Compact projection lens

Claim 2

A projection lens for a cathode ray tube display, said lens consisting of three groups from the image end to the object end, as follows: a first group comprising an element of relatively weak optical power having at last one aspheric surface; a second positive group air spaced from said first group providing substantially all the positive power of said lens; a third group air spaced from said second group and comprising a negative element having a surface concave to the image end and serving as a field flattener essentially correcting the Petzval curvature of the first and second groups; wherein said three groups have optical powers K1, K2, and K3, the overall lens has an optical power of 1.0, and

Claim 3

25<K1<0.50, 0.85<K2<1.20, -1.4<K3<-0.9

Claim 4

25<K1<0.50, 0.85<K2<1.20, -1.4<K3<-0.9

Claim 5

A lens according to claim 1 having aspheric surfaces wherein each aspheric lens surface is defined by the following relationship: ##EQU2## where X is the surface sag at a semi-aperture distance y from the optical axis of the lens, C is the curvature of the lens surface of the optical axis A equal to the reciprocal of the radius of the lens at the optical axis, k is a conic constant, D, E, F, and G are constants.

Claim 6

A lens according to claim 2 scaled to an EFL of 116.5 mm and relative aperture of f/1.0 described substantially as follows: ______________________________________ Surface Axial Distance Radius (mm) Between Surfaces (mm) N.sub.d V.sub.d ______________________________________ S1 201.04 L1 16.00 1.492 57.1 S2 -6569.50 114.00 S3 68.36 L2 32.50 1.492 57.1 S4 -198.13 57.58 S5 -43.66 L3 3.00 1.492 57.1 S6 -5397.88 6.00 ______________________________________ Aspheric surfaces: S1, S4, S5 S1 S4 S5 ______________________________________ D -.1316 × 10.sup.-6 .3056 × 10.sup.-6 -.6240 × 10.sup.-5 E .8734 × 10.sup.-11 .6813 × 10.sup.-10 .1576 × 10.sup.-8 F -.2910 × 10.sup.-14 -.4657 × 10.sup.-13 .3861 × 10.sup.-12 G .1959 × 10.sup.-18 .8216 × 10.sup.-17 -.4809 × 10.sup.-15 C 1.326 -5.183 -5.599 ______________________________________ Where L1-L3 are successive lens elements from the image end, S1-S6 are successive element surfaces, the surface radii where positive are surfaces convex to the image end and where negative are concave to 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 the Abbe number, and surfaces S1, S4, and S5 are aspheric.

Claim 7

A lens according to claim 2 scaled to an EFL of 117.4 mm and relative aperture of f/1.0 is described substantially as follows: ______________________________________ Surface Axial Distance Radius (mm) Between Surfaces (mm) N.sub.d V.sub.d ______________________________________ S1 167.81 Ll 16.00 1.492 57.1 S2 1230.59 114.00 S3 68.56 L2 30.69 1.492 57.1 S4 -207.25 58.65 S5 -47.89 L3 3.00 1.492 57.1 S6 6.00 ______________________________________ Aspheric surfaces: S2, S4, S5 S2 S4 S5 ______________________________________ D .1194 × 10.sup.-6 .3971 × 10.sup.-6 .1488 × 10.sup.-5 E -.1066 × 10.sup.-10 .2482 × 10.sup.-10 -.1112 × 10.sup.-8 F .2273 × 10.sup.-14 -.2710 × 10.sup.-13 .1395 × 10.sup.-11 G -.7673 × 10.sup.-19 .4807 × 10.sup.-17 -.6276 × 10.sup.-15 C -1.000 -1.000 -1.000 ______________________________________ Where L1-L3 are successive lens elements from the image end, S1-S6 are successive element surfaces, the surface radii where positive are surfaces convex to the image end and where negative are concave to 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 the Abbe number, and surfaces S2, S4 and S5 are aspheric.

