Projection lens and projection television system using the same

• US 5,099,361 A
• Filed: 02/28/1990
• Issued: 03/24/1992
• Est. Priority Date: 03/01/1989
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Yamamoto, Yoshiharu, Nakajima, Yasuo
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): Gass, Rebecca D.
• Application Number:
  US07/486,101
• Time in Patent Office: 755 Days
• Field of Search: 350/463, 350/458, 350/349, 350/415, 350/412, 350/432, 350/331 R
• US Class Current: 359/708
• CPC Class Codes: G02B 13/16 for use in conjunction with image converters or intensifiers , or for use with projectors, e.g. objectives for projection TV
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence

Abstract

A projection lens for projecting images displayed on an image display device having angle-of-view dependency has high image focusing characteristics corresponding to high definition images, wide field angle, and telecentric characteristics. In addition, a projection television system using the same can be minimized in its size.

Claims

1. A projection lens for projecting on a screen a transmission or reflection light from an image display device which forms from a light emitted from a light source an image as changes of transmittance or reflectivity in response to an electric signal applied thereto, said projection lens comprising an inverted telephoto type front lens group at a screen side and rear lens group having a front focal point nearby an exit pupil of said front lens group, and having telecentric characteristics, wherein the front lens group includes seven lenses, and the rear lens group includes three lenses, and wherein said projection lens meets the following condition:

space="preserve" listing-type="equation">0.8<

f.sub.1,7 /f<

1.4

where

f₁,7 ;

a total focal length of the front lens group, namely the first to seventh lenses

f;

a total focal length of the entire system.

3. A projection lens according to claim 1 meeting the following conditions:

space="preserve" listing-type="equation">0.5<

k.sub.15 /f<

0.9

when a distance between surfaces of the front and rear lens groups is given as d₁₅, and a total focal length of the entire system is given as f.

2. A projection lens for projecting on a screen a transmission or reflection light from an image display device which forms form a light emitted from a light source an image as changes of transmittance or reflectivity in response to an electric signal applied thereto, said projection lens comprising an inverted telephoto type front lens group at a screen side and a rear lens group having a front focal point nearby an exit pupil of said front lens group, and having telecentric characteristics, wherein the front lens group includes seven lenses, and the rear lens group includes three lenses, and wherein starting from the screen side, a first lens is a positive lens, a second lens is a negative meniscus lens having its convex surface facing the screen side, a third lens is a negative meniscus lens having its convex surface facing the screen side, a fourth lens is a bi-convex lens, a fifth lens is a negative meniscus lens including a cemented surface and having its convex surface facing the screen side, a sixth lens is a positive meniscus lens having its concave surface facing the screen side, a seventh lens is a bi-convex lens, an eighth lens is a bi-concave lens, a ninth lens is a positive lens, and a tenth lens is a bi-convex lens.

4. A projection lens according to claim 2 meeting the following conditions:

space="preserve" listing-type="equation">d.sub.17 /f<

0.3

space="preserve" listing-type="equation">-1.5<

f.sub.8 /f.sub.9.10 <

-1.2

when it is given that a distance between surfaces of the eighth and ninth is d₁₇, a focal length of the eighth lens is f₈, a total focal length of the ninth and tenth lens is f₉,10, and a total focal length of the entire system is f.

5. A projection lens according to claim 2, satisfying substantially the following conditions:

space="preserve" listing-type="tabular">______________________________________ f = 49.86 Aperture 1;

2.8 ratio Projection 16.89 ω

= 36.2°

magnification f.sub.1.7 f = 1.08 d.sub.15 /f = 0.72 d.sub.17 /f = 0.12 f.sub.8 /f.sub.9.10 = -1.42 ______________________________________ r.sub.1 = 136.783 d.sub.1 = 8.10 n.sub.1 = 1.51825 ν

.sub.1 = 63.8 r.sub.2 = 961.173 d.sub.2 = 5.18 r.sub.3 = 69.975 d.sub.3 = 6.00 n.sub.2 = 1.51825 ν

.sub.2 = 63.8 r.sub.4 = 27.036 d.sub.4 = 8.97 r.sub.5 = 121.495 d.sub.5 = 2.21 n.sub.3 = 1.52555 ν

.sub.3 = 50.5 r.sub.6 = 29.715 d.sub.6 = 18.76 r.sub.7 = 74.902 d.sub.7 = 17.33 n.sub.4 = 1.85503 ν

.sub.4 = 23.7 r.sub.8 = 327.104 d.sub.8 = 6.68 r.sub.9 = 271.686 d.sub.9 = 17.77 n.sub.5 = 1.79013 ν

.sub.5 = 43.9 r.sub.10 = -25.786 d.sub.10 = 2.00 n.sub.6 = 1.76169 ν

.sub.6 = 27.3 r.sub.11 = 74.081 d.sub.11 = 4.62 r.sub.12 = -81.511 d.sub.12 = 4.50 n.sub.7 = 1.77622 ν

.sub.7 = 49.4 r.sub.13 = 43.199 d.sub.13 = 1.49 r.sub.14 = 204.097 d.sub.14 = 4.11 n.sub.8 = 1.79196 ν

.sub.8 = 47.1 r.sub.15 = -122.218 d.sub.15 = 35.89 r.sub.16 = -68.864 d.sub.16 = 2.66 n.sub.9 = 1.61075 ν

.sub.9 = 40.0 r.sub.17 = 275.832 d.sub.17 = 6.11 r.sub.18 = -1075.96 d.sub.18 = 10.52 n.sub.10 = 1.68083 ν

.sub.10 = 55.1 r.sub.19 = -88.713 d.sub.19 = 0.25 r.sub.20 = 128.275 d.sub.20 = 10.01 n.sub.11 = 1.7762 ν

.sub.11 = 49.4 r.sub.21 = -276.533 d.sub.21 = 4.70 r.sub.22 = 0.000 d.sub.22 = 41.10 n.sub.12 = 1.51825 ν

.sub.12 = 63.8 r.sub.23 = 0.000 ______________________________________

where r₁, r₂, . . . are a radius of curvature of each surface starting from the screen side, d₁, d₂, . . . are a distance between each of said surfaces, n₁, n₂, . . . are a refractive index at an e-line of each lens, and ν

₁, ν

₂, . . . are an Abbe'"'"'s number corresponding to the e-line of each of the above lens.

