U.S. patent application number 09/793561 was filed with the patent office on 2002-01-24 for projection lens system and projection image display apparatus using the same.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Hirata, Koji, Mori, Shigeru, Nakagawa, Kazunari, Ogura, Naoyuki, Yoshida, Takahiro.
Application Number | 20020008918 09/793561 |
Document ID | / |
Family ID | 26461022 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020008918 |
Kind Code |
A1 |
Hirata, Koji ; et
al. |
January 24, 2002 |
Projection lens system and projection image display apparatus using
the same
Abstract
When a projection lens system used for a rear projection type
image display apparatus has a first lens group having an aspherical
lens surface, a second lens group, a third lens group sharing
almost all the positive refractive power of the overall system, a
fourth lens group having an aspherical lens surface, a fifth lens
group, and a sixth lens group including a lens having a profile of
aspherical surface in which the concave surface thereof faces the
screen side and the refractive power in the marginal area is weaker
than the refractive power around the optical axis, a projection
lens system having a large aperture ratio (low F-number), high
focus, wide field angle, and sufficient marginal light amount ratio
can be realized at a low cost. When a predetermined opening portion
is formed in the projection lens and lens barrel, the lens elements
are cooled by air suction and exhaust and the lowering of the lens
performance due to temperature change can be prevented. When a
flange is arranged in a suitable location of the opening portion,
entry of a foreign material from the opening portion and light
leakage from the inside are prevented and the contrast performance
of the projection type image display apparatus can be prevented
from lowering.
Inventors: |
Hirata, Koji; (Yokohama-shi,
JP) ; Ogura, Naoyuki; (Ebina-shi, JP) ; Mori,
Shigeru; (Chigasaki-shi, JP) ; Yoshida, Takahiro;
(Miura-shi, JP) ; Nakagawa, Kazunari; (Ebina-shi,
JP) |
Correspondence
Address: |
EVENSON, McKEOWN, EDWARDS & LENAHAN, P.L.L.C.
Suite 700
1200 G Street, N. W.
Washington
DC
20005
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
26461022 |
Appl. No.: |
09/793561 |
Filed: |
February 27, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09793561 |
Feb 27, 2001 |
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09495908 |
Feb 2, 2000 |
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6243211 |
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09495908 |
Feb 2, 2000 |
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09340198 |
Jun 28, 1999 |
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6046860 |
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09340198 |
Jun 28, 1999 |
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08764649 |
Dec 11, 1996 |
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5946142 |
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Current U.S.
Class: |
359/649 ;
348/E5.137; 359/648; 359/756; 359/759 |
Current CPC
Class: |
H04N 5/74 20130101; G02B
13/06 20130101 |
Class at
Publication: |
359/649 ;
359/648; 359/759; 359/756 |
International
Class: |
G02B 003/00; G02B
009/00; G02B 009/62 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 11, 1995 |
JP |
7-321430 |
May 20, 1996 |
JP |
8-124330 |
Claims
What is claimed is:
1. A projection lens system for enlarging and displaying an
original image displayed on an image generating source on a screen,
comprising a first lens group including a meniscus lens having
positive refractive power in which the profile of the central area
thereof is convex on the screen side, a second lens group including
a lens having weak positive refractive power in which the profile
of the central area thereof has a convex lens surface on the image
generating source side, a third lens group including a lens having
strong positive refractive power, a fourth lens group including a
lens having negative refractive power and a concave lens surface on
the screen side, a fifth lens group including a lens having weak
refractive power in which the profile of the central area thereof
has a convex lens surface on the image generating source side, and
a sixth lens group including a lens having a concave lens surface
on the screen side and negative refractive power sequentially from
the screen side.
2. A projection lens system according to claim 1, wherein said
first lens group and said second lens group have the following
relation of an axial distance between surfaces of lens L 12 to a
focal length f0 of the overall projection lens system:
(L12/f0)<0.25
3. A projection lens system according to claim 1, wherein said
first lens group, said second lens group, and said third lens group
have the following relation between said axial distance between
surfaces of lens L 12 of said first lens group and said second lens
group and an axial distance between surfaces of lens L 23 of said
second lens group and said third lens group: (L12/L23)>1.3
4. A projection lens system according to claim 1, wherein said
third lens group has the following relation between a radius of
curvature Ra3 of the lens surface of a lens having strongest
positive refractive power on the screen side among the lenses
thereof and a radius of curvature Rb3 of the lens surface on the
image generating source side: .vertline.Ra3.vertline.-
<.vertline.Rb3.vertline.
5. A projection lens system according to claim 1, wherein said
fourth lens group has the following relation between a radius of
curvature Ra4 of the lens surface of a lens having strongest
negative refractive power on the screen side among the lenses
thereof and a radius of curvature Rb4 of the lens surface on the
image generating source side: .vertline.Ra4.vertline.-
<.vertline.Rb4
6. A projection lens system according to claim 5, wherein said
fourth lens group uses a high dispersion material having an Abbe's
number d of 45 or less as a material of said lens having strongest
negative refractive power among the lenses thereof.
7. A projection lens system according to claim 5, wherein a
refractive index n3 of said lens having strongest positive
refractive power among the lenses constituting said third lens
group and a refractive index n4 of a lens closest to said third
lens group among the lenses constituting said fourth lens group are
almost equal to each other.
8. A projection lens system according to claim 1, wherein a
projection tube is used as said image generating source, and said
sixth lens group comprises a lens having lens surfaces with the
concave surface thereof facing the screen and negative refractive
power, a liquid coolant for cooling said projection tube, and
fluorescent face glass of said projection tube, and the center of
curvature of said fluorescent face glass exists on the screen
side.
9. A projection lens system for enlarging and displaying an
original image displayed on an image generating source on a screen,
comprising a first lens group including at least one meniscus lens
having positive refractive power in which the profile of the
central area thereof is convex on the screen side, a second lens
group including a lens having weak positive refractive power in
which the profile of the central area thereof has a convex lens
surface on the image generating source side, a third lens group
including a lens having strong positive refractive power, a fourth
lens group including a lens having negative refractive power and a
concave lens surface on the screen side, a fifth lens group
including a lens having weak refractive power in which the profile
of the central area thereof has a convex lens surface on the image
generating source side, and a sixth lens group including a lens
having a concave lens surface on the screen side and negative
refractive power sequentially from the screen side, wherein said
system satisfies the following conditions: 0.24<f0/f1<0.35,
0.0<f0/f2<0.18, 0.78<f0/f3<0.91, -0.20<f0/f4<0.0,
0.0<f0/f5<0.21, and -0.61<f0/f6<-0.55 where f.sub.0:
Focal length of overall projection lens system, f.sub.1: Focal
length of first lens group, f.sub.2: Focal length of second lens
group, f.sub.3: Focal length of third lens group, f.sub.4: Focal
length of fourth lens group, f.sub.5: Focal length of fifth lens
group, and f.sub.6: Focal length of sixth lens group.
10. A projection lens system according to claim 9, wherein said
first lens group and said second lens group have the following
relation of an axial distance between surfaces of lens L 12 to a
focal length f0 of the overall projection lens system:
(L12/f0)<0.25
11. A projection lens system according to claim 9, wherein said
first lens group, said second lens group, and said third lens group
have the following relation between said axial distance between
surfaces of lens L 12 of said first lens group and said second lens
group and an axial distance between surfaces of lens L 23 of said
second lens group and said third lens group: (L12/L23)>1.3
12. A projection lens system according to claim 9, wherein said
third lens group has the following relation between a radius of
curvature Ra3 of the lens surface of a lens having strongest
positive refractive power on the screen side among the lenses
thereof and a radius of curvature Rb3 of the lens surface on the
image generating source side: .vertline.Ra3.vertline.-
<.vertline.Rb3.vertline.
13. A projection lens system according to claim 9, wherein said
fourth lens group has the following relation between a radius of
curvature Ra4 of the lens surface of a lens having strongest
negative refractive power on the screen side among the lenses
thereof and a radius of curvature Rb4 of the lens surface on the
image generating source side:
.vertline.Ra4.vertline.<.vertline.Rb4.vertline.
14. A projection lens system according to claim 13, wherein said
fourth lens group uses a high dispersion material having an Abbe's
number d of 45 or less as a material of said lens having strongest
negative refractive power among the lenses thereof.
15. A projection lens system according to claim 13, wherein a
refractive index n3 of said lens having strongest positive
refractive power among the lenses constituting said third lens
group and a refractive index n4 of a lens closest to said third
lens group among the lenses constituting said fourth lens group are
almost equal to each other.
16. A projection lens system according to claim 9, wherein a
projection tube is used as said image generating source, and said
sixth lens group comprises a lens having lens surfaces with the
concave surface thereof facing the screen and negative refractive
power, a liquid coolant for cooling said projection tube, and
fluorescent face glass of said projection tube, and the center of
curvature of said fluorescent face glass exists on the screen
side.
17. A projection lens system for enlarging and displaying an
original image displayed on an image generating source on a screen,
comprising a first lens group including a lens having a surface in
which the central area thereof has a convex profile for the screen
and the profile gradually changes to a concave profile toward the
marginal area, a second lens group including a lens having a
surface in which the central area thereof has a convex profile for
the image generating source and the profile gradually changes to a
concave profile toward the marginal area, a third lens group
including a lens having positive refractive power, a fourth lens
group including a lens having negative refractive power and a
concave lens surface on the screen side, a fifth lens group
including at least one lens having positive refractive power in
which the central area thereof has a convex profile on the image
generating source side and the profile gradually changes to a
concave profile toward the marginal area, and a sixth lens group
including a lens having a concave lens surface on the screen side
and negative refractive power sequentially from the screen side,
wherein said system satisfies the following conditions:
0.24<f0/f1<0.35, 0.0<f0/f2<0.18, 0.78<f0/f3<0.91,
-0.20<f0/f4<0.0, 0.0<f0/f5<0.21, and
-0.61<f0/f6<-0.55 where f.sub.0: Focal length of overall
projection lens system, f.sub.1: Focal length of first lens group,
f.sub.2: Focal length of second lens group, f.sub.3: Focal length
of third lens group, f.sub.4: Focal length of fourth lens group,
f.sub.5: Focal length of fifth lens group, and f.sub.6: Focal
length of sixth lens group.
18. A projection lens system according to claim 17, wherein said
first lens group includes a lens having the following relation of
the aspherical surface amount of the lens surface on the screen
side to the spherical surface amount: (As/Ss)>-0.1 where As:
aspherical sag amount, and Ss: spherical sag amount.
19. A projection lens system according to claim 17, wherein said
fourth lens group includes a lens having the following relation of
the aspherical surface amount of the lens surface on the image
generating source side to the spherical surface amount:
(As/Ss)>-21.2 where As: aspherical sag amount, and Ss: spherical
sag amount.
20. A projection lens system according to claim 17, wherein said
fifth lens group includes a lens having the following relation of
the aspherical surface amount of the lens surface on the image
generating source side to the spherical surface amount:
(As/Ss)<-0.6 where As: aspherical sag amount, and Ss: spherical
sag amount.
21. A projection lens system according to claim 17, wherein said
sixth lens group includes a lens having the following relation of
the aspherical surface amount of the lens surface on the screen
side to the spherical surface amount: (As/Ss)<1.1 where As:
aspherical sag amount, and Ss: spherical sag amount.
22. A projection lens system according to claim 17, wherein said
fourth lens group is structured so that the lens surface of a lens
having strongest negative refractive power on the screen side among
the lenses thereof has a concave lens profile on the screen side,
and so that the central area of the lens surface on the image
generating source side has a concave lens profile on the image
generating source side, and so that the marginal area of the lens
surface has a convex lens profile on the image generating source
side and so that a radius of curvature Ra4 of the lens surface on
the screen side and a radius of curvature Rb4 of the lens surface
on the image generating source side have the following relation:
.vertline.Ra4.vertline.<.vertline.Rb4.vertline.
23. A projection lens system according to claim 22, wherein said
fourth lens group uses a high dispersion material having an Abbe's
number d of 45 or less as a material of said lens having strongest
negative refractive power among the lenses thereof.
24. A projection lens system according to claim 17, wherein a
refractive index n3 of said lens having strongest positive
refractive power among the lenses constituting said third lens
group and a refractive index n4 of a lens closest to said third
group among the lenses constituting said fourth lens group are
almost equal to each other.
25. A projection lens system according to claim 17, wherein said
first lens group and said second lens group have the following
relation of an axial distance between surfaces of lens L 12 to a
focal length f0 of the overall projection lens system:
(L12/f0)<0.25
26. A projection lens system according to claim 17, wherein said
first lens group, said second lens group, and said third lens group
have the following relation between said axial distance between
surfaces of lens L 12 of said first lens group and said second lens
group and an axial distance between surfaces of lens L 23 of said
second lens group and said third lens group: (L12/L23)>1.3
27. A projection lens system according to claim 17, wherein a
projection tube is used as said image generating source, and said
sixth lens group comprises a lens having a concave surface on the
screen side and negative refractive power, a liquid coolant for
cooling said projection tube, and fluorescent face glass of said
projection tube, and the center of curvature of said fluorescent
face glass exists on the screen side.
28. A projection lens system according to claim 17, wherein at
least one surface of the lenses constituting said first lens group,
said second lens group, said fourth lens group, said fifth lens
group, and said sixth lens group is an aspherical surface.
29. A projection lens system according to claim 28, wherein said
first lens group includes a lens having the following relation of
the aspherical surface amount of the lens surface on the screen
side to the spherical surface amount: (As/Ss)>-0.1 where As:
aspherical sag amount, and Ss: spherical sag amount.
30. A projection lens system according to claim 28, wherein said
fourth lens group includes a lens having the following relation of
the aspherical surface amount of the lens surface on the image
generating source side to the spherical surface amount:
(As/Ss)>-21.2 where As: aspherical sag amount, and Ss: spherical
sag amount.
31. A projection lens system according to claim 28, wherein said
fifth lens group includes a lens having the following relation of
the aspherical surface amount of the lens surface on the image
generating source side to the spherical surface amount:
(As/Ss)<-0.6 where As: aspherical sag amount, and Ss: spherical
sag amount.
32. A projection lens system according to claim 28, wherein said
sixth lens group includes a lens having the following relation of
the aspherical surface amount of the lens surface on the screen
side to the spherical surface amount: (As/Ss)<1.1 where As:
aspherical sag amount, and Ss: spherical sag amount.
