.8019 × 10.sup.-12 G 0.9965 × 10.sup.-17 0.5435 × 10.sup.-15 H 0.1264 × 10.sup.-19 0.5326 × 10.sup.-18 I -0.6475 × 10.sup.-25 -0.4744 × 10.sup.-21 K -1.0 ______________________________________ where L1-L5 are lens elements from the image end, N d is the index of refraction of the lens elements, V d is the dispersion of the lens elements measured by their Abbe number, S1-S9 are successive lens surfaces from the image end, the surfaces where positive are on radii struck from the right and where negative are on radii struck from the left, and surfaces S1, S2, S3, S4, and S5 are aspheric as shown.

Claim 17

A lens according to claim 8 having a semi-field angle of approximately 36.6° defined substantially as follows: ______________________________________ AXIAL DISTANCE SURFACE BETWEEN SURFACES LENS RADII (mm) (mm) N.sub.d V.sub.d ______________________________________ S1 52.476 L1 9.000 1.491 57.2 S2 117.720 16.640 S3 95.471 L2 26.000 1.491 57.2 S4 -61.646 35.750 S5 -40.480 L3 2.000 1.586 34.0 S6 -45.194 L4 8.200 1.460 50.0 S7 Plano L5 15.500 1.526 60.03 S8 -600.001 ______________________________________ Aspheric Surfaces S1, S2, S3, S4, S5 S1 S2 S3 ______________________________________ D -0.5367 × 10.sup.-6 0.8323 × 10.sup.-6 -0.5358 × 10.sup.-6 E -0.7618 × 10.sup.-9 0.1028 × 10.sup.-9 0.2188 × 10.sup.-9 F 0.1948 × 10.sup.-12 0.2659 × 10.sup.-12 0.6487 × 10.sup.-13 G -0.9533 × 10.sup.-17 0.2195 × 10.sup.-15 -0.1189 × 10.sup.-16 H -0.1828 × 10.sup.-18 -0.1797 × 10.sup.-18 -0.8486 × 10.sup.-20 I -0.1243 × 10.sup.-21 -0.7675 × 10.sup.-23 0.1435 × 10.sup.-22 K -1.0 ______________________________________ S4 S5 ______________________________________ D -0.5070 × 10.sup.-6 -0.6246 × 10.sup.-5 E -0.7779 × 10.sup.-10 0.6940 × 10.sup.-8 F -0.1567 × 10.sup.-12 -0.9249 × 10.sup.-11 G 0.4046 × 10.sup.-18 0.4418 × 10.sup.-14 H 0.4275 × 10.sup.-19 -0.1729 × 10.sup.-18 I 0.4210 × 10.sup.-23 -0.4298 × 10.sup.-21 K -1.0 .01 ______________________________________ where L1-L5 are lens elements from the image end, N d is the index of refraction of the lens elements, V d is the dispersion of the lens elements measured by their Abbe number, S1-S8 are successive lens surfaces from the image end, the surfaces where positive are on radii struck from the right and where negative are on radii struck from the left, and surfaces S1, S2, S3, S4, and S5 are aspheric as shown.

Claim 18

A lens according to claim 8 having a semi-field angle of approximately 36.1° defined substantially as follows: ______________________________________ AXIAL DISTANCE SURFACE BETWEEN SURFACES LENS RADII (mm) (mm) N.sub.d V.sub.d ______________________________________ S1 64.923 L1 8.000 1.491 57.2 S2 167.500 31.649 S3 77.213 L2 19.000 1.491 57.2 S4 -82.190 41.256 S5 -37.991 L3 2.000 1.491 57.2 S6 Plano ______________________________________ Aspheric Surfaces S1, S2, S3, S4, S5 S1 S2 S3 ______________________________________ D -0.4147 × 10.sup.-6 0.4570 × 10.sup.-6 0.3570 × 10.sup.-6 E -0.3654 × 10.sup.-9 -0.6796 × 10.sup.-11 -0.7170 × 10.sup.-10 F 0.3099 × 10.sup.-14 0.1413 × 10.sup.-12 0.3577 × 10.sup.-12 G 0.3136 × 10.sup.-16 0.2399 × 10.sup.-16 -0.3528 × 10.sup.-16 H 0.3928 × 10.sup.-20 -0.2066 × 10.sup.-18 -0.1217 × 10.sup.-18 I -0.1607 × 10.sup.-21 -0.4910 × 10.sup.-22 0.5967 × 10.sup.-22 K -1.00 ______________________________________ S4 S5 ______________________________________ D 0.3820 × 10.sup.-6 -0.2344 × 10.sup.-5 E -0.3734 × 10.sup.-9 -0.8612 × 10.sup.-9 F 0.4649 × 10.sup.-12 -0.1620 × 10.sup.-11 G 0.2219 × 10.sup.-16 0.3729 × 10.sup.-14 H -0.2364 × 10.sup.-18 -0.3887 × 10.sup.-17 I 0.1021 × 10.sup.-21 0.1684 × 10.sup.-20 K -1.00 0.01 ______________________________________ where L1-L3 are lens elements from the image end, N d is the index of refraction of the lens elements, V d is the dispersion of the lens elements measured by their Abbe number, S1-S6 are successive lens surfaces from the image end, the surfaces where positive are on radii struck from the right and where negative are on radii struck from the left, and surfaces S1, S2, S3, Sr, and S5 are aspheric as shown.