6. A projection lens according to claim 2, wherein at least one surface of the first, second, eighth, ninth and tenth lenses has an aspheric surface.

7. A projection lens according to claim 6, satisfying substantially the following conditions:

space="preserve" listing-type="tabular">______________________________________ f = 49.82 Aperture 1;

2.8 ratio Projection 16.94 ω

= 36.2°

magnification f.sub.1.7 /f = 1.05 d.sub.15 /f = 0.74 d.sub.17 /f = 0.16 f.sub.8 /f.sub.9.10 = -1.33 ______________________________________ r.sub.1 = 104.034 d.sub.1 = 11.00 n.sub.1 = 1.49384 ν

.sub.1 = 57.4 * r.sub.2 = 466.780 d.sub.2 = 5.00 * r.sub.3 = 73.295 d.sub.3 = 2.00 n.sub.2 = 1.49384 ν

.sub.2 = 57.4 * r.sub.4 = 26.295 d.sub.4 = 11.00 * r.sub.5 = 121.495 d.sub.5 = 2.21 n.sub.3 = 1.52555 ν

.sub.3 = 50.5 r.sub.6 = 29.715 d.sub.6 = 18.76 r.sub.7 = 74.902 d.sub.7 = 17.33 n.sub.4 = 1.85503 ν

.sub.4 = 23.7 r.sub.8 = -372.104 d.sub.8 = 6.68 r.sub.9 = 271.686 d.sub.9 = 17.77 n.sub.5 = 1.79013 ν

.sub.5 = 43.9 r.sub.10 = -25.786 d.sub.10 = 2.00 n.sub.6 = 1.76169 ν

.sub.6 = 27.3 r.sub.11 = 74.081 d.sub.11 = 4.62 r.sub.12 = -81.511 d.sub.12 = 4.50 n.sub.7 = 1.77622 ν

.sub.7 = 49.4 r.sub.13 = -43.199 d.sub.13 = 1.49 r.sub.14 = 204.097 d.sub.14 = 4.11 n.sub.8 = 1.79196 ν

.sub.8 = 47.1 r.sub.15 = -122.218 d.sub.15 = 35.89 r.sub.16 = -62.109 d.sub.16 = 2.66 n.sub.9 = 1.61075 ν

.sub.9 = 40.0 r.sub.17 = 213.114 d.sub.17 = 7.80 r.sub.18 = 847.406 d.sub.18 = 10.30 n.sub.10 = 1.68083 ν

.sub.10 = 55.1 r.sub.19 = -95.951 d.sub.19 = 0.63 r.sub.20 = 121.641 d.sub.20 = 10.45 n.sub.11 = 1.77622 ν

.sub.11 = 49.4 r.sub.21 = -255.505 d.sub.21 = 4.50 r.sub.22 = 0.000 d.sub.22 = 41.10 n.sub.12 = 1.51825 ν

.sub.12 = 63.8 r.sub.23 = 0.000 ______________________________________ Aspheric coefficient First surface;

K = 0.655275 AD = 0.626082 ×

10.sup.-7 AE = -0.144786 ×

10.sup.-10 AF = -0.109334 ×

10.sup.-14 Second surface;

K = 0.367907 ×

10.sup.2 Third surface;

K = 0.440304 AD = 0.126898 ×

10.sup.-7 AE = 0.634832 ×

10.sup.-11 AF = 0.928375 ×

10.sup.-14 Fourth surface;

K = -0.241861 ×

10.sup.-1 AD = 0.166124 ×

10.sup.-6 AE = 0.434466 ×

10.sup.-9 AF = 0.561828 ×

10.sup.-12 ______________________________________

where r₁, r₂, . . . represent a radius of curvature of each surface starting from the screen side, d₁, d₂, . . . represent a distance between each of said surfaces, n₁, n₂, . . . represent a refractive index at an e-line of each lens, ν

₁, ν

₂, . . . represent an Abbe'"'"'s number corresponding to the e-line of each of the above lens, surfaces represented by * . . . are the aspheric surfaces, and if Z is supposed a displacement amount from a vertex of a lens at a position away from an optical axis of the lens in a radius distance Y of an opening, it can be expressed as ##EQU2## and where AD, AE, AF, and AG are aspherical coefficients and K is a conical constant.

