Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-10-20
2001-10-09
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S094000, C345S096000, C345S208000
Reexamination Certificate
active
06300925
ABSTRACT:
The invention relates to a display device comprising an electro-optical material sandwiched between two substrates, at least one substrate being transparent, while a first substrate is provided with a matrix of picture electrodes, each picture electrode being coupled, via a switching element, to a row electrode and a column electrode, and the picture electrode being capacitively coupled to a further electrode, first drive means for providing the row electrodes, during a selection period, with a selection signal, and the row electrode or the further electrode with a bias signal, second drive means for providing the column electrodes with a data signal which, during successive selections, changes sign relative to a reference voltage.
In this application, the expression “capacitively coupled” is to be taken to mean that there is a coupling via an (auxiliary) capacitance, for example, in that a picture electrode associated with a row and a part of the row electrode associated with a subsequent (or preceding) row demonstrate a partial) overlap.
Such display devices are used, for example, in television and monitor applications.
A display device of the type mentioned in the opening paragraph is described in EP-A-0.657.864. In said document, a description is given of the way in which a DC-component across the liquid-crystal material is precluded in a liquid-crystal display device by adapting a selection signal. To achieve this, the selection signal consisting of a gate pulse is extended by so-called gate-bias voltages. In this application, the term selection signal is to be taken to mean the signal which causes the switching element to conduct (in general, the actual gate pulse of a TFT transistor). In this application, the terms bias signal or bias voltage, “(gate)-bias signal” or “(gate)-bias voltage”, are to be taken to mean a bias signal or bias voltage as described in EP-A-0.657.864, and therefore not, when the gate-bias signal is presented to a selection electrode, the voltage on a row electrode during non-selection. Instead of being presented to a row electrode, the bias signal may also be presented, for example, to a common connection for a number of capacitances within one row. In this application, the term selection period is to be taken to mean the period which, for one selection, comprises the selection signal and the bias signal.
True, the capacitive coupling between a picture electrode and an adjoining row electrode leads to a substantial increase in speed of the display device, but still flicker has been found to occur frequently.
It is an object of the invention to provide, inter alia, a display device of the above-mentioned type in which the above drawbacks are at least partly overcome.
To achieve this, a display device in accordance with the invention is characterized in that the drive means comprise means for presenting an auxiliary signal to the row electrodes outside the selection periods for at least one of two successive selections of the same pixel.
The invention is based on the recognition that, for data signals of practically the same amplitude (for example the amplitude associated with median grey), the above-mentioned capacitive coupling gives rise, during successive selections of a pixel, to a difference in amplitude of the signal across the pixel and hence of the transmission. Besides, it has been found that the behavior of the pixel is subject to substantial variation. In particular, the difference in transmission of the signal across the pixel during successive selections gives rise to flicker. Via the above-mentioned capacitive coupling, the auxiliary signal influences the amplitude of the pixels in a subsequent or preceding row in such a manner that this difference in amplitude is compensated substantially completely.
The second substrate generally is provided with one or more counter-electrodes but this is not strictly necessary, as in the case of e.g. IPS (In Plane Switching).
A first embodiment of a display device in accordance with the invention is characterized in that the drive means comprise means for presenting auxiliary signals to the row electrodes outside the selection periods for two successive selections of the same pixel, which auxiliary signals change sign relative to a second reference voltage. In general, the second reference voltage is the voltage on the row electrodes during non-selection. The auxiliary signals generate, also outside the actual selection (bias) period, a correction signal across the pixel via the same capacitive coupling. The amplitude selected for the auxiliary signal can be such that, if said signal is presented via the row electrode, it does not select switches of the relevant row. As, in addition, it is presented outside the period associated with the bias signal, the above-mentioned DC-component remains negligible.
A second embodiment of a display device in accordance with the invention is characterized in that during two successive selections of the same pixel, the selection signals have different amplitudes. By virtue thereof, a difference in response of the display cell for data signals of opposite sign is obviated.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
REFERENCES:
patent: 5128663 (1992-07-01), Furuhashi et al.
patent: 5426447 (1995-06-01), Lee
patent: 5510807 (1996-04-01), Lee et al.
patent: 5526015 (1996-06-01), Tsuboyama et al.
patent: 5555001 (1996-09-01), Lee et al.
patent: 5818409 (1998-10-01), Furuhashi et al.
patent: 0394903 A2 (1990-10-01), None
patent: 0657864A1 (1995-06-01), None
Johnson Mark T.
Knapp Alan G.
Van Der Put Adrianus A.
Hjerpe Richard
Nguyen Kimnhung
U.S. Philips Corporation
LandOfFree
Display device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Display device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Display device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2609484