Claim 19

A projection lens for a cathode ray tube consisting from the image side a first lens unit having two aspheric surfaces, said first lens unit consisting of a single element of generally positive meniscus form, a second lens unit consisting of a single positive lens element having at least one aspheric surface, said second lens unit providing the majority of the positive power of the overall lens, and a third lens unit having a strongly concave image side surface and correcting for field curvature, and 0.47>|D.sub.12 /F.sub.3 |>0.16 where D 12 is the axial spacing between said first and second lens units and F 3 is the equivalent focal length of said third lens unit.

Claim 20

A projection lens for a cathode ray tube consisting from the image side a first lens unit having two aspheric surfaces, said first lens unit consisting of a single element of generally positive meniscus form, a second lens unit consisting of a single positive lens element having at least one aspheric surface, said second lens unit providing the majority of the positive power of the overall lens, and a third lens unit having a strongly concave image side surface and correcting for field curvature, and 0.47>|D.sub.12 /F.sub.3 |>0.16 where D 12 is the axial spacing between said first and second lens units and F 3 is the equivalent focal length of said third lens unit.

Claim 21

The lens of claim 18 where said third lens unit comprises a liquid optical coupling between said third lens unit and the cathode ray tube and said liquid coupling provides optical power to the overall lens.

Claim 22

The lens of claim 18 wherein said third lens unit comprises a housing member having a liquid therein in contact with the faceplate of the cathode ray tube and said housing member is closed on the image side by a meniscus element having both surfaces convex to the cathode ray tube.

Claim 23

The lens of claim 20 wherein the image side surface of said second meniscus element is aspheric to provide correction for distortion.

Claim 24

The lens of claim 20 wherein said lens further includes a second meniscus element between said second and third lens units having surfaces convex to the object end and one of the surfaces is aspheric to provide correction for distortion.

Claim 25

The lens of claim 18 wherein the image side surface of said first lens element is generally convex to the image side but becomes concave to the image side as the height of the lens from the optical axis approaches the clear aperture of said lens element.

Claim 26

A projection lens for a cathode ray tube consisting from the image side of a first lens unit having at least one aspheric surface and consisting of a single element of generally positive meniscus form convex to the image side, said first lens unit being of relatively weak optical power, a second lens unit consisting of a single positive lens element, said second lens unit providing the majority of the positive power of the overall lens, and a third lens group having a strongly concave image side surface and contributing to correction of field curvature, said element of said first lens unit having an image side aspheric power changing from positive on axis to negative adjacent the edge of the clear aperture, and |Ky.sub.CA /Ky.sub.A |>2.5 where Ky CA is the aspheric optical power of the lens element of said first lens unit at the maximum clear aperture, and Ky A is the optical power of the lens at the optical axis thereof, and a corrector lens unit having an aspheric surface positioned-between said second and third lens units.

