CA1306884C - Projection lens for high definition tv - Google Patents
Projection lens for high definition tvInfo
- Publication number
- CA1306884C CA1306884C CA000556009A CA556009A CA1306884C CA 1306884 C CA1306884 C CA 1306884C CA 000556009 A CA000556009 A CA 000556009A CA 556009 A CA556009 A CA 556009A CA 1306884 C CA1306884 C CA 1306884C
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- Canada
- Prior art keywords
- lens
- optical power
- lenses
- projection lens
- crt
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/16—Optical objectives specially designed for the purposes specified below for use in conjunction with image converters or intensifiers, or for use with projectors, e.g. objectives for projection TV
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
Abstract
ABSTRACT OF THE DISCLOSURE
A high definition projection lens for projecting on a screen an enlargement of an image appearing on a high resolution CRT is disclosed. The projection lens comprises a first lens having a positive optical power and a convex surface facing the screen, a meniscus second lens having a positive optical power, a third lens having bi-concave surfaces and a negative optical power, a fourth lens having a positive optical power, a fifth lens having bi-convex surfaces and a positive optical power, and a sixth lens having a negative power and an aspheric concave surface facing the fifth lens.
A high definition projection lens for projecting on a screen an enlargement of an image appearing on a high resolution CRT is disclosed. The projection lens comprises a first lens having a positive optical power and a convex surface facing the screen, a meniscus second lens having a positive optical power, a third lens having bi-concave surfaces and a negative optical power, a fourth lens having a positive optical power, a fifth lens having bi-convex surfaces and a positive optical power, and a sixth lens having a negative power and an aspheric concave surface facing the fifth lens.
Description
TITLE OF T~TE IN~TENTION
Projection Lens for High Definition TV
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to a projection lens used in a video projector for projectins on a screen an enlargement of an image appearing on a cathode-ray tube (CRT), and more particularly to a high resolution projec-tion lens applicable to a high definition video projector employing a high resolution CRT.
Projection Lens for High Definition TV
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to a projection lens used in a video projector for projectins on a screen an enlargement of an image appearing on a cathode-ray tube (CRT), and more particularly to a high resolution projec-tion lens applicable to a high definition video projector employing a high resolution CRT.
2. Description of the Prior Art Conventional projection lenses as disclosed in Japanese Laid-Open Patent Applications Nos. 58-125007 and 59-155818 and U.S. Patent Nos. 4,300,817 and 4,348,081 are for the CRT on which an image is formed by 525 scanning lines(resolution is 525 lines), and most of them do not provide correction for chromatic aberration.
Some projection lenses which provide correction for chromatic aberration have been proposed as disclosed in the Japanese Laid-Open Patent Application No. 59-170812 and U.S. Patent No. 3,868,173.
However, these conventional projection lenses have, because of large residual aberrations, a serious deficiency of performance as a projection lens for use in a high definition video projector of 1,125 scanning lines.
1~0~
SU;`l~IARY OE T~E INVENTION
It is an object of the present invention to solve disadvantages of the prior art described above and provide a large aperture and high definition projection lens.
Another object of this invention is to provide a new an~ improved projection lens for a high resolution CRT on which an image is formed by 1,125 scanning lines, while maitaining satisfactorily excellent aberration correction.
A projection lens of the present invention comprises first, second, third, fourth, fifth and sixth lenses which are disposed successively in a direction from a screen end to a CRT end. The first lens has a positive optical power and a convex surface that faces the screen. The second lens is a meniscus lens having a positive optical power. The third lens is a bi-concave lens having a negative optical power. The fourth lens has a positive optical power. The fifth lens is a bi-convex lens having a positive optical power. The sixth lens has a negative optical power and an aspheric concave surface that faces the fifth lens. Optical parameters of the projection lens according to the present invention are selected to satisfy the following conditions:
2.5 _ fa/f - 5 0 45 _ d8/dlo _ 1.0 ~2 ~ 50 v3 _ 38 13(~84 where: f is a focal length of the overall projection lens system; fa is a combined focal length of the first, second and third lenses; d8 is a distance between the fourth and fifth lenses; dlo is a distance between the fifth and si~th lenses; and v2, v3 are respectively Abbe numbers of the second and thira lenses.
