Computer graphics processing and selective visual display system – Display peripheral interface input device – Light pen for fluid matrix display panel
Reexamination Certificate
1997-12-23
2001-08-21
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Light pen for fluid matrix display panel
C345S182000, C345S089000, C358S451000, C358S451000
Reexamination Certificate
active
06278437
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an LCD (liquid crystal display) apparatus, and more particularly to an LCD apparatus that can display images in different video formats of different sizes (pixel configurations).
2. Description of the Prior Art
LCD panels are available in different pixel configurations for different video formats such as XGA, SVGA, and VGA. The numbers of columns and rows of pixels that these LCD panels can display are as follows:
XGA
1,024 × 768 pixels
SVGA
800 × 600 pixels
VGA
640 × 480 pixels
On the other hand, images to be displayed on an LCD panel are generally produced on a personal computer, which can output images in any of XGA, SVGA, and VGA formats depending on the video mode in which it is operating. This means that the pixel configuration of the LCD panel does not always agree with that of the video format in which the LCD panel receives images. For example, this happens when an XGA-type LCD panel receives SVGA- or VGA-format images, or when an SVGA-type LCD panel receives VGA-format images.
In such cases, a blank area appears on the screen of the LCD panel, and the screen therefore looks unnatural. To avoid this, Japanese Laid-open Patent Application No. H7-191630 discloses a method of filling the blank area with a particular color (e.g. black). Specifically, according to this method, false image data of a particular color is written to the blank area on the LCD panel through high-speed image data processing performed during the blanking intervals of the input video signal, whereas the real image data is written to the image area at the normal speed. As a result, a background of that particular color is displayed around the image area.
However, in this conventional method, the blank area needs to be filled with the particular color anew every time the screen (i.e. frame) is refreshed. This wastes processing time, requires high-speed processing, and therefore necessitates extremely efficient circuitry. In particular, this conventional method is especially disadvantageous in that it requires the dot clock to be switched in the middle of scanning between a high-speed dot clock for the blank area and a normal-speed dot clock for the image area. In addition, conventional LCD apparatus generally suffer from noticeable flickers in displayed images.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an LCD apparatus that, even when fed with images in a video format whose pixel configuration is smaller than that of the LCD screen, can fill the resulting blank area with a particular color through simpler and lower-speed image data processing than ever.
Another object of the present invention is to provide an LCD apparatus that can display images without noticeable flickers.
To achieve the above objects, according to one aspect the present invention, an LCD apparatus in which a blank area that appears on an LCD screen of the LCD apparatus as a result of displaying a screen smaller than the LCD screen is displayed in a particular color is provided with a rewritable memory; filling means for writing data of the particular color to the rewritable memory at all addresses corresponding to the LCD screen; overwriting means for overwriting the rewritable memory with image data only at addresses corresponding to the smaller screen: and means for reading all data stored in the rewritable memory and for feeding that data to an LCD module of the LCD apparatus.
In this construction, once data of a particular color is written to the memory in such a way that the entire screen of the LCD module is filled with that color, thereafter it is only necessary to refresh the data in the memory in accordance with input image data. Accordingly, it is not necessary to rewrite the entire screen including blank areas every time the screen (frame) is refreshed.
According to another aspect of the present invention, in the LCD apparatus described above, the smaller screen displayed within the LCD screen has different sizes in different video modes, and the filling means writes data of the particular color to the rewritable memory only once when the video modes are switched. When the video mode is switched from a mode for displaying SVGA-format images on an XGA-type LCD panel to a mode for displaying VGA-format images on the same LCD panel, the image area becomes smaller. As a result, an SVGA-format image may remain displayed around the new image area. However, in the above construction, since the entire screen is filled with a particular color anew on such an occasion, any image remaining at that moment is also overwritten by the filling, and thus no image of the previous video mode remains displayed.
According to another aspect of the present invention, an LCD apparatus in which an image created for a screen smaller in size than an LCD screen of the LCD apparatus is displayed with enlargement is provided with a rewritable memory; a latch circuit for latching input image data and for outputting a predetermined number of bits of the latched image data at a time; a latch control circuit for making the latch circuit latch the input image data in such a way that the input image data is duplicated partially in accordance with a given enlargement factor; a write control circuit for writing image data outputted from the latch circuit to the rewritable memory; and means for reading the image data written to the rewritable memory and feeding that data to an LCD module of the LCD apparatus.
In this construction, displayed images can be enlarged in the horizontal direction simply by making latch circuits latch input image data in such a way that the image data for one line (row of pixels) is uniformly distributed over the actual number of pixels in a line. Thus, enlargement of displayed images can be achieved easily.
According to another aspect of the present invention, an LCD apparatus is provided with a pattern generating circuit for generating a dithering pattern for each of a plurality of shades of color in such a way that the dithering pattern is changed every time an LCD screen of the LCD apparatus is refreshed; a detecting circuit for detecting a shade of color of input image data; and a selecting circuit for selecting, in accordance with an output of the detecting circuit, one of dithering patterns generated by the pattern generating circuit. In addition, in this LCD apparatus, images are displayed on the LCD screen by use of a dithering pattern selected by the selecting circuit.
In this construction, picture-by-picture output of dithering patterns can be easily performed in accordance with the shades of color of input image data.
According to another aspect of the present invention, in the LCD apparatus described above, the LCD screen is refreshed every ½f second, where f represents a vertical frequency of an input video signal. In this construction, flickers on the screen are less noticeable.
According to another aspect of the present invention, in the LCD apparatus described above, the changing of the dithering pattern is achieved by shifting the dithering pattern a predetermined number of bits upward or downward every time the LCD screen of the LCD apparatus is refreshed. In this construction, the picture-by-picture change of a dithering pattern is achieved by the use of regularly recurring patterns.
According to a further aspect of the present invention, display on the LCD panel is temporarily kept turned off during an operation for setting a video mode. In this construction, disturbance of displayed images can be prevented.
REFERENCES:
patent: 5293159 (1994-03-01), Bassetti, Jr. et al.
patent: 5389948 (1995-02-01), Liu
patent: 5488385 (1996-01-01), Sanghai
patent: 5548305 (1996-08-01), Rupei
patent: 5598184 (1997-01-01), Barkans
patent: 5712657 (1998-01-01), Eglit et al.
patent: 5757347 (1998-05-01), Han
patent: 5805126 (1998-09-01), Bassetti
patent: 5812149 (1998-09-01), Kawasaki et al.
patent: 5835117 (1998-11-01), Small
patent: H7-191630 (1995-07-01),
Iga Tomoyoshi
Inoue Kiyoji
Inoue Takeshi
Togawa Shingo
Dinh Duc Q.
Hjerpe Richard
McDermott & Will & Emery
Sanyo Electric Co,. Ltd.
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