Claim 27

A projection lens for a cathode ray tube consisting from the image side of a first lens unit having at least one aspheric surface and consisting of a single element of generally positive meniscus form convex to the image side, said first lens unit being of relatively weak optical power, a second lens unit consisting of a single positive lens element, said second lens unit providing the majority of the positive power of the overall lens, and a third lens group having a strongly concave image side surface and contributing to correction of field curvature, said element of said first lens unit having an image side aspheric power changing from positive on axis to negative adjacent the edge of the clear aperture, and |Ky.sub.CA /Ky.sub.A |>2.5 where Ky CA is the aspheric optical power of the lens element of said first lens unit at the maximum clear aperture, and Ky A is the optical power of the lens at the optical axis thereof, and a corrector lens unit having an aspheric surface positioned-between said second and third lens units.

Claim 28

The lens of claim 24 where said third lens unit comprises a liquid optical coupling between said third lens unit and the cathode ray tube and said liquid coupling provides optical power to the overall lens.

Claim 29

The lens of claim 24 where 0.47>|D.sub.12 /F.sub.3 |>0.16 where D 12 is the axial spacing between said first and second lens units and F 3 is the equivalent focal length of the third lens unit.

Claim 30

The lens of claim 25 wherein said third lens unit comprises a housing member having a liquid therein in contact with the faceplate of the cathode ray tube and said housing member is closed by a meniscus element having both surfaces convex to the cathode ray tube.

Claim 31

The lens of claim 27 wherein the image side surface of said meniscus element is aspheric to provide correction for distortion.

Claim 32

The lens of claim 27 wherein said lens further includes a second meniscus element between said second and third lens units and having surfaces convex to the object end and one of the surfaces is aspheric to provide correction for distortion.

Claim 33

The lens of claim 24 wherein the image side surface of said first lens element is generally convex to the image side but becomes concave to the image side as the height of the lens from the optical axis approaches the clear aperture of said lens element.

Claim 34

A projection lens for a cathode ray tube consisting from the image side of a first lens unit having two aspheric surfaces, said first lens unit consisting of a single element of generally positive meniscus form, a second lens unit consisting of a single positive lens element, said second lens unit providing the majority of the positive power of the overall lens, and a third lens unit having a strongly concave image side surface and providing correction for field curvature, and 0.47>|D.sub.12 /F.sub.3 |>0.16 where D 12 is the axial spacing between said first and second lens units and F 3 is the equivalent focal length of the third lens unit, and a corrector lens unit having an aspheric surface positioned between said second and third lens units.

Claim 35

A projection lens for a cathode ray tube consisting from the image side of a first lens unit having two aspheric surfaces, said first lens unit consisting of a single element of generally positive meniscus form, a second lens unit consisting of a single positive lens element, said second lens unit providing the majority of the positive power of the overall lens, and a third lens unit having a strongly concave image side surface and providing correction for field curvature, and 0.47>|D.sub.12 /F.sub.3 |>0.16 where D 12 is the axial spacing between said first and second lens units and F 3 is the equivalent focal length of the third lens unit, and a corrector lens unit having an aspheric surface positioned between said second and third lens units.

Claim 36

The lens of claim 31 where said third lens unit comprises a liquid optical coupling between said third lens unit and the cathode ray tube and said liquid coupling provides optical power to the overall lens.

Claim 37

The lens of claim 32 wherein said third lens unit comprises a housing member having a liquid therein adjacent the faceplate of the cathode ray tube and said housing member is closed by a meniscus element having both surfaces convex to the cathode ray tube.

Claim 38

The lens of claim 31 wherein the image side surface of said first lens element being generally convex to the image side but becoming concave to the image side as the height of the lens from the optical axis approaches the clear aperture of said lens element.

Claim 39

A projection lens for a cathode ray tube consisting from the image side of a first lens unit having two aspheric surfaces, said first lens unit consisting of a single element of generally positive meniscus form, said element having an image side surface which changes from convex at the optical axis to concave as the height of the lens approaches the clear aperture of said lens element, the optical power of said element changing from positive on axis to negative at the edge of the clear aperture of that element, a second lens unit consisting of a single biconvex lens element, said second lens unit providing the majority of the positive power of the overall lens, and a third lens unit having a strongly concave image side surface and contributing to correction of field curvature, and 0.47>|D.sub.12 /F.sub.3 |>0.16 where D 12 is the axial spacing between said first and second lens units and F 3 is the equivalent focal length of the third lens unit, and a corrector lens unit having an aspheric surface positioned between said second and third lens units.