The above and other objects, features and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view showing a structure of projection lenses of embodiments 1 ana 2; and FIG. 2 and FIG. 3 are respectively aberration diagrams of embodiments 1 and 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a sectional view showing a structure of a projection lens of the present invention. In FIG. 1, a first lens L1 is an element of a positive optical power having a concave surface that faces a screen S. A second lens L2 is an element of a positive optical power having a meniscus shape. A third lens L3 is an element of a negative optical power having bi-concave surfaces.
A fourth lens L4 is an element having a positive optical power. A fifth lens L5 is an element of a positive optical ~3(;~
power having ~i-convex surfaces. A sixth lens L6 is ar.
element of a negative optical power having an aspheric surface that is a concave surface facing the fifth lens.
An element P is a face plate of a CRT. A space between the sixth lens L6 and the face plate P of the CRT is filled with an optical transparent medium G. The optical transparent medium G may be ethylene glycol or silicone gel or other materials having a refractive index that is almost the same as that of each of the face plate P and the sixth lens L6. In the projection system having the projection lens shown in FIG. 1, reflections at the surface of the face plate P and at the surface of the sixth lens L6 facing the CRT can be prevented, so that a high contrast image can be obtained.
The projection lens of the present invention is as bright as about 1.45 or less in terms of F number and has a semi-field angle ranging from 20 to 30. It is required for effectively correctina spherical aberration that the second lens L2 is meniscus shaped and a surface facing the screen is convex. It is also required for effectively correcting field curvature that the sixth lens has at least an aspheric concave surface facing the fifth lens.
Moreover, selection of optical parameters is important for realizing a hish definition projection lens. The projec-tion lens of the present invention satisfies the following 13(~6~1~4 conditions, in which the focal length of the overall projection lens system is f, the combined focal length of the first, second and third lenses is fa, the distance between the fourth and fifth lenses is d8, the distance between the fifth and sixth lenses is dlo, the Abbe numbers of the second an~ third lenses are respectively v2 and v3:
2.5 _ fa/f - 5 (1) 0.45 < d8/dlo < 1.0 (2) V2 ~ 50 (3) V4 _ 38 (4) The condition (1) relates to distribution of combined optical power of the first, second and third lenses Ll, L2 and L3. If fa/f is below the lower limit of condition (1), the lens system is superior in compactness, but the combined optical power is too strong to properly correct for spherical aberration. If fa/f exceeds the upper limit of condition (1), the optical power of the fourth lens becomes too strong to properly correct for on-axis and off-axis aberration.
The condition (2) defines the position of the fifth lense L5 in relation to the fourth and sixth lenses L4 and L6. If d8/dlo is below the lower limit of condition (2), correction ror off-axis aberration becomes difficult.
The lower limit of condition (2) also serves to maintain a focal point shift caused by a temperature variation 130~;1Y84 which occurs when a plastic lens is used as the fifth lens within an allowable range free of any obstacle in practical use. If d8/dlo exceeds the upper limit of condition (2), correction for field curvature becomes difficult.
If the Abbe numbers of the first and second lenses do not respectively satisfy conditions (3) and (4), correction for chromatic aberration becomes difficult.
Moreover, it is preferable to satisfy the following conditions for realizing a projection lens having further improved optical performance, in which the focal length of the fourth lens L4 is f4 and that of the fifth lens L5 is f5:
1-25 _ f4/f _ 1-8 (5) 0.5 _ f4/f5 _ 1.0 (6) The condition (5) relates to distribution of the focal length of the fourth lens. If f4/f is belo~the lower limit of condition (5), the optical power of the fourth lens is too strong to properly correct for spherical aberration. If f4/f exceeds the upper limit of condition (5), the optical power is too weak to properly correct for coma.
The condition (6) relates to distribution of the focal length of the fifth and sixth lenses L5 and L6.
If f4/f5 is below the lower limit of condition (6), the 130~
optical power of the fourth lens is too strong to properly correct for spherical aberration. If f4~f5 exceecs the upper limit of condition (6), the optical power of the fifth lens is too strong to properly correct for off-axis aberration. The upper limit of condition (6) also serves to maintain a focal point shift caused by a temperature variation which occurs when a plastic lens is used as the fifth lens within an allowable range free of any obstacle in practical use.
The fifth lens L5 may be preferably an aspheric lens for a further improved correctlon of aberration.
The fifth lens L5 and sixth lens L6, which are positioned near the CRT, are re~uirea to have a large effective aperture. So, the fifth and sixth lenses may be plastic lenses to attain reduction of weisht a~d cost.