8. A projection lens according to claim 6, satisfying substantially the following conditions:

space="preserve" listing-type="tabular">______________________________________ f = 52.47 Aperture 1;

2.8 ratio Projection 17.19 ω

= 33.8°

magnification f.sub.1.7 /f = 1.09 d .sub.15 /f = 0.64 d .sub.17 /f = 0.12 f .sub.8 /f.sub.9.10 = -1.31 ______________________________________ r.sub.1 = 148.519 d.sub.1 = 8.40 n.sub.1 = 1.51825 ν

.sub.1 = 63.8 * r.sub.2 = -6939.731 d.sub.2 = 5.18 r.sub.3 = 49.137 d.sub.3 = 6.00 n.sub.2 = 1.51825 ν

.sub.2 = 63.8 r.sub.4 = 29.177 d.sub.4 = 9.37 * r.sub.5 = 608.860 d.sub.5 = 2.21 n.sub.3 = 1.52555 ν

.sub.3 = 50.5 r.sub.6 = 28.525 d.sub.6 = 18.76 r.sub.7 = 74.902 d.sub.7 = 17.33 n.sub.4 = 1.85503 ν

.sub.4 = 23.7 r.sub.8 = -372.104 d.sub.8 = 6.68 r.sub.9 = 271.686 d.sub.9 = 17.77 n.sub.5 = 1.79013 ν

.sub.5 = 43.9 r.sub.10 = -25.786 d.sub.10 = 2.00 n.sub.6 = 1.76169 ν

.sub.6 = 27.3 r.sub.11 = 74.081 d.sub.11 = 4.62 r.sub.12 = -81.511 d.sub.12 = 4.50 n.sub.7 = 1.77622 ν

.sub.7 = 49.4 r.sub.13 = -43.199 d.sub.13 = 1.49 r.sub.14 = 204.097 d.sub.14 = 4.11 n.sub.8 = 1.79196 ν

.sub.8 = 47.1 r.sub.15 = -122.218 d.sub.15 = 33.60 r.sub.16 = -49.674 d.sub.16 = 2.66 n.sub.9 = 1.62059 ν

.sub.9 = 36.4 r.sub.17 = 298.959 d.sub.17 = 6.11 * r.sub.18 = -275.028 d.sub.18 = 10.70 n.sub.10 = 1.68083 ν

.sub.10 = 55.1 * r.sub.19 = -56.037 d.sub.19 = 0.25 r.sub.20 = 341.327 d.sub.20 = 11.05 n.sub.11 = 1.77622 ν

.sub.11 = 49.4 * r.sub.21 = -103.830 d.sub.21 = 6.70 r.sub.22 = 0.000 d.sub.22 = 43.30 n.sub.12 = 1.51825 ν

.sub.12 = 63.8 r.sub.23 = 0.000 ______________________________________ Aspheric coefficient First surface;

K = -0.2749912 ×

10.sup.-1 AD = 0.2548179 ×

10.sup.-7 AE = - 0.2056712 ×

10.sup.-10 AF = -0.4319405 ×

10.sup.-14 AG = 0.8811238 ×

10.sup.-18 Fourth surface;

K = 0.3668809 ×

10.sup.-1 AD = 0.1536691 ×

10.sup.-6 AE = -0.1142634 ×

10.sup.-10 AF = 0.8573753 ×

10.sup.-12 AG = 0.2158643 ×

10.sup.-15 Seventeenth surface;

K = 0.2637872 ×

10.sup.2 AD = 0.1858271 ×

10.sup.-6 AE = 0.1334531 ×

10.sup.-10 AF = 0.2612238 ×

10.sup.-13 AG = 0.9178511 ×

10.sup.-17 Eighteenth surface;

K = 0.5903051 ×

10.sup.1 AD = -0.2472130 ×

10.sup.-6 AE = 0.1460313 ×

10.sup.-9 AF = 0.3400976 ×

10.sup.-13 AG = 0.3706282 ×

10.sup.-17 Twentieth surface;

K = -0.9201606 AD = -0.1022347 ×

10.sup.-6 AE = 0.7465995 ×

10.sup.-10 AF = 0.1567219 ×

10.sup.-13 AG = 0.1032802 ×

10.sup.-17 ______________________________________

where r₁, r₂, . . . represent a radius of curvature of each surface starting from the screen side, d₁, d₂, represent a distance between each of said surfaces, n₁, n₂, . . . . . . represent a refractive index at an e-line of each lens, ν

₁, ν

₂, . . . represent an Abbe'"'"'s number corresponding to the e-line of each of the above lens, surfaces represented by * . . . are the aspheric surfaces, and if Z is supposed a displacement amount from a vertex of a lens at a position away from an optical axis of the lens in radius distance Y of an opening, it can be expressed as ##EQU3## and where AD, AE, AF, and AG are aspherical coefficients, and K is a conical constant.

9. A projection lens according to claim 6, satisfying substantially the following conditions:

space="preserve" listing-type="tabular">______________________________________ f = 49.94 Aperture 1;

2.8 ratio Projection 18.09 magnification ω

= 34.1°

f.sub.1.7 /f =1.14 d.sub.15 /f = 0.67 d.sub.17 /f = 0.12 f.sub.8 /f.sub.9.10 = -1.37 ______________________________________ r.sub.1 = 146.163 d.sub.1 = 8.40 n.sub.1 = 1.51825 ν

.sub.1 = 63.8 * r.sub.2 = 0.000 d.sub.2 = 5.18 r.sub.3 = 49.670 d.sub.3 = 6.00 n.sub.2 = 1.51825 ν

.sub.2 = 63.8 r.sub.4 = 29.101 d.sub.4 = 9.39 * r.sub.5 = 937.536 d.sub.5 = 2.21 n.sub.3 = 1.52555 ν

.sub.3 = 50.5 r.sub.6 = 28.141 d.sub.6 = 18.76 r.sub.7 = 74.902 d.sub.7 = 17.33 n.sub.4 = 1.85503 ν

.sub.4 = 23.7 r.sub.8 = -372.104 d.sub.8 = 6.68 r.sub.9 = 271.686 d.sub.9 = 17.77 n.sub.5 = 1.79013 ν

.sub.5 = 43.9 r.sub.10 = -25.786 d.sub.10 = 2.00 n.sub.6 = 1.76169 ν

.sub.6 = 27.3 r.sub.11 = 74.081 d.sub.11 = 4.62 r.sub.12 = -81.511 d.sub.12 = 4.50 n.sub.7 = 1.77622 ν