Claim 40

A projection lens for a cathode ray tube consisting from the image side of a first lens unit having two aspheric surfaces, said first lens unit consisting of a single element of generally positive meniscus form, said element having an image side surface which changes from convex at the optical axis to concave as the height of the lens approaches the clear aperture of said lens element, the optical power of said element changing from positive on axis to negative at the edge of the clear aperture of that element, a second lens unit consisting of a single biconvex lens element, said second lens unit providing the majority of the positive power of the overall lens, and a third lens unit having a strongly concave image side surface and contributing to correction of field curvature, and 0.47>|D.sub.12 /F.sub.3 |>0.16 where D 12 is the axial spacing between said first and second lens units and F 3 is the equivalent focal length of the third lens unit, and a corrector lens unit having an aspheric surface positioned between said second and third lens units.

Claim 41

The lens of claim 35 where said concave surface of said third lens unit is spheric.

Claim 42

The lens of claim 35 where said third lens unit comprises a liquid optical coupling between said third lens unit and the cathode ray tube and said liquid coupling provides optical power to the overall lens.

Claim 43

The lens of claim 37 wherein said third lens unit comprises a housing member having a liquid therein adjacent the faceplate of the cathode ray tube and said housing member is closed by a meniscus element having both surfaces convex to the cathode ray tube.

Claim 44

The lens of claim 35 wherein the image side surface of said first lens element is generally convex but becomes concave to the image side as the height of the lens from the optical axis approaches the clear aperture of said lens element.

Claim 45

The lens of claim 39 wherein said third lens unit comprises a housing member having a liquid therein adjacent the faceplate of the cathode ray tube and said housing member is closed by a meniscus element having both surfaces convex to the cathode ray tube.

Claim 46

The lens of claim 35 wherein the image side surface of said meniscus element is aspheric to provide correction for distortion.

Claim 47

The lens of claim 40 wherein said third lens unit further includes a second meniscus element having surfaces convex to the object end and one of the surfaces is asperhic to provide correction for distortion.

Claim 48

A projection lens for a cathode ray tube consisting from the image side of a first lens unit having two aspheric surfaces, said first lens unit consisting of a single element of generally positive meniscus form, a second lens unit consisting of a single positive lens element, said second lens unit providing the majority of the positive power of the overall lens, and a third lens group having a strongly concave image side surface and contributing to correction of field curvature, said element of said first lens unit having an optical power changing from positive on axis to negative at the edge of the clear aperture, and |Ky.sub.CA /Ky.sub.A |>2.5 where Ky CA is the aspheric optical power of the lens element of said first lens unit at the maximum clear aperture, and Ky A is the optical power of the lens at the optical axis thereof, and a corrector lens unit having an aspheric surface positioned between said second and third lens units.

Claim 49

A projection lens for a cathode ray tube consisting from the image side of a first lens unit having two aspheric surfaces, said first lens unit consisting of a single element of generally positive meniscus form, a second lens unit consisting of a single positive lens element, said second lens unit providing the majority of the positive power of the overall lens, and a third lens group having a strongly concave image side surface and contributing to correction of field curvature, said element of said first lens unit having an optical power changing from positive on axis to negative at the edge of the clear aperture, and |Ky.sub.CA /Ky.sub.A |>2.5 where Ky CA is the aspheric optical power of the lens element of said first lens unit at the maximum clear aperture, and Ky A is the optical power of the lens at the optical axis thereof, and a corrector lens unit having an aspheric surface positioned between said second and third lens units.

Claim 50

The lens of claim 43 where said third lens unit comprises a liquid optical coupling between said third lens unit and the cathode ray tube and said liquid coupling provides optical power to the overall lens.

Claim 51

The lens of claim 44 where said third lens unit comprises a housing member having a liquid therein adjacent the faceplate of the cathode ray tube and said housing member is closed on the image side by a meniscus element having both surfaces convex to the cathode ray tube.

Claim 52

A projection lens consisting from the image end of a first lens unit consisting of a generally meniscus shaped element having an aspheric image side surface which is convex to the image and adjacent the optical axis of the lens but changes to concave to the image adjacent the clear aperture thereof, a second positive lens unit consisting of a single biconvex element providing the majority of the positive power of said projection lens, a third negative lens unit having a concave image side surface and contributing to correction of field curvature, and a corrector lens element of weak optical power having an aspheric surface positioned between said second and third lens units, said element of said first lens unit having positive optical power at the axis thereof and negative optical power adjacent the clear aperture thereof, said concave image side surface of said third lens unit being spherical.