Claim 8

A lens according to claim 2 scaled to an EFL of 116.6 mm and relative aperture of f/1.0 is described substantially as follows: __________________________________________________________________________ Surface Axial Distance Radius (mm) Between Surfaces (mm) N.sub.d V.sub.d __________________________________________________________________________ S1 201.71 L1 16.00 1.492 57.1 S2 114.00 S3 68.84 L2 32.50 1.492 57.1 S4 -196.58 58.85 S5 -44.84 L3 3.00 1.492 57.1 S6 6.00 __________________________________________________________________________ Aspheric surfaces: S1, S3, S4, and S5 S1 S3 S4 S5 __________________________________________________________________________ D -.1284 × 10.sup.-6 -.2543 × 10.sup.-7 .2749 × 10.sup.-6 -.5975 × 10.sup.-5 E .7793 × 10.sup.-11 .2858 × 10.sup.-11 .7423 × 10.sup.-10 .1478 × 10.sup.-8 F -.2784 × 10.sup.-14 -.4865 × 10.sup.-16 -.4456 × 10.sup.-13 .3204 × 10.sup.-12 G .1840 × 10.sup.-18 -.1098 × 10.sup.-18 .7464 × 10.sup.-17 -.4199 × 10.sup.-15 C 1.326 .0001 -5.183 -5.599 __________________________________________________________________________ Where L1-L3 are successive lens elements from the image end, S1-S6 are successive element surfaces, the surface radii where positive are surfaces convex to the image end and where negative are concave to 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 the Abbe number, and surfaces S1, S3, S4, and S5 are aspheric.

Claim 9

A projection lens for a cathode ray tube display, said lens consisting of three groups from the image end to the object end, as follows: a first group comprising an element of relatively weak optical power having an aspheric surface and serving to correct aperture dependent aberrations; a second positive group air spaced from said first group and providing substantially all the positive power of said lens and comprising a biconvex element; a third group air spaced from said second group and comprising a negative element having an image side surface concave to the image end of strong negative power and a substantially plano object side surface, said third group essentially correcting the Petzval curvature of said first and second groups; said three groups have optical powers K1, K2, and K3, the overall lens has an optical power of 1.0, and 0.25<K1<0.50, 0.85<K2<1.20, -1.40<K3<-0.9

Claim 10

A projection lens for a cathode ray tube display, said lens consisting of three groups from the image end to the object end, as follows: a first group comprising an element of relatively weak optical power having an aspheric surface and serving to correct aperture dependent aberrations; a second positive group air spaced from said first group and providing substantially all the positive power of said lens and comprising a biconvex element; a third group air spaced from said second group and comprising a negative element having an image side surface concave to the image end of strong negative power and a substantially plano object side surface, said third group essentially correcting the Petzval curvature of said first and second groups; said three groups have optical powers K1, K2, and K3, the overall lens has an optical power of 1.0, and 0.25<K1<0.50, 0.85<K2<1.20, -1.40<K3<-0.9

Claim 11

A lens as defined in claims 1 or 6, wherein the concave surface is aspheric.

Claim 12

A projection lens for a cathode ray tube display consisting from the image end of three groups as follows: a first group of relatively weak optical power comprising an element having at least one aspheric surface and serving primarily to correct aperture dependent aberrations, a second positive group air spaced from said first group providing substantially all of the positive power of said lens, and a third negative group air spaced from said second group comprising an element having a concave image side surface and serving as a field flattener essentially correcting the Petzval curvature of the elements of said first and second groups, said lens having an optical power of 1.0 and 0.85<K.sub.2 <1.20 -1.4<K.sub.3 <-0.9 where K 2 and K 3 are the optical powers of said second and third groups, respectively.

Claim 13

A projection lens for a cathode ray tube display consisting from the image end of three groups as follows: a first group of relatively weak optical power comprising an element having at least one aspheric surface and serving primarily to correct aperture dependent aberrations, a second positive group air spaced from said first group providing substantially all of the positive power of said lens, and a third negative group air spaced from said second group comprising an element having a concave image side surface and serving as a field flattener essentially correcting the Petzval curvature of the elements of said first and second groups, said lens having an optical power of 1.0 and 0.85<K.sub.2 <1.20 -1.4<K.sub.3 <-0.9 where K 2 and K 3 are the optical powers of said second and third groups, respectively.

Claim 14

The lens of claim 8 where the image and object side surfaces of said second group are bi-convex.

Claim 15

The lens of claim 8 where said concave surface of said element of said third group is aspheric.

Claim 16

The lens of claim 8 where 0.25<K.sub.1 <0.5 where K 1 is the optical power of said first group.

Claim 17

The lens of claim 8 where said first group consists of a single element.

Claim 18

A projection lens for a cathode ray tube display consisting of three optical groups, said groups from the image end comprising a first group serving to correct aperture dependent aberrations, said first group having at least one aspheric surface, a second group of strong positive power air spaced from said first group and having biconvex object and image side surfaces, and a third group of negative optical power having an aspheric surface concave to the image end and air spaced from said second group, said third group serving as a field flattener and essentially correcting the Petzval curvature of the elements of said first and second groups, said lens having an optical power of 1.0 and 0.85<K.sub.2 <1.20 -1.4<K.sub.3 <-0.9 where K 2 and K 3 are the optical powers of said second and third groups, respectively.