33. A projection lens system according to claim 28, wherein said
fourth lens group is structured so that the lens surface of a lens
having strongest negative refractive power on the screen side among
the lenses thereof has a concave lens profile on the screen side,
and so that the central area of the lens surface on the image
generating source side has a concave lens profile on the image
generating source side, and so that the marginal area of the lens
surface has a convex lens profile on the image generating source
side and so that a radius of curvature Ra4 of the lens surface on
the screen side and so that a radius of curvature Rb4 of the lens
surface on the image generating source side have the following
relation: .vertline.Ra4.vertline.<.vertline.Rb4.vertline.
34. A projection lens system according to claim 33, wherein said
fourth lens group uses a high dispersion material having an Abbe's
number d of 45 or less as a material of said lens having strongest
negative refractive power among the lenses thereof.
35. A projection lens system according to claim 28, wherein a
refractive index n3 of said lens having strongest positive
refractive power among the lenses constituting said third lens
group and a refractive index n4 of a lens closest to said third
group among the lenses constituting said fourth lens group are
almost equal to each other.
36. A projection lens system according to claim 28, wherein said
first lens group and said second lens group have the following
relation of an axial distance between surfaces of lens L 12 to a
focal length f0 of the overall projection lens system:
(L12/f0)<0.25
37. A projection lens system according to claim 28, wherein said
first lens group, said second lens group, and said third lens group
have the following relation between said axial distance between
surfaces of lens L 12 of said first lens group and said second lens
group and an axial distance between surfaces of lens L 23 of said
second lens group and said third lens group: (L12/L23)>1.3
38. A projection lens system according to claim 28, wherein a
projection tube is used as said image generating source, and said
sixth lens group comprises a lens having a concave surface on the
screen side and negative refractive power, a liquid coolant for
cooling said projection tube, and fluorescent face glass of said
projection tube, and the center of curvature of said fluorescent
face glass exists on the screen side.
39. A projection lens system for enlarging and displaying an
original image displayed on an image generating source on a screen,
comprising a lens (first lens) having positive refractive power, an
aberration correction lens (second lens), and a lens (third lens)
having a lens surface with the concave surface thereof facing the
screen side and negative refractive power, wherein said third lens
has a surface profile which is expressed by a function Z(r) of a
distance (r) from the optical axis of said projection lens system
and is symmetrical with said optical axis and said function has a
point of inflection.
40. A projection lens system according to claim 39, wherein said
image generating source comprises a projection tube in which the
center of curvature of fluorescent face glass exists on the screen
side.
41. A projection lens system for enlarging and displaying an
original image displayed on the fluorescent face of a projection
tube on a screen, comprising a first lens group including a
meniscus lens having positive refractive power in which the profile
of the central area thereof is convex on the screen side, a second
lens group including a lens having positive refractive power in
which the profile of the central area thereof has a convex lens
surface on the projection tube side, a third lens group including a
lens having positive refractive power, a fourth lens group
including a lens having negative refractive power and a concave
lens surface on the screen side, a fifth lens group including a
lens having positive refractive power in which the profile of the
central area thereof has a convex lens surface on the projection
tube side, and a sixth lens group including a lens having a lens
surfaces with the concave surface thereof facing the screen side
and negative refractive power in which said lens surface on the
screen side has a surface profile which is expressed by a function
Z(r) of a distance (r) from the optical axis of said projection
lens system and is symmetrical with said optical axis and said
function has a point of inflection and having a liquid coolant for
cooling said projection tube and fluorescent face glass of said
projection tube sequentially from the screen side.
42. A projection lens system according to claim 41, wherein said
image generating source comprises the center of curvature of
fluorescent face glass of said projection tube exists on the screen
side.
43. A projection lens system for enlarging and displaying an
original image displayed on an image generating source on a screen,
comprising a lens (first lens) having positive refractive power, an
aberration correction lens (second lens), and a lens (third lens)
having a concave lens surface on the screen side and negative
refractive power, wherein said third lens has a surface profile
which is expressed by a function Z(r) of a distance (r) from the
optical axis of said projection lens system and is symmetrical with
said optical axis, and the absolute value of a value obtained by
substituting said distance from said optical axis in a second
derivative obtained by differentiating said function quadratically
changes with said distance from said optical axis, and said change
is an increase in an area from the neighborhood of said optical
axis to the central area and is a decrease in an area from the
central area to the effective radius of lens.
44. A projection lens system according to claim 43, wherein said
image generating source comprises a projection tube in which the
center of curvature of fluorescent face glass exists on the screen
side.
45. A projection lens system for enlarging and displaying an
original image displayed on the fluorescent face of a projection
tube on a screen, comprising a first lens group including a
meniscus lens having positive refractive power in which the profile
of the central area thereof is convex on the screen side, a second
lens group including a lens having a lens surface in which the
profile of the central area thereof is convex on the projection
tube side, a third lens group including a lens having positive
refractive power, a fourth lens group including a lens having
negative refractive power and a concave lens surface on the screen
side, a fifth lens group including a lens having positive
refractive power in which the profile of the central area thereof
has a convex lens surface on the projection tube side, and a sixth
lens group including a lens having negative refractive power and a
concave lens surface on the screen side which has a surface profile
which is expressed by a function Z(r) of a distance (r) from the
optical axis of said projection lens system and is symmetrical with
said optical axis and is a profile that the absolute value of a
value obtained by substituting said distance from said optical axis
in a second derivative obtained by differentiating said function
quadratically changes with said distance from said optical axis and
said change is an increase in an area from the neighborhood of said
optical axis to the central area and is a decrease in an area from
the central area to the effective radius of lens and having a
liquid coolant for cooling said projection tube and fluorescent
face glass of said projection tube sequentially from the screen
side.
46. A projection lens system according to claim 45, wherein the
center of curvature of fluorescent face glass of said projection
tube exists on the screen side.
47. A rear projection type image display apparatus including a
projection lens system according to claim 1 in front of said image
generating source, wherein a transmission type screen is arranged
on a focusing plane in front of said projection lens system.
48. A rear projection type image display apparatus according to
claim 47, wherein between a distance L (mm) from the lens surface
of a lens positioned on the screen side among the lenses of said
first lens group constituting said projection lens system on the
screen side to said transmission type screen and a diagonal
effective size M (inch) of said transmission type screen, the
following relation is held: 17.3<(L/M)<17.6
49. A projection lens system for enlarging and displaying an
original image displayed on an image generating source on a screen,
wherein said projection lens system comprises a plurality of lens
elements, a lens element holding member for holding at least one
lens element among said plurality of lens elements and covering the
spaces among said lens element, and a connection member for
connecting said lens holding member to said image generating source
and also includes at least one communicating opening or
communicating window connecting to the outside of said projection
lens system from said spaces between said lens elements.
50. A projection lens system according to claim 49, wherein in at
least one space among said spaces between said lens elements, said
communicating opening or communicating window is arranged
individually in each of at least two leveling locations practically
on the basis of the horizontal plane in the operation status of
said projection lens system or continuously over said
locations.
51. A projection lens system according to claim 49, wherein at
least one communicating opening or communicating window among said
communicating openings or communicating windows is arranged as a
space surrounded by at least said lens element holding member and
said connection member around the connection point of said lens
element holding member and said connection member.
52. A projection lens system according to claim 51, wherein said
space surrounded by said lens element holding member and said
connection member is structured so that the space volume thereof is
restricted by the size of a protrusion provided in said lens
element holding member or a protrusion provided in said connection
member.
53. A projection lens system according to claim 49, wherein at
least one communicating opening or communicating window among said
communicating openings or communicating windows is arranged in said
lens element holding member.
54. A projection lens system according to claim 49, wherein said
lens element holding member comprises at least a first holding
member for holding at least one lens element among said plurality
of lens elements and a second holding member for fitting and
holding said first holding member and at least one communicating
opening or communicating window among said communicating openings
or communicating windows is arranged between said first holding
member and said second holding member of said lens element holding
member.
55. A projection lens system according to claim 54, wherein at
least one groove provided in a concave shape on the inner side of
said second holding member is said communicating opening or
communicating window.
56. A projection lens system according to claim, 49, wherein at
least one communicating opening or communicating window among said
communicating openings or communicating windows is arranged around
the periphery of said lens element.
57. A projection lens system according to claim 49, wherein in at
least one communicating opening or communicating window among said
communicating openings or communicating windows, a dust-proof
member is arranged in the opening portion thereof toward the
outside of said projection lens system.
58. A projection lens system according to claim 49, wherein at
least one communicating opening or communicating window among said
communicating openings or communicating windows has a bent, or
curved, or twisted profile.
59. A projection lens system according to claim 49, wherein said
space between said lens elements to which at least one said
communicating opening or communicating window is connected is a
space between a lens element arranged closest to said image
generating source and a lens element second closest to said image
generating source.
60. A projection lens system according to claim 49, wherein a lens
element arranged closest to said image generating source among said
plurality of lens elements constitutes a lens group by combining a
transparent medium on the image display surface of said image
generating source and a transparent liquid filled up in a space
between said lens element arranged closest to said image generating
source and said transparent medium.
61. A projection lens system according to claim 60, wherein said
transparent medium on said image display surface of said image
generating source is a face panel of a projection type cathode ray
tube.
62. A rear projection type image display apparatus wherein a
projection lens system according to claim 49 is arranged in front
of said image generating source and a transmission type screen is
arranged on a focusing plane in front of said projection lens
system.
63. A rear projection type image display apparatus according to
claim 62, wherein said image generating source is a projection type
cathode ray tube.
64. A rear projection type image display apparatus according to
claim 62, wherein said image generating source is a liquid crystal
panel.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a projection lens system
and particularly to a projection lens system with a wide field
angle which provides a bright image having an excellent focus
performance even in the marginal area, uses an inexpensive glass
material, and has a short projection distance and a projection
image display apparatus using the system which is excellent in cost
performance.
[0002] Recently, a television set as an image display apparatus for
home use is proceeding to a larger screen size as the wide aspect
ratio increases. As an image display apparatus for home use, there
are two types available such as a direct view type using a cathode
ray tube and a so-called projection type for enlarging and
projecting an image on a miniature projection tube, whose screen
size is about 7 inch of diagonal on the screen by a projection lens
system. However, due to restrictions to compactness and weight of a
TV set, for a screen size of more than about 37 inch of diagonal, a
projection image display apparatus is mainly used.
[0003] At first, this projection image display apparatus was
inferior to the direct view type in screen brightness and focus
performance. However, recently, the performance of each of the
components such as the projection lens system, screen, and
projection tube is improved, so that both the screen brightness and
focus performance are approaching those of the direct view type. In
the performance improvement process of the projection image display
apparatus, various arts have been developed in the projection lens
system which is a key device. Firstly, at the first step of
development, to obtain screen brightness equivalent to that of the
direct view type or higher, as disclosed in U.S. Pat. No.
4,682,862, reduction of the F-number has been tried by using many
plastic aspherical lens elements.
[0004] Next, at the second step, a projection lens system for
realizing improvement of screen brightness and improvement of focus
performance at the same time has been developed. With respect to
this projection lens system, as disclosed in Japanese Patent
Application Laid-Open No. 3-137610, there is an example using a
plastic aspherical lens and a doublet glass lens. As a result, in
the current projection TV set, a projection lens system having an
F-number of about f/1.1 is used and both brightness and focus
performance are improved on the whole screen.
[0005] At the third step, a projection lens system with a wide
field angle by which a compact set dimension can be realized on
account of the short projection distance has been developed mainly.
A reference describing an actual art for realizing a projection
lens system with a wide field angle without reducing the brightness
and focus performance in the marginal area and an actual projection
lens system is disclosed in Japanese Patent Application Laid-Open
No. 4- 5608. Hereinafter, the art disclosed in this patent is
referred to as a first prior art.
[0006] In this first prior art, by combining plastic aspherical
lens elements and glass lens elements effectively in a projection
lens system of six lens groups, the aforementioned problem is
solved. Furthermore, the projection lens system is structured so
that almost all the positive refractive power of the projection
lens system is shared by the glass lenses and the plastic
aspherical lens elements have little refractive power, so that the
peculiar drift of the focus performance due to a temperature change
is reduced even if the plastic aspherical lens elements are used is
reduced.
[0007] In this first prior art, the profile of the fluorescent face
of projection tube has a curvature so that it is convex on the
electron gun side. As a result, the projection lens system is
structured so that the normal of the fluorescent face in the
marginal area is in the direction of the entrance pupil of the
projection lens system and can fetch more light fluxes in
comparison with the case using a flat fluorescent face. Therefore,
even if the field angle is widened, a relative illuminance of a
level which is almost no problem practically can be obtained in the
marginal area.
[0008] The curvature of field is corrected by the lens element of
the sixth lens group (hereinafter referred to as sixth lens).
However, if the fluorescent face of projection tube has a curvature
so that it is convex on the electron gun side, the generation
amount of curvature of field is reduced and the focus performance
in the marginal area is improved.
[0009] Furthermore, a projection lens system with a wide field
angle which realizes a more excellent focus performance without
reducing the brightness in the marginal area and an actual art for
realizing it are disclosed in U.S. Pat. No. 5,272,540. Hereinafter,
the art is referred to as a second prior art.
[0010] In the second prior art, a projection lens system having a
constitution of five groups by six elements is disclosed and the
profile of the fluorescent face of projection tube which is an
object is an aspherical profile which is convex on the electron gun
side. And has when the curvature of the profile in the marginal
area is smaller than that in the neighborhood of the optical axis.
By doing this, highly precise correction of the curvature of field
and astigmatism are compatible with each other and the satisfactory
focus performance and the light amount which is practically
sufficient are reserved in the marginal area of screen.
[0011] In this projection lens system, the lens element of the
third lens group (hereinafter referred to as third lens) sharing
almost all refractive power of the overall lens system has a
constitution that a concave lens of large dispersion glass and a
convex lens of small dispersion glass are stuck together, and the
chromatic aberration is corrected, and the large aperture (the
F-number is 0.96) and the high focus performance are compatible
with each other. Furthermore, it is structured that combination of
the lens element of the first lens group (hereinafter referred to
as first lens) and the lens element of the second lens group
(hereinafter referred to as second lens) offsets the lowering of
the focus performance generated by deformation and expansion of
each lens element due to temperature change and humidity change
which is an intrinsic problem when plastic lens elements are
used.
[0012] On the other hand, in a conventional projection lens system,
as a lens barrel for assembling each lens element with high
precision, a lens barrel having the constitution disclosed in, for
example, Japanese Utility Model Application Laid- Open No. 2-51478
is often used. The lens barrel of the prior art has an outer barrel
and an inner barrel which is installed inside the outer barrel and
can slide in the direction of optical axis of the lens without
axial shift. The inner barrel has a constitution that it can be
divided into two parts longitudinally in the direction of diameter
of the lens along the optical axis of the lens and it has slits for
holding a plurality of lens elements at predetermined intervals
with high precision on its inner surface.