Claim 53

A projection lens consisting from the image end of a first lens unit consisting of a generally meniscus shaped element having an aspheric image side surface which is convex to the image and adjacent the optical axis of the lens but changes to concave to the image adjacent the clear aperture thereof, a second positive lens unit consisting of a single biconvex element providing the majority of the positive power of said projection lens, a third negative lens unit having a concave image side surface and contributing to correction of field curvature, and a corrector lens element of weak optical power having an aspheric surface positioned between said second and third lens units, said element of said first lens unit having positive optical power at the axis thereof and negative optical power adjacent the clear aperture thereof, said concave image side surface of said third lens unit being spherical.

Claim 54

The projection lens of claim 46 having a semi-field angle of at least thirty-five degrees.

Claim 55

The projection lens of claim 46 where the object side surface of said element of said first lens unit is also aspheric.

Claim 56

The lens of claim 46 where 0.47>|D.sub.12 /F.sub.3 |>0.16 where D 12 is the axial spacing between said first and second lens units and F 3 is the equivalent focal length of the third lens unit.

Claim 57

The lens of claim 46 where said third lens unit comprises a liquid optical coupling between sid third lens unit and the cathode ray tube and said liquid coupling provides optical power to the overall lens.

Claim 58

The lens of claim 50 wherein said third lens unit comprises a housing member having a liquid therein in contact with the faceplate of the cathode ray tube and said housing member is closed on the image side by a meniscus element having aboth surfaces convex to the cathode ray tube.

Claim 59

The projection lens of claim 46 where |Ky.sub.CA /Ky.sub.A |>2.5 where Ky CA is the aspherical optical power of the lens element of said first lens unit adjacent the clear aperture thereof, and Ky A is the optical power of the lens element of said first lens unit at the optical axis thereof.

Claim 60

A projection lens for a cathode ray tube consisting from the image side a first lens unit having an aspheric image side surface, said first lens unit consisting of a single element of generally positive meniscus form and providing correction for aperture dependent aberrations, a second lens unit consisting of a single positive biconvex lens element, said second lens unit providing the majority of the positive power of the overall lens, and a third lens unit having a strongly concave image side surface and providing correction for field curvature, said first element having an aspheric optical power changing from positive on axis to negative adjacent the clear aperture thereof, and |Ky.sub.CA /Ky.sub.A |>2.5 where Ky CA is the optical power of the lens element of said first lens unit adjacent the clear aperture thereof, and Ky A is the optical power of the lens element at the optical axis thereof.

Claim 61

A projection lens for a cathode ray tube consisting from the image side a first lens unit having an aspheric image side surface, said first lens unit consisting of a single element of generally positive meniscus form and providing correction for aperture dependent aberrations, a second lens unit consisting of a single positive biconvex lens element, said second lens unit providing the majority of the positive power of the overall lens, and a third lens unit having a strongly concave image side surface and providing correction for field curvature, said first element having an aspheric optical power changing from positive on axis to negative adjacent the clear aperture thereof, and |Ky.sub.CA /Ky.sub.A |>2.5 where Ky CA is the optical power of the lens element of said first lens unit adjacent the clear aperture thereof, and Ky A is the optical power of the lens element at the optical axis thereof.

Claim 62

The projection lens of claim 53 having a semi-field angle of at least thirty-five degrees.

Claim 63

The projection lens of claim 53 where the object side surface of said element of said first lens unit is also aspheric.

Claim 64

The lens of claim 53 where 0.47>|D.sub.12 /F.sub.3 |>0.16 where D 12 is the axial spacing between said first and second lens units and F 3 is the equivalent focal length of the third lens unit.

Claim 65

The lens of claim 53 where said third lens unit comprises a liquid optical coupling between said third lens unit and the cathode ray tube and said liquid coupling provides optical power to the overall lens.

Claim 66

The lens of claim 53 wherein said third lens unit comprises a housing member having a liquid therein in contact with the faceplate of the cathode ray tube and said housing member is closed on the image side by a meniscus element having both surfaces convex to the cathode ray tube.

Claim 67

The lens of claim 53 where said concave image side surface of said third lens unit is spherical.

Claim 68

The lens of claim 53 further including a corrector lens unit having an aspheric surface positioned between said second and third lens unit.