Gray scale and color display methods and apparatus

Details Gray scale and color display methods and apparatus Gray scale and color display methods and apparatus

1998-11-13

2003-06-10

Shankar, Vijay (Department: 2673)

Computer graphics processing and selective visual display system

Plural physical display element control system

Display elements arranged in matrix

C345S087000, C345S088000

Reexamination Certificate

active

06577291

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 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 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. 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 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 comparably 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.
Over the years, most image processing techniques, including the generation and display of fonts, e.g., sets of characters, on computer screens, have been developed and optimized for display on CRT display devices.
Unfortunately, existing text display routines fail to take into consideration the unique physical characteristics of flat panel display devices. These physical characteristics differ considerably from the characteristics of CRT devices particularly in regard to the physical characteristics of the RGB color light sources.
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 single pixel element which usually 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. LCD displays of the known type 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. 2A
illustrates a known LCD screen
200
comprising a plurality of rows (R1-R12) and columns (C1-C16) which may be used as the display
102
. Each row/column intersection forms a square which represents one pixel element.
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 (R1, C4) 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. 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. Note that known display devices normally involve the display being arranged in landscape fashion, i.e., with the monitor being wider than it is high as illustrated in
FIG. 2A
, and with stripes running in the vertical direction.
LCDs are 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 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.
2
C. In
FIG. 2C
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. 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 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 depend on the value of each of the three pixel sub-components. Say, for example, each pixel sub-component has a potential 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, 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 extr

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