Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-07-22
2004-11-09
Eisen, Alexander (Department: 2774)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S087000
Reexamination Certificate
active
06816145
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to the field of display devices. More specifically, the present invention relates to the field of flat panel display devices utilizing liquid crystal display (LCD) technology.
(2) Prior Art
Flat panel displays or liquid crystal displays (LCDs) are popular display devices for conveying information generated by a computer system. Many types of flat panel displays are typically back-lit or edge-lit. That is, a source of illumination is placed behind the LCD layers to facilitate visualization of the resultant image. Flat panel LCD units are used today in many applications including the computer component and computer peripheral industries where flat panel LCD units are an excellent display choice for lap-top computers and other portable electronic devices.
In the field of flat panel LCD unit devices, much like conventional cathode ray tube (CRT) displays, a white pixel is composed of a red, a green and a blue color point or “spot.” When each color point of the pixel is illuminated simultaneously and with the appropriate intensity, white can be perceived by the viewer at the pixel's screen position. To produce different colors at the pixel, the intensities (e.g., brightness) to which the red, green and blue points are driven are altered in well known fashions. The separate red, green and blue data that correspond to the color intensities of a particular pixel are called the pixel's color data. Color data is often called gray scale data. The degree to which different colors can be achieved by a pixel is referred to as gray scale resolution. Gray scale resolution is directly related to the amount of different intensities to which each red, green and blue point can be driven.
The aspect ratio of a monitor refers to the number of pixels the monitor provides along the horizontal direction with respect to the number of pixels the monitor provides along the vertical direction. Assuming that the pixels are square, e.g., the pitch between each RGB triad is the same in both horizontal and vertical directions, the aspect ratio can also refer to the horizontal length with respect to the vertical height. Monitors not having a wide aspect ratio include the VGA standard, the SVGA standard, the XGA standard, SXGA standard and the UXGA standard. For instance, the VGA standard has 640 pixels by 480 pixels having a 1.3 to 1 aspect ratio (“1.3:1”). The SVGA standard has 800 pixels by 600 pixels having an aspect ratio of 1.3:1. The XGA standard has 1024 pixels by 768 pixels having an aspect ratio of 1.3:1. The SXGA standard has 1280 pixels by 1024 pixels having an aspect ratio of 1.25 to 1 (“1.25:1”). And, the UXGA standard has 1600 pixels by 1200 pixels having an aspect ratio of 1.3:1. The VGA standard, the SVGA standard, the XGA standard, SXGA standard and the UXGA standard have been commonly implemented in CRT display technology and also in some flat panel display technologies.
The areas of photography and publishing require the manipulation of high information content images and text. These areas are limited in the amount of information that can be displayed at one time by the size and aspect ratio of their display devices, typically CRT displays. It would be preferable, within these industries, to be able to display multiple photos, pages of text, or images side by side for either absorbing information at a higher rate or comparing them with each other, e.g., by using a wide aspect ratio display.
Wide aspect ratio displays include the high definition television standard, or HDTV standard, having 1920 pixels by 1080 pixels with an aspect ratio of 1.9 to 1 (“1.9:1”). Also, the UXGA-Wide standard is a wide aspect ratio display and has 1920 pixels by 1200 pixels with aspect ratio of 1.6 to 1 (“1.6:1”). The SXGA-Wide standard is a wide aspect ratio display and has 1600×1024 pixels with an aspect ratio of 1.6:1. And the XGA-Wide standard is a wide-aspect ratio display and has 1280 pixels by 768 pixels having a 1.7 to 1 aspect ratio (“1.7:1”). However, CRT monitors have difficulty in displaying information in a wide aspect ratio format for several reasons. First, because the bulb of a CRT encloses a large volume of high vacuum, it is structurally unsound for the bulb to deviate from a shape roughly square in cross section.
Second, as shown in
FIG. 1
, CRT display technology has some trouble individually addressing the edge located pixels
14
a
and
14
c
in a wide aspect display format.
FIG. 1
illustrates a top view of a cathode ray tube
10
that can be used for a wide aspect ratio CRT display including an electron gun
12
with beam directing magnets
5
. Because each phosphor dot in a CRT
10
is addressed by a beam from one of three electron guns
12
being fired from a common point located behind but centered over the active area
14
, addressing a dot at the extreme edge
14
a
of the screen or at the corners is very difficult. This is because of the oblique angle that the beam
12
must make with the area surface of the phosphor screen
14
and its shadow mask which can cause scanning errors. These errors result in nonuniform color and/or brightness of the displayed image.
Specifically, as the aspect ratio of the CRT increases, the angle at
18
becomes larger. As angle
18
becomes larger, the pixels
14
a
, which are located along the edge of the screen within phosphor layer
14
, become more difficult for the beam
12
a
of the electron gun
12
to individually resolve. As a result, pixel cross-over or “bleeding” may occur for the pixels located at the edges of the screen. This bleeding does not occur with the pixels
14
b
which are located in the screen center because beam
12
b
can individually resolve pixels
14
b
. The result can be a non-uniform image which is very disadvantageous. One way to resolve this problem within CRT displays is to place the electron gun
12
back farther away from phosphor layer
14
thereby decreasing the maximum angle
18
for edge-located pixels
14
a
and
14
c
. However, this solution unfortunately leads to heavier, larger, bulkier glass leading to larger and more expensive CRT displays. The larger the vacuum tube
15
becomes, the harder it is to maintain the vacuum seal.
Another way to solve the above problem of individually addressing edge-located pixels is to slightly curve the display screen as shown in
FIG. 1
to assist electron gun
12
in resolving the edge located pixels
14
a
and
14
c
. However, commercially a flat screen is the first choice for viewing images, not a curved screen, which tends to distort images and text displayed thereon. A third manner in which to solve the above problem is to alter the pixel density of the pixels located along the edge (e.g., pixels
14
a
and
14
c
) with respect to the pixel density of the center located pixels
14
b
. In other words, this solution increases the pixel pitch (e.g., distance from pixel center to pixel center) for pixels
14
a
and for pixels
14
c
compared to the center pixels
14
b
. For instance, pixel pitch for center pixels
14
b
is 0.25 mm and pixel pitch for corner pixels
14
a
is 0.28 mm in some prior art CRT displays. By increasing the pixel pitch for the edge located pixels
14
a
and
14
c
, the electron gun 1.2 can better resolve individual edge located pixels
14
a
and
14
c
. However, this solution adds the unfortunate side-effect of producing a non-uniform image with noticeable non-uniformities (e.g., non-linearity) located along the screen periphery.
In either of the solutions described above, wide aspect ratios CRTs are large and bulky. It would be advantageous to provide a wide aspect CRT that avoids the above problems. Liquid crystal flat panel displays have been used in the past. For example, U.S. Pat. Nos. 5,696,529 and 5,593,221 describe a flat panel display. However, LCD flat panel displays as needed in desktop publishing and other high quality image applications have heretofore not been manufactured with a wide aspect ratio.
Accordingly, the present invention off
Eisen Alexander
Silicon Graphics Inc.
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