Computer graphics processing and selective visual display system – Display peripheral interface input device – Light pen for fluid matrix display panel
Patent
1994-12-22
1998-04-07
Powell, Mark R.
Computer graphics processing and selective visual display system
Display peripheral interface input device
Light pen for fluid matrix display panel
345132, 345213, 348448, 348555, 348556, E09G 116
Patent
active
057369712
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for the display of graphic images of a predetermined number of dots and lines on connected CRT display devices.
A graphic display device for the display of images on a CRT display device is generally equipped with a video controller (CRTC) where the resolution (the number of dots by the number of lines) of a displayed image can be freely set to some extent. The video controller is equipped with registers for setting the parameters, such as for the frequencies of a horizontal synchronizing signal and a vertical synchronizing signal which are contained in the video signal. The video controller is connected to a bus of a computer or such device and the computer can set the values of these registers. The values corresponding to the number of dots and lines available for the connected CRT display device are set for these registers in the video controller as default values or by a CPu. The video controller generates the video signal which contains the horizontal synchronizing signal and the vertical synchronizing signal corresponding to the number of dots and lines that are available for the CRT display device based on the values set for the register; thus the desired image is displayed on the CRT display device.
Along with the spread of such device as graphical user interfaces (GUI) in recent years, there is an increasing demand for a display offering a larger number of dots and lines of not less than 640 dots by 480 lines. Therefore, a graphic display device which is to be mounted inside an expansion slot for an increase in the number of dots and lines of a conventional device has been proposed.
However, for users of such a graphic display device, there has remained a problem that the number of dots and lines of the actually displayed image cannot be increased by the addition of the graphical display device unless the number of dots and lines available for the CRT display device correspond to them. Although a CRT display device, named as a multisynchronization type or such, where the number of dots and lines to be displayed are variable has been proposed, the number of dots and lines to be displayed on an ordinary CRT display device are fixed at certain values (ex. 640 dots by 400 lines); therefore, if the graphic display device outputs a signal corresponding to a display of 640 dots by 480 lines, the graphic image cannot be accurately displayed.
Further consideration is given to this problem. So long as the number of images (number of frames) to be displayed in a certain period of time is fixed, an increase in the number of displayed dots (the number of lines in the vertical direction) requires higher horizontal synchronizing frequency (lower vertical synchronizing frequency). Since a clock is not commonly used on the side where a video signal is output and on the CRT display device side, their signals never coincide. Therefore, the CRT display device synchronizes the horizontal images so that such images will be located properly in the horizontal direction on the screen by the video signal inserted between the horizontal synchronizing signals, utilizing the horizontal synchronizing signal as a reference. The vertical images are similarly synchronized with the use of the vertical synchronizing signals. Therefore, an accurate display is available when the deviation of the frequencies of the horizontal and the vertical synchronizing signals occurs; but screen images become synchronous due to failure in the image synchronization if a video signal of a frequency out of the correspondable allowance range is input.
The graphic display device and Computer by the present invention are purposed to solve these problems and to enable the display of images in the number of dots and lines larger than those originally available to the CRT display device.
To solve the above-described problems, the graphic display devices by the present invention: which consist of such a graphic display device to output a video signal containing a horizontal synchronizing signal and a vertical synchr
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Kovalick Vincent E.
Melco Inc.
Powell Mark R.
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