Computer graphics processing and selective visual display system – Plural physical display element control system – Segmented display elements
Patent
1994-06-29
1996-10-08
Brier, Jeffery
Computer graphics processing and selective visual display system
Plural physical display element control system
Segmented display elements
345 88, G09G 336
Patent
active
055636217
DESCRIPTION:
BRIEF SUMMARY
DISPLAY APPARATUS
The present invention relates to colour display apparatus, and particularly, though not exclusively, to display apparatus for use in the advertising industry, public information displays and other such applications, including static or animated displays.
Numerous different devices are known which are able to display text, graphics or moving characters. Many of these comprise moving parts which can reduce reliability and increase manufacturing costs. Others comprise cathode-ray tubes which are bulky and require high-voltage power supplies.
As an alternative, display devices are known which comprise pixels having red, green and blue phosphor pixel elements energised by an ultra-violet light source to emit light. Different colours are generated from each pixel by selecting different combinations of the light emitted by these phospor elements. This is done by using liquid crystal shutter elements which are switched on or off to transmit or block the light from the phosphor elements. These display devices have many advantages, but suffer from only being able to generate a limited colour range.
It would be possible to generate a broader colour range by only partially switching the liquid crystal shutters on or off, or by providing a duty cycle to rapidly switch the shutters on or off. Unfortunately however, the effect produced by either of these methods is reduced as the viewing angle is increased, and so both methods effectively narrow the viewing angle of the display device.
The present invention provides a display device including pixels having red, green, blue and white colour pixel elements, and shutter means which may be turned on or off to allow or prevent light from the colour pixel elements to be emitted from the display.
The apparatus may take a number of forms. For example, the colour pixel elements could be filters illuminated by a white light source or by a combination of red, blue and green light sources. Preferably, however, the red, green and blue colour pixel elements comprise red, green and blue phosphors respectively, and the white colour element comprises either white phosphors or a mixture of red, green and blue phosphors, the phosphors being excited by a source of electromagnetic radiation, such as an ultra-violet light source. The shutter means preferably comprises liquid crystal pixels having shutter pixel elements in alignment with the colour pixel elements.
The use of the white colour elements enables a possible sixteen different colour combinations to be produced (having predetermined differences in hue and saturation) by switching the shutter means on or off, and allows the display to have both a broad colour range and wide viewing angle (although, if a large viewing angle is not required then there is no reason why the shutter means could not be turned partially on or off or used with a duty cycle as mentioned above).
Thus, the invention is particularly useful in relation to large display devices such as for advertising purposes, although the invention may also be used in small scale devices.
A further advantage of the invention is that the display device colour set is compatible with standard EGA (extended graphics adaptor) software packages, which are used in the graphics industry and are based on a range of 16 colours. Therefore, the device does not need to have a large amount of software written specifically for it, and may take advantage of the numerous EGA software packages already in existence.
Moreover, four digital bits, which is equal to half a byte, may be used to control the four colour elements of each pixel, and this results in the full utilisation of digital circuitry associated with the display, which is not possible with only three colour elements per pixel. A minimum number of electronic control components may therefore be used, reducing space requirements.
Preferably, the amount of light emitted from the white element is set to such a value that desired colour saturations are achieved when the white element is on at the same time as one or more o
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Black Box Vision Limited
Brier Jeffery
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