Projection lens

Claim 2

A projection lens for enlargedly projecting an image onto a screen, comprising, in succession from the screen side: a first lens having a positive refractive power; a second lens having a positive refractive power and having meniscus shape convex to the screen, said second lens being disposed substantially at the entrance pupil position of the entire system and having the function of chiefly correcting the balance of coma, a biconvex third lens having a positive refractive power; and a fourth lens having a negative refractive power and having its surface of sharper curvature facing to the screen.

Claim 3

A projection lens according to claim 1, which satisfies the following condition: 1/3D.sub.13 <d.sub.2 <#D.sub.13, where d 2 is the on-axis spacing between the lens surface of said second lens which is adjacent to the screen side and the lens surface of said first lens which is adjacent to said second lens, and D 13 is the on-axis spacing between the lens surface of said first lens which is adjacent to said second lens and the lens surface of said third lens which is adjacent to the screen side.

Claim 4

A projection lens according to claim 2, wherein said first, second, third and fourth lenses are single lenses.

Claim 5

A projection lens according to claim 3, wherein each lens of said lenses has an aspherical surface.

Claim 6

A projection lens for enlargedly projecting the image of a cathode ray tube onto a screen, consisting essentially of, in succession from the screen side: a first lens having a positive refractive power; a second lens having a positive refractive power and having its surface of sharper curvature facing the screen side, said second lens being disposed at or near the entrance pupil position of the entire system; a biconvex third lens having a positive refractive power; and a fourth lens having a negative refractive power and having its surface of sharper curvature facing the screen side, and wherein said projection lens satisfies the following condition: 1/3D.sub.13 <d.sub.2 <2/3D.sub.13, where d 2 is the on-axis spacing between the lens surface of said second lens which is adjacent to the screen side and the lens surface of said first lens which is adjacent to said second lens, and D 13 is the on-axis spacing between the lens surface of said first lens which is adjacent to said second lens and the lens surface of said third lens which is adjacent to the screen side.

Claim 7

A projection lens for enlargedly projecting the image of a cathode ray tube onto a screen, consisting essentially of, in succession from the screen side: a first lens having a positive refractive power; a second lens having a positive refractive power and having its surface of sharper curvature facing the screen side, said second lens being disposed at or near the entrance pupil position of the entire system; a biconvex third lens having a positive refractive power; and a fourth lens having a negative refractive power and having its surface of sharper curvature facing the screen side, and wherein said projection lens satisfies the following condition: 1/3D.sub.13 <d.sub.2 <2/3D.sub.13, where d 2 is the on-axis spacing between the lens surface of said second lens which is adjacent to the screen side and the lens surface of said first lens which is adjacent to said second lens, and D 13 is the on-axis spacing between the lens surface of said first lens which is adjacent to said second lens and the lens surface of said third lens which is adjacent to the screen side.

Claim 8

A projection lens according to claim 5, wherein said second lens is a positive meniscus lens having its convex surface facing the screen side.

Claim 9

A projection lens according to claim 6, which satisfies the following condition: 3.0<q<8.0 when the shape factor q is defined as ##EQU3## where r 3 is the radius of curvature of the lens surface of said second lens which is adjacent to the screen side and r 4 is the radius of curvature of the other surface of said second lens.

Claim 10

A projection lens according to claim 7, which satisfies the following condition: 0.5f.sub.2 <f.sub.1 <f.sub.2, where f 1 and f 2 are the focal lengths of said first lens and said second lens, respectively.

Claim 11

A projection lens according to claim 8, wherein the lens surfaces of said first, said second and said fourth lens, respectively, which are adjacent to the screen side and the lens surface of said third lens which is adjacent to said fourth lens are non-spherical surfaces.

