Computer graphics processing and selective visual display system – Computer graphics processing – Attributes
Reexamination Certificate
1999-04-29
2002-05-28
Brier, Jeffery (Department: 2672)
Computer graphics processing and selective visual display system
Computer graphics processing
Attributes
C345S589000
Reexamination Certificate
active
06396505
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and apparatus for displaying images, and more particularly, to methods and apparatus for detecting and/or compensating for color errors in images intended to be displayed using multiple displaced portions of an output device, e.g., liquid crystal display.
BACKGROUND OF THE INVENTION
Color display devices have become the principal display devices of choice for most computer users. The display of color on a monitor is normally achieved by operating the display device to emit light, e.g., a combination of red, green, and blue light, which results in one or more colors being perceived by a human viewer.
In cathode ray tube (CRT) display devices, the different colors of light are generated via the use of phosphor coatings which may be applied as dots in a sequence on the screen of the CRT. A different phosphor coating is normally used to generate each of the three colors, red, green, and blue resulting in repeating sequences of phosphor dots which, when excited by a beam of electrons will generate the colors red, green and blue.
The term pixel is commonly used to refer to one spot in, e.g., a rectangular grid of thousands of such spots. The spots are individually used by a computer to form an image on the display device.
In color displays, the intensity of the light emitted corresponding to the additive primary colors, red, green and blue, can be varied to get the appearance of almost any desired color pixel. Adding no color, i.e., emitting no light, produces a black pixel. Adding 100 percent of all three colors results in white.
FIG. 1
illustrates a known portable computer
100
, which comprises a housing
101
, a disk drive
105
, keyboard
104
and a flat panel display
102
.
Portable personal computers
100
tend to use liquid crystal displays (LCD) or other flat panel display devices
102
, as opposed to CRT displays. This is because flat panel displays tend to be small and lightweight as compared to CRT displays. In addition, flat panel displays tend to consume less power than comparable sized CRT displays making them better suited for battery powered applications than CRT displays.
As the quality of flat panel color displays continues to increase and their cost decreases, flat panel displays are beginning to replace CRT displays in desktop applications. Accordingly, flat panel displays, and LCDs in particular, are becoming ever more common.
Color LCD displays are exemplary of display devices which utilize multiple distinctly addressable elements, referred to herein as pixel sub-elements or pixel sub-components, to represent each pixel of an image being displayed. Normally, each pixel on a color LCD display is represented by a set of pixel sub-components which usually comprises three non-square elements, i.e., red, green and blue (RGB) pixel sub-components. Thus, in such systems, a set of RGB pixel sub-components together make up a single pixel. In the patent applications cited in the related applications section set forth above, a set of R, G, B pixel sub-components which comprise a pixel, was sometimes referred to as a pixel element.
LCD displays, of one known type commonly used in computer systems, comprise sets of RGB pixel sub-components which are used to represent pixels. In such systems, the RGB pixel sub-components are commonly arranged to form stripes along the display. The RGB stripes normally run the entire length of the display in one direction. The resulting RGB stripes are sometimes referred to as “RGB striping”. Common LCD monitors used for computer applications, which are wider than they are tall, tend to have RGB stripes running in the vertical direction.
FIG. 2A
illustrates a known LCD screen
200
comprising a plurality of rows (R
1
-R
12
) and columns (C
1
-C
16
) which may be used as the display
102
. Each row/column intersection forms a square which represents one pixel.
FIG. 2B
illustrates the upper left hand portion of the known display
200
in greater detail.
Note in
FIG. 2B
how each pixel element, e.g., the (R
2
, C
1
) pixel element, comprises three distinct sub-elements or sub-components, a red sub-component
206
, a green sub-component
207
and a blue sub-component
208
. Each known pixel sub-component
206
,
207
,
208
is ⅓ or approximately ⅓ the width of a pixel while being equal, or approximately equal, in height to the height of a pixel. Thus, when combined, the three ⅓ width pixel sub-components
206
,
207
,
208
form a single pixel element.
As illustrated in
FIG. 2A
, one known arrangement of RGB pixel sub-components
206
,
207
,
208
form what appear to be vertical color stripes down the display
200
. Accordingly, the arrangement of ⅓ width color sub-components
206
,
207
,
208
, in the known manner illustrated in
FIGS. 2A and 2B
, is sometimes called “vertical striping”.
While only 12 rows and 16 columns are shown in
FIG. 2A
for purposes of illustration, common column×row ratios include, e.g., 640×480, 800×600, and 1024×768.
LCDs are manufactured with pixel sub-components arranged in several additional patterns including, e.g., zig-zags and a delta pattern common in camcorder view finders. While features of the present invention can be used with such pixel sub-component arrangements, since the RGB striping configuration is more common, the exemplary embodiments of the present invention will be explained in the context of using RGB striped displays.
Traditionally, each set of pixel sub-components for a pixel is treated as a single pixel unit. Accordingly, in most known systems luminous intensity values for all the pixel sub-components of a pixel are generated from the same portion of an image. Consider for example, the image represented by the grid
220
illustrated in FIG.
2
C. In
FIG. 2C
each square represents an area of an image which is to be represented by a single pixel, e.g., a red, green and blue pixel sub-component of the corresponding square of the grid
230
. In
FIG. 2C
a shaded circle is used to represent a single image sample from which luminous intensity values are generated. Note how a single sample
222
of the image
220
is used in known systems to generate the luminous intensity values for each of the red, green, and blue pixel sub-components
232
,
233
,
234
. Thus, in such known systems, the RGB pixel sub-components are generally used as a group to generate a single colored pixel corresponding to a single sample of the image to be represented.
The light from each pixel sub-component group effectively adds together to create the effect of a single color whose hue, saturation, and intensity depends on the luminous intensity value of each of the three pixel sub-components. Say, for example, each pixel sub-component has a potential luminous intensity of between 0 and 255. If all three pixel sub-components are given 255 intensity, the pixel will be perceived as being white. However, if all three pixel sub-components are given a value turning off each of the three pixel sub-components, e.g., a value 0, the pixel will be perceived as black. By varying the respective intensities of each pixel sub-component, it is possible to generate millions of colors in between these two extremes.
Since, in the known system a single sample is mapped to a triple of pixel sub-components which are each ⅓ of a pixel in width, spatial displacement of the left and right pixel sub-components occurs since the centers of these elements are ⅓ from the center of the sample.
Consider for example that an image to be represented was a red cube with green and blue components equal to zero. As a result of the displacement between the sample and green image sub-component, when displayed on an LCD display of the type illustrated in
FIG. 2A
, the apparent position of the cube on the display will be shifted ⅓ of a pixel to the left of its actual position. Similarly, a blue cube would appear to be displaced ⅓ of a pixel to the right. Thus, known imaging techniques used with LCD screens can r
Cukierman Ryan E.
Hitchcock Gregory C.
Keely, Jr. Leroy B.
Lui Charlton E.
Brier Jeffery
Microsoft Corporation
Workman & Nydegger & Seeley
Yang Ryan
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