Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1997-03-06
2002-06-11
Lao, Lun-Yi (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S060000, C345S067000, C365S116000
Reexamination Certificate
active
06404412
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a plasma-addressed colour display device comprising: a layer of electro-optical material sandwiched between elongated data electrodes and plasma channels to obtain a matrix structure of pixelelements, and colour filters being associated with the pixelelements for obtaining groups of adjacent pixelelements representing different colours enabling display of a colour picture.
The publication “A 16 Inch Full Colour Plasma-addressed Active-Matrix LCD”, Digest of Technical Papers, 1993 SID International Symposium, Soc. for Info. Display pp. 883-886 by Buzak et al., discloses a plasma-addressed liquid crystal display, commonly referred to as “PALC” display device, more specifically a colour PALC display device. The known PALC display device comprises: a first substrate on which parallel transparent column electrodes are deposited, a second substrate which has parallel sealed plasma channels corresponding to rows of the display, and a liquid crystal material (LC-material) sandwiched between the substrates. Each of the plasma channels of the second substrate is filled with a low pressure ionizable gas, such as helium, and contains spaced cathode and anode electrodes along the channel for ionizing the gas to create a conductive plasma. The channels are closed off by a thin transparent dielectric sheet. Each of the plasma channels crosses all of the column electrodes to form a matrix of overlapping regions. The overlapping regions correspond to pixelelements of the electro-optical material.
The operation of the PALC display device is elucidated below. The plasma channel acts as a row switch capable of selectively addressing a row of liquid crystal pixel elements (LC-pixels). Successive lines of data signals representing an image to be displayed are sampled at column positions and the sampled data voltages are respectively applied to the column electrodes. All but one of the row plasma channels are in the deionized or non-conducting state. The plasma of the one ionized selected plasma channel is conducting and, in effect, establishes a reference potential on the adjacent side of a row of LC-pixels, causing each LC-pixel to charge to the difference of the reference potential and the column potential. Then, the ionized channel is turned off for isolating the LC-pixel charge and storing the data voltage for a frame period. When the next row of data appears on the column electrodes, only the succeeding plasma channel row is ionized to store the data voltages in the succeeding row of LC-pixels, and so on. As is well known, the attenuation of each LC-pixel to backlight or incident light is a function of the stored voltage across the pixel.
The plasma channels can be activated successively, for example by applying successively a large voltage pulse to the anode electrodes, whereby each of the cathode electrodes is coupled to a reference voltage.
To obtain a colour display, colour filters are provided representing three primary colours. The colour filters each are spatially aligned with a corresponding one of the data columns. Each intersection of one plasma channel extending in the row direction with three data columns (one for red, green, and blue) extending in the column direction defines a full colour pixel. In this way groups of three adjacent LC pixels are obtained of which each pixel is associated with another of the primary colours.
The known display device has as a drawback that many data drivers are needed to supply the data signals to the data columns.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to provide a display device of which a total number of drivers is decreased.
An aspect of the invention is characterized in that the display device is adapted to comprise groups of pixelelements each being constituted with a common data electrode cooperating with a group of plasma channels, the colour filters being aligned with the plasma channels. The groups of pixelelements form a full colour pixelelement. A group of pixelelements is constituted out of one data electrode extending in the column direction and a group of plasma channels extending in the row direction instead of one plasma channel extending in the row direction and a group of data electrodes each extending in the column direction. Different colour filters are aligned with each of the plasma channels of the group. So, the colour filters now extend in the row direction instead of the column direction. The number of plasma channels and colour filters in a group may be three such that each of the colour filters represent a primary colour. In this case, the number of data electrodes and thus the number data drivers connected thereto reduces by a factor three, and the number of plasma channels increases with a factor three. The total number of drivers decreases if in the known PALC display the number of colour pixelelements in a row (so, the number of data electrodes divided by three) is larger than the number of rows (which are the plasma channels). This is usually the case as in most display panels the number of pixelelements in a row is larger than the number of rows. As an example, suppose a known PALC display device with an 3:4 aspect ratio has 600 rows (plasma channels) and 3*800 columns (data electrodes). The total number of drivers is not less than 3000, viz. 600 pulse drivers connected to the anode electrodes (all the cathode electrodes may be interconnected to receive the reference voltage, as will be further explained below) and 2400 data drivers connected to the data electrodes. The PALC display device according to the invention comprises 800 data columns and 3*600 plasma channels. The total number of drivers is only 2600, viz. 3*600 for the anode and cathode electrodes and 800 for the data electrodes.
In accordance with an embodiment of the invention an advantageous way of driving the plasma-addressed colour display device will be described. In the known PALC display a video signal has to be processed into data signals representing three primary colours (usually: red, green, blue). The data signals are supplied to corresponding data electrodes via a data driver circuit. The data driver circuit supplies the data signals associated with the different colours in parallel to all column electrodes. The plasma channels are selected one by one via a plasma driver circuit and thus a row of pixels corresponding to the selected plasma channel will be charged. A common plasma channel cooperates with a group of three data electrodes to obtain a full colour pixel. In contrast with the known PALC display, the plasma driver circuit according to the invention is adapted to select the plasma channels in a group one by one. The data driver circuit according to the invention is adapted to supply the data signals belonging to the group of colours one by one to the common data electrode such that the data of a specific colour is presented to the activated plasma channel associated to a colour filter corresponding to that colour.
In accordance with another embodiment of invention, a further reduction of the total number of drivers is reached.
EP-B-0,325,387 shows that the number of drivers needed to drive a PALC display panel decreases by taking together in groups both the anode and the cathode electrodes. In EP-B-0,325,387 two possibilities are disclosed to select the plasma channels
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one by one. The first possibility shows that one electrode of each plasma channel is connected to a reference potential. So, all these electrodes can be interconnected to receive the reference potential. The remaining electrode of each plasma channel is connected to a pulse driver supplying a pulse signal. The plasma channels are selected one by one by supplying one pulse signal with a voltage pulse which has a value with respect to the reference voltage that is large enough to ionize the plasma, while all other pulse signals supply a voltage which has a value with respect to the reference voltage that is too low to ionize the plasma. Assuming a PALC display device with N rows o
Bartlett Ernestine C.
Koninklijke Philips Electronics , N.V.
Lao Lun-Yi
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