[0013] In the aforementioned projection lens system having a
constitution of six lens groups of the first prior art, there are
several problems to be solved.
[0014] The first problem is a problem caused by the lens
constitution. In the aforementioned projection lens system, the
third lens having negative refractive power is arranged on the
screen side of the lens element of the fourth lens group
(hereinafter referred to as fourth lens) sharing almost all the
positive refractive power of the overall lens system. The spherical
aberration and coma aberration are corrected by the third lens.
[0015] Therefore, the location of the entrance pupil of the overall
lens system moves to the screen side from the center of the fourth
lens. As a result, if an attempt is made to realize a wider field
angle (reduction of the projection distance) in the aforementioned
lens constitution, correction of the distortion and astigmatism
becomes difficult.
[0016] Next, the second problem is a point that if an attempt is
made to reduce the F-number or (increase the aperture ratio) of the
projection lens system having this lens constitution and obtain a
sufficient marginal light amount ratio, the apertures of the first,
second, and third lenses become larger and the production cost
increases.
[0017] The share of correction of each lens group in aberration
correction of the aforementioned projection lens system is shown
below.
[0018] The first lens is a spherical lens element of a meniscus
profile having positive refractive power and corrects spherical
aberration and coma aberration.
[0019] The second lens is a plastic aspherical lens element of a
meniscus profile having weak positive refractive power and corrects
spherical aberration and coma aberration.
[0020] The third lens is a spherical lens element having a weak
divergent action and corrects spherical aberration and coma
aberration.
[0021] The fourth lens is a convex-convex glass spherical lens
element having a strong convergent action.
[0022] Furthermore, the lens element of the fifth lens group
(hereinafter referred to as fifth lens) is a plastic aspherical
lens element of a meniscus profile having weak positive refractive
power and corrects astigmatism, distortion, and coma
aberration.
[0023] The sixth lens has a constitution that it has a concave
surface facing the screen side, has negative refractive power
accompanied by a liquid coolant (A), and corrects curvature of
field.
[0024] Among them, the second lens and fifth lens are a plastic
aspherical lens element and have a meniscus profile having weak
positive refractive power respectively. This projection lens system
of prior art has a constitution that each plastic lens element has
little refractive power and the peculiar shift of the focus
performance due to a temperature change when the plastic aspherical
lens element is used is reduced.
[0025] There is a third problem imposed that as mentioned above, in
the projection lens system using the first prior art, the
applicable lens profile of the plastic aspherical lens is limited
to a specific profile and that the aberration correction cannot be
attained sufficiently.
[0026] A fourth problem is also imposed that since four glass lens
elements are included, the cost is increased.
[0027] Furthermore, the aspherical surface amount of the fifth lens
is little, and the sixth lens is a glass lens element, whereof the
lens surface on the screen side is a spherical surface; so that
correction of astigmatism and correction of curvature of field are
not compatible with each other.
[0028] Therefore, a fifth problem arises that correction of
astigmatism in the marginal area is difficult.
[0029] In the first prior art, it is a subject (of the design) to
solve these problems.
[0030] A problem of the projection lens system having a
constitution of five groups by six elements to be solved in the
second prior art is reduction in cost.
[0031] The two factors for an increase in the cost of the
projection lens system are described below.
[0032] The first factor for an increase in cost is the profile of
fluorescent face of the projection tube. The main profile of
fluorescent face of the projection tube is a spherical fluorescent
face at present. When this projection lens system is applied, it is
necessary to make the profile of fluorescent face aspherical and
the projection tube is to be produced under a special
specification, so that it is a factor for an increase in the cost
of the set.
[0033] The second factor for an increase in cost is that it is
essential to use a doublet lens comprising a large dispersion
concave lens with a large diameter and a small dispersion convex
lens with a large diameter which are stuck together for the third
lens so as to realize a large aperture ratio (the F-number is 0.96)
in this projection lens system and correct chromatic aberration
satisfactorily.
[0034] Generally, the price of optical glass increases as the
refractive index increases and as the dispersion decreases. In the
second prior art, the optical glass used as a third lens of the
projection lens system described in Embodiment 1 includes large
dispersion glass of SF11 and small dispersion glass of SK16. The
prices of these optical glass materials are more than 2 times as
expensive as the price of SK5 which is a typical one of optical
glass used in the projection lens system such that the price is 2.3
for SF11 and is 2.1 for SK16 (those glass names are abbreviations
of Schott, Ltd. and often used in this field).
[0035] On the other hand, a problem when the aforementioned
conventional lens barrel is used in the projection lens system is
that the air temperature in the sealed space inside the lens barrel
and the temperature of the lens elements rise, and the heated lens
elements expands and deforms, and the focus performance of the
projection lens system is lowered extremely.
[0036] As a result, it is a subject (of the design) to suppress
rising of the air temperature in the sealed space inside the lens
barrel and the temperature of the lens elements and to prevent the
lens elements from expansion and deformation even if the heat
generated from an image generating source is high.
SUMMARY OF THE INVENTION
[0037] An object of the present invention is to solve the problems
of the projection lens system of the prior art mentioned above and
to provide a projection lens system of a wide field angle which
uses inexpensive optical glass, has an excellent focus performance
even in the marginal area even if the heat generated from an image
generating source is high, obtains a bright image, and has a short
projection distance and a projection image display apparatus using
the system which is excellent in cost performance.
[0038] To accomplish the above object, the projection lens system
of the present invention uses technical means as described
below.
[0039] Firstly, to solve the first and second problems of the first
prior art, almost all the positive refractive power of the overall
lens system is shared by the glass lens elements (hereinafter
described as glass power lens). In this case, a lens having
negative refractive power is not arranged on the screen side of the
lens group including the glass power lens but a plastic aspherical
lens element having weak positive refractive power around the
optical axis is arranged there. As a result, the entrance pupil
does not move to the screen side from the glass power lens, so that
the first problem can be solved and a projection lens system with a
wide field angle can be realized.
[0040] Furthermore, a light flux passing through the lens group
including the glass power lens diverges and enters the lens groups
positioned on the screen side, so that the aperture of each of lens
groups can be made as small as possible and the second problem can
be solved.
[0041] In the projection lens system of the present invention, to
minimize the lowering of the focus performance due to temperature
and humidity changes, the refractive power of the plastic
aspherical lens element around the optical axis is reduced to 30%
of that of the glass power lens or less.
[0042] The aberration depending on the aperture is corrected
according to the profile of lens surface including aspherical
system in the area (the marginal area of the lens element) apart
from the optical axis. The system is structured so that the drift
of the local refractive power obtained according to the profile of
lens surface including aspherical system in the marginal area of
the lens due to temperature and humidity changes is offset by
combining a plurality of plastic aspherical lens elements. By doing
this, the profile of lens element can be decided without affecting
aberration correction restrictively and the third problem can be
solved.
[0043] Many plastic aspherical lens elements having a lens surface
including strong aspherical system can be used by the
aforementioned technical means, so that the number of glass lens
elements can be reduced and the fourth problem can be solved.
[0044] To solve the fifth problem, a lens element having negative
refractive power with the concave surface facing the screen side is
arranged in the location closest to the projection tube which is an
image light source, and the lens surface of the lens element on the
screen side is formed as an aspherical shape, and hence the
astigmatism in the marginal area of the image is reduced.
Furthermore, with respect to the lens element arranged on the
screen side of this lens element, the profile of lens surface on
the projection tube side is formed in a convex shape on the
projection tube side around the optical axis and a concave shape on
the projection tube side in the marginal area and hence the
astigmatism in the marginal area of the image can be reduced with
higher precision.
[0045] To realize a reduction in cost which is a problem of the
projection lens system having the constitution in the second prior
art, the two following means are used.
[0046] The first means is to form the fluorescent face of a
projection tube to be applied to the projection lens system as a
spherical fluorescent face. When the fluorescent face of the
projection lens system heaving a constitution of five group by six
elements described in the first embodiment of the second prior art
is changed to a spherical surface as it is, the length of optical
path from an object point in the marginal area on the fluorescent
face to the exit surface of the fifth lens is different between a
beam of light passing through the saggital plane and a beam of
light passing through the meridional plane, so that a great
difference is generated in the focus performance between the
saggital direction and the meridional direction because astigmatism
conspicuously increases in the marginal area. This trend is
specially remarkable in the marginal area between 90% of the
distance (relative image height from center to corner) from the
center of the screen to each corner and each corner.
[0047] Therefore, according to the present invention, when the lens
surface of the sixth lens having negative refractive power on the
screen side is formed in a profile that the lens action (divergent
action) in the lens area through which the light flux from an
object in the marginal area on the fluorescent face becomes weaker
in comparison with that around the optical axis of the lens, the
difference between the length of optical path on the saggital plane
and that on the meridional plane is reduced. Furthermore, when in
the lens element arranged on the screen side of the above-mentioned
lens element having negative refractive power, the profile of lens
surface on the projection tube side is formed in a convex shape on
the projection tube side around the optical axis and in a concave
shape on the projection tube side in the marginal area, the
difference of length of optical path can be made smaller and the
astigmatism in the marginal area can be reduced remarkably.
[0048] The second means is to change the third lens to inexpensive
optical glass.
[0049] For that purpose, correction of chromatic aberration is
realized by a large dispersion plastic concave lens element and an
inexpensive small dispersion glass convex lens.
[0050] It is also effective to install a filter for cutting the
spurious component other than the dominant wavelength component
among the light emission spectrum of a phosphorescent substance in
at least one lens element of the lenses constituting the projection
lens system and reduce the generated chromatic aberration
itself.
[0051] Furthermore, to realize a large aperture, the aforementioned
large dispersion plastic concave lens element is formed in a
profile of strong aspherical shape and the aberration is corrected
with higher precision. Furthermore, the lens profile is formed in a
concave meniscus profile in which the concave surface faces the
screen side around the optical axis and particularly in a profile
that with respect to the lens surface on the projection tube side,
the inclination of the lens surface in the marginal area of lens
apart from the optical axis is increased. As a result, the entrance
height of light flux into the third lens (glass) can be decreased
and the diameter of the third lens (glass) can be made smaller when
the same F-number is to be obtained, so that the cost can be
reduced.
[0052] On the other hand, the projection lens system of the present
invention is structured so that at least one communicating opening
or communicating window extending outside of the projection lens
system from the spaces between the lens elements is installed.
[0053] Furthermore, at least one space among the spaces between the
lens elements is structured so that the communicating opening or
communicating window is arranged individually in each of at least
two leveling locations practically on the basis of the horizontal
plane in the operation status of the projection lens system or
continuously over those locations. In this case, the communicating
opening or communicating window in the low location functions as an
inlet of air and the communicating opening or communicating window
in the high location functions as an outlet of air.
[0054] To install the communicating opening or communicating
window, one of the methods (1) to (4) shown below is used or these
methods are used together.
[0055] (1) Around the connection point of a lens element holding
member for holding at least one lens element and covering the
spaces among the lens elements and a connection member for
connecting the lens element holding member to the image generating
source, a communicating opening or communicating window is arranged
as a space surrounded by at least the lens element holding member
and the connection member. In this case, it is possible that the
volume of this space is restricted by the size of protrusion
provided in the lens element holding member or the size of
protrusion provided in the connection member.
[0056] (2) A communicating opening or communicating window is
arranged in the lens element holding member itself.
[0057] (3) A lens element holding member comprising a first holding
member for holding at least one lens element and a second holding
member for fitting and holding the first holding member is
structured and a communicating opening or communicating window is
arranged between the first holding member and the second holding
member. In this case, at lease one groove provided in a concave
shape on the inner side of the second holding member may be
functioned as a communicating opening or communicating window.
[0058] (4) A communicating opening or communicating window is
arranged around the periphery of the lens element.
[0059] When a communicating opening or communicating window is
arranged by one of the aforementioned methods, it is desirable to
set the space between the lens element arranged closest to the
image generating source among a plurality of lens elements and the
lens element second closest to the image generating source as a
corresponding space.
[0060] The aforementioned communicating opening or communicating
window is arranged so as to replace heated air in the spaces among
the lens elements with air outside the projection lens system. In
this case, new problems may arise that a foreign material such as
dust enters from the communicating opening or communicating window
and adheres to the lens elements, or an external light enters the
projection lens system and the image contrast performance of the
projection lens system is lowered, or when the projection lens
system is used in a projection type image display apparatus, the
image contrast performance of the projection type image display
apparatus is remarkably lowered due to light leakage from the
inside of the projection lens system.
[0061] To eliminate the problems, in the aforementioned projection
lens system, in the opening portion of the communicating opening or
communicating window toward the outside of the projection lens
system, a dust-proof member, for example, a flange-shaped member is
arranged in the way to protect the air permeability. Or, the
communicating opening or communicating window itself is formed in a
bent, or curved, or twisted shape.
[0062] In the projection lens system of the present invention, the
aforementioned communicating opening or communicating window
functions as an air inlet through which air at a low temperature
(open air) is introduced and an air outlet through which heated air
is ejected in the space among the lens elements in which the
communicating opening or communicating window is provided. By doing
this, the efficiency of heat radiation from the lens elements is
increased by convection of air and the lens elements are suppressed
in rising of temperature and hence the expansion and deformation
due to rising of temperature are suppressed and as a result, the
lens performance, particularly the focus performance are prevented
from lowering.
[0063] When a projection type cathode ray tube is used as an image
generating source, the projection type cathode ray tube becomes a
heat generating source. Therefore, when the aforementioned
communicating opening or communicating window is provided in the
space between the lens element closest to the projection type
cathode ray tube and the lens element second closest to it, the
effect of the aforementioned action is remarkable. Air has a
property that when it is heated, the specific gravity thereof
decreases and it flows upward. Therefore, when the height of
location of the communicating opening or communicating window which
is used as an air outlet is set higher than the height of location
of the communicating opening or communicating window which is used
as an air inlet on the basis of a certain horizontal plane, a
practically sufficient effect can be obtained in the aforementioned
action.