.sub.7 = 49.4 r.sub.13 = -43.199 d.sub.13 = 1.49 r.sub.14 = 204.097 d.sub.14 = 4.11 n.sub.8 = 1.79196 ν

.sub.8 = 47.1 r.sub.15 = -122.218 d.sub.15 = 33.60 r.sub.16 = -49.674 d.sub.16 = 2.66 n.sub.9 = 1.62059 ν

.sub.9 = 36.4 r.sub.17 = 303.305 d.sub.17 = 6.11 * r.sub.18 = -310.381 d.sub.18 = 10.70 n.sub.10 = 1.68083 ν

.sub.10 = 55.1 * r.sub.19 = -54.486 d.sub.19 = 0.25 r.sub.20 = 275.356 d.sub.20 = 11.05 n.sub.11 = 1.77622 ν

.sub.11 = 49.4 * r.sub.21 = -108.456 d.sub.21 = 6.70 r.sub.22 = 0.000 d.sub.22 = 43.30 n.sub.12 = 1.51825 ν

.sub.12 = 63.8 r.sub.23 = 0.000 ______________________________________ Aspheric coefficient First surface;

K = -0.2301050 ×

10.sup.-1 AD = 0.2511178 ×

10.sup.-7 AE = -0.1943356 ×

10.sup.-10 AF = -0.3619595 ×

10.sup. -14 AG = 0.8095271 ×

10.sup.-18 Fourth surface;

K = 0.3295092 ×

10.sup.-1 AD = -0.4594244 ×

10.sup.-7 AE = 0.7461787 ×

10.sup.-10 AF = 0.4135199 ×

10.sup.-12 AG = -0.3071122 ×

10.sup.-15 Seventeenth surface;

K = 0.2504243 ×

10.sup.2 AD = 0.1782731 ×

10.sup.-6 AE = -0.1529465 ×

10.sup.-11 AF = 0.2164382 ×

10.sup.-13 AG = -0.7725707 ×

10.sup.-17 Eighteenth surface;

K = 0.1032711 ×

10.sup.-2 AD = -0.2772488 ×

10.sup.-6 AE = 0.1544648 ×

10.sup.-9 AF = 0.2193979 ×

10.sup.-13 AG = -0.1042978 ×

10.sup.-16 Twentieth surface;

K = -0.5525461 ×

10.sup.1 AD = -0.1231838 ×

10.sup.-6 AE = 0.8516421 ×

10.sup.-10 AF = 0.1510178 ×

10.sup.-13 AG = 0.1229936 ×

10.sup.-18 ______________________________________

where r₁, r₂, . . . represent a radius of curvature of each surface starting from the screen side, d₁, d₂, . . . represent a distance between each of said surfaces, n₁, n₂, . . . represent a refractive index at an e-line of each lens, ν

₁, ν

₂, . . . represent an Abbe'"'"'s number corresponding to the e-line of each of the above lens, surfaces represented by * . . . are the aspheric surfaces, and if Z is supposed a displacement amount from a vertex of a lens at a position away from an optical axis of the lens in a radius distance Y of an opening, it can be expressed as ##EQU4## and where AD, AE, AF, and AG are aspherical coefficients, and K is a conical constant.

10. A projection lens according to claim 6, satisfying substantially the following conditions:

space="preserve" listing-type="tabular">______________________________________ f = 50.00 Aperture 1;

2.8 ratio Projection 18.10 ω

= 34.0°

magnification f.sub.1.7 /f = 1.14 d.sub.15 /f = 0.67 d.sub.17 /f = 0.12 f.sub.8 /f.sub.9.10 = -1.35 r.sub.1 = 139.093 d.sub.1 = 8.40 n.sub.1 = 1.51825 ν

.sub.1 = 63.8* r.sub.2 = 1883.809 d.sub.2 = 5.18 r.sub.3 = 44.322 d.sub.3 = 6.00 n.sub.2 = 1.51825 ν

.sub.2 = 63.8 r.sub.4 = 26.610 d.sub.4 = 11.06 r.sub.5 = 1031.968 d.sub.5 = 2.21 n.sub.3 = 1.52555 ν

.sub.3 = 50.5 r.sub.6 = 28.804 d.sub.6 = 18.76 r.sub.7 = 74.902 d.sub.7 = 17.33 n.sub.4 = 1.85503 ν

.sub.4 = 23.7 r.sub.8 = - 372.104 d.sub.8 = 6.68 r.sub.9 = 271.686 d.sub.9 = 17.77 n.sub.5 = 1.79013 ν

.sub.5 = 43.9 r.sub.10 = -25.786 d.sub.10 = 2.00 n.sub.6 = 1.76169 ν

.sub.6 = 27.3 r.sub.11 = 74.081 d.sub.11 = 4.62 r.sub.12 = -81.511 d.sub.12 = 4.50 n.sub.7 = 1.77622 ν

.sub.7 = 49.4 r.sub.13 = -43.199 d.sub.13 = 1.49 r.sub.14 = 204.097 d.sub.14 = 4.11 n.sub.8 = 1.79196 ν

.sub.8 = 47.1 r.sub.15 = -122.218 d.sub.15 = 33.60 r.sub.16 = -48.652 d.sub.16 = 2.66 n.sub.9 = 1.62059 ν

.sub.9 = 36.4 r.sub.17 = 293.965 d.sub.17 = 6.11 * r.sub.18 = -406.452 d.sub.18 = 10.70 n.sub.10 = 1.68083 ν

.sub.10 = 55.1* r.sub.19 = -56.325 d.sub.19 = 0.25 r.sub.20 = 243.391 d.sub.20 = 11.05 n.sub.11 = 1.77622 ν