Two preferred embodiments of the present invention will be indicated below. Embodiments l and 2 have the structure shown in FIG. l. In the tables of these embodiments: I is a focal length of the overall lens system; FNO is F number; ~ is a magnification factor of the projected enlarged image; ~ is a semi-field angle;
fa is a combined focal len~th of the first, secor.d and third lenses; f4 is a focal length of the fourth lens;
f5 is a focal lenath of the fifth lens; rl, r2, --- are radii of curvature of lens surfaces disposed successively 13~
from the screen end; d', d2, --- are axial distances between each adjacent two of thi- lens su-faces; nl, r.2, ---are refractive indices with respect to e-line of the lenses; vl, v2, --- are Abbe numbers of the lenses. In addition, each lens surface indicated by asterisk (*) means an aspheric surface. The shape of each aspheric surface is expressed by the followin~ equation, in which the optical axis direction is X axis, Y axis is set perpendicular to X axis, curvature at the apex of the aspheric surface is C(=l/r), the conic constant is K, and the coefficients of the aspheric surfaces are AD, AE, AF
and AG: .
X = cy2 + AD-y4 + AE.y6 1 + /1 - (1 +K)C2Y~
+ AF-y8 + AG~ylO
Embodiment 1:
f=260.076mm FNO=1.45 ~=-18.0 ~=24.6 fa=920.865mm f4=350.273mm f5=440.981mm { rl=304.091 dl=17.50 nl=1.59143 Vl=61.25 r2=279l.969 d2=1.00 { r3=172.476 d3=23.50 n2=1.68082 v2=55.52 r4=638.510 d4=23.76 { r5=-1583.198 d5=8.50 n3=l.76l68 J3=27.53 r6=184.524 d6=59.22 13C~6&184 { r7=261.306 d7=17.50 n4=1.59143 V4=61.25 r8=-974.879 d8=59.53 ~ r9*=302.376 dg=29~50 n5=1.49383 v =57 70 r10*=-753.190 dlo=83.65 { r *=-100.754 dll=5.00 n6=1.49383 v6=s7.70 G~ rl2 dl2=23.83 n7=1.40000 v7=5c.70 p{ rl3 dl3=16.00 n8=1.54000 v8=50.70 rl4=4000.000 Aspheric sur~ace coefficients -9th surface (r9) 10th surface (r10) 11th surface (rll) K=1.19206xlO K=-2.16641xlO K=-5.91635xlO
AD=0 AD=0 AD=-2.64843xlO
AE=0 AE=0 AE=5.16019xlO 1 AF=0 AF=0 AF=0 AG=0 AG=0 AG=0 Embodiment 2:
f=259.729mm FNO=1.45 ~=-20.0 ~=25.0 fa=900.418mm f4=369.449mm f5=395.394mm ,( rl=304.403 dl=18.00 nl=1.59143 vl=61.25 r2=312Y.676 d2=l.OU
{ r3=173.581 d3=24.00 n2=1.68082 v2=55.52 F4=666.633 d4=22.05 13~6~
{ r5=-157'.059 d5=9.00 n3=1.76168 v3=27.53 r6=184.935 d6=~6.84 J r7=314.512 d7=15.00 n4=1.68082 v4=55.52 r8=-1231.735 d8=67.33 { r9*=280.976 dg=33.50 n5=1.49383 v5=57.70 r10*'=-614.804 dlo=78.35 { r *=-96.269 dll=5.00 n6=1.49383 v6=s7.7 6 { rl2= ~ dl2=22.27 n7=1.40000 v7=50.70 p { rl3 dl3=16.00 n8=1.54000 v8=50.70 rl4=4000.000 Aspheric surface coefficients -9th surface (r9) 10th surface (r10) 11th surface (rll) -K=7.03666xlO K=-5.60962 K=-8.98400xlO
AD=0 AD=0 AD=-2.09391xlO 8 AE=0 AE=0 AE=3.26864xlO 12 AF=0 AF=0 AF=0 AG=0 AG=0 AG=0 FIG. 2 and FIG. 3 respectively show aberration perfor-mances of embodiments 1 and 2. In each of FIGS.2 and 3, (a), (b) and (c) respectively show spherical aberration for the e-line and the g-line, astigmatism and distortion.
