Computer graphics processing and selective visual display system – Computer graphics processing – Attributes
Reexamination Certificate
1999-03-19
2002-01-29
Luu, Matthew (Department: 2672)
Computer graphics processing and selective visual display system
Computer graphics processing
Attributes
C345S549000, C345S591000, C345S601000
Reexamination Certificate
active
06342896
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and apparatus for displaying images, and more particularly, to display methods and apparatus which utilize multiple displaced portions of an output device, e.g., liquid crystal display, to represent a single pixel of an image.
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 the human eye.
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. The coating results 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. For a color CRT, where a single triad of red, green and blue phosphor dots cannot be addressed, the smallest possible pixel size will depend on the focus, alignment and bandwidth of the electron guns used to excite the phosphors. The light emitted from one or more triads of red, green and blue phosphor dots, in various arrangements known for CRT displays, tend to blend together giving, at a distance, the appearance of a single colored light source.
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 a white pixel.
Portable computing devices, including hand held devices and portable computers, 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 light weight as compared to CRT displays. In addition, flat panel displays tend to consume less power than comparable sized CRT displays making them well suited for battery powered applications.
Color LCD displays are exemplary of display devices which utilize multiple distinctly addressable elements, referred to herein as pixel sub-components or pixel sub-elements, to represent each pixel of an image being displayed. Normally, each pixel element of a color LCD display comprises three non-square elements, i.e., red, green and blue (RGB) pixel sub-components. Thus, a set of RGB pixel sub-components together make up a single pixel element. Known LCD displays generally comprise a series of RGB pixel sub-components which 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. 1
illustrates a known LCD screen
200
comprising a plurality of rows (R
1
-R
12
) and columns (C
1
-C
16
). Each row/column intersection forms a square which represents one pixel element.
FIG. 2
illustrates the upper left hand portion of the known display
200
in greater detail.
Note in
FIG. 2
how each pixel element, e.g., the (R
1
, C
4
) pixel element, comprises three distinct sub-element 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. 1
, one known arrangement of RGB pixel sub-components 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. 1 and 2
, is sometimes called “vertical striping”.
Traditionally, each set of pixel sub-components for a pixel element is treated as a single pixel unit. Accordingly, in known systems luminous intensity values for all the pixel sub-components of a pixel element are generated from the same portion of an image. Consider for example, the image represented by the grid
220
illustrated in FIG.
3
. In
FIG. 3
each square represents an area of an image which is to be represented by a single pixel element, e.g., a red, green and blue pixel sub-component of the corresponding square of the grid
230
. In
FIG. 3
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 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.
While individual RGB sub-component intensities can be varied to support a wide range of different colors, frequently, only a limited number of colors are actually supported by the display hardware and/or software. A supported set of colors is referred to commonly as a color palette. Each color in a color palette corresponds to a different combination of R, G, and B pixel sub-component luminance intensity values. While a computer system may support multiple color palettes, normally only one palette may be used to generate the images displayed at any given time.
In the case of text rendering, a user normally selects a foreground and background color to be used. Commonly, a dark foreground and a light background color is selected to produce dark text on a light colored field. Such an approach mimics printed text which frequently tends to be black on a white background.
As an alternative to a dark foreground and a light background, a user may select a light foreground and a dark background. While such a text option is less common, it is sometimes used, e.g., to highlight text on the screen.
In the case where text is rendered at pixel resolution as is commonly done, pixels used to represent a character are set to the selected foreground color, e.g., black, and pixels used to represent the background are set to white. As discussed above, to produce a black pixel the R, G, and B pixel sub-components of the black pixel are set to output the minimum possible luminous intensity. In the case of a white pixel the R, G, and B pixel sub-components are set to their maximum luminous intensity.
Frequently, because of the relatively low display resolution of most video display devices, not enough pixels are available to draw smooth character shapes, especially at common text sizes of 10, 12, and 14 point type.
Portable computing devices, and hand held computing devices in particular, face power consumption problems and, in many cases, cost constraints, which are frequently less of an issue in desk top computing devices.
As discussed above, power constraints often lead to the use of LCD display devices in an attempt to minimize power consumption. Power concerns also often result in the use of a processor, e.g., CPU, designed with power saving features. Since there are more desk top PCs than portable computers, most CPU manufactures give priority to developing fast CPUs for desktop computers, as opposed to CPUs with power saving features for portable computers. For this reason processors in portable computing dev
Dresevic Bodin
Hitchcock Gregory C.
Shetter Martin T.
Luu Matthew
Microsoft Corporation
Sajous Wesner
Workman & Nydegger & Seeley
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