.sub.11 = 49.4 r.sub.21 = -112.964 d.sub.21 = 6.70 r.sub.22 = 0.000 d.sub.22 = 43.30 n.sub.12 = 1.51825 ν

.sub.12 = 63.8 r.sub.23 = 0.000 Aspheric coefficient First surface;

K = 0.3664325 AD = 0.4574458 ×

10.sup.-7 AE = -0.3507965 ×

10.sup.-10 AF = 0.2388062 ×

10.sup.-14 AG = 0.2247566 ×

10.sup.-19 Seventeenth surface;

K = 0.1229070 ×

10.sup.2 AD = 0.9272514 ×

10.sup.-7 AE = -0.3770400 ×

10.sup.-10 AF = 0.1428259 ×

10.sup.-12 AG = 0.5601794 ×

10.sup.-16 Eighteenth surface;

K = 0.2118076 ×

10.sup.2 AD = -0.4127061 ×

10.sup.-6 AE = 0.2205876 ×

10.sup.-9 AF = 0.6059036 ×

10.sup.-13 AG = 0.6235547 ×

10.sup.-16 ______________________________________

where r₁, r₂, . . . represent a radius of curvature of each surface starting from the screen side, d₁, d₂, . . . represent a distance between each of said surfaces, n₁, n₂, . . . represent a refractive index at an e-line of each lens, ν

₁, ν

₂, . . . represent an Abbe'"'"'s number corresponding to the e-line of each of the above lens, surfaces represented by * . . . are the aspheric surfaces, and if Z is supposed a displacement amount from a vertex of a lens at a position away from an optical axis of the lens in a radius distance Y of an opening, it can be expressed as ##EQU5## and where AD, AE, AF, and AG are aspherical coefficients, and K is a conical constant.

11. A projection lens according to claim 6, satisfying substantially the following conditions:

space="preserve" listing-type="tabular">______________________________________ f = 50.15 Aperture 1;

2.8 ratio Projection 18.09 ω

= 34.1°

magnification f.sub.1.7 /f = 1.15 d.sub.15 /f = 0.67 d.sub.17 /f = 0.12 f.sub.8 /f.sub.9.10 = -1.33 r.sub.1 = 138.102 d.sub.1 = 8.40 n.sub.1 = 1.51825 ν

.sub.1 = 63.8* r.sub.2 = 3278.162 d.sub.2 = 5.18 r.sub.3 = 48.685 d.sub.3 = 6.00 n.sub.2 = 1.51825 ν

.sub.2 = 63.8 r.sub.4 = 29.654 d.sub.4 = 11.06 r.sub.5 = 1869.065 d.sub.5 = 2.21 n.sub.3 = 1.52555 ν

.sub.3 = 50.5 r.sub.6 = 27.929 d.sub.6 = 18.76 r.sub.7 = 74.902 d.sub.7 = 17.33 n.sub.4 = 1.85503 ν

.sub.4 = 23.7 r.sub.8 = -372.104 d.sub.8 = 6.68 r.sub.9 = 271.686 d.sub.9 = 17.77 n.sub.5 = 1.79013 ν

.sub.5 = 43.9 r.sub.10 = -25.786 d.sub.10 = 2.00 n.sub.6 = 1.76169 ν

.sub.6 = 27.3 r.sub.11 = 74.081 d.sub.11 = 4.62 r.sub.12 = -81.511 d.sub.12 = 4.50 n.sub.7 = 1.77622 ν

.sub.7 = 49.4 r.sub.13 = -43.199 d.sub.13 = 1.49 r.sub.14 = 204.097 d.sub.14 = 4.11 n.sub.8 = 1.79196 ν

.sub.8 = 47.1 r.sub.15 = -122.218 d.sub.15 = 33.60 r.sub.16 = -45.791 d.sub.16 = 2.66 n.sub.9 = 1.62059 ν

.sub.9 = 36.4 r.sub.17 = 288.771 d.sub.17 = 6.11 * r.sub.18 = -339.448 d.sub.18 = 11.20 n.sub. 10 = 1.68083 ν

.sub.10 = 55.1 r.sub.19 = -52.879 d.sub.19 = 0.25 r.sub.20 = 237.092 d.sub.20 = 11.05 n.sub.11 = 1.77622 ν

.sub.11 = 49.4* r.sub.21 = -107.581 d.sub.21 = 6.70 r.sub.22 = 0.000 d.sub.22 = 43.30 n.sub.12 = 1.51825 ν

.sub.12 = 63.8 r.sub.23 = 0.000 Aspheric coefficient First surface;

K = -0.8676696 AD = 0.4922937 ×

10.sup.-7 AE = -0.2681624 ×

10.sup.-10 AF = 0.4039305 ×

10.sup.-14 AG = -0.6315714 ×

10.sup.-18 Seventeenth surface;

K = 0.1204351 ×

10.sup.2 AD = 0.8134826 ×

10.sup.-7 AE = 0.3285905 ×

10.sup.-11 AF = -0.3382158 ×

10.sup.-13 AG = 0.1685514 ×

10.sup.-16 Eighteenth surface;

K = -0.1760054 ×

10.sup.2 AD = -0.2229407 ×

10.sup.-6 AE = 0.8474120 ×

10.sup.-10 AF = 0.3501296 ×

10.sup.-13 AG = -0.6162020 ×

10.sup.-17 ______________________________________

where r₁, r₂, . . . represent a radius of curvature of each surface starting from the screen side, d₁, d₂, . . . represent a distance between each of said surfaces, n₁, n₂, . . . represent a refractive index at an e-line of each lens, ν

₁, ν

₂, . . . represent an Abbe'"'"'s number corresponding to the e-line of each of the above lens, surfaces represented by * . . . are the aspheric surfaces, and if Z is supposed a displacement amount from a vertex of a lens at a position away from an optical axis of the lens in a radius distance Y of an opening, it can be expressed as ##EQU6## and where AD, AE, AF, and AG are aspherical coefficients, and K is a conical constant.