[0064] On the other hand, when a dust-proof member is arranged in
the opening portion of the communicating opening or communicating
window toward the outside of the projection lens system when the
communicating opening or communicating window itself is formed in a
bent, or curved, or twisted shape, entry of a foreign material or
light into the projection lens system and light leakage from the
inside of the projection lens system can be prevented. As a result,
the contrast performance of the projection lens system itself will
not be lowered and neither will be readuced the image contrast of
the projection type image display apparatus using the projection
lens system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0065] FIG. 1 is a cross sectional view showing the essential
section of an embodiment of the projection lens system of the
present invention;
[0066] FIG. 2 is a cross sectional view showing the arrangement of
lens elements and outline of the ray tracing result in Embodiment 1
of the projection lens system of the present invention;
[0067] FIG. 3 is a cross sectional view showing the arrangement of
lens elements and outline of the ray tracing result in Embodiment 7
of the projection lens system of the present invention;
[0068] FIG. 4 is a cross sectional view showing the arrangement of
lens elements and outline of the ray tracing result in Embodiment
10 of the projection lens system of the present invention;
[0069] FIG. 5 is a drawing showing the definition of the axes of
coordinates in the equation of the profile of lens surface;
[0070] FIG. 6 is an illustration for explaining differences between
the aspherical surface and the spherical surface;
[0071] FIG. 7 is a characteristic diagram showing second derivative
values of the function indicating the aspherical surface profile of
the lens surface of the sixth lens 6 on the screen side;
[0072] FIG. 8 is a characteristic diagram showing a deviation of
the aspherical surface profile of the lens surface of the sixth
lens 6 on the screen side from the spherical surface profile;
[0073] FIG. 9 is an MTF characteristic diagram showing the focus
performance of Embodiment 1 of the projection lens system of the
present invention;
[0074] FIG. 10 is an MTF characteristic diagram showing the focus
performance of Embodiment 2 of the projection lens system of the
present invention;
[0075] FIG. 11 is an MTF characteristic diagram showing the focus
performance of Embodiment 3 of the projection lens system of the
present invention;
[0076] FIG. 12 is an MTF characteristic diagram showing the focus
performance of Embodiment 4 of the projection lens system of the
present invention;
[0077] FIG. 13 is an MTF characteristic diagram showing the focus
performance of Embodiment 5 of the projection lens system of the
present invention;
[0078] FIG. 14 is an MTF characteristic diagram showing the focus
performance of Embodiment 6 of the projection lens system of the
present invention;
[0079] FIG. 15 is an MTF characteristic diagram showing the focus
performance of Embodiment 7 of the projection lens system of the
present invention;
[0080] FIG. 16 is an MTF characteristic diagram showing the focus
performance of Embodiment 8 of the projection lens system of the
present invention;
[0081] FIG. 17 is an MTF characteristic diagram showing the focus
performance of Embodiment 9 of the projection lens system of the
present invention;
[0082] FIG. 18 is an MTF characteristic diagram showing the focus
performance of Embodiment 10 of the projection lens system of the
present invention;
[0083] FIG. 19 is a characteristic diagram showing an example of
general light emission spectrum characteristics of green
phosphorescent substance;
[0084] FIG. 20 is a cross sectional view showing the essential
section of an example of a projection lens system of the prior
art;
[0085] FIG. 21 is a cross sectional view showing the essential
section of the 11th embodiment of the projection lens system of the
present invention;
[0086] FIG. 22 is a cross sectional view showing the essential
section when the cross section of the lens barrel 9 of the
projection lens system shown in FIG. 21 is seen in the direction of
the arrow A;
[0087] FIG. 23 is a cross sectional view showing the essential
section of the 12th embodiment of the projection lens system of the
present invention;
[0088] FIG. 24 is a perspective view of the essential section
showing the actual constitution of the first communicating opening
27 shown in FIG. 23;
[0089] FIG. 25 is a cross sectional view showing the essential
section of the 13th embodiment of the projection lens system of the
present invention;
[0090] FIG. 26 is a cross sectional view showing the essential
section of the 14th embodiment of the projection lens system of the
present invention;
[0091] FIG. 27 is a cross sectional view showing the essential
section of the 15th embodiment of the projection lens system of the
present invention;
[0092] FIG. 28 is a cross sectional view showing the essential
section of the longitudinal cross section of a rear projection type
image display apparatus using the projection lens system of the
present invention;
[0093] FIG. 29 is a cross sectional view showing the essential
section of the longitudinal cross section of another embodiment of
a rear projection type image display apparatus using the projection
lens system of the present invention;
[0094] FIG. 30 is a cross sectional view showing the projection
lens system of the rear projection type image display apparatus
shown in FIG. 28 in detail; and
[0095] FIG. 31 is a cross sectional view showing the projection
lens system of the rear projection type image display apparatus
shown in FIG. 29 in detail.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0096] The embodiments of the present invention will be explained
hereunder with reference to the accompanying drawings.
[0097] FIG. 1 is a cross sectional view showing the essential
section of an embodiment of the projection lens system of the
present invention.
[0098] In FIG. 1, numeral 1 indicates a first lens, 2 a second
lens, 3 a third lens, 4 a fourth lens, 5 a 5 fifth lens, 6 a sixth
lens, 7 a liquid coolant, 8 a projection type cathode ray tube
(hereinafter abbreviated to projection tube) which is an image
generating source, 8a a face panel of the projection tube, P1 a
fluorescent face of the projection tube, and 9 a lens barrel. The
lens barrel 9 is separated into an inner barrel 9a and an outer
barrel 9b and the inner barrel 9a includes the first lens to the
fifth lens which are incorporated and is fixed to the outer barrel
9b with a set screws 12. Furthermore, the outer barrel 9b is fixed
to a coupling bracket 11 via a holding plate 13 with screws (not
shown in the drawing). The system is structured so as to enlarge
and project an image on the fluorescent face of the projection tube
P1 which is an object surface on a screen 14.
[0099] Tables 1 to 10 (Embodiments 1, 2, 3, . . . , and 10 are used
respectively) show actual lens data which can be fetched by the
projection lens system of the present invention.
1TABLE 1 f = 90.49 mm, F.sub.NO = 0.96 Axial distance Abbe's number
Radius of between .nu.d/refractive curvature RD surfaces index
Screen Lens surface .infin. 1042.6 1.0 1st lens S.sub.1 91.403
8.874 57.9/1.49334 S.sub.2 280.37 2nd lens S.sub.3 -596.50 15.473
1.0 S.sub.4 -590.00 9.200 57.9/1.49334 3rd lens S.sub.5 81.066
8.7068 1.0 S.sub.6 -235.00 25.000 61.25/1.59137 4th lens S.sub.7
-270.00 1.008 1.0 S.sub.8 -450.00 4.000 30.30/1.58890 5th lens
S.sub.9 18535.00 10.80 1.0 S.sub.10 -225.00 8.400 57.9/1.49334 6th
lens S.sub.11 -56.000 30.000 1.0 S.sub.12 -58.000 3.405
57.9/1.49334 Transparent .infin. 11.49 1.44704 medium Cathode-ray
Face -350.00 14.10 1.56232 tube panel Fluorescent face P.sub.1 Lens
Surface CC AE AF AG AH 1st lens S.sub.1 -14.205306 l.27801 .times.
E-6 -1.35740 .times. E-9 3.77495 .times. E-13 -3.40452 .times. E-17
S.sub.2 1.5000000 -9.32634 .times. E-8 1.54377 .times. E-10
-7.28237 .times. E-14 2.08918 .times. E-17 2nd lens S.sub.3
8.0000000 2.38533 .times. E-6 1.25739 .times. E-10 -1.02973 .times.
E-13 2.20148 .times. E-17 S.sub.4 8.3999996 1.91166 .times. E-6
-5.03454 .times. E-10 1.55701 .times. E-13 -1.27999 .times. E-l7
4th lens S.sub.7 0.0000 0.0000 0.0000 0.0000 0.0000 S.sub.8 0.0000
-l.74446 .times. E-7 l.55853 .times. E-10 -l.07123 .times. E-13
2.70771 .times. E-17 5th lens S.sub.9 -15.300000 -2.64597 .times.
E-7 l.96982 .times. E-9 -1.17973 .times. E-12 l.13858 .times. E-16
S.sub.10 0.000 9.74735 .times. E-7 1.85426 .times. E-9 -7.84582
.times. E-13 4.27076 .times. E-17 6th lens S.sub.11 0.000 -1.34293
.times. E-6 7.37058 .times. E-l0 1.53851 .times. E-13 2.42038
.times. E-17 1 Z = r 2 / RD 1 + 1 - ( 1 + CC ) r 2 / RD 2 + AE r 4
+ AF r 6 + AG r 8 + AH r 10
[0100]
2TABLE 2 f = 90.31 mm, F.sub.NO = 1.02 Axial distance Abbe's number
Radius of between .nu.d/refractive curvature RD surfaces index
Screen Lens surface .infin. 1042.6 1.0 1st lens S.sub.1 85.301
8.874 57.9/1.49334 S.sub.2 248.10 2nd lens S.sub.3 -596.50 20.146
1.0 S.sub.4 -590.00 9.200 57.9/1.49334 3rd lens S.sub.5 81.066
4.933 1.0 S.sub.6 -235.00 22.700 61.25/1.59137 4th lens S.sub.7
-270.00 1.080 1.0 S.sub.8 -450.00 4.000 30.30/1.58890 5th lens
S.sub.9 18535.00 10.80 1.0 S.sub.10 -241.19 8.400 57.9/1.49334 6th
lens S.sub.11 -56.000 30.000 1.0 S.sub.12 -58.000 3.405
57.9/1.49334 Transparent .infin. 11.49 1.44704 medium Cathode-ray
Face -350.00 14.10 1.56232 tube panel Fluorescent face P.sub.1 Lens
Surface CC AE AF AG AH 1st lens S.sub.1 -14.205306 1.92669 .times.
E-6 -1.85054 .times. E-9 5.75077 .times. E-13 -6.05405 .times. E-17
.sub.S2 1.5000000 7.18758 .times. E-8 -4.05008 .times. E-10 2.13l88
.times. E-13 l.61270 .times. E-17 2nd lens S.sub.3 8.0000000
2.07465 .times. E-6 4.74347 .times. E-11 6.19323 .times. E-14
-1.8l834 .times. E-17 S.sub.4 8.3999996 l.76511 .times. E-6
-2.71126 .times. E-10 1.43099 .times. E-13 -2.74519 .times. E-17
4th lens 5.sub.7 0.0000 0.0000 0.0000 0.0000 0.0000 S.sub.8 0.0000
-3.76S60 .times. E-7 1.20340 .times. E-10 -3.00848x5-14
6.05881x5-18 5th lens S.sub.9 -15.300000 -2.64S97 .times. E-7
1.96982 .times. E-9 -l.l7973 .times. E-12 l.13858 .times. E-16
S.sub.10 0.000 l.16291 .times. E-6 l.80247xE-9 7.02182 .times. E-13
1.93070 .times. E-17 6th lens S.sub.11 0.000 -1.59847 .times. E-6
1.35363x5-9 -6.40009 .times. E-13 1.66139 .times. E-16 2 Z = r 2 /
RD 1 + 1 - ( 1 + CC ) r 2 / RD 2 + AE r 4 + AF r 6 + AG r 8 + AH r
10
[0101]
3TABLE 3 f = 90.77 mm, F.sub.NO = 1.01 Axial distance Abbe's number
Radius of between .nu.d/refractive curvature RD surfaces index
Screen Lend surface .infin. 1042.6 1.0 1st lens S.sub.1 106.180
8.874 57.9/1.49334 S.sub.2 267.06 18.075 1.0 2nd lens S.sub.3
-1483.80 9.200 57.9/1.49334 S.sub.4 -339.15 9.1674 1.0 3rd lens
S.sub.5 76.594 22.700 61.25/1.59137 S.sub.6 -235.00 1.080 1.0 4th
lens S.sub.7 -270.00 4.000 30.30/1.58890 S.sub.8 -450.00 10.80 1.0
5th lens S.sub.9 18535.00 8.400 57.9/1.49334 S.sub.10 -577.72
30.000 1.0 6th lens S.sub.11 -55.500 3.405 57.9/1.49334 S.sub.12
-58.000 11.49 1.44704 Transparent .infin. medium Cathode-ray Face
14.10 1.56232 tube panel Fluorescent face P.sub.1 -350.00 Lens
Surface CC AE AF AG AH 1st lens S.sub.1 -14.205306 -4.17615 .times.
E-7 -7.58755 .times. E-10 3.11083 .times. E-13 -3.26331 .times.
E-17 S.sub.2 1.5000000 -1.25741 .times. E-6 5.87530 .times. E-10
-1.83314 .times. E-13 3.84552 .times. E-17 2nd lens S.sub.3
8.0000000 2.05903 .times. E-6 7.77375 .times. E-10 -3.99801 .times.
E-13 7.17568 .times. E-17 S.sub.4 8.3999996 1.58107 .times. E-6
3.39912 .times. E-10 -1.74104 .times. E-13 3.07068 .times. E-17 4th
lens S.sub.7 0.0000 0.0000 0.0000 0.0000 0.0000 S.sub.8 0.0000
-5.47788 .times. E-7 3.08341 .times. E-10 -6.34311 .times. E-14
9.31559 .times. E-18 5th lens S.sub.9 -15.300000 -3.22064 .times.
E-7 2.42981 .times. E-9 -1.69278 .times. E-12 2.46305 .times. E-16
S.sub.10 0.000 1.58758 .times. E-6 2.05251 .times. E-9 -9.15005
.times. E-13 5.00000 .times. E-17 6th lens S.sub.11 0.000 -1.62384
.times. E-6 1.46180 .times. E-9 -6.25537 .times. E-13 1.79061
.times. E-16 3 Z = r 2 / RD 1 + 1 - ( 1 + CC ) r 2 / RD 2 + AE r 4
+ AF r 6 + AG r 8 + AH r 10
[0102]
4TABLE 4 f = 89.47 mm, F.sub.NO = 1.00 Axial distance Abbe's number
Radius of between .nu.d/refractive curvature RD surfaces index
Screen Lens surface .infin. 1042.6 1.0 1st lens S.sub.1 87.060
8.874 57.9/1.49334 S.sub.2 166.59 13.907 1.0 2nd lens S.sub.3
-737.56 9.200 57.9/1.49334 S.sub.4 -188.83 10.482 1.0 3rd lens
S.sub.5 90.712 22.700 61.25/1.59137 S.sub.6 -235.00 1.080 1.0 4th
lens S.sub.7 -270.00 4.000 30.30/1.58890 S.sub.8 -450.00 10.80 1.0
5th lens S.sub.9 18535.00 8.400 57.9/1.49334 S.sub.10 -241.19
30.000 1.0 6th lens S.sub.11 -52.268 3.405 57.9/1.49334 S.sub.12
-58.000 11.49 1.44704 Transparent .infin. medium Cathode-ray Face
14.10 1.56232 tube panel Fluorescent face P.sub.1 -350.00 Lens
Surface CC AE AF AG AH 1st lens S.sub.1 -14.205306 1.81161 .times.