Claim 19

A projection lens for a cathode ray tube display consisting of three optical groups, said groups from the image end comprising a first group serving to correct aperture dependent aberrations, said first group having at least one aspheric surface, a second group of strong positive power air spaced from said first group and having biconvex object and image side surfaces, and a third group of negative optical power having an aspheric surface concave to the image end and air spaced from said second group, said third group serving as a field flattener and essentially correcting the Petzval curvature of the elements of said first and second groups, said lens having an optical power of 1.0 and 0.85<K.sub.2 <1.20 -1.4<K.sub.3 <-0.9 where K 2 and K 3 are the optical powers of said second and third groups, respectively.

Claim 20

The lens of claim 13 where said first and second groups are air spaced a substantial percentage of the equivalent focal length of said lens.

Claim 21

The lens of claim 13 where said first and second groups are air spaced more than 0.9 of the equivalent focal length of said lens.

Claim 22

The lens of claim 13 where said second group consists of a biconvex element.

Claim 23

The lens of claim 13 where said first group consists of a single element.

Claim 24

A projection lens for a cathode ray tube display consisting of three optical groups, said groups from the image end comprising a first group serving to correct aperture dependent aberrations, said first group consisting of a single element having at least one aspheric surface, a second group of strong positive power air spaced from said first group and a third group of negative optical power having an aspheric surface concave to the image end and air spaced from said second group, said third group serving as a field flattener and essentially correcting the Petzval curvature of the elements of said first and second groups, said lens having an optical power of 1.0 and 0.85<K.sub.2 <1.20 -1.4<K.sub.3 <-0.9 where K 2 and K 3 are the optical powers of said second and third groups, respectively.

Claim 25

A projection lens for a cathode ray tube display consisting of three optical groups, said groups from the image end comprising a first group serving to correct aperture dependent aberrations, said first group consisting of a single element having at least one aspheric surface, a second group of strong positive power air spaced from said first group and a third group of negative optical power having an aspheric surface concave to the image end and air spaced from said second group, said third group serving as a field flattener and essentially correcting the Petzval curvature of the elements of said first and second groups, said lens having an optical power of 1.0 and 0.85<K.sub.2 <1.20 -1.4<K.sub.3 <-0.9 where K 2 and K 3 are the optical powers of said second and third groups, respectively.

Claim 26

The lens of claim 18 where said first and second groups are air spaced a substantial percentage of the equivalent focal length of said lens.

Claim 27

The lens of claim 18 where the air spacing between said first and second groups is at least 0.9 of the equivalent focal length of said lens.

Claim 28

The lens of claim 18 where said second group has biconvex object and image side surfaces.

Claim 29

The lens of claim 18 where said second group has biconvex image and object side surfaces.

Claim 30

The lens of claim 22 where said second group comprises a single element.

Claim 31

A projection lens for a cathode ray tube display consisting of three optical groups, said groups from the image end comprising a first group serving to correct aperture dependent aberrations, said first group consisting of a single element, a second group of strong positive power air spaced from said first group and having biconvex object and image side surfaces, said second group being of substantially greater optical power than said first group, and a third group of negative optical power having a surface concave to the image end and air spaced from said second group and serving as a field flattener and essentially correcting the Petzval curvature of the elements of said first and second groups, said lens having an optical power of 1.0 and 0.85<K.sub.2 <1.20 -1.4<K.sub.3 <-0.9 where K 2 and K 3 are the optical powers of said second and third groups, respectively.

Claim 32

A projection lens for a cathode ray tube display consisting of three optical groups, said groups from the image end comprising a first group serving to correct aperture dependent aberrations, said first group consisting of a single element, a second group of strong positive power air spaced from said first group and having biconvex object and image side surfaces, said second group being of substantially greater optical power than said first group, and a third group of negative optical power having a surface concave to the image end and air spaced from said second group and serving as a field flattener and essentially correcting the Petzval curvature of the elements of said first and second groups, said lens having an optical power of 1.0 and 0.85<K.sub.2 <1.20 -1.4<K.sub.3 <-0.9 where K 2 and K 3 are the optical powers of said second and third groups, respectively.

Claim 33

The lens of claim 24 where said first and second groups are air spaced a substantial percentage of the equivalent focal length of said lens.

Claim 34

The lens of claim 24 where the air spacing between said first and second groups is at least 0.9 of the equivalent focal length of said lens.

Claim 35

The lens of claim 24 where said second group consists of a single element.