Computer graphics processing and selective visual display system – Computer graphics processing – Character generating
Reexamination Certificate
1999-04-29
2002-01-15
Luu, Matthew (Department: 2672)
Computer graphics processing and selective visual display system
Computer graphics processing
Character generating
C345S469100, C345S470000, C345S690000, C345S947000
Reexamination Certificate
active
06339426
ABSTRACT:
§ 1. BACKGROUND OF THE INVENTION
§ 1.1 FIELD OF THE INVENTION
The present invention concerns producing more legible text on video displays, such as flat panel video monitors including liquid crystal display (or LCD) video monitors for example, having horizontal striping.
§ 1.2 RELATED ART
The present invention may be used in the context of flat panel video monitors, such as LCD video monitors for example. In particular, the present invention may be used as a part of processing to produce more legible text on LCD video monitors having horizontal striping.
Color display devices have become the principal display devices of choice for most computer users. Color is rendered on a display monitor by operating the display monitor to emit light (such as a combination of red, green, and blue light for example) which results in one or more colors being perceived by the human eye. Although color video monitors in general, and LCD video monitors in particular, are known to those skilled in the art, they are introduced below for the reader's convenience. In § 1.2.1 below, cathode ray tube (or CRT) video monitors are first introduced. Then, in § 1.2.2 below, LCD video monitors are introduced.
§ 1.2.1 CRT VIDEO MONITORS
Cathode ray tube (CRT) display devices include a screen having phosphor coatings which may be applied as dots in a sequence. A different phosphor coating is normally associated with the generation of different colors, such as red, green, and blue for example. Consequently, repeated sequences of phosphor dots are defined on the screen of the video monitor. One or more electron guns generate electron beams which are swept, typically left to right and top to bottom, across the screen. When a phosphor dot is irradiated by an electron beam, it will glow thereby rendering its associated color, such as red, green and blue for example.
The term “pixel” is commonly used to refer to one spot in a group of spots, such as a rectangular grid of thousands of such spots for example. The spots are selectively activated to form an image on the display device. In most color CRTs, a single triad of red, green and blue phosphor dots cannot be uniquely selected. Consequently, the smallest possible pixel size will depend on the focus, alignment and bandwidth of the electron guns used to excite the phosphor dots. 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 from the additive primary colors (such as red, green and blue for example) can be varied to achieve the appearance of almost any desired color pixel. Adding no color, that is, emitting no light, produces a black pixel. Adding 100 percent of all three (3) colors produces a white pixel.
Having introduced color CRT video monitors, color LCD video monitors are now introduced in § 1.2.2 below.
§ 1.2.2 LCD VIDEO MONITORS
Portable computing devices (also referred to generally as computing appliances or untethered computing appliances) often use liquid crystal displays (LCDs) or other flat panel display devices, instead of CRT displays. This is because flat panel displays tend to be smaller and lighter than CRT displays. In addition, flat panel displays are well suited for battery powered applications since they typically consume less power than comparably sized CRT displays.
Color LCD displays are examples of display devices which distinctly address pixel elements to represent each pixel of an image being displayed. Normally, each pixel element of a color LCD display includes three (3) non-square elements (also referred to as “sub-pixel elements” or “sub-pixel components”). More specifically, each pixel element may include adjacent red, green and blue (RGB) sub-pixel elements. Thus, a set of RGB sub-pixel elements together define a single pixel element. Some LCD displays may have non-square pixels and/or pixels which are defined by more than three (3) sub-pixel elements.
Known LCD displays generally include a series of RGB sub-pixel elements 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”. Many LCD monitors, used for computer applications, are wider than they are tall, and tend to have RGB vertical stripes. On the other hand, many LCD monitors used in untethered or handheld computing appliances are taller than they are wide, and tend to have RGB horizontal stripes. The present invention may be used when rendering text on monitors, such as LCD RGB monitors for example, which have horizontal striping.
FIG. 1
illustrates a known LCD screen
100
comprising pixels arranged in a plurality of rows (R1-R8) and columns (C1-C6). That is, a pixel is defined at each row-column intersection. Each pixel includes a red sub-pixel element, depicted with hatching, a green sub-pixel element, depicted with cross hatching, and a blue sub-pixel element, depicted with no hatching.
FIG. 2
illustrates the upper portion of the known display
100
in greater detail. Note how each pixel element, e.g., the (R1, C6) pixel element, comprises three distinct sub-pixel elements or sub-pixel components; a red sub-pixel element
210
, a green sub-pixel element
220
and a blue sub-pixel element
230
. Each known sub-pixel element
210
,
220
,
230
is ⅓, or approximately ⅓, the height of a pixel while being equal, or approximately equal, in width to the width of a pixel. Thus, when combined, the three ⅓ height, full width, sub-pixel elements
210
,
220
,
230
define a single pixel element.
Referring back to
FIG. 1
, one known arrangement of RGB pixel sub-components
210
,
220
,
230
define horizontal color stripes on the display
100
. Accordingly, the arrangement of ⅓ height color sub-pixel elements
210
,
220
,
230
, in the known manner illustrated in
FIGS. 1 and 2
, exhibit what is sometimes called “horizontal striping.”.
In known systems, the RGB sub-pixel elements are generally addressed and used as a group to generate a single colored pixel corresponding to a single sample of the image to be represented. More specifically, in known systems, luminous intensity values for all of the sub-pixel elements of a pixel element are generated from a single sample of the image to be represented. For example, referring to
FIG. 3
, an image section
300
is segmented into twelve (12) squares by the grid
310
. Each square of the grid
310
defined by the segmented image section
300
represents an area of the image section
300
which is to be represented by a single pixel element. In
FIG. 3
, a hatched circle
320
is used to represent a single image sample from which luminous intensity values associated with the red, green, and blue sub-pixel elements
330
,
332
, and
334
of the associated pixel are generated.
Having introduced the general structure and operation of known LCD displays, known techniques for rendering text on such LCD displays, as well as perceived shortcomings of such known techniques, are introduced in § 1.2.2.1 below.
§ 1.2.2.1 RENDERING TEXT ON LCD DISPLAYS
Apart from pure image or video information, LCD displays are often used for rendering textual information. For example, a personal information manager may be used to render contact information, such as a person's address, telephone number, fax number, and e-mail address for example, on an untethered computing device.
The expression of textual information using font sets is introduced in § 1.2.2.1.1 below. Then, the rendering of textual information using so-called pixel precision and perceived shortcomings of doing so are introduced in § 1.2.2.1.2 below.
§ 1.2.2.1.1 FONT SETS
A “font” is a set of characters of the same typeface (such as Times Roman, Courier New, etc.), the same style (such as italic), the same weight (such as bold and, strictly speaking, the same size). Characte
Cukierman Ryan E.
Hitchcock Gregory C.
Keely, Jr. Leroy B.
Lui Charlton E.
Havan Thu-Thao
Luu Matthew
Workman & Nydegger & Seeley
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