E-6 -1.81880 .times. E-9 4.93904 .times. E-13 -4.44977 .times. E-17
S.sub.2 1.5000000 4.78526 .times. E-7 -5.76838 .times. E-10 3.61505
.times. E-13 -5.85045 .times. E-17 2nd lens S.sub.3 8.0000000
1.05968 .times. E-6 2.18392 .times. E-10 3.29367 .times. E-15
-9.38718 .times. E-18 S.sub.4 8.3999996 6.04039 .times. E-7
-1.05414 .times. E-10 2.82509 .times. E-14 1.17689 .times. E-17 4th
lens S.sub.7 0.0000 0.0000 0.0000 0.0000 0.0000 S.sub.8 0.0000
-5.23821 .times. E-7 3.86150 .times. E-11 3.41462 .times. E-16
1.15405 .times. E-18 5th lens S.sub.9 -15.300000 -2.81921 .times.
E-7 1.77440 .times. E-9 -1.02161 .times. E-12 1.07908 .times. E-16
S.sub.10 0.000 1.16291 .times. E-6 1.80247 .times. E-9 -7.02182
.times. E-13 1.93070 .times. E-17 6th lens S.sub.11 0.000 -8.30584
.times. E-7 -3.19962 .times. E-10 7.06789 .times. E-13 -2.63143
.times. E-16 4 Z = r 2 / RD 1 + 1 - ( 1 + CC ) r 2 / RD 2 + AE r 4
+ AF r 6 + AG r 8 + AH r 10
[0103]
5TABLE 5 f = 90.13 mm, F.sub.NO = 1.00 Axial distance Abbe's number
Radius of between .nu.d/refractive curvature RD surfaces index
Screen Lens surface .infin. 1042.6 1.0 1st lens S.sub.1 112.98
8.874 57.9/1.49334 S.sub.2 415.40 17.286 1.0 2nd lens S.sub.3
-562.36 9.200 57.9/1.49334 S.sub.4 -339.15 8.1494 1.0 3rd lens
S.sub.5 76.594 22.700 61.25/1.59137 S.sub.6 -235.00 3.080 1.0 4th
lens S.sub.7 -270.00 4.000 30.30/1.58840 S.sub.8 -450.00 9.300 1.0
5th lens S.sub.9 18535.00 8.400 57.9/1.49334 S.sub.10 -400.00
29.500 1.0 6th lens S.sub.11 -55.499 3.405 57.9/1.49334 S.sub.12
-58.000 11.49 1.44704 Transparent .infin. medium Cathode-ray Face
14.1 1.56232 tube panel Fluorescent face P.sub.1 -350.00 Lens
Surface CC AE AF AG AH 1st lens S.sub.1 14.205306 -4.99132 .times.
E-7 -7.52281 .times. E-10 3.04572 .times. E-13 -3.17985 .times.
E-17 S.sub.2 1.500000 -9.63142 .times. E-7 -4.48452 .times. E-10
-1.48606 .times. E-13 3.24547 .times. E-17 2nd lens S.sub.3
8.000000 2.70666 .times. E-6 3.50490 .times. E-10 -2.62215 .times.
E-13 4.22459 .times. E-17 S.sub.4 8.340000 2.08869 .times. E-6
-1.90134 .times. E-10 2.77475 .times. E-14 -1.42593 .times. E-17
4th lens S.sub.7 0.000000 -7.29331 .times. E-7 -1.99626 .times.
E-10 6.48129 .times. E-15 -1.12055 .times. E-18 S.sub.8 0.000000
-1.29715 .times. E-6 1.84357 .times. E-10 -1.46193 .times. E-13
2.60704 .times. E-17 5th lens S.sub.9 -15.300000 -1.70710 .times.
E-7 2.13023 .times. E-9 -1.37605 .times. E-12 1.09708 .times. E-16
S.sub.10 0.00000 1.58758 .times. E-6 2.05252 .times. E-9 -9.15005
.times. E-13 5.00000 .times. E-17 6th lens S.sub.11 0.000000
-1.89756 .times. E-6 1.72825 .times. E-9 1.08034 .times. E-12
3.39635 .times. E-16 5 Z = r 2 / RD 1 + 1 - ( 1 + CC ) r 2 / RD 2 +
AE r 4 + AF r 6 + AG r 8 + AH r 10
[0104]
6TABLE 6 f = 90.28 mm, F.sub.NO = 1.00 Axial distance Abbe's number
Radius of between .nu.d/refractive curvature RD surfaces index
Screen Lens surface .infin. 1050.0 1.0 1st lens S.sub.1 115.670
8.874 57.9/1.49334 S.sub.2 335.03 17.162 1.0 2nd lens S.sub.3
-1054.40 9.200 57.9/1.49334 S.sub.4 -261.89 5.8105 1.0 3rd lens
S.sub.5 71.717 22.700 61.25/1.59137 S.sub.4 -325.88 2.267 1.0 4th
lens S.sub.7 -290.07 4.000 30.30/1.58890 S.sub.8 5000.00 9.300 1.0
5th lens S.sub.9 928.70 8.400 57.9/1.49334 S.sub.10 -336.67 30.189
1.0 6th lens S.sub.11 -54.636 3.405 57.9/1.49334 S.sub.12 -58.000
11.49 1.44704 Transparent .infin. medium Cathode-ray Face 14.10
1.56232 tube panel Fluorescent face P.sub.1 -350.00 Lens Surface CC
AE AF AG AH 1st lens S.sub.1 -14.898250 -7.47696 .times. E-7
-7.73792 .times. E-10 3.44880 .times. E-13 -3.75545 .times. E-17
S.sub.2 5.5688664 -1.09894 .times. E-6 5.28791 .times. E-10
-2.05281 .times. E-13 4.66837 .times. E-17 2nd lens S.sub.3
-2316.3117 2.54450 .times. E-6 5.62992 .times. E-10 -3.61632
.times. E-13 5.44320 .times. E-17 S.sub.4 11.690594 1.79735 .times.
E-6 4.46261 .times. E-11 -1.10792 .times. E-13 6.60349 .times. E-18
4th lens S.sub.7 22.120667 -5.45630 .times. E-7 -1.25450 .times.
E-10 1.70354 .times. E-14 -1.41437 .times. E-17 S.sub.8 -719.55890
-1.28076 .times. E-6 1.68255 .times. E-10 -1.91393 .times. E-13
3.00716 .times. E-17 5th lens S.sub.9 -15.300000 -4.49218 .times.
E-7 1.60071 .times. E-9 -1.19463 .times. E-12 -5.83877 .times. E-17
S.sub.10 0.00000 1.58758 .times. E-6 2.05251 .times. E-9 -9.15005
.times. E-13 5.00000 .times. E-17 6th lens S.sub.11 -0.5923559
-1.91950 .times. E-6 1.26443 .times. E-9 -7.45525 .times. E-13
2.90386 .times. E-16 6 Z = r 2 / RD 1 + 1 - ( 1 + CC ) r 2 / RD 2 +
AE r 4 + AF r 6 + AG r 8 + AH r 10
[0105]
7TABLE 7 f = 90.34 mm, F.sub.NO = 1.00 Axial distance Abbe's number
Radius of between .nu.d/refractive curvature RD surfaces index
Screen Lens surface .infin. 1050.0 1.0 1st lens S.sub.1 114.560
8.874 57.9/1.49334 S.sub.2 299.87 17.162 1.0 2nd lens S.sub.3
-866.97 9.200 57.9/1.49334 S.sub.4 -239.70 5.0793 1.0 3rd lens
S.sub.5 71.114 22.700 61.25/1.59137 S.sub.6 -378.83 2.737 1.0 4th
lens S.sub.7 -287.97 4.000 30.30/1.58890 S.sub.8 4000.00 9.300 1.0
5th lens S.sub.9 613.06 8.400 57.9/1.49334 S.sub.10 -344.07 30.312
1.0 6th lens S.sub.11 -54.393 3.405 57.9/1.49334 S.sub.12 -58.000
11.490 1.44704 Transparent .infin. medium Cathode-ray Face 14.10
1.56232 tube panel Fluorescent face P.sub.1 -350.00 Lens Surface CC
AE AF AG AH 1st lens S.sub.1 13.429961 -8.40169 .times. E-7
-7.76450 .times. E-10 3.51328 .times. E-13 -3.82801 .times. E-17
S.sub.2 -3.3351539 -1.11543 .times. E-6 5.31625 .times. E-10
-2.10620 .times. E-13 4.81196 .times. E-17 2nd lens S.sub.3
-959.82674 2.58831 .times. E-6 5.51215 .times. E-10 -3.56294
.times. E-13 5.36534 .times. E-17 S.sub.4 10.354769 1.80263 .times.
E-6 7.19625 .times. E-11 -1.18864 .times. E-13 7.75962 .times. E-18
4th lens S.sub.7 22.120667 -5.45630 .times. E-7 -1.25450 .times.
E-10 1.70354 .times. E-14 -1.41437 .times. E-17 S.sub.8 -3630.1763
-1.25638 .times. E-6 1.51585 .times. E-10 -1.90122 .times. E-13
3.04799 .times. E-17 5th lens S.sub.9 -15.300000 -4.18973 .times.
E-7 1.51153 .times. E-9 -1.11826 .times. E-12 1.08743 .times. E-16
S.sub.10 0.000 1.58758 .times. E-6 2.05251 .times. E-9 -9.15005
.times. E-13 4.99999 .times. E-17 6th lens S.sub.11 -0.0354248
-1.33128 .times. E-6 1.27556 .times. E-9 -6.55222 .times. E-13
3.04020 .times. E-16 7 Z = r 2 / RD 1 + 1 - ( 1 + CC ) r 2 / RD 2 +
AE r 4 + AF r 6 + AG r 8 + AH r 10
[0106]
8TABLE 8 f = 90.10 mm, F.sub.NO = 1.00 Axial distance Abbe's number
Radius of between .nu.d/refractive curvature RD surfaces index
Screen Lens surface .infin. 1042.6 1.0 1st lens S.sub.1 110.91
8.874 57.9/1.49334 S.sub.2 393.88 17.431 1.0 2nd lens S.sub.3
-562.36 9.200 57.9/1.49334 S.sub.4 -339.15 7.8423 1.0 3rd lens
S.sub.5 76.594 22.700 61.25/1.59137 S.sub.6 -235.00 2.080 1.0 4th
lens S.sub.7 -270.00 4.000 30.30/1.58840 S.sub.8 -450.00 10.300 1.0
5th lens S.sub.9 18535.00 8.400 57.9/1.49334 S.sub.10 -400.00
29.500 1.0 6th lens S.sub.11 -55.499 3.405 57.9/1.49334 S.sub.12
-58.000 11.49 1.44704 Transparent .infin. medium Cathode-ray Face
14.1 1.56232 tube panel Fluorescent face P.sub.1 -350.00 Lens
Surface CC AE AF AG AH 1st lens S.sub.1 -14.205306 -3.49264 .times.
E-7 -7.51764 .times. E-10 2.98572 .times. E-13 -3.16781 .times.
E-17 S.sub.2 1.500000 -8.62273 .times. E-7 4.44555 .times. E-10
-1.36020 .times. E-13 2.95057 .times. E-17 2nd lens S.sub.3
8.000000 2.63183 .times. E-6 3.36531 .times. E-10 -2.58187 .times.
E-13 4.36505 .times. E-17 S.sub.4 8.340000 2.02573 .times. E-6
-2.24606 .times. E-10 2.83556 .times. E-14 -1.05000 .times. E-17
4th lens S.sub.7 0.000000 -5.45630 .times. E-7 -1.25450 .times.
E-10 1.70354 .times. E-14 -1.41437 .times. E-17 S.sub.8 0.000000
-1.02404 .times. E-6 2.45508 .times. E-10 -1.44920 .times. E-13
1.38124 .times. E-17 5th lens S.sub.9 -15.300000 -7.06392 .times.
E-7 2.06151 .times. E-9 -1.30794 .times. E-12 7.28924 .times. E-17
S.sub.10 0.00000 1.58758 .times. E-6 2.05252 .times. E-9 -9.15005
.times. E-13 5.00000 .times. E-17 6th lens S.sub.11 0.000000
-1.82729 .times. E-6 1.68806 .times. E-9 -1.07491 .times. E-12
3.50966 .times. E-16 8 Z = r 2 / RD 1 + 1 - ( 1 + CC ) r 2 / RD 2 +
AE r 4 + AF r 6 + AG r 8 + AH r 10
[0107]
9TABLE 9 f = 90.33 mm, F.sub.NO = 1.00 Axial distance Abbe's number
Radius of between .nu.d/refractive curvature RD surfaces index
Screen Lens surface .infin. 1050.0 1.0 1st lens S.sub.1 109.780
8.874 57.9/1.49334 2nd lens S.sub.3 -562.36 9.200 57.9/1.49334
S.sub.4 -339.15 10.013 1.0 3rd lens S.sub.5 76.594 22.300
61.25/1.59137 S.sub.6 -235.00 2.080 1.0 4th lens S.sub.7 -270.00
4.000 30.30/1.58890 S.sub.8 -450.00 10.300 1.0 5th lens S.sub.9
18535.00 8.400 57.9/1.49334 S.sub.10 -400.00 29.500 1.0 6th lens
S.sub.11 -55.499 3.405 57.9/1.49334 S.sub.12 -58.000 11.49 1.44704
Transparent .infin. medium Cathode-ray Face 14.10 1.56232 tube
panel Fluorescent face P.sub.1 -350.00 Lens Surface CC AE AF AG AH
1st lens S.sub.1 -14.205306 -3.77711 .times. E-7 -6.80543 .times.