Claim 12

A projection lens according to claim 9, wherein numerical data are as follows: ______________________________________ f = 134.115 mm Aperture Ratio 1:1.18 Projection Magnification 9.19 Half Angle of View 22.7° r.sub.1 = 205.166 d.sub.1 = 10.0 n.sub.1 = 1.49397 f.sub.1 = 559.798 L.sub.1 r.sub.2 = 782.238 d.sub.2 = 52.0 r.sub.3 = 118.384 d.sub.3 = 10.0 n.sub.2 = 1.49397 f.sub.2 = 781.946 L.sub.2 r.sub.4 = 165.936 d.sub.4 = 40.0 r.sub.5 = 148.675 d.sub.5 = 22.0 n.sub.3 = 1.49397 f.sub.3 = 155.791 L.sub.3 r.sub.6 = -151.726 d.sub.6 = 86.0 r.sub.7 = -49.814 d.sub.7 = 6.0 n.sub.4 = 1.49397 f.sub.4 = -106.353 L.sub.4 r.sub.8 = -1000.0 d.sub.8 = 5.0 r.sub.9 = ∞ r.sub.10 = ∞ Non-spherical Surface Coefficients ______________________________________ r.sub.1 (L.sub.1) r.sub.3 (L.sub.2) K = 1.0 K = 1.0 C.sub.2 = 0 C.sub.2 = 0 C.sub.4 = -0.7338372 × 10.sup.-7 C.sub.4 = -0.9699471 × 10.sup.-7 C.sub.6 = -0.4898615 × 10.sup.-11 C.sub.6 = +0.5237790 × 10.sup.-11 C.sub.8 = +0.1589234 × 10.sup.-14 C.sub.8 = -0.7595132 × 10.sup.-14 C.sub.10 = -0.3713102 × 10.sup.-18 C.sub.10 = +0.6318694 × 10.sup.-18 r.sub.6 (L.sub.3 ) r.sub.7 (L.sub.4) K = 2.5 K = 0 C.sub.2 = 0 C.sub.2 = 0 C.sub.4 = -0.3986701 × 10.sup.-7 C.sub.4 = -0.1974215 × 10 .sup.-6 C.sub.6 = -0.113604 × 10.sup.-10 C.sub.6 = -0.8182484 × 10.sup.-10 C.sub.8 = +0.2190766 × 10.sup.-14 C.sub.8 = +0.9704079 × 10.sup.-15 C.sub.10 = -0.3620652 × 10.sup.-18 C.sub.10 = +0.1116255 × 10.sup.-17 ______________________________________ where r 1 , r 2 , r 3 , . . . represent the radii of curvature of the successive lens surfaces from the screen side, d 1 , d 2 , d 3 , . . . represent the center thicknesses of and the spacings between the lenses, n 1 , n 2 , . . . represent the refractive indices of the respective lenses for green light (λ=531 nm), f 1 , f 2 , . . . represent the focal lengths of the respective lenses, f represents the focal length of the entire system, K is a cone constant and C 2 , C 4 , . . . , C 10 are high-order constants.

Claim 13

A projection lens according to claim 9, wherein numerical data are as follows: ______________________________________ f = 134.08 mm Aperture Ratio 1:1.18 Projection Magnification 9.24 Half Angle of View 22.8° r.sub.1 = 205.836 d.sub.1 = 10.0 n.sub.1 = 1.49397 f.sub.1 = 551.191 L.sub.1 r.sub.2 = 830.020 d.sub.2 = 60.0 r.sub.3 = 119.150 d.sub.3 = 10.0 n.sub.2 = 1.49397 f.sub.2 = 792.175 L.sub.2 r.sub.4 = 166.558 d.sub.4 = 32.0 r.sub.5 = 152.310 d.sub.5 = 22.0 n.sub.3 = 1.49397 f.sub.3 = 157.057 L.sub.3 r.sub.6 = -150.573 d.sub.6 = 87.0 r.sub.7 = -50.148 d.sub.7 = 6.0 n.sub.4 = 1.49397 f.sub.4 = -107.104 L.sub.4 r.sub.8 = -1000.0 d.sub.8 = 5.0 r.sub.9 = ∞ d.sub.9 = 10.0 n.sub.5 = 1.151953 r.sub.10 = ∞ Non-spherical Surface Coefficients ______________________________________ r.sub.1 (L.sub.1 ) r.sub.3 (L.sub.2) K = 1.0 K = 1.0 C.sub.2 = 0 C.sub.2 = 0 C.sub.4 = -0.8255398 × 10.sup.-7 C.sub.4 = -0.9678115 × 10.sup.-7 C.sub.6 = -0.6631743 × 10.sup.-11 C.sub.6 = +0.7935195 × 10.sup.-11 C.sub.8 = +0.2421203 × 10.sup.-14 C.sub.8 = -0.9401774 × 10.sup.-14 C.sub.10 = -0.4982642 × 10.sup.-18 C.sub.10 = +0.7315130 × 10.sup.-18 r.sub.6 (L.sub.3) r.sub.7 (L.sub.4) K = -2.5 K = 0.0 C.sub.2 = 0 C.sub.2 = 0 C.sub.4 = -0.4548829 × 10.sup.-7 C.sub.4 = -0.2067195 × 10.sup.-6 C.sub.6 = -0.1385337 × 10.sup.-10 C.sub.6 = -0.1038184 × 10.sup.-9 C.sub.8 = +0.2155369 × 10.sup.-14 C.sub.8 = +0.1031064 × 10.sup.-13 C.sub.10 = -0.3659516 × 10.sup.-18 C.sub.10 = -0.7903129 × 10.sup.-18 ______________________________________ where r 1 , r 2 , r 3 , . . . represent the radii of curvature of the successive lens surfaces from the screen side, d 1 , d 2 , d 3 , . . . represent the center thicknesses of and the spacings between the lenses, n 1 , n 2 , . . . represent the refractive indices of the respective lenses for green light (λ=531 nm), f 1 , f 2 , . . . represent the focal lengths of the respective lenses, f represents the focal length of the entire system, K is a cone constant and C 2 , C 4 , . . . , C 10 are high-order constants.