12. A projection lens according to claim 6, satisfying substantially the following conditions:

space="preserve" listing-type="tabular">______________________________________ f = 49.98 Aperture 1;

2.8 ratio Projection 18.09 ω

= 34.2°

magnification f.sub.1.7 /f = 1.16 d.sub.15 /f = 0.67 d.sub.17 /f = 0.12 f.sub.8 /f.sub.9.10 = -1.33 r.sub.1 = 97.304 d.sub.1 = 8.40 n.sub.1 = 1.51825 ν

.sub.1 = 63.8 r.sub.2 = 419.135 d.sub.2 = 5.18 r.sub.3 = 71.654 d.sub.3 = 6.00 n.sub.2 = 1.51825 ν

.sub.2 = 63.8 r.sub.4 = 34.797 d.sub.4 = 7.04 r.sub.5 = 373.100 d.sub.5 = 2.21 n.sub.3 = 1.52555 ν

.sub.3 = 50.5 r.sub.6 = 27.138 d.sub.6 = 18.76 r.sub.7 = 74.902 d.sub.7 = 17.33 n.sub.4 = 1.85503 ν

.sub.4 = 23.7 r.sub.8 = - 372.104 d.sub.8 = 6.68 r.sub.9 = 271.686 d.sub.9 = 17.77 n.sub.5 = 1.79013 ν

.sub.5 = 43.9 r.sub.10 = -25.786 d.sub.10 = 2.00 n.sub.6 = 1.76169 ν

.sub.6 = 27.3 r.sub.11 = 74.081 d.sub.11 = 4.62 r.sub.12 = -81.511 d.sub.12 = 4.50 n.sub.7 = 1.77622 ν

.sub.7 = 49.4 r.sub.13 = -43.199 d.sub.13 = 1.49 r.sub.14 = 204.097 d.sub.14 = 4.11 n.sub.8 = 1.79196 ν

.sub.8 = 47.1 r.sub.15 = -122.218 d.sub.15 = 33.60 r.sub.16 = -47.158 d.sub.16 = 2.66 n.sub.9 = 1.62059 ν

.sub.9 = 36.4 r.sub.17 = 234.453 d.sub.17 = 6.11 * r.sub.18 = d.sub.18 = n.sub.10 = 1.68083 ν

.sub.10 = 55.1* r.sub.19 = -50.375 d.sub.19 = 0.25 r.sub.20 = 387.424 d.sub.20 = 11.05 n.sub.11 = 1.77622 ν

.sub.11 = 49.4* r.sub.21 = -89.653 d.sub.21 = 6.70 r.sub.22 = 0.000 d.sub.22 = 43.30 n.sub.12 = 1.51825 ν

.sub.12 = 63.8 r.sub.23 = 0.000 Aspheric coefficient Seventeenth surface;

K = 0.3064228 ×

10.sup.2 AD = 0.3424168 ×

10.sup.-6 AE = 0.1524318 ×

10.sup.-11 AF = 0.2578158 ×

10.sup.-14 AG = -0.1657459 ×

10.sup.-16 Eighteenth surface;

K = -0.1540423 ×

10.sup.2 AD = -0.1423166 ×

10.sup.-6 AE = 0.2421751 ×

10.sup.-9 AF = 0.9010286 ×

10.sup.-13 AG = 0.6174771 ×

10.sup.-16 Twentieth surface;

K = -0.1023903 ×

10.sup.3 AD = -0.2301108 ×

10.sup.-6 AE = 0.1076672 ×

10.sup.-9 AF = -0.1514403 ×

10.sup.-14 AG = -0.3385086 ×

10.sup.-17 ______________________________________

where r₁, r₂, . . . represent a radius of curvature of each surface starting from the screen side, d₁, d₂, . . . represent a distance between each of said surfaces, n₁, n₂, . . . represent a refractive index at an e-line of each lens, ν

₁, ν

₂, . . . represent an Abbe'"'"'s number corresponding to the e-line of each of the above lens, surfaces represented by * . . . are the aspheric surfaces, and if Z is supposed a displacement amount from a vertex of a lens at a position away from an optical axis of the lens in a radius distance Y of an opening, it can be expressed as ##EQU7## and where AD, AE, AF, and AG are aspherical coefficients, and K is a conical constant.

13. A projection lens according to claim 6, satisfying substantially the following conditions:

space="preserve" listing-type="tabular">______________________________________ f = 50.09 Aperture 1;

2.8 ratio Projection 18.09 ω

= 34.1°

magnification f.sub.1.7 /f = 1.13 d.sub.15 /f = 0.67 d.sub.17 /f = 0.12 f.sub.8 /f.sub.9.10 = -1.34 r.sub.1 = 100.392 d.sub.1 = 8.40 n.sub.1 = 1.51825 ν

.sub.1 = 63.8* r.sub.2 = 203.275 d.sub.2 = 5.18 r.sub.3 = 39.627 d.sub.3 = 6.00 n.sub.2 = 1.51825 ν

.sub.2 = 63.8 r.sub.4 = 24.889 d.sub.4 = 12.47 r.sub.5 = 566.809 d.sub.5 = 2.21 n.sub.3 = 1.52555 ν

.sub.3 = 50.5 r.sub.6 = 29.209 d.sub.6 = 18.76 r.sub.7 = 74.902 d.sub.7 = 17.33 n.sub.4 = 1.85503 ν