E-10 2.76889 .times. E-13 -2.92638 .times. E-17 S.sub.2 1.5000000
-9.39630 .times. E-7 5.48052 .times. E-10 -1.69877 .times. E-13
3.37537 .times. E-17 2nd lens S.sub.3 8.0000000 2.50070 .times. E-6
4.30750 .times. E-10 -2.98735 .times. E-13 5.40955 .times. E-17
S.sub.4 8.4000000 1.94248 .times. E-6 -1.45666 .times. E-10
-7.76624 .times. E-15 3.96630 .times. E-18 4th lens S.sub.7
0.000000 -1.11617 .times. E-7 -2.69651 .times. E-11 -1.97791
.times. E-15 -1.56427 .times. E-17 S.sub.8 0.000000 -5.02307
.times. E-7 3.06274 .times. E-10 -1.28546 .times. E-13 -1.80677
.times. E-19 5th lens S.sub.9 -15.300000 2.76587 .times. E-8
2.13667 .times. E-9 -1.35824 .times. E-12 1.19636 .times. E-16
S.sub.10 0.00000 1.58758 .times. E-6 2.05251 .times. E-9 -9.15005
.times. E-13 5.00000 .times. E-17 6th lens S.sub.11 0.00000
-1.62935 .times. E-6 1.40012 .times. E-9 -7.34993 .times. E-13
2.07431 .times. E-16 9 Z = r 2 / RD 1 + 1 - ( 1 + CC ) r 2 / RD 2 +
AE r 4 + AF r 6 + AG r 8 + AH r 10
[0108]
10TABLE 10 f = 90.28 mm, F.sub.NO = 1.00 Axial distance Abbe's
number Radius of between .nu.d/refractive curvature RD surfaces
index Screen Lens surface .infin. 1042.6 1.0 1st lens S.sub.1
110.220 8.874 57.9/1.49334 S.sub.2 376.07 16.478 1.0 2nd lens
S.sub.3 -562.36 9.200 57.9/1.49334 S.sub.4 -339.15 8.9875 1.0 3rd
lens S.sub.5 76.594 22.700 61.25/1.59137 S.sub.6 -235.00 3.080 1.0
4th lens S.sub.7 -270.00 4.000 30.30/1.58890 S.sub.8 -450.00 9.300
1.0 5th lens S.sub.9 18535.00 8.400 57.9/1.49334 S.sub.10 -400.00
29.500 1.0 6th lens S.sub.11 -55.499 3.405 57.9/1.49334 S.sub.12
-58.000 11.490 1.44704 Transparent .infin. medium Cathode-ray Face
14.10 1.56232 tube panel Fluorescent face P.sub.1 -350.00 Lens
Surface CC AE AF AG AH 1st lens S.sub.1 -14.205306 -6.05201 .times.
E-7 -7.33372 .times. E-10 3.22224 .times. E-13 -3.52762 .times.
E-17 S.sub.2 1.5000000 -1.21465 .times. E-6 6.09643 .times. E-10
-1.89740 .times. E-13 3.97475 .times. E-17 2nd lens S.sub.3
8.0000000 2.38762 .times. E-6 6.05052 .times. E-10 -3.78418 .times.
E-13 5.98085 .times. E-17 S.sub.4 8.4000000 1.78170 .times. E-6
6.59630 .times. E-11 -1.20208 .times. E-13 1.50850 .times. E-17 4th
lens S.sub.7 0.000000 -5.45630 .times. E-7 -1.25450 .times. E-10
1.70354 .times. E-14 -1.41437 .times. E-17 S.sub.8 0.000000
-1.10393 .times. E-6 3.73070 '3 E-10 -2.13647 .times. E-13 2.70690
.times. E-17 5th lens S.sub.9 -15.300000 -3.51269 .times. E-8
2.02646 .times. E-9 -1.25938 .times. E-12 8.23050 .times. E-17
S.sub.10 0.00000 1.58758 .times. E-6 2.05251 .times. E-9 -9.15005
.times. E-13 4.99999 .times. E-17 6th lens S.sub.11 0.00000
-1.90908 .times. E-6 1.65847 .times. E-9 -9.59000 .times. E-13
2.77588 .times. E-16 10 Z = r 2 / RD 1 + 1 - ( 1 + CC ) r 2 / RD 2
+ AE r 4 + AF r 6 + AG r 8 + AH r 10
[0109] According to the embodiments of the present invention, the
focal length of the single sixth lens and the focal length of the
overall projection lens system synthesizing every lens are
calculated including the face panel 8a of the projection tube, the
liquid coolant 7, and the fluorescent face P1.
[0110] FIGS. 2, 3, and 4 are cross sectional views showing the
arrangement of lens elements and outline of the ray tracing result
in the projection lens system shown in Embodiments 1, 7, and 10 and
the lens barrel and other components are omitted from reason of
explanation. The lens profile and arrangement shown in FIG. 4 are
the same as those shown in FIG. 1.
[0111] The projection lens system used in the embodiments of the
present invention is structured so that when rasters with a
diagonal of 5.33 inch are displayed on the fluorescent face of the
projection tube P1 and enlarged and projected as image with a
diagonal of 60 inch onto the screen, a best performance can be
obtained. The semi-field angle of the projection lens system is 360
and a wide field angle is realized. Therefore, as described later,
in a rear projection type image display apparatus such as a
projection television set having a constitution of one reflecting
mirror for folding the light path, a sufficiently compact set can
be realized.
[0112] Next, how to read the lens data will be explained on the
basis of Table 1. Table 1 divides and displays data into spherical
surface data mainly handling the lens area in the neighborhood of
the optical axis and aspherical surface data in the marginal area
thereof.
[0113] The table shows that the radius of curvature of the screen
is infinity (that is, a plane), and the distance (axial distance
between surfaces) on the optical axis from the screen to the
surface S1 of the first lens 1 is 1042.6 mm, and the refractive
index of the medium between them is 1.0. The table also shows that
the radius of curvature of the lens surface S1 is 91.403 mm (the
center of curvature is on the image generating source side), and
the distance (axial distance between surfaces) on the optical axis
between the lens surfaces S1 and S2 is 8.874 mm, and the refractive
index of the medium between them is 1.49334. In the same way, the
table shows lastly that the radius of curvature of the fluorescent
face P1 of the face panel 8a of the projection tube is 350 mm, and
the thickness of the face panel of the projection tube on the
optical axis is 14.10 mm, and the refractive index thereof is
1.56232. The transparent medium described in each table indicates
the aforementioned liquid coolant 7.
[0114] With respect to the surfaces S1 and S2 of the first lens 1,
the surfaces S3 and S4 of the second lens 2, the surfaces S7 and S8
of the fourth lens 4, the surfaces S9 and S10 of the fifth lens 5,
and the surface S11 of the sixth lens 6, aspherical coefficients
are shown.
[0115] The aspherical coefficients are constants when the profile
of lens surface is expressed by the following equation. The
exponent expression in each table uses a base of 10. 11 Z ( r ) = r
2 / RD 1 + 1 - ( 1 + CC ) r 2 / RD 2 + AE r 4 + AF r 6 + AG r 8 +
AH r 10 + + A r 2 n (Equation 1)
[0116] where RD, CC, AE, AF, AG, AH, . . . , and A indicate
arbitrary constants and n indicates an arbitrary natural number. S5
and S6 indicate surfaces of the third lens 3. S13 indicates a
surface of the face panel of the projection tube and S12 indicates
another surface of the sixth lens 6.
[0117] FIG. 5 is a drawing showing the definition of the axes of
coordinates in Equation 1 of the aforementioned profile of lens
surface, and the direction of optical axis from the screen toward
the image generating source is set as a Z axis, and the radial
direction of lens is set as an r axis. In this case, Z(r) indicates
the height of lens surface (surface sag). r indicates the distance
from the optical axis of the system, and RD indicates the radius of
curvature, and CC indicates a conic constant. Therefore, when each
coefficient such as CC, AE, AF, AG, and AH is given, the height of
lens surface (hereinafter referred to as the surface sag), that is,
the profile is decided according to the aforementioned
equation.
[0118] FIG. 6 is an illustration for explaining differences between
the aspherical surface and the spherical surface. In FIG. 6, As(r)
indicates a value which is obtained by substituting the values of
respective coefficients in Equation 1 of the profile of lens
surface Z(r) and Ss(r) indicates a value when only the radius of
curvature RD is substituted in Equation 1 of the profile of lens
surface Z(r) and the other coefficients are set to 0. As the
absolute value of the ratio ((As(r)-Ss(r))/Ss(r)) of the difference
of these values (As(r)-Ss(r)) to Ss(r) increases, the degree of the
aspherical surface increases in strength.
[0119] The above is how to read the data shown in Table 1. With
respect to Tables 2 to 10, how to read is the same.
[0120] Next, the action of each lens group of the projection lens
system of the present invention will be explained hereunder.
[0121] The first lens 1 has a concave profile in the marginal area
as shown in FIGS. 2, 3, and 4 and corrects the spherical aberration
for the light flux (upper ray RAY1, lower ray RAY2) from an object
A on the axis and the coma aberration for the light flux (upper ray
RAY3, lower ray RAY4) from an object B in the marginal area. The
location (the marginal area of the lens apart from the optical axis
of the lens surface on the screen side) through which the light
from the upper ray RAY3 to the lower ray RAY4 passes has a profile
of aspherical surface which is concave on the screen side.
[0122] The second lens 2 has a profile of aspherical surface so
that the marginal area of the lens apart from the optical axis of
the lens surface on the screen side is convex on the screen side as
shown in FIGS. 2, 3, and 4 so as to correct astigmatism and coma
aberration. When this lens is combined with the first lens 1, the
system is structured so that the negative refractive power on the
basis of the lens profile (concave) in the marginal area of the
first lens and the positive refractive power on the basis of the
lens profile (convex) in the marginal area of the second lens
offset each other. Therefore, even if both lens are plastic
products, the lowering of the focus performance of the projection
lens system due to changes in temperature and absorption of
moisture can be suppressed as much as possible.
[0123] The third lens 3 is made of glass so as to reduce the drift
of the focus performance due to temperature changes and structured
so as to increase the positive refractive power as much as
possible. According to this embodiment, to reduce the production
cost of the projection lens system, SK5 which is inexpensive
optical glass is used.
[0124] The fourth lens 4 has a meniscus profile which is concave on
the screen side as shown in FIGS. 2, 3, and 4 or a lens profile
which is concave on both sides (the embodiments shown in Tables 6
and 7) in the center area thereof and has an aspherical surface
profile which is a meniscus profile which is concave on the screen
side in the marginal area thereof.
[0125] For the light flux (upper ray RAY1, lower ray RAY2) from the
object point A on the axis, the fourth lens 4 corrects the
spherical aberration by the concave profile in the marginal area of
lens/and reduces the chromatic aberration in combination with the
third lens 3 by using a high dispersion material having an Abbe's
number of 45 or less.
[0126] On the other hand, the fourth lens 4 of the present
invention is a lens element with an almost uniform thickness as a
whole due to the aforementioned aspherical surface profile and for
example, even if a plastic material having poor fluidity for
molding such as PC (polycarbonate) is used, a high profile accuracy
can be obtained. Furthermore, the lens profile of the fourth lens 4
is a lens profile that the neighborhood of the optical axis has a
concave meniscus profile whose concave surface faces the screen
side and that particularly with respect to the lens surface on the
projection tube side, the inclination of the lens surface in the
marginal area of lens apart from the optical axis is large and the
lens surface is almost parallel with the lens surface on the screen
side. As a result, as shown in FIGS. 2 to 4, the upper ray (RAY1,
RAY2) of the light flux generated from the object point A on the
optical axis can be shifted toward the optical axis. Therefore, the
light entry height into the third lens (glass) is lowered and the
diameter of a glass lens can be smaller than that is when the same
F-number is obtained without the fourth lens. As a result, the cost
of a glass lens can be reduced.
[0127] Furthermore, since the inclination of the lens surface in
the marginal area of the fourth lens 4 is large, the incident angle
into the third lens 3 is increased and the refractive power of the
third lens 3 is decreased. Therefore, an inexpensive glass material
with a refractive index nd of 1.6 or less can be used for the third
lens and the cost can be reduced.
[0128] The fifth lens 5 corrects coma aberration of higher order
generated by the light flux (upper ray RAY3, lower ray RAY4) from
the object point B in the marginal area as shown in FIGS. 2, 3, and
4, so that the profile in the neighborhood of the location (the
marginal area of the lens surface on the projection tube side which
is an image generating source) through which the lower ray RAY4
passes is an aspherical surface profile which is concave on the
projection tube side. The profile in the neighborhood of the
location through which the upper ray RAY3 passes is also an
aspherical surface profile which is concave locally on the screen
side.
[0129] Therefore, the lens surface of this lens on the projection
tube side has an aspherical surface profile in which the
neighborhood of the optical axis is convex on the projection tube
side and the marginal area is concave on the projection tube side
as a whole. To suppress the lowering of the focus performance of
the projection lens system due to changes in temperature and
absorption of moisture as much as possible, the refractive power is
made as small as possible.
[0130] The sixth lens 6 corrects the curvature of field accompanied
by the fluorescent face P1. The fluorescent face P1 is a spherical
fluorescent face unlike the prior art 2, so that as shown in FIGS.
2, 3, and 4, the aspherical surface profile of the lens surface of
the sixth lens 6 on the screen side is a profile that the
refractive power in the area through which the light flux (upper
ray RAY3, lower ray RAY4) from the object point B in the marginal
area passes is weaker than the refractive power in the neighborhood
of the optical axis and the sixth lens 6 corrects the astigmatism
at the same time.
[0131] FIG. 7 is a characteristic diagram in which values obtained
by substituting a distance of r from the optical axis in a second
derivative obtained by differentiating the function indicating the
profile of aspherical surface of the lens surface of the sixth lens
6 on the screen side quadratically are graphed. On the lens
surfaces by the first prior art (prior art 1) and the second prior
art (prior art 2) mentioned above, the absolute values of
derivative values between the optical axis and the marginal area of
the lens increase monotonously. This shows that the refracting
action of the lens increases monotonously from the optical axis
toward the marginal area of the lens. On the other hand, in the
embodiments of the present invention, a value obtained in the same
way has a point of inflection as shown in Embodiment 8 or reduces
in an area more than 70% of the effective radius as shown in
Embodiments 9 and 10. As a result, it is found that the refracting
action of the lens increases once from the optical axis toward the
marginal area and decreases thereafter.
[0132] FIG. 8 is a characteristic diagram in which the distance of
the aspherical surface profile of the lens surface of the sixth
lens 6 on the screen side from the lens surface Ss(r) only of the
spherical surface system is obtained by calculation. The horizontal
axis shown in FIG. 8 indicates a relative value of the
aforementioned distance r to the effective lens radius and the
vertical axis indicates a difference between As(r) and Ss(r). In
comparison with the first prior art (prior art 1 shown in the
drawing), in the embodiments of the present invention, the
difference between As(r) and Ss(r) is small such as about 1/2 of
that in prior art 1 or less and the marginal area of the sixth lens
6 is not thick but almost uniform in thickness, so that
satisfactory moldability can be obtained.
[0133] FIGS. 9 to 18 are characteristic diagrams showing evaluation
results of the focus performance by the MTF (modulation transfer
function) when rasters with a diagonal of 5.33 inch are displayed
on the fluorescent face of the projection tube using the
aforementioned projection lens system of the present invention and
enlarged and displayed on the screen (60 inch) and correspond to
Embodiments 1, 2, 3, . . . , and 10 sequentially. The horizontal
axis in these drawings indicates a relative image height from
center on the screen.
[0134] As a spatial frequency as an evaluation condition, a case
that 300 TV lines are taken as a stripe signal of white and black
on the screen, that is, 150 pair lines are taken for the
longitudinal dimension of the screen is shown. As shown in these
drawings, by the projection lens system having this constitution, a
satisfactory MTF characteristic can be obtained.
