Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-10-08
2002-10-08
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C359S621000, C353S032000
Reexamination Certificate
active
06462794
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image display apparatus provided with an liquid crystal display element and a back light for lighting the liquid crystal display element, and relates to an light image forming unit, and light enlarging unit, or optical parts which are components of the image display apparatus.
2. Description of the Related Art
With rapid progress of computers, recently the resolution of the image display apparatus has been improved rapidly and along with the size of the display screen has been increased.
Though the cathode ray tube type image display apparatus, which has been used conventionally, is excellent in resolution, the weight and power consumption increases in proportion to the resolution, and also price has risen. Because the large size display screen involves increased weight and depth, the degree of high resolution and size of display screen is naturally limited.
Significant progress has been conducted in the aspect of resolution of the liquid crystal display element type image display apparatus and the high resolution has been realized always in conformity with market needs, however not so rapid progress has been conducted in the aspect of size of display screen because the liquid crystal element is fabricated almost by mean of semiconductor process.
To realize the liquid crystal display element type large size display screen, various trials have been made. Among these trials, a method in which a small size display screen is enlarged and projected by use of a projection lens has been practically progressed particularly. However, this method requires a long projection distance. A large size display screen by means of the method loses the advantage of the liquid crystal display element, namely the advantage of thinness of the liquid crystal display element.
Some alternative methods in which liquid crystal panels are jointed without seam have been proposed. For example, Japanese Unexamined Patent Publication No. Hei 5-188340 discloses a method in which a liquid crystal panel is provided with an image forming unit and enlarging unit and the liquid crystal panel are enlarged only to the magnitude to cover the seam portion between adjacent liquid crystal panels. In this conventional method, the thinning is easy because the magnitude of enlargement is small. An image display apparatus associated with the present invention is described with reference to FIG.
23
and FIG.
24
.
FIG. 23
is a plan view of an image display apparatus for covering the seam of liquid crystal panels, and
FIG. 24
is a cress sectional view along the line A-A
1
in FIG.
23
. In FIG.
23
and
FIG. 24
,
51
a
and
51
b
denote transmission type liquid crystal display elements,
52
denotes a back light for lighting the above-mentioned liquid crystal display element,
53
denotes a cathode ray tube which is an component of the back light,
54
denotes a means for narrowing the divergent angle of output light of the back light, namely divergent angle control means,
55
a
and
55
b
denote image forming unit for projecting the display image (not shown in the drawing) on the liquid crystal display elements
51
a
and
51
b
to form an erect life-size real image(that is, erect real image having roughly same size in the embodiment),
56
a
and
56
b
denote enlarging units for enlarging the projected erect real image formed by
55
a
and
55
b
,
57
denotes a back side projection type screen, and
58
denotes a chassis for containing these parts therein.
Next, the operation of component parts is described. The back light
52
lights the transmission type liquid crystal display elements
51
a
and
51
b
with a light emitted from the cathode ray tube
53
which is a component of the back light
52
. However the transmission type liquid crystal display element is disadvantageous in view angle characteristic and the contrast is inverted on the portion where the light is irradiated with an angle larger than a certain angle. To prevent the contrast inversion, the divergent angle control means
54
for narrowing the divergent angle of output light of the back light is provided between the back light
52
and the transmission type liquid crystal display elements
51
a
and
51
b
. As the divergent angle control means
54
for narrowing the divergent angle of the output light of the back light, a means in which the angle of light having the incident angle within a certain angle range is narrowed and the light having the incident angle exceeding the certain angle range is returned back so as not to be output light has been known. According to Fujitsu Giho (FUJITSU. 47, 4, (07, 1996), p355), the same effect is realized by arranging light transmissible cones. As the result, the display image displayed on the transmission type liquid crystal display elements
51
a
and
51
b
has a predetermined divergent angle. A display image displayed on the liquid crystal display elements
51
a
and
51
b
by use of image forming units
55
a
and
55
b
having an image taking angle larger than the divergent angle is projected to form an erect life-size image. The image forming units
55
a
and
55
b
are disclosed in, for example, Japanese Unexamined Patent Publication No. Sho 64-17017. In the application, the divergent angle control means is realized by a rod lens eye structure comprising many connected lenses, each connected lens comprises two lenses connected longitudinally. A display image projected by means of the image forming units
55
a
and
55
b
is enlarged by means of the enlarging units
56
a
and
56
b
, and an image is formed on the back projection type screen
57
. As the enlarging units
56
a
and
56
b
, a concave Fresnel lens which are disclosed in, for example, Japanese Unexamined Patent Publication No. Hei 9-96704 may be used.
A plurality of projection units described herein above are arranged so that respective projection images are joined without seam on the back projection type screen
57
to thereby obtain a large size high resolution image.
However, rod lens eyes are used as the image forming units
55
a
and
55
b
in the conventional art described herein above, the image forming units
55
a
and
55
b
having a rod lens array is not only expensive but also not suitable for mass-production in association with the manufacturing process of rod lens arrays.
To solve the above-mentioned problem, a pair of micro-lens arrays disclosed in, for example, Japanese Unexamined Patent Publication No. Hei 9-274177 may be used because the micro-lens array can be easily mass-produced by means of die molding. However, manufacturing is involved in difficult problem because it is difficult to match the optical axis of the micro-lenses on the incident and emission surfaces of respective micro-lens array of a pair of micro-lens arrays and also it is difficult to match the optical axis of respective micro-lenses of two micro-lens arrays. Particularly in the case of a large size micro-lens array, it is required to fit a pair of micro-lens arrays on the entire surface, however a thin-walled large size molded product is apt to deform easily depending on the environmental humidity and temperature condition and large size micro-lens arrays can not be tightly fit invariantly.
Furthermore, the conventional art described herein above requires the narrow divergent angle of the output light from the back light
52
. The output light of the cathode ray tube
53
which is an component of the back light
52
has significantly wide divergent angle, and the narrowing of the divergent angle causes serious reduction of the efficiency. Furthermore, the means
54
for narrowing the divergent angle of the output light of a back light having the above-mentioned arranged light transmissible cones has a large depth, therefore the means
54
causes the loss of the advantage of the liquid crystal display apparatus namely thin depth.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above-mentioned problems and to provides a thin efficient image dis
Igarashi Takeshi
Iwata Takashi
Maruyama Takesuke
Ohishi Tetsu
Ohnishi Goro
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