As seen from FIGS.2 and 3, these aberrations are excellently corrected in both of embodiments 1 and 2.
Some projection lenses which provide correction for chromatic aberration have been proposed as disclosed in the Japanese Laid-Open Patent Application No. 59-170812 and U.S. Patent No. 3,868,173.
However, these conventional projection lenses have, because of large residual aberrations, a serious deficiency of performance as a projection lens for use in a high definition video projector of 1,125 scanning lines.
1~0~
SU;`l~IARY OE T~E INVENTION
It is an object of the present invention to solve disadvantages of the prior art described above and provide a large aperture and high definition projection lens.
Another object of this invention is to provide a new an~ improved projection lens for a high resolution CRT on which an image is formed by 1,125 scanning lines, while maitaining satisfactorily excellent aberration correction.
A projection lens of the present invention comprises first, second, third, fourth, fifth and sixth lenses which are disposed successively in a direction from a screen end to a CRT end. The first lens has a positive optical power and a convex surface that faces the screen. The second lens is a meniscus lens having a positive optical power. The third lens is a bi-concave lens having a negative optical power. The fourth lens has a positive optical power. The fifth lens is a bi-convex lens having a positive optical power. The sixth lens has a negative optical power and an aspheric concave surface that faces the fifth lens. Optical parameters of the projection lens according to the present invention are selected to satisfy the following conditions:
2.5 _ fa/f - 5 0 45 _ d8/dlo _ 1.0 ~2 ~ 50 v3 _ 38 13(~84 where: f is a focal length of the overall projection lens system; fa is a combined focal length of the first, second and third lenses; d8 is a distance between the fourth and fifth lenses; dlo is a distance between the fifth and si~th lenses; and v2, v3 are respectively Abbe numbers of the second and thira lenses.
The above and other objects, features and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view showing a structure of projection lenses of embodiments 1 ana 2; and FIG. 2 and FIG. 3 are respectively aberration diagrams of embodiments 1 and 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a sectional view showing a structure of a projection lens of the present invention. In FIG. 1, a first lens L1 is an element of a positive optical power having a concave surface that faces a screen S. A second lens L2 is an element of a positive optical power having a meniscus shape. A third lens L3 is an element of a negative optical power having bi-concave surfaces.
A fourth lens L4 is an element having a positive optical power. A fifth lens L5 is an element of a positive optical ~3(;~
power having ~i-convex surfaces. A sixth lens L6 is ar.
element of a negative optical power having an aspheric surface that is a concave surface facing the fifth lens.
An element P is a face plate of a CRT. A space between the sixth lens L6 and the face plate P of the CRT is filled with an optical transparent medium G. The optical transparent medium G may be ethylene glycol or silicone gel or other materials having a refractive index that is almost the same as that of each of the face plate P and the sixth lens L6. In the projection system having the projection lens shown in FIG. 1, reflections at the surface of the face plate P and at the surface of the sixth lens L6 facing the CRT can be prevented, so that a high contrast image can be obtained.
The projection lens of the present invention is as bright as about 1.45 or less in terms of F number and has a semi-field angle ranging from 20 to 30. It is required for effectively correctina spherical aberration that the second lens L2 is meniscus shaped and a surface facing the screen is convex. It is also required for effectively correcting field curvature that the sixth lens has at least an aspheric concave surface facing the fifth lens.
Moreover, selection of optical parameters is important for realizing a hish definition projection lens. The projec-tion lens of the present invention satisfies the following 13(~6~1~4 conditions, in which the focal length of the overall projection lens system is f, the combined focal length of the first, second and third lenses is fa, the distance between the fourth and fifth lenses is d8, the distance between the fifth and sixth lenses is dlo, the Abbe numbers of the second an~ third lenses are respectively v2 and v3:
2.5 _ fa/f - 5 (1) 0.45 < d8/dlo < 1.0 (2) V2 ~ 50 (3) V4 _ 38 (4) The condition (1) relates to distribution of combined optical power of the first, second and third lenses Ll, L2 and L3. If fa/f is below the lower limit of condition (1), the lens system is superior in compactness, but the combined optical power is too strong to properly correct for spherical aberration. If fa/f exceeds the upper limit of condition (1), the optical power of the fourth lens becomes too strong to properly correct for on-axis and off-axis aberration.