.sub.4 = 23.7 r.sub.8 = - 372.104 d.sub.8 = 6.68 r.sub.9 = 271.686 d.sub.9 = 17.77 n.sub.5 = 1.79013 ν

.sub.5 = 43.9 r.sub.10 = -25.786 d.sub.10 = 2.00 n.sub.6 = 1.76169 ν

.sub.6 = 27.3 r.sub.11 = 74.081 d.sub.11 = 4.62 r.sub.12 = -81.511 d.sub.12 = 4.50 n.sub.7 = 1.77622 ν

.sub.7 = 49.4 r.sub.13 = -43.199 d.sub.13 = 1.49 r.sub.14 = 204.097 d.sub.14 = 4.11 n.sub.8 = 1.79196 ν

.sub.8 = 47.1 r.sub.15 = -122.218 d.sub.15 = 35.89 r.sub.16 = -49.808 d.sub.16 = 2.66 n.sub.9 = 1.62059 ν

.sub.9 = 36.4 r.sub.17 = 275.553 d.sub.17 = 6.11 * r.sub.18 = -519.026 d.sub.18 = 10.70 n.sub.10 = 1.68083 ν

.sub.10 = 55.1 r.sub.19 = -60.159 d.sub.19 = 0.25 r.sub.20 = 250.814 d.sub.20 = 11.05 n.sub.11 = 1.77622 ν

.sub.11 = 49.4 r.sub.21 = -108.683 d.sub.21 = 6.70 r.sub.22 = 0.000 d.sub.22 = 43.30 n.sub.12 = 1.51825 ν

.sub.12 = 63.8 r.sub.23 = 0.000 Aspheric coefficient First surface;

K = 0.9525501 AD = 0.2216984 ×

10.sup.-6 AE = -0.4500812 ×

10.sup.-10 AF = 0.1270679 ×

10.sup.-13 AG = -0.2481052 ×

10.sup.-17 Seventeenth surface;

K = 0.3154613 ×

10.sup.2 AD = 0.5889586 ×

10.sup.-6 AE = -0.5654111 ×

10.sup.-9 AF = 0.5498361 ×

10.sup.-13 AG = 0.2775640 ×

10.sup.-16 ______________________________________

where r₁, r₂, . . . represent a radius of curvature of each surface starting from the screen side, d₁, d₂, . . . represent a distance between each of said surfaces, n₁, n₂, . . . represent a refractive index at an e-line of each lens, ν

₁, ν

₂, . . . represent an Abbe'"'"'s number corresponding to the e-line of each of the above lens, surfaces represented by * . . . are the aspheric surfaces, and if Z is supposed a displacement amount from a vertex of a lens at a position away from an optical axis of the lens in a radius distance Y of an opening, it can be expressed as ##EQU8## and where AD, AE, AF, and AG are aspherical coefficients, and K is a conical constant.

14. A projection lens according to claim 6, satisfying substantially the following conditions:

space="preserve" listing-type="tabular">______________________________________ f = 49.91 Aperture 1;

2.8 ratio Projection 18.07 ω

= 34.2°

magnification f.sub.1.7 /f = 1.13 d.sub.15 /f = 0.67 d.sub.17 /f = 0.12 f.sub.8 /f.sub.9.10 = -1.39 r.sub.1 = 92.116 d.sub.1 = 8.40 n.sub.1 = 1.51825 ν

.sub.1 = 63.8* r.sub.2 = 256.167 d.sub.2 = 5.18 r.sub.3 = 60.670 d.sub.3 = 6.00 n.sub.2 = 1.51825 ν

.sub.2 = 63.8 r.sub.4 = 29.056 d.sub.4 = 8.80 r.sub.5 = 222.628 d.sub.5 = 2.21 n.sub.3 = 1.52555 ν

.sub.3 = 50.5 r.sub.6 = 28.187 d.sub.6 = 18.76 r.sub.7 = 74.902 d.sub.7 = 17.33 n.sub.4 = 1.85503 ν

.sub.4 = 23.7 r.sub.8 = - 372.104 d.sub.8 = 6.68 r.sub.9 = 271.686 d.sub.9 = 17.77 n.sub.5 = 1.79013 ν

.sub.5 = 43.9 r.sub.10 = -25.786 d.sub.10 = 2.00 n.sub.6 = 1.76169 ν

.sub.6 = 27.3 r.sub.11 = 74.081 d.sub.11 = 4.62 r.sub.12 = -81.511 d.sub.12 = 4.50 n.sub.7 = 1.77622 ν

.sub.7 = 49.4 r.sub.13 = -43.199 d.sub.13 = 1.49 r.sub.14 = 204.097 d.sub.14 = 4.11 n.sub.8 = 1.79196 ν

.sub.8 = 47.1 r.sub.15 = -122.218 d.sub.15 = 35.89 r.sub.16 = -55.629 d.sub.16 = 2.66 n.sub.9 = 1.62059 ν

.sub.9 = 36.4 r.sub.17 = 243.662 d.sub.17 = 6.11 r.sub.18 = -319.338 d.sub.18 = 10.70 n.sub.10 = 1.68083 ν

.sub.10 = 55.1* r.sub.19 = -61.756 d.sub.19 = 0.25 r.sub.20 = 302.607 d.sub.20 = 11.05 n.sub.11 = 1.77622 ν

.sub.11 = 49.4 r.sub.21 = -96.776 d.sub.21 = 6.70 r.sub.22 = 0.000 d.sub.22 = 43.30 n.sub.12 = 1.51825 ν

.sub.12 = 63.8 r.sub.23 = 0.000 Aspheric coefficient First surface;

K = 0.3399632 AD = 0.7523389 ×

10.sup.-7 AE = -0.6005325 ×

10.sup.-10 AF = 0.2647887 ×

10.sup.-13 AG = -0.5935675 ×

10.sup.-17 Eighteenth surface;