Claim 14

A projection lens according to claim 9, wherein numerical data are as follows: ______________________________________ f = 133.18 mm Aperture Ratio 1:1.17 Projection Magnification 9.20 Half Angle of View 22.8° r.sub.1 = 198.894 d.sub.1 = 10.0 n.sub.1 = 1.49397 f.sub.1 = 518.543 L.sub.1 r.sub.2 = 874.182 d.sub.2 = 44.0 r.sub.3 = 119.071 d.sub.3 = 10.0 n.sub.2 = 1.49397 f.sub.2 = 821.254 L.sub.2 r.sub.4 = 163.860 d.sub.4 = 48.0 r.sub.5 = 141.441 d.sub.5 = 22.0 n.sub.3 = 1.49397 f.sub.3 = 152.243 L.sub.3 r.sub.6 = -152.328 d.sub.6 = 82.0 r.sub.7 = -49.821 d.sub.7 = 6.0 n.sub.4 = 1.49397 f.sub.4 = -106.396 L.sub.4 r.sub.8 = - 1000.0 d.sub.8 = 5.0 r.sub.9 = ∞ d.sub.9 = 10.0 n.sub.5 = 1.51953 r.sub.10 = ∞ Non-spherical Surface Coefficients ______________________________________ r.sub.1 (L.sub.1) r.sub.3 (L.sub.2) K = 1.0 K = 1.0 C.sub.2 = 0 C.sub.2 = 0 C.sub.4 = -0.6857408 × 10.sup.-7 C.sub.4 = -0.8396169 × 10.sup.-7 C.sub.6 = -0.3088194 × 10.sup.-11 C.sub.6 = -0.8889261 × 10 .sup.-11 C.sub.8 = +0.1494529 × 10.sup.-14 C.sub.8 = -0.1569215 × 10.sup.-14 C.sub.10 = -0.3949006 × 10.sup.-18 C.sub.10 = -0.1548692 × 10.sup.-18 r.sub.6 (L.sub.3) r.sub.7 (L.sub.4) K = -2.5 K = 0 C.sub.2 = 0 C.sub.2 = 0 C.sub.4 = -0.1526258 × 10.sup.-7 C.sub.4 = -0.6069569 × 10.sup.-6 C.sub.6 = -0.3354777 × 10.sup.-10 C.sub.6 = +0.3456111 × 10.sup.-9 C.sub.8 = +0.1358833 × 10.sup.-13 C.sub.8 = -0.1650687 × 10.sup.-12 C.sub.10 = -0.2310083 × 10.sup.-17 C.sub.10 = +0.2463624 × 10.sup.-16 ______________________________________ where r 1 , r 2 , r 3 , . . . represent the radii of curvature of the successive lens surfaces from the screen side, d 1 , d 2 , d 3 , . . . represent the center thicknesses of and the spacings between the lenses, n 1 , n 2 , . . . represent the refractive indices of the respective lenses for green light (λ=531 nm), f 1 , f 2 , . . . represent the focal lengths of the respective lenses, f represents the focal length of the entire system, K is a cone constant and C 2 , C 4 , . . . , C 10 are high-order constants.