The condition (2) defines the position of the fifth lense L5 in relation to the fourth and sixth lenses L4 and L6. If d8/dlo is below the lower limit of condition (2), correction ror off-axis aberration becomes difficult.
The lower limit of condition (2) also serves to maintain a focal point shift caused by a temperature variation 130~;1Y84 which occurs when a plastic lens is used as the fifth lens within an allowable range free of any obstacle in practical use. If d8/dlo exceeds the upper limit of condition (2), correction for field curvature becomes difficult.
If the Abbe numbers of the first and second lenses do not respectively satisfy conditions (3) and (4), correction for chromatic aberration becomes difficult.
Moreover, it is preferable to satisfy the following conditions for realizing a projection lens having further improved optical performance, in which the focal length of the fourth lens L4 is f4 and that of the fifth lens L5 is f5:
1-25 _ f4/f _ 1-8 (5) 0.5 _ f4/f5 _ 1.0 (6) The condition (5) relates to distribution of the focal length of the fourth lens. If f4/f is belo~the lower limit of condition (5), the optical power of the fourth lens is too strong to properly correct for spherical aberration. If f4/f exceeds the upper limit of condition (5), the optical power is too weak to properly correct for coma.
The condition (6) relates to distribution of the focal length of the fifth and sixth lenses L5 and L6.
If f4/f5 is below the lower limit of condition (6), the 130~
optical power of the fourth lens is too strong to properly correct for spherical aberration. If f4~f5 exceecs the upper limit of condition (6), the optical power of the fifth lens is too strong to properly correct for off-axis aberration. The upper limit of condition (6) also serves to maintain a focal point shift caused by a temperature variation which occurs when a plastic lens is used as the fifth lens within an allowable range free of any obstacle in practical use.
The fifth lens L5 may be preferably an aspheric lens for a further improved correctlon of aberration.
The fifth lens L5 and sixth lens L6, which are positioned near the CRT, are re~uirea to have a large effective aperture. So, the fifth and sixth lenses may be plastic lenses to attain reduction of weisht a~d cost.
Two preferred embodiments of the present invention will be indicated below. Embodiments l and 2 have the structure shown in FIG. l. In the tables of these embodiments: I is a focal length of the overall lens system; FNO is F number; ~ is a magnification factor of the projected enlarged image; ~ is a semi-field angle;
fa is a combined focal len~th of the first, secor.d and third lenses; f4 is a focal length of the fourth lens;
f5 is a focal lenath of the fifth lens; rl, r2, --- are radii of curvature of lens surfaces disposed successively 13~
from the screen end; d', d2, --- are axial distances between each adjacent two of thi- lens su-faces; nl, r.2, ---are refractive indices with respect to e-line of the lenses; vl, v2, --- are Abbe numbers of the lenses. In addition, each lens surface indicated by asterisk (*) means an aspheric surface. The shape of each aspheric surface is expressed by the followin~ equation, in which the optical axis direction is X axis, Y axis is set perpendicular to X axis, curvature at the apex of the aspheric surface is C(=l/r), the conic constant is K, and the coefficients of the aspheric surfaces are AD, AE, AF
and AG: .
