Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Patent
1997-09-02
2000-08-29
Liang, Regina
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
345 76, G09G 336
Patent
active
061115606
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a display, and particularly to a display comprising a light modulator and a light source.
BACKGROUND OF THE INVENTION
Liquid crystal devices are the dominant technology presently used as light modulators in flat-panel displays. They operate by a shuttering principle in which selected pixels of the display are chosen--normally by application of an electric field across the liquid crystal layer--either to block or to transmit light. This occurs through a change in the optical properties of the liquid crystal material, often in combination with a static optical element such as a polariser. Thus a pattern of dark and bright pixels can be formed dynamically. The light required for an image to be seen can either be provided by a light source behind the liquid crystal shutter (i.e. the other side of the liquid crystal layer from the observer) or in front. In the latter case the light is either blocked, or transmitted and then reflected back to the observer. In general for graphic displays (high information content with a large number of pixels, typically >10,000), the light source takes the form of a backlight to the liquid crystal device. The power efficiency of the display is determined by a combination of the efficiency of the backlight, and the efficiency of transmission through the liquid crystal shutter when it is open. For colour displays, where red, green and blue absorbing filters are used to provide individual colours to each pixel, the typical efficiency overall is about 2 to 5%.
Pixels are selectively controlled to transmit or block light by electrically addressing the display. Row and column electrodes are provided which define pixels where they overlap. Row and column drivers apply voltages respectively to the row electrodes and column electrodes.
One of the most common configurations for such flat panel displays is passive matrix addressing, where line by line addressing of a display takes place through application of row selection voltages to select each row in turn while data voltages are applied to the columns. In this way individual pixels in each line are selected by selection of the field applied across each pixel in the line, the field being dependent on the difference between the row selection voltage and the data voltage. Each row in turn is selected until a whole frame has been addressed. Liquid crystal material does not respond immediately to a change in applied field. The time for a liquid crystal to change its state is its response time. Most liquid crystal devices use liquid crystals that have a response time that is of the same order as the frame time That is, by the time a frame has been addressed, selected pixels in the first rows will have changed state. The state is determined by the root mean square voltage V.sub.rms applied during the frame. The idea is that the final state of any pixel will be determined ideally by the column data voltage applied during row selection of that pixel. Thus a differential in V.sub.rms is created between selected pixels and non-selected pixels. One potential difficulty with this scheme is cross-talk between rows, which means that pixels in rows that are not selected may be affected by the column data voltages intended for selected rows--i.e. the field across a pixel in a given row will change even when that line has not been selected. The effect to the viewer of this cross-talk is reduced contrast of the image.
Where the response time of the liquid crystal is faster than the frame time, then by choosing suitable row select and column data (pixel on and off) voltages the number of lines which have been addressed before the liquid crystal changes state is reduced, and thus the cross-talk problem which arises as outlined above diminishes. However, when the liquid crystals are designed for higher speed operation, other problems can arise. For video rate operation of a display then the frame time for a display needs to be less than 20 ms (allowing flicker free presentation of images to the eye). Th
REFERENCES:
patent: 4667189 (1987-05-01), Den Boer et al.
patent: 4945009 (1990-07-01), Taguchi et al.
patent: 5247190 (1993-09-01), Friend et al.
patent: 5414442 (1995-05-01), Yamazaki et al.
patent: 5835173 (1998-11-01), Inbar et al.
Journal of Applied Physics, vol. 65, No. 9, May 1, 1989, pp. 3610-3616, XP000038779 Tang C W et al: "Electroluminescence of Doped Organic Thin Films".
Cambridge Display Technology Limited
Liang Regina
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