[0135] On the other hand, when three primary-color projection tube
of red, green, and blue are used as projection tubes which is image
generating sources, the spurious component other than the dominant
wave length component is generally included in the light emission
spectrum of the phosphorescent substance of each projection
tube.
[0136] FIG. 19 is a characteristic diagram showing an example of
the light emission spectrum of a general green phosphorescent
substance. In the green light emission spectrum shown in FIG. 19, a
spurious component of several wave lengths can be seen in addition
to a dominant wave length component of 545 nm.
[0137] If a filter for cutting the aforementioned spurious
component is installed in at least one of the lens elements
constituting the projection lens system so as to reduce the
generated chromatic aberration itself, a more satisfactory focus
performance can be obtained.
[0138] Next, power distribution to each lens group in the
aforementioned embodiments of the projection lens system of the
present invention will be explained.
[0139] Table 11 is a table showing power distribution when the
focal length of the overall projection lens system is assumed as f0
and the focal lengths of the first lens 1, second lens 2, third
lens 3, fourth lens 4, fifth lens 5, and sixth lens 6 are assumed
as f1, f2, f3, f4, f5, and f6 respectively in the embodiments of
the present invention shown in Tables 1 to 10.
[0140] The ranges of power distribution shown in Table 11 are shown
below.
0.24<f0/f1<0.35
0.0<f0/f2<0.18
0.78<f0/f3<0.91
-0.20<f0/f4<0.0
0.0<f0/f5<0.21
-0.61<f0/f6<-0.55
[0141] According to this embodiment, by sharing the greater part of
the positive refractive power of the overall projection lens system
by the third lens which is a glass lens element, the drift of the
focus performance by temperature change is reduced.
11TABLE 11 Focal length Lens Lens power distribution f.sub.0 No.
f.sub.0/f.sub.1 f.sub.0/f.sub.1 f.sub.0/f.sub.3 f.sub.0/f.sub.4
f.sub.0/f.sub.5 f.sub.0/f.sub.6 (mm) 1 0.3343 0.00121 0.8617
-0.0783 0.2008 -0.5550 90.486 2 0.3489 0.00121 0.8624 -0.0781
0.1871 -0.5544 90.310 3 0.2587 0.1021 0.9041 -0.0785 0.0799 -0.5640
90.775 4 0.2510 0.1749 0.7875 -0.0774 0.1854 -0.6037 89.473 5
0.2893 0.0527 0.8977 -0.0780 0.1135 -0.5602 90.130 6 0.2555 0.1283
0.8889 -0.1940 0.1798 -0.5734 90.276 7 0.2442 0.1352 0.8755 -0.1981
0.2016 -0.5773 90.339 8 0.2909 0.0527 0.8974 -0.0780 0.1135 -0.5600
90.098 9 0.2936 0.0529 0.9001 -0.0782 0.1138 -0.5614 90.330 10
0.2888 0.0528 0.8992 -0.0781 0.1138 -0.5611 90.277 f.sub.0: Focal
length of overall lens system (mm) f.sub.1: Focal length of first
lens (mm) f.sub.2: Focal length of second lens (mm) f.sub.3: Focal
length of third lens (mm) f.sub.4: Focal length of fourth lens (mm)
f.sub.5: Focal length of fifth lens (mm) f.sub.6: Focal length of
sixth lens (mm)
[0142] Next, characteristics of the profile of lens surface will be
explained.
[0143] The profiles of aspherical surfaces of the lens surface S1
of the first lens 1 on the screen side, the lens surface S8 of the
fourth lens 4 on the image generating source side, the lens surface
S10 of the fifth lens 5 on the image generating source side, and
the lens surface S11 of the sixth lens 6 on the screen side have
the following characteristics.
[0144] In FIG. 6, As(r) indicates a value which is obtained by
substituting the values of respective coefficients in Equation 1 of
the profile of lens surface Z(r) and Ss(r) indicates a value when
only the radius of curvature RD is substituted in Equation 1 of the
profile of lens surface Z(r) and the other coefficients are set to
0. In this case, the value of As(r)/Ss(r) is assumed as an index
indicating the degree of the aspherical surface. In this case, the
aforementioned ratio of As and Ss of the lens surface S1 of the
first lens 1 on the screen side is within the following range as
shown in Table 12.
(As/Ss)>-0.1
[0145] The aforementioned ratio of As and Ss of the lens surface S8
of the fourth lens 4 on the image generating source side is within
the following range as shown in Table 13.
(As/Ss)>-21.2
[0146] Furthermore, the aforementioned ratio of As and Ss of the
lens surface S10 of the fifth lens 5 on the image generating source
side is within the following range as shown in Table 14.
(As/Ss)<-0.6
[0147] Furthermore, the aforementioned ratio of As and Ss of the
lens surface S11 of the sixth lens 6 on the screen side is within
the following range as shown in Table 15.
(As/Ss)<1.1
[0148] Next, the condition for making the light amount ratio of the
middle field of the screen satisfactory and some other conditions
will be described. Assuming the distance (axial distance between
surfaces) on the optical axis between the first lens 1 and the
second lens 2 as L12, the ratio of it to the focal length f0 of the
overall projection lens system relates to the light amount in the
middle field of the screen and the following relation is held as
shown in Table 16.
(L 12/f0)<0.25
[0149] Beyond this range, the light amount ratio of the middle
field of the screen area is reduced.
[0150] The ratio of the distance (axial distance between surfaces)
L 12 on the optical axis between the first lens 1 and the second
lens 2 to the distance (axial distance between surfaces) L 23 on
the optical axis between the second lens 2 and the third lens 3 is
decided by the balance of correction of aberration and the
following relation is held as shown in Table 16.
(L12/L23)>1.3
[0151] Below this range, no satisfactory focus performance can be
obtained.
[0152] Between the absolute value of radius of curvature Ra3 of the
lens surface S5 of the third lens 3 on the screen side and the
absolute value of radius of curvature Rb3 of the lens surface S6 of
the third lens 3 on the image generating source side, the following
relation is held:
.vertline.Ra3.vertline.<.vertline.Rb3.vertline.
[0153] The reason is that the spherical aberration and coma
aberration caused by the third lens 3 are reduced. Between the
absolute value of radius of curvature Ra4 of the lens surface S7 of
the fourth lens 4 on the screen side and the absolute value of
radius of curvature Rb4 of the lens surface S8 of the fourth lens 4
on the image generating source side, the following relation is
held:
.vertline.Ra4.vertline.<.vertline.Rb4.vertline.
[0154] The reason is that the reduction in the share of the
positive refractive power to the third lens 3 and the correction of
chromatic aberration and spherical aberration are balanced. When a
material of an Abbe's number of 45 or less is used for the fourth
lens 4, the chromatic aberration can be reduced.
[0155] The characteristics of the profile of lens surface are
mentioned above on the basis of the lens data of the projection
lens system in the embodiments of the present invention.
[0156] In this embodiment, the aspherical surfaces using up to the
aspherical coefficient of 10th order AH are described. Needless to
say, a constitution that a coefficient of 12th order or higher is
included is also included in the present invention.
12TABLE 12 Effective radius of Lens Lens surface S.sub.1 surface
S.sub.1 No. As (mm) Ss (mm) As/Ss (mm) 1 6.861 19.164 0.358 56.0 2
8.846 18.227 0.485 52.7 3 2.023 15.968 0.127 56.0 4 6.381 17.763
0.359 52.7 5 0.773 14.855 0.052 56.0 6 -0.402 14.460 -0.028 56.0 7
-0.693 14.620 -0.047 56.0 8 1.801 15.176 0.119 56.0 9 2.397 15.358
0.156 56.0 10 1.074 15.286 0.070 56.0 As: Aspherical surface sag
amount (mm) Ss: Spherical surface sag amount (mm)
[0157]
13TABLE 13 Effective radius of Lens Lens surface S.sub.8 surface
S.sub.8 No. As (mm) Ss (mm) As/Ss (mm) 1 -2.759 -2.461 1.121 47.0 2
-2.386 -1.781 1.340 40.0 3 -2.239 -1.781 1.257 40.0 4 -2.950 -1.781
1.656 40.0 5 -5.032 -1.781 2.825 40.0 6 -3.409 0.161 -21.18 40.1 7
-3.376 0.201 -16.80 40.1 8 -4.202 -1.781 2.359 40.0 9 -2.657 -1.781
1.492 40.0 10 -4.196 -1.781 2.356 40.0 As: Aspherical surface sag
amount (mm) Ss: Spherical surface sag amount (mm)
[0158]
14TABLE 14 Effective radius of Lens Lens surface S.sub.10 surface
S.sub.10 No. As (mm) Ss (mm) As/Ss (mm) 1 2.389 -3.955 -0.604 42.0
2 2.621 -3.340 -0.785 40.0 3 5.613 -1.386 -4.050 40.0 4 2.621
-3.340 -0.785 40.0 5 4.994 -2.005 -2.491 40.0 6 3.675 -2.151 -1.709
38.0 7 3.721 -2.105 -1.767 38.0 8 4.994 -2.005 -2.491 40.0 9 4.994
-2.005 -2.491 40.0 10 4.994 -2.005 -2.491 40.0 As: Aspherical
surface sag amount (mm) Ss: Spherical surface sag amount (mm)
[0159]
15TABLE 15 Effective radius of Lens Lens surface S.sub.11 surface
S.sub.11 No. As (mm) Ss (mm) As/Ss (mm) 1 -20.744 -19.534 1.062
42.5 2 -18.823 -17.856 1.054 41.0 3 -18.330 -18.094 1.013 41.0 4
-21.605 -19.850 1.088 41.0 5 -19.314 -18.094 1.067 41.0 6 -17.858
-18.524 0.964 41.0 7 -17.680 -18.650 0.948 41.0 8 -19.111 -18.094
1.056 41.0 9 -19.132 -18.094 1.057 41.0 10 -19.542 -18.094 1.080
41.0 As: Aspherical surface sag amount (mm) Ss: Spherical surface
sag amount (mm)
[0160]
16 TABLE 16 Axisal distance Lens Focal length between lenses No.
f.sub.0 (mm) L.sub.12 (mm) L.sub.23 (mm) L.sub.12/L.sub.23
L.sub.12/f.sub.0 1 90.486 15.473 8.707 1.777 0.171 2 90.310 20.146
4.933 4.084 0.223 3 90.775 18.075 9.167 1.972 0.199 4 89.473 13.907
10.482 1.327 0.155 5 90.130 17.286 8.149 2.121 0.192 6 90.276
17.162 5.811 2.954 0.190 7 90.339 17.162 5.079 3.379 0.190 8 90.098
17.431 7.842 2.223 0.194 9 90.330 16.778 10.013 1.676 0.186 10
90.277 16.478 8.988 1.833 0.183 L.sub.12: Axial distance between
first lens group and second lens group L.sub.23: Axial distance
between second lens group and third lens group f.sub.0: Focal
length of overall projection lens system
[0161] Next, a method that in the projection lens system of the
present invention, at least one communicating opening or
communicating window extending outside of the projection lens
system from the spaces between the lens elements is installed and
that even if the heat quantity generated from the image generating
source is large, the air temperature in the sealed space inside the
lens barrel and the temperature of the lens elements are prevented
from rising will be explained.
[0162] FIG. 20 is a cross sectional view showing the essential
section of an example of a projection lens system of the prior
art.
[0163] In FIG. 20, numeral 17 indicates a projection lens system, 8
a projection type cathode ray tube as an image generating source, 7
a liquid coolant, 20 lens elements, 9 a lens barrel as a lens
element holding member, 11 a bracket as a connection member, and 10
elastic bodies. The lens barrel 9 has an inner barrel 9a and an
outer barrel 9b and the lens elements 20 except the lens element
20a which is closest to the projection type cathode ray tube 8 are
held in the inner barrel 9a with high precision. Both the lens
element 20a and the projection type cathode ray tube 8 are pressed
and held by the bracket 11 by a suitable holding means via the
elastic bodies 10 and the liquid coolant 7 is sealed in the space
surrounded by the lens element 20a, the projection type cathode ray
tube 8, and the bracket 11. At this time, the inside of the lens
barrel 9 is a sealed structure practically. As a result, by the
heat generated by the projection type cathode ray tube 8 which is
an image generating source, the lens element 20a closest to the
projection type cathode ray tube 8 and the air in the space between
the lens element 20a and the lens element 20b second closest to the
projection type cathode ray tube 8 are heated sequentially and
furthermore, the temperature of the overall lens elements 20 and
the air temperature in the sealed spaces between the lens elements
rise gradually. This heat is radiated outside the projection lens
system 17 almost only by heat transfer from the outer surface of
the bracket 11, the outer surface of the lens barrel 9, and the
outer surface of the lens element farthest away from the projection
type cathode ray tube 8 among the lens elements 20. However, the
material of lens elements is generally glass or plastics and when
the lens barrel 9 is made of plastics from the point of view of
moldability, the heat transfer coefficient from these outer
surfaces is smaller than the heat transfer coefficient from the
metal surface, so that the heat radiation amount is smaller than
the exothermic amount of the projection type cathode ray tube 8 and
others and the air temperature in the sealed spaces and the
temperature of the lens elements rise furthermore. As a result, a
problem arises that the heated lens elements are expanded or
deformed and hence the focus performance of the projection lens
system is extremely lowered. Therefore, it is a subject for design
to suppress rising of the air temperature in the sealed space in
the lens barrel and the temperature of the lens elements and to
prevent the lens elements from expansion and deformation even if
the heat quantity from the image generating source is large.
[0164] FIG. 21 is a cross sectional view showing the essential
section of the 11th embodiment of the projection lens system 17 of
the present invention and the same numeral is assigned to the part
which is equivalent to a part shown in FIG. 20. The lens barrel 9
has an inner barrel 9a and an outer barrel 9b holding the inner
barrel 9a in the slidable state and the lens elements 20 except the
lens element 20a which is closest to the projection type cathode
ray tube 8 are held in the inner barrel 9a with high precision.
[0165] In FIG. 21, in the outer barrel 9b of the lens barrel 9, at
least one communicating opening (a communicating window when the
overall length Or the opening is short) 27 for connecting the
inside of the lens barrel 9 and the outside of the projection lens
system is installed.
[0166] FIG. 22 is a cross sectional view showing the essential
section when the cross section of the lens barrel 9 of the
projection lens system 17 shown in FIG. 21 is seen in the direction
of the arrow A. The inner barrel 9a is fitted and held by a
plurality of fitting protrusions 25 installed on the inner surface
of the outer barrel 9b and grooves 28a between the fitting
protrusions 25 become a second communicating opening 28. In FIG.