X = cy2 + AD-y4 + AE.y6 1 + /1 - (1 +K)C2Y~
+ AF-y8 + AG~ylO
Embodiment 1:
f=260.076mm FNO=1.45 ~=-18.0 ~=24.6 fa=920.865mm f4=350.273mm f5=440.981mm { rl=304.091 dl=17.50 nl=1.59143 Vl=61.25 r2=279l.969 d2=1.00 { r3=172.476 d3=23.50 n2=1.68082 v2=55.52 r4=638.510 d4=23.76 { r5=-1583.198 d5=8.50 n3=l.76l68 J3=27.53 r6=184.524 d6=59.22 13C~6&184 { r7=261.306 d7=17.50 n4=1.59143 V4=61.25 r8=-974.879 d8=59.53 ~ r9*=302.376 dg=29~50 n5=1.49383 v =57 70 r10*=-753.190 dlo=83.65 { r *=-100.754 dll=5.00 n6=1.49383 v6=s7.70 G~ rl2 dl2=23.83 n7=1.40000 v7=5c.70 p{ rl3 dl3=16.00 n8=1.54000 v8=50.70 rl4=4000.000 Aspheric sur~ace coefficients -9th surface (r9) 10th surface (r10) 11th surface (rll) K=1.19206xlO K=-2.16641xlO K=-5.91635xlO
AD=0 AD=0 AD=-2.64843xlO
AE=0 AE=0 AE=5.16019xlO 1 AF=0 AF=0 AF=0 AG=0 AG=0 AG=0 Embodiment 2:
f=259.729mm FNO=1.45 ~=-20.0 ~=25.0 fa=900.418mm f4=369.449mm f5=395.394mm ,( rl=304.403 dl=18.00 nl=1.59143 vl=61.25 r2=312Y.676 d2=l.OU
{ r3=173.581 d3=24.00 n2=1.68082 v2=55.52 F4=666.633 d4=22.05 13~6~
{ r5=-157'.059 d5=9.00 n3=1.76168 v3=27.53 r6=184.935 d6=~6.84 J r7=314.512 d7=15.00 n4=1.68082 v4=55.52 r8=-1231.735 d8=67.33 { r9*=280.976 dg=33.50 n5=1.49383 v5=57.70 r10*'=-614.804 dlo=78.35 { r *=-96.269 dll=5.00 n6=1.49383 v6=s7.7 6 { rl2= ~ dl2=22.27 n7=1.40000 v7=50.70 p { rl3 dl3=16.00 n8=1.54000 v8=50.70 rl4=4000.000 Aspheric surface coefficients -9th surface (r9) 10th surface (r10) 11th surface (rll) -K=7.03666xlO K=-5.60962 K=-8.98400xlO
AD=0 AD=0 AD=-2.09391xlO 8 AE=0 AE=0 AE=3.26864xlO 12 AF=0 AF=0 AF=0 AG=0 AG=0 AG=0 FIG. 2 and FIG. 3 respectively show aberration perfor-mances of embodiments 1 and 2. In each of FIGS.2 and 3, (a), (b) and (c) respectively show spherical aberration for the e-line and the g-line, astigmatism and distortion.
As seen from FIGS.2 and 3, these aberrations are excellently corrected in both of embodiments 1 and 2.
Claims (15)
1. A projection lens for projecting on a screen an en-largement of an image appearing on a cathode ray tube (CRT), comprising, successively in a direction from the screen end to the CRT end: a first lens having a positive optical power and a convex surface facing the screen; a second lens having a positive optical power and a meniscus shape;
a third lens having a negative optical power and bi-concave surfaces; a fourth lens having a positive optical power;
a fifth lens having a positive optical power and bi-convex surfaces; and a sixth lens having a negative optical power and an aspheric concave surface facing said fifth lens, wherein the projection lens satisfies the following condition:
a third lens having a negative optical power and bi-concave surfaces; a fourth lens having a positive optical power;
a fifth lens having a positive optical power and bi-convex surfaces; and a sixth lens having a negative optical power and an aspheric concave surface facing said fifth lens, wherein the projection lens satisfies the following condition:
2.5 ? fa/f ? 5 0.45 ? d8/d10 ? 1.0 ?2 ? 50 ?3 ? 38 where: f is a focal length of the overall projection lens system; fa is a combined focal length of the first, second and third lenses; d8 is a distance between the fourth and fifth lenses; d10 is a distance between the fifth and sixth lenses; and ?2 and ?3 are respectively Abbe numbers of the second and third lenses.
2. The projection lens according to claim 1, further satisfying the following condition:
1.25 ? f4/f ? 1.8 0.5 ? f4/f5 ? 1.0 where f4 is a focal length of the fourth lens and f5 is a focal length of the fifth lens.
2. The projection lens according to claim 1, further satisfying the following condition:
1.25 ? f4/f ? 1.8 0.5 ? f4/f5 ? 1.0 where f4 is a focal length of the fourth lens and f5 is a focal length of the fifth lens.
3. The projection lens according to claim 1, wherein said fifth lens has an aspheric surface.
4. The projection lens according to claim 1, wherein said fifth lens is a plastic lens.
5. The projection lens according to claim 1, wherein said sixth lens is a plastic lens.
6. The projection lens according to claim 1, wherein a space between the sixth lens and a face plate of the CRT
is filled with a transparent medium.
is filled with a transparent medium.