K= 0.2756654 ×

10.sup.2 AD = -0.7554289 ×

10.sup.-6 AE = 0.3478933 ×

10.sup.-9 AF = -0.7082334 ×

10.sup.-13 AG = 0.2544740 ×

10.sup.-16 ______________________________________

where r₁, r₂, . . . represent a radius of curvature of each surface starting from the screen side, d₁, d₂, . . . represent a distance between each of said surfaces, n₁, n₂, . . . represent a refractive index at an e-line of each lens, ν

₁, ν

₂, . . . represent an Abbe'"'"'s number corresponding to the e-line of each of the above lens, surfaces represented by * . . . are the aspheric surfaces, and if Z is supposed a displacement amount from a vertex of a lens at a position away from an optical axis of the lens in a radius distance Y of an opening, it can be expressed as ##EQU9## and where AD, AE, AF, and AG are aspherical coefficients, and K is a conical constant.

15. A projection lens according to claim 6, satisfying substantially the following conditions:

space="preserve" listing-type="tabular">______________________________________ f = 50.04 Aperture 1;

2.8 ratio Projection 18.10 ω

= 34.2°

magnification f.sub.1.7 /f = 1.14 d.sub.15 /f = 0.67 d.sub.17 /f = 0.12 f.sub.8 /f.sub.9.10 = -1.31 r.sub.1 = 114.457 d.sub.1 = 8.40 n.sub.1 = 1.51825 ν

.sub.1 = 63.8* r.sub.2 = 483.920 d.sub.2 = 5.18 r.sub.3 = 48.101 d.sub.3 = 6.00 n.sub.2 = 1.51825 ν

.sub.2 = 63.8 r.sub.4 = 28.146 d.sub.4 = 9.91 r.sub.5 = 575.308 d.sub.5 = 2.21 n.sub.3 = 1.52555 ν

.sub.3 = 50.5 r.sub.6 = 28.386 d.sub.6 = 18.76 r.sub.7 = 74.902 d.sub.7 = 17.33 n.sub.4 = 1.85503 ν

.sub.4 = 23.7 r.sub.8 = - 372.104 d.sub.8 = 6.68 r.sub.9 = 271.686 d.sub.9 = 17.77 n.sub.5 = 1.79013 ν

.sub.5 = 43.9 r.sub.10 = -25.786 d.sub.10 = 2.00 n.sub.6 = 1.76169 ν

.sub.6 = 27.3 r.sub.11 = 74.081 d.sub.11 = 4.62 r.sub.12 = -81.511 d.sub.12 = 4.50 n.sub.7 = 1.77622 ν

.sub.7 = 49.4 r.sub.13 = -43.199 d.sub.13 = 1.49 r.sub.14 = 204.097 d.sub.14 = 4.11 n.sub.8 = 1.79196 ν

.sub.8 = 47.1 r.sub.15 = -122.218 d.sub.15 = 33.60 r.sub.16 = -46.081 d.sub.16 = 2.66 n.sub.9 = 1.62059 ν

.sub.9 = 36.4 r.sub.17 = 228.576 d.sub.17 = 6.11 r.sub.18 = -509.475 d.sub.18 = 10.70 n.sub.10 = 1.68083 ν

.sub.10 = 55.1 r.sub.19 = -54.905 d.sub.19 = 0.25 r.sub.20 = 238.750 d.sub.20 = 11.05 n.sub.11 = 1.77622 ν

.sub.11 = 49.4* r.sub.21 = -103.160 d.sub.21 = 6.70 r.sub.22 = 0.000 d.sub.22 = 43.30 n.sub.12 = 1.51825 ν

.sub.12 = 63.8 r.sub.23 = 0.000 Aspheric coefficient First surface;

K = 0.7070278 AD = 0.1345127 ×

10.sup.-7 AE = -0.3754727 ×

10.sup.-10 AF = 0.6046046 ×

10.sup.-14 AG = -0.1657469 ×

10.sup.-17 Twentieth surface;

K= -0.1850460 ×

10.sup.2 AD = -0.2560358 ×

10.sup.-6 AE = 0.6946116 ×

10.sup.-10 AF = 0.3196880 ×

10.sup.-13 AG = -0.5231959 ×

10.sup.-17 ______________________________________

where r₁, r₂, . . . represent a radius of curvature of each surface starting from the screen side, d₁, d₂, . . . represent a distance between each of said surfaces, n₁, n₂, . . . represent a refractive index at an e-line of each lens, ν

₁, ν

₂, . . . represent an Abbe'"'"'s number corresponding to the e-line of each of the above lens, surfaces represented by * . . . are the aspheric surfaces, and if Z is supposed a displacement amount from a vertex of a lens at a position away from an optical axis of the lens in a radius distance Y of an opening, it can be expressed as ##EQU10## and where AD, AE, AF, and AG are aspherical coefficients, and K is a conical constant.

16. A projection lens for projecting on a screen a transmission or reflection light from an image display device which forms from a light emitted from a light source an image as changes of transmittance or reflectivity in response to an electric signal applied thereto, said projection lens comprising an inverted telephoto type front lens group at a screen side, and a rear lens group having a front focal point nearby an exit pupil of said front lens group, wherein said projection lens has telecentric characteristics and satisfies the following condition:

space="preserve" listing-type="equation">0.8<

f.sub.1 /f<

1.4

where f₁ is a total focal length of the front lens group, and f is a total focal length of the entire system.

17. A projection lens according to claim 16, satisfying the following condition:

space="preserve" listing-type="equation">0.5<

d.sub.15 /f<

0.9

where d₁₅ is a distance between opposing surfaces of the front and rear lens group.