22, the fitting protrusions 25 on the inner surface side of the
outer barrel 9b are structured so that they are arranged at four
locations on a cross section perpendicular to the optical axis.
However, the present invention is not limited to this constitution.
For example, the number of arrangement locations of the fitting
protrusions 25 may be 3 or any other number. These fitting
protrusions 25 may be in a shape that they are cut into pieces in
the direction of the optical axis and any constitution that the
inner barrel 9a can slide inside the outer barrel 9b smoothly and
that the grooves 28a can fulfill the function as a communicating
opening fully is acceptable.
[0167] In this constitution, when the projection lens system is
actually used, for example, when it is incorporated and used in a
rear projection type image display apparatus, the right side (the
projection type cathode ray tube side) of FIG. 21 is generally
located low and the left side (the lens element side) is generally
located up, so that the location of the second communicating
opening 28 is generally higher than the location of the first
communicating opening 27. Therefore, low-temperature air C (open
air) introduced from the first communicating opening 27 is heated
by the projection type cathode ray tube 8 in the space between the
lens element 20a closest to the projection type cathode ray tube 8
and the lens element 20b second closest to it, and the temperature
thereof rises, and the air becomes light due to volume expansion.
Air H which is heated and lightened flows out of the second
communicating opening 28. The lens elements 20 radiate heat
efficiently by repetition of this series of phenomena, so that the
expansion and deformation thereof can be suppressed and the focus
performance of the projection lens system can be prevented from
lowering.
[0168] FIG. 23 is a cross sectional view showing the essential
section of the 12th embodiment of the projection lens system of the
present invention, and the same numeral is assigned to the part
which is equivalent to a part shown in FIG. 21, and explanation is
omitted.
[0169] Although the first communicating opening is installed in the
outer barrel 9b of the lens barrel 9 in the aforementioned 11th
embodiment, the 12th embodiment, as shown in FIG. 23, has a
constitution that junction protrusions 26 are installed, for
example, at three locations on one of the outer barrel 9b and the
bracket 11 or both of them, and the outer barrel 9b and the bracket
11 are joined at the junction protrusions 26, and a gap portion 27a
is provided in the portion other than the junction protrusions 26.
Therefore, this gap portion 27a functions as the first
communicating opening 27 connected from the spaces between the lens
elements to the outside of the projection lens system.
[0170] FIG. 24 is a perspective view of the essential section
showing the actual constitution of the first communicating opening
27 shown in FIG. 23. In FIG. 24, the junction protrusions 26 are
installed at three locations on the end face of the bracket 11 and
the gap portion 27a between the junction protrusions 26 is the
first communicating opening 27. The junction protrusions 26 may be
installed on the flange surface at the end of the outer barrel 9b
instead of the end face of the bracket 11 or may be installed on
both of them and put opposite to each other free of substantial
difference. In either case, the same effect as that in the 11th
embodiment can be obtained.
[0171] FIG. 25 is a cross sectional view showing the essential
section of the 13th embodiment of the projection lens system of the
present invention, and the same numeral is assigned to the part
which is equivalent to a part shown in FIGS. 21 and 23, and
explanation is omitted.
[0172] A difference of the 13th embodiment from the 12th embodiment
is a point that in the opening portions of the first communicating
opening 27 and the second communicating opening 28 toward the
outside of the projection lens system, a first flange 29 and a
second flange 30 are arranged as a dust-proof member respectively.
In this case, assuming the communicating openings including
portions along the dust-proof members 29 and 30 as a communicating
opening respectively, the shape of each communicating opening
itself can be regarded as a bent shape. In this embodiment, in
addition to the effects obtained in the 11th and 12th embodiments,
since the system has a function for preventing a foreign material
and light from entering the projection lens system and light
leakage from the projection lens system, the contrast performance
of the projection lens system itself will not be lowered and the
image contrast of a rear projection type image display apparatus
using the projection lens system will neither be lowered. Even if a
curved shape or twisted shape is used as a shape of communicating
opening in addition to the bent shape, the same effect can be
obtained.
[0173] FIG. 26 is a cross sectional view showing the essential
section of the 14th embodiment of the projection lens system of the
present invention, and the same numeral is assigned to the part
which is equivalent to a part shown in FIGS. 21, 23, and 25, and
explanation is omitted.
[0174] A difference of the 14th embodiment from the 11th embodiment
is a point that the lens barrel 9 is of an integrated type that it
is not separated into an outer barrel and an inner barrel. In this
embodiment, the second communicating opening 28 is formed as a
through hole inside the wall surface of the lens barrel 9. Even if
this constitution is used, the same effect as that in the 11th and
12th embodiments can be obtained. In the same way as with the 13th
embodiment, when a dust-proof member (not shown in the drawing) is
installed in the opening portion of the communicating opening
toward the outside of the projection lens system, the same effect
as that in the 13th embodiment is obtained.
[0175] FIG. 27 is a cross sectional view showing the essential
section of the 15th embodiment of the projection lens system of the
present invention, and the same numeral is assigned to the part
which is equivalent to a part shown in FIGS. 21, 23, 25, and 26,
and explanation is omitted. A difference of the 15th embodiment
from the 14th embodiment is a point that the second communicating
opening 28 is formed as a through hole in the neighborhood of the
periphery of each lens element instead of a through hole inside the
wall surface of the lens barrel 9. Even if this constitution is
used, the same effect as that in the 11th, 12th, and 14th
embodiments can be obtained. In the same way as with the 13th
embodiment, when a dust-proof member (not shown in the drawing) is
installed in the opening portion of the communicating opening
toward the outside of the projection lens system, the same effect
as that in the 13th embodiment is obtained.
[0176] Next, the constitution when the projection lens system as
explained in each aforementioned embodiment is used in a projection
type image display apparatus will be explained.
[0177] FIG. 28 is a cross sectional view showing the essential
section of the longitudinal cross section of a rear projection type
image display apparatus using the projection lens system 17 of the
present invention. Numeral 15 indicates a reflecting mirror, 16 a
transmission type screen, 21 a cabinet, and 22 a projection lens
system holding member. The inside of the cabinet 21 is partitioned
into an upper space 23 and a lower space 24 by the projection lens
system holding member 22. The same numeral is assigned to the part
which is equivalent to a part shown in each of FIGS. 21 to 27, and
explanation is omitted.
[0178] In the rear projection type image display apparatus shown in
FIG. 28, the aforementioned projection lens system 17 is held by
the projection lens system holding member 22 and the lens barrel 9,
each lens element therein, and the bracket 11 are arranged in the
upper space 23 in the cabinet. An original image displayed on the
projection type cathode ray tube 8 which is an image generating
source is enlarged by the projection lens system 17, and the
optical path thereof is folded by the reflecting mirror 15, and the
enlarged image is projected on the transmission type screen 16.
[0179] When the projection lens system according to the lens data
shown in Tables 1 to 10 which is explained previously is used as a
projection lens system, a compact set can be realized as the rear
projection type image display apparatus shown in FIG. 28.
[0180] FIG. 29 is a cross sectional view showing the longitudinal
cross section of a rear projection type image display apparatus
when the rear projection type image display apparatus shown in FIG.
28 is structured so as to stand on end as another embodiment of a
rear projection type image display apparatus using the projection
lens system 17 of the present invention. Numerals 23' and 24'
indicate an upper space and a lower space in the cabinet 21
respectively. The same numeral is assigned to the part which is
equivalent to a part shown in FIG. 28.
[0181] FIG. 30 is a cross sectional view showing the projection
lens system 17 of the rear projection type image display apparatus
shown in FIG. 28 in detail.
[0182] FIG. 31 is a cross sectional view showing the projection
lens system 17 of the rear projection type image display apparatus
shown in FIG. 29 in detail.
[0183] The projection lens system 17 shown in FIGS. 30 and 31 has a
constitution equivalent to that of the 14th embodiment of the
aforementioned projection lens system 17.
[0184] In the projection lens system 17 shown in FIG. 30, by the
heat generated by the projection type cathode ray tube 8 which is
an image generating source, the lens element 20a closest to the
projection type cathode ray tube 8 and the air in the space between
the lens element 20a and the lens element 20b second closest to the
projection type cathode ray tube 8 are heated sequentially, and the
heated air H at high temperature flows out from the second
communicating opening 28 formed in the lens barrel 9 into the upper
space 23, and on the other hand, low-temperature air (open air) C
flows in from the first communicating opening 27. Also in the
projection lens system 17 shown in FIG. 31, by the heat generated
by the projection type cathode ray tube 8, the lens element 20a
closest to the projection type cathode ray tube 8 and the air in
the space between the lens element 20a and the lens element 20b
second closest to the projection type cathode ray tube 8 are heated
sequentially, and the heated air H at high temperature flows out
from the first communicating opening 27 into the lower space 24',
and on the other hand, low-temperature air (open air) C flows in
from the second communicating opening 28 formed in the lens barrel
9. By these operations, the efficiency of heat radiation from the
lens elements increases, and the lens elements 20a and 20b are
prevented from rising of temperature, and expansion and heat
deformation are generated little, and the focus performance as a
projection lens system is prevented from changing due to
temperature.
[0185] The projection lens system 17 shown in FIGS. 30 and 31 may
have the constitution shown in another embodiment of the projection
lens system 17 and the same effect as that in the aforementioned
case can be obtained. Furthermore, as shown in the 13th embodiment,
when a dust-proof member (not shown in the drawing) is installed in
the opening portion of each communicating opening toward the
outside of the projection lens system, since the projection lens
system 17 has a function for preventing a foreign material and
light from entering the projection lens system and light leakage
from the projection lens system, the image contrast of the rear
projection type image display apparatus will not be lowered.
[0186] In the above description, the constitution that each
communicating opening is arranged in the space between the lens
element closest to the image generating source and the lens element
second closest to it is mainly explained. However, the location of
each communication opening to be arranged is not limited to it.
Even if it is arranged in a space between other lens elements, the
same effect can be obtained though it is inferior slightly.
[0187] Only a case that the projection type cathode ray tube is
used as an image generating source is explained. However, even if a
constitution that a liquid crystal panel is combined with the light
source is used, since the light source becomes a heat generating
source, the same effect as the aforementioned can be obtained.
Furthermore, as an example of the projection type image display
apparatus using the projection lens system of the present
invention, a rear projection type image display apparatus is
explained. However, needless to say, even a case of a front
projection type image display apparatus can obtain the same
effect.
[0188] The present invention obtains many good results indicated
below.
[0189] (1) Since a constitution that no concave lens is arranged on
the screen side of the third lens having almost all the positive
refractive power of the overall projection lens system is used,
even if the field angle is widened, distortion and astigmatism can
be corrected and a high focus and a wide field angle are compatible
with each other.
[0190] (2) Since a constitution that no concave lens is arranged
between the third lens having the positive refractive power and the
first lens closest to the screen side is used, the light focused in
the marginal area is not diverged between them. As a result, the
height of light can be lowered and a good marginal light amount
ratio can be realized.
[0191] (3) Almost all the positive refractive power of the overall
projection lens system is shared by the third lens and by
combination of local aspherical surface profiles of the first and
second lenses, the lowering of the focus performance due to changes
in temperature and absorption of moisture can be reduced.
[0192] (4) When a lens having negative refractive power with the
concave surface facing the screen side is installed in the location
closest to the projection tube which is an image light source as a
sixth lens and the lens surface of the lens on the screen side is
formed as a profile that the lens refractive power in the area
through which the light flux from an object in the marginal area on
the fluorescent face passes is weaker than that in the neighborhood
of the optical axis of the lens, the difference in length of
optical path between the saggital plane and the meridional plane is
made smaller. Furthermore, in a lens arranged next on the screen
side to the above-mentioned lens having negative refractive power,
when the profile of the lens surface on the projection tube side is
convex on the projection tube side in the neighborhood of the
optical axis and concave on the projection tube side in the
marginal area, the above difference in length of optical path can
be made more smaller and the astigmatism in the marginal area can
be corrected with higher precision.
[0193] (5) The third lens is an inexpensive low dispersion glass
convex lens and the cost of the overall projection lens system is
reduced. To correct chromatic aberration, the fourth lens is a high
dispersion plastic concave lens and used in combination with the
third lens. Furthermore, a filter for cutting the spurious
component other than the dominant wavelength component of the light
emission spectrum of a phosphorescent substance is installed in at
least one lens of the lenses constituting the projection lens
system and the generated chromatic aberration itself is
reduced.
[0194] (6) Furthermore, to realize a large aperture, the
aforementioned fourth lens is a large dispersion plastic concave
lens, and the profile thereof is formed in a protile of strong
aspherical surface, and the aberration can be corrected with high
precision.
[0195] The entry height of the upper ray into the third lens (glass
lens) can be lowered by the aspherical surface profile of the
fourth lens, so that the diameter of the third lens (glass lens)
can be decreased for the same F-number and the cost can be
reduced.
[0196] Furthermore, the incident angle of the upper ray into the
third lens (glass lens) can be increased, so that the refractive
power of the third lens 3 can be made smaller. As a result, an
inexpensive glass material with a refractive index nd of 1.6 or
less can be used and the cost can be reduced.
[0197] When the aforementioned projection lens system is used, a
bright and high focus image can be obtained in the overall area of
the screen and a compact projection type display apparatus can be
realized. When the projection lens system of the present invention
is applied, between the distance (projection distance) L (mm) from
the top of the lens surface of the lens closest to the screen in
the first lens on the screen side to the transmission type screen
and the diagonal effective size M (inch) of the transmission type
screen, the following relation is held:
17.3<(L/M)<17.6
[0198] and a compact set can be realized.
[0199] On the other hand, according to the present invention, when
the communicating opening or communicating window explained in each
aforementioned embodiment is arranged in the lens barrel of the
projection lens system or others, the efficiency of heat radiation
from the lens elements is increased by the convection action of
air, and the lens elements are suppressed in rising of temperature,
and the expansion and deformation due to rising of temperature are
suppressed, and as a result, the lens performance, particularly the
focus performance are prevented from lowering.
[0200] Furthermore, when a dust-proof member in a shape such as a
flange is arranged in a suitable location of the opening portion of
the aforementioned communicating opening or communicating window
toward the outside of the projection lens system or when the
communicating opening or communicating window itself is formed in a
bent, or curved, or twisted shape, entry of a foreign material or
light into the projection lens system and light leakage from the
inside of the projection lens system are prevented, and the
contrast performance of the projection lens system itself will not
be lowered, and the image contrast of a projection type image
display apparatus using the projection lens system will be neither
reduced.
* * * * *