7. The projection lens according to claim 6, defined substantially as follows:
Aspheric surface coefficients where: L1-L6, G and P denote the first through sixth lenses, the transparent medium and the face plate of the CRT, respectively, which are elements for constituting the pro-jection lens; FNO is F number; .beta. is a magnification factor of an projected enlarged image; .omega. is a semi-field angle; f4 is a focal length of the fourth lens; f5 is a focal length of the fifth lens; r1-r14 are radii of curvature of successive surfaces of the elements in the direction from the screen end to the CRT end; d1-d13 are axial distances between the surfaces; n1-n8 are refractive indices with respect to e-line of the elements; ?1-?8 are Abbe numbers of the elements; K is a conic constant; AD, AE, AF, and AG
are coefficients of respective aspheric surfaces each being indicated by *.
Aspheric surface coefficients where: L1-L6, G and P denote the first through sixth lenses, the transparent medium and the face plate of the CRT, respectively, which are elements for constituting the pro-jection lens; FNO is F number; .beta. is a magnification factor of an projected enlarged image; .omega. is a semi-field angle; f4 is a focal length of the fourth lens; f5 is a focal length of the fifth lens; r1-r14 are radii of curvature of successive surfaces of the elements in the direction from the screen end to the CRT end; d1-d13 are axial distances between the surfaces; n1-n8 are refractive indices with respect to e-line of the elements; ?1-?8 are Abbe numbers of the elements; K is a conic constant; AD, AE, AF, and AG
are coefficients of respective aspheric surfaces each being indicated by *.
8. The projection lens according to claim 6, defined substantially as follows:
Aspheric surface coefficients where: L1-L6, G and P denote the first through sixth lenses, the transparent medium and the face plate of the CRT, respectively, which are elements for constituting the projection lens; FNO is F number; .beta. is a magnification factor of an projected enlarged image; .omega. is a semi-field angle; f4 is a focal length of the fourth lens; f5 is a focal length of the fifth lens; r1-r14 are radii of curvature of successive surfaces of the elements in the direction from the screen end to the CRT end; d1-d13 are axial distances between the surfaces; n1 - n8 are refractive indices with respect to e-line of the elements; ?1-?8 are Abbe numbers of the elements; K is a conic constant; AD, AE, AF and AG are coefficients of respective aspheric surfaces each being indicated by *.
Aspheric surface coefficients where: L1-L6, G and P denote the first through sixth lenses, the transparent medium and the face plate of the CRT, respectively, which are elements for constituting the projection lens; FNO is F number; .beta. is a magnification factor of an projected enlarged image; .omega. is a semi-field angle; f4 is a focal length of the fourth lens; f5 is a focal length of the fifth lens; r1-r14 are radii of curvature of successive surfaces of the elements in the direction from the screen end to the CRT end; d1-d13 are axial distances between the surfaces; n1 - n8 are refractive indices with respect to e-line of the elements; ?1-?8 are Abbe numbers of the elements; K is a conic constant; AD, AE, AF and AG are coefficients of respective aspheric surfaces each being indicated by *.
9. A high resolution projection lens for projecting on a screen an enlargement of an image of a resolution of more than 525 lines appearing on a high resolution cathode ray tube (CRT), comprising, successively in a direction from the screen end to the CRT end: a first lens of a positive optical power having a convex surface facing the screen;
a second lens of a positive optical power having a meniscus shape; a third lens of a negative optical power having bi-concave surfaces; a fourth lens of a positive optical power; a fifth lens of a positive optical power having bi-convex surfaces; and a sixth lens of a negative optical power having an aspheric concave surface facing the fifth lens.
a second lens of a positive optical power having a meniscus shape; a third lens of a negative optical power having bi-concave surfaces; a fourth lens of a positive optical power; a fifth lens of a positive optical power having bi-convex surfaces; and a sixth lens of a negative optical power having an aspheric concave surface facing the fifth lens.
10. The projection lens according to claim 9, satisfying the following condition:
2-5 ? fa/f ? 5 0.45 ? d8/d10 ? 1.0 ?2 ? 50 ?3 ? 38 where: f is a focal length of the overall lens system;
fa is a combined focal length of the first through third lenses; d8 is a distance between the fourth and fifth lenses; d10 is a distance between the fifth and sixth lenses; and ?2 and ?3 are respectively Abbe numbers of the second and third lenses.
