Projection lens

Claim 2

A lens comprising three elements, a first biconvex element, a second biconcave element, and a third biconvex element, and further defined by the following relationship 1.6<1/2(k1+k3)<1.8 3.0<|k2|<3.2 0.22<F.sub.N (T1+T3)<0.26 where k1, k2 and k3 are the powers of the first, second and third elements, respectively; T1 and T3 are the axial thicknesses of the first and third elements as a fraction of the equivalent focal length, and F N is the F-number of the lens.

Claim 3

The lens of claim 1 where one surface of each lens has an aspheric surface.

Claim 4

A lens according to claim 1 wherein the first element has surfaces S1 and S2, the second element has surfaces S3 and S4, and the third element has surfaces S5 and S6, and the surfaces S2, S3, and S5 are aspheric in accordance with 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 surface at the optical axis, K is a conic constant, and D, E, F, and G are constants.

Claim 5

A lens according to claim 3 having an equivalent focal length of essentially 299.0 mm and defined substantially as follows: ______________________________________ Axial Distance Radius (mm) Between Surfaces (mm) N.sub.d V.sub.d ______________________________________ S1 147.7 L1 29.7 1.491 57.2 S2 -181.5 34.1 S3 -70.9 L2 4.0 1.562 35.0 S4 225.1 55.9 S3 123.1 L3 26.8 1.491 57.2 S6 -221.5 ______________________________________ where L1-L3 are the lens elements, N d is the index of refraction, V d is the Abbe number, and the constants D, E, F, and G for surfaces S2, S3, and S5 are ______________________________________ S2 S3 S5 ______________________________________ D .203 × 10.sup.-6 .896 × 10.sup.-6 .368 × 10.sup.-6 E -.127 × 10.sup.-10 -.961 × 10.sup.-10 .366 × 10.sup.-10 F .129 × 10.sup.-15 -.212 × 10.sup.-14 -.169 × 10.sup.-14 G .256 × 10.sup.-19 .101 × 10.sup.-17 -.155 × 10.sup.-19 ______________________________________

Claim 6

A lens according to claim 3 having an equivalent focal length of essentially 299.0 mm and defined substantially as follows: ______________________________________ Axial Distance Radius (mm) Between Surfaces (mm) N.sub.d V.sub.d ______________________________________ S1 208.4 L1 30.5 1.491 57.2 S2 -176.2 39.9 S3 -65.2 L2 4.0 1.491 57.2 S4 208.4 53.0 S5 126.1 L3 34.4 1.491 57.2 S6 -186.8 ______________________________________ where L1-L3 are the lens elements, N d is the index of refraction, V d is the Abbe number, and the constants D, E, F, and G for surfaces S2, S3 and S5 are ______________________________________ S2 S3 S5 ______________________________________ D .197 × 10.sup.-6 .100 × 10.sup.-5 -.366 × 10.sup.-6 E -.174 × 10.sup.-10 -.106 × 10.sup.-9 .344 × 10.sup.-10 F .129 × 10.sup.-14 -.218 × 10.sup.-14 -.102 × 10.sup.--14 G -.36 × 10.sup.-19 .106 × 10.sup.-17 -.549 × 10.sup.-19 ______________________________________

Claim 7

A lens according to claim 3 having an equivalent focal length of essentially 299.0 mm and defined substantially as follows: ______________________________________ Axial Distance Radius (mm) Between Surfaces (mm) N.sub.d V.sub.d ______________________________________ S1 188.2 L1 31.9 1.491 57.2 S2 -173.6 36.6 S3 -70.1 L2 4.0 1.562 35.0 S4 247.0 53.9 S5 126.1 L3 35.3 1.491 57.2 S6 -186.5 ______________________________________ where L1-L3 are the lens elements, N d is the index of refraction, V d is the Abbe number, and the constants D, E, F, and G for surfaces S2, S3 and S5 are ______________________________________ S2 S3 S5 ______________________________________ D .214 × 10.sup.-6 .894 × 10.sup.-6 -.366 × 10.sup.-6 E -.167 × 10.sup.-10 -.943 × 10.sup.-10 .334 × 10.sup.-10 F .852 × 10.sup.-15 -.219 × 10.sup.-14 -.102 × 10.sup.-14 G .201 × 10.sup.-19 .967 × 10.sup.-19 -.549 × 10.sup.-19 ______________________________________

Claim 8

A lens according to claim 3 having an equivalent focal length of essentially 299.0 mm and defined substantially as follows: ______________________________________ Axial Distance Radius (mm) Between Surfaces (mm) N.sub.d V.sub.d ______________________________________ S1 169.7 L1 39.5 1.491 57.2 S2 -188.9 38.4 S3 -68.5 L2 4.0 1.491 57.2 S4 169.7 51.8 S5 126.1 L3 46.4 1.491 57.2 S6 -186.8 ______________________________________ where L1-L3 are the lens elements, N d is the index of refraction, V d is the Abbe number, and the constants D, E, F, and G for surfaces S2, S3 and S5 are ______________________________________ S2 S3 S5 ______________________________________ D .168 × 10.sup.-6 .984 × 10.sup.-6 -.366 × 10.sup.-6 E -.808 × 10.sup.-11 -.128 × 10.sup.-9 .334 × 10.sup.-10 F .201 × 10.sup.-16 .770 × 10.sup.-14 -.109 × 10.sup.-14 G .110 × 10.sup.-19 -.528 × 10.sup.-19 -.549 × 10.sup.-19 ______________________________________

Claim 9

A lens according to claim 3 having an equivalent focal length of essentially 299.0 mm and defined substantially as follows: ______________________________________ Axial Distance Radius (mm) Between Surfaces (mm) N.sub.d V.sub.d ______________________________________ S1 186.8 L1 39.5 1.491 57.2 S2 -188.9 39.8 S3 -74.5 L2 4.0 1.562 35.0 S4 208.4 53.0 S5 126.1 L3 46.4 1.491 57.2 S6 -169.7 ______________________________________ where L1-L3 are the lens elements, N d is the index of refraction, V d is the Abbe number, and the constants D, E, F, and G for surfaces S2, S3 and S5 are ______________________________________ S2 S3 S5 ______________________________________ D .168 × 10.sup.-6 .819 × 10.sup.-6 -.366 × 10.sup.-6 E -.808 × 10.sup.-11 -.920 × 10.sup.-10 .334 × 10.sup.-10 F .201 × 10.sup.-16 .132 × 10.sup.-14 -.102 × 10.sup.-14 G .110 × 10.sup.-19 .460 × 10.sup.-18 -.549 × 10.sup.-19 ______________________________________

Claim 10

A lens consisting of three elements, a first biconvex element, a second biconcave element, and a third biconvex element, each of said elements having at least one aspheric surface and further defined by the following relationship 1.6<1/2(k1+k3)<1.8 3.01 k2<3.2 where k1, k2 and k3 are the powers of the first, second, and third elements, respectively.

Claim 11

A lens consisting of three elements, a first biconvex element, a second biconcave element, and a third biconvex element, each of said elements having at least one aspheric surface and further defined by the following relationship 1.6<1/2(k1+k3)<1.8 3.01 k2<3.2 where k1, k2 and k3 are the powers of the first, second, and third elements, respectively.

Claim 12

The lens of claim 9 further defined by 0.22<F.sub.N (T1+T3)<0.26 where F N is the F-number of the lens and T1 and T3 are the thicknesses of the first and third elements at the optical axis.