Illumination – Light source and modifier – Including reflector
Reexamination Certificate
2000-08-30
2002-09-03
Tso, Laura K. (Department: 2875)
Illumination
Light source and modifier
Including reflector
C362S800000, C362S302000, C362S307000, C362S259000
Reexamination Certificate
active
06443597
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plane display unit in which pixels using light-emitting elements are arranged in a plural number on a substrate, and to a plane display apparatus using the plane display unit.
2. Description of the Related Art
A plane display unit having a plurality of pixels of LEDs (light-emitting diodes) arranged on a substrate has been widely used by itself as a display unit for constituting a screen or as a display unit for constituting a large screen by being arranged in a plural number like tiles.
Among the conventional LED plane display units, the one which displays the image upon inputting video signals is so constructed, as shown in
FIG. 7
, that a pixel is formed by a total of three light-emitting portions (in the drawing, these light-emitting portions are denoted by R, G and B), i.e., a light-emitting portion having a red LED pellet (LED chip), a light-emitting portion having a green LED pellet and a light-emitting portion having a blue LED pellet, and a plurality of the pixels are arranged in the transverse direction and in the longitudinal direction.
Further, among the LED plane display units, the one which displays various guide data in the form of characters is so constructed, as shown in
FIG. 8
, that LED pellets
21
and
22
of two different colors (e.g., yellowish green color and red color) are mounted on a substrate
23
being brought close to each other, the circumference of these LED pellets
21
and
22
is surrounded by a reflector frame
24
, the upper portion thereof is covered with a disk-like transparent scattering plate
25
to form a pixel
26
having a circular light-emitting surface as shown in
FIG. 9
, and a plurality of these pixels
26
are arranged in the transverse direction and in the longitudinal direction as shown.
In the LED plane display unit for displaying image shown in
FIG. 7
, however, each light-emitting portion emits light of only one color. Unless a person views the screen from a certain amount of distance, therefore, the colors of the individual light-emitting portions appear separately, which is a deterioration in the picture quality.
In the future, however, it is considered that the LED plane display unit for displaying image might be installed not only on a place at where it is viewed from a distance, such as on the wall of a building outdoors but also on a place at where it is viewed from a close range and, hence, that the above inconvenience may become conspicuous.
This inconvenience can be solved by, for example, narrowing the gap among the light-emitting portions in a pixel as shown in FIG.
10
. When the gap among the light-emitting portions is narrowed in each pixel under a fixed pixel pitch condition, however, the gap increases among the pixels as shown. When the screen is viewed from a close range, therefore, the individual pixels can be clearly discerned and the picture may appear as a set of so-called lumpy dots, which is a deterioration in the picture quality, too.
With the element of the LED plane display unit for displaying characters as shown in
FIGS. 8 and 9
, on the other hand, light from the LED pellet
21
and light from the LED pellet
22
are scattered through the scattering plate
25
. Therefore, the light-emitting surface emits light of a color which is a mixture of yellowish green color and red color. Even when the screen is viewed from a close range, therefore, yellowish green color and red color do not appear separately. However, since the light-emitting surface is of a circular shape, the areas among the light-emitting surfaces are never small compared to the areas of the light-emitting surfaces as shown in FIG.
9
. When the screen is viewed from a close range, therefore, the individual pixels
26
are clearly discerned and the character appears as a set of lumpy dots, which, still, is a deterioration in the picture quality.
The LED plane display elements for displaying characters have now been installed in many places at where it can be seen from a close range, such as in the trains, letting the above-mentioned inconvenience to appear conspicuously.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a plane display unit which improves the separate and distinguished appearance of the pixels that use light-emitting elements such as LEDs and improves the appearance of a set of visible dots even when the screen displaying pictures and characters is viewed from a close range, as well as to provide a plane display apparatus using the above plane display unit.
The plane display unit of this invention and the plane display apparatus in which the above units are arranged in plural numbers like a matrix of this invention, are characterized in that the pixels having light-emitting surfaces of nearly a rhombic shape are arranged on a substrate in a direction inclined toward the right and in a direction inclined toward the left with the sides of the light-emitting surfaces being opposed to each other.
The rhombic shape, in general, stands for a quadrilateral of which the sides all have an equal length, and the angle subtended by the neighboring sides is not 90°. In this specification, however, “nearly rhombic shape” encompasses not only the rhombic shape but also those close to the rhombic shape, such as a quadrilateral (i.e., a square that is inclined by 45°) of which the sides all have an equal length and the angle subtended by the neighboring sides is 90°.
In this plane display unit, plural pixels having a light-emitting surface of nearly a rhombic shape are arranged on the substrate in a direction inclined toward the right and in a direction inclined toward the left with the sides of the light-emitting surfaces being opposed to each other or, in other words, are so arranged that the gaps among the light-emitting surfaces form an inclined lattice shape.
Due to the shape and arrangement of the light-emitting surfaces, the plane display unit has a small ratio of the areas among the light-emitting surfaces to the areas of the light-emitting surfaces. Even when viewed from a close range, therefor, the individual pixels do not appear distinctly as compared to the conventional plane display unit shown in FIG.
9
. When viewed in a close range, therefore, the image and characters do not appear as a set of visible pixels.
In the plane display unit, further, the pixel pitch in the transverse direction of the screen is not the pixel pitch among the pixels neighboring in the transverse direction but is the transverse direction component of the pixel pitch among the pixels neighboring in a inclined direction. Therefore, the pixel pitch becomes shorter than the pixel pitch in the transverse direction of the plane display unit in which the pixels having circular or square light-emitting surfaces are arranged in the transverse direction and in the longitudinal direction. Similarly, the pixel pitch in the longitudinal direction on the screen is not apparently the pixel pitch among the pixels neighboring in the longitudinal direction but is the longitudinal direction component of the pixel pitch among the pixels neighboring in the inclined direction. Therefore, the pixel pitch becomes shorter than the pixel pitch in the longitudinal direction of the plane display unit on which the pixels having circular or square light-emitting surfaces are arranged in the transverse direction and in the longitudinal direction.
As described above, the pixel pitch which is apparently small in the transverse direction and in the longitudinal direction on the screen, contributes to enhancing the transverse resolution and the longitudinal resolution.
In the plane display unit, it is desired that the surface of the substrate has a shape nearly the same as the contours of the light-emitting surfaces of all pixels on the substrate or, in other words, has a saw-tooth shape to meet the contours of the light-emitting surfaces instead of the square shape and that the distance from the light-emitting surface located closest to the edge of the substr
Maioli Jay H.
Sony Corporation
Tso Laura K.
LandOfFree
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