2-5 ? fa/f ? 5 0.45 ? d8/d10 ? 1.0 ?2 ? 50 ?3 ? 38 where: f is a focal length of the overall lens system;
fa is a combined focal length of the first through third lenses; d8 is a distance between the fourth and fifth lenses; d10 is a distance between the fifth and sixth lenses; and ?2 and ?3 are respectively Abbe numbers of the second and third lenses.
11. The projection lens according to claim 10, further satisfying the following condition:
1.25 ? f4/f ? 1.8 0.5 ? f4/f5 ? 1.0 where f4 and f5 are focal lengths of the fourth and fifth lenses, respectively.
1.25 ? f4/f ? 1.8 0.5 ? f4/f5 ? 1.0 where f4 and f5 are focal lengths of the fourth and fifth lenses, respectively.
12. The projection lens according to claim 9, wherein the fifth lens has an aspheric surface.
13. The projection lens according to claim 9, wherein the fifth lens is a plastic lens.
14. The projection lens according to claim 9, wherein the sixth lens is a plastic lens.
15. The projection lens according to claim 9, wherein a space between the sixth lens and a face plate of the CRT
is filled with a transparent medium having a refractive index which is almost the same as that of each of the sixth lens and the face plate of the CRT.
is filled with a transparent medium having a refractive index which is almost the same as that of each of the sixth lens and the face plate of the CRT.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62002380A JP2506709B2 (en) | 1987-01-08 | 1987-01-08 | Projection lens for high definition TV |
| JP62-2380/1987 | 1987-01-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1306884C true CA1306884C (en) | 1992-09-01 |
Family
ID=11527630
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000556009A Expired - Lifetime CA1306884C (en) | 1987-01-08 | 1988-01-07 | Projection lens for high definition tv |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US4792218A (en) |
| JP (1) | JP2506709B2 (en) |
| CA (1) | CA1306884C (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02167514A (en) * | 1988-12-21 | 1990-06-27 | Konica Corp | Projection lens for projector |
| JPH0364716A (en) * | 1989-08-03 | 1991-03-20 | Pioneer Electron Corp | Projection lens for projection television |
| US4963007A (en) * | 1989-09-05 | 1990-10-16 | U.S. Precision Lens, Inc. | Color corrected projection lens |
| US5196957A (en) * | 1990-03-20 | 1993-03-23 | Olive Tree Technology, Inc. | Laser scanner with post-facet lens system |
| US5946142A (en) | 1995-12-11 | 1999-08-31 | Hitachi Ltd. | Projection lens system and projection image display apparatus using the same |
| US6008950A (en) * | 1997-01-30 | 1999-12-28 | Matsushita Electric Industrial Co., Ltd. | Projection lens |
| CN201974571U (en) * | 2011-01-27 | 2011-09-14 | 大立光电股份有限公司 | Image capturing lens assembly |
| US11262537B2 (en) * | 2017-02-17 | 2022-03-01 | Zhejiang Sunny Optical Co., Ltd | Camera lens assembly including six lenses each having refractive power |
| TWI656377B (en) | 2018-03-28 | 2019-04-11 | 大立光電股份有限公司 | Image taking optical lens, image taking device and electronic device |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3868173A (en) * | 1973-01-18 | 1975-02-25 | Ambatis Maris | Objective lens assembly for projection television |
| US3961844A (en) * | 1973-03-01 | 1976-06-08 | Optigon Research & Development Corporation | Lens |
| US4300817A (en) * | 1978-09-08 | 1981-11-17 | U.S. Precision Lens Incorporated | Projection lens |
| US4348081A (en) * | 1979-09-05 | 1982-09-07 | U.S. Precision Lens Inc. | Projection lens |
| JPS58125007A (en) * | 1982-01-20 | 1983-07-25 | Matsushita Electric Ind Co Ltd | Projection lens |
| JPS59155818A (en) * | 1983-02-25 | 1984-09-05 | Hitachi Ltd | Projection lens |
| JPS59170812A (en) * | 1983-03-18 | 1984-09-27 | Hitachi Ltd | Projection lens |
-
1987
- 1987-01-08 JP JP62002380A patent/JP2506709B2/en not_active Expired - Lifetime
- 1987-12-30 US US07/139,451 patent/US4792218A/en not_active Expired - Fee Related
-
1988
- 1988-01-07 CA CA000556009A patent/CA1306884C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JP2506709B2 (en) | 1996-06-12 |
| JPS63169610A (en) | 1988-07-13 |
| US4792218A (en) | 1988-12-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |