Abstract: A plasma display panel is a pure linear display and does not provide a non-linear gamma behaviour like a CRT so that an artificial gamma function has to be applied to the signal in digital form. This gamma function increases the quantization steps in the dark areas whereas the quantization steps will be reduced in the luminous areas. The basic idea is to apply an adaptive noise filtering after the gammatization process. The adaptive filtering is a specific filtering which is adapted to the gammatization quantization noise. In other words, the filtering will be maximum for dark areas and its efficacy will be automatically decreased when the luminance of the area is increasing.

Abstract: The differences between the time responses of phosphor elements of a plasma display panel (17) shall be reduced by signal processing means without a need of a motion estimator. Therefore, the sub-fields for driving the luminous elements are reorganized in at least two groups of sub-fields arranged one after the other within one frame period. Luminous elements with long time responses are driven by the sub-fields of the first group and luminous elements with short time responses are driven by sub-fields of the first and second group. Thus, the phosphor lag effects are reduced.

Abstract: With the new plasma display panel technology new kinds of artefacts can occur in video pictures due to the principle that brightness control is done with a modulation of small lighting pulses in a number of periods called sub-fields. These artefacts are commonly described as ‘dynamic false contour effect’. To compensate for this effect motion estimators are used and with the resulting motion vectors corrected sub-field code words are calculated for the critical pixels. Today's motion estimators work with the luminance signal component of the pixels. This is not sufficient for plasma displays. It is therefore proposed to make the motion vector calculation separately for the color components and with either the sub-field code words as data input or with single bit data input for performing motion estimation separately for single sub-fields or for a sub-group of bits from the sub-field code words. The proposal also concerns apparatuses for performing the inventive method.

Abstract: The present invention relates to a method and an apparatus for generating subfield codes for pictures displayed on a display device like plasma display panels (PDPs) or display devices wherein the grey level of the pixels of the pictures displayed by the display device is obtained by modulating the number of light pulses per frame or sustain pulses (PWM for Pulse Width Modulation), the number of sustain pulses per subfield of the frame depending on the power average level of the picture to be displayed. The video levels of the pictures are first transcoded into luminance codes and then coded into subfield codes. In order to reduce the memory size required for implementing this transcoding, offset values between luminance codes are stored in a look-up table instead of storing the luminance codes. The luminance codes are then regenerated in the controller of the display device.

Abstract: The noise occurring when applying dithering on a transfer function shall be reduced. Therefore, a first output value and a second output value are associated to a discrete input value of the transfer function. On the basis of a given number of dithering bits, an intermediate value being equal to and/or lying between the first output value and the second output value and using the least number of dithering bits is chosen. Finally this intermediate value is taken as an output value for the discrete input value. Thus, the dithering noise can be reduced tremendously.

Abstract: The EMI spectrum of a display device is to comply with respective norms. Therefore, the clock for loading data into data drivers of a display panel is designed to be variable. Consequently, the electromagnetic radiation produced by the loading clock is broadened thereby reducing the peak amplitude. Thus, the limitations of radiation norms can be complied with.

Abstract: The present invention relates to a method and an apparatus for controlling the power level and/or the contrast in a display device having a plurality of luminous elements corresponding to the colour components of the pixels of a picture, wherein the luminance generated by each of said luminous element is based on the intensity of the signal supplied to the luminous element and the power level and/or contrast for each picture is controlled by adjusting the intensity of the signal to be supplied to each luminous element. The invention is applicable to organic light emitting displays (OLED). According to the invention, the intensity of the signal to be supplied to each luminous element is based on reference signals and the adjustment of the signal intensity is made by adjusting the level of the reference signals.

Abstract: The present invention relates to a method for improving grey scale fidelity portrayal of pictures displayed on matrix display screens. The method comprises the following steps: a) for a given peak white level, distributing the sustain pulses among the sub-fields, the number of pulses corresponding to the sub-field weighting, b) mapping the sub-field codes to luminance codes, c) re-ordering luminance codes in a definite order, d) mapping the video levels to the available luminance codes, e) processing the video levels to achieve intermediate levels of luminance f) then, mapping luminance codes to the output sub-field codes. The method is used in plasma display panels (PDP).

Abstract: Plasma Display Panels (PDP) are becoming more and more interesting for TV technology. One important criterion for picture quality is the Peak White Enhancement Factor (PWEF). From a previous patent application of the applicant it is known to have a table of power level modes in a control unit for the display device. The average picture power value is measured and a corresponding power level mode will be selected from the table for sub-field coding. The power level modes have been made variable in respect to a number of parameters, namely: the number of sub-fields the sub-field type the sub-field positioning the sub-field weight the sub-field pre-scaling a factor for the sub-field weights which is used to vary the amount of small pulses generated during each sub-field. According to the invention it is now proposed to use one or both of the following parameters in addition for varying the power level modes: the sustain frequency the sustain pulse slope.

Abstract: For stereoscopic displaying the new plasma display panels are providing promising results. When using shutter glasses that are controlled by the PDP, it is possible to display left and right image in short succession for stereoscopic displaying. However, there is the phosphor lag effect that is really disturbing and can totally impede the stereovision. The frame period of a stereoscopic picture is divided to at least one left period and at least one right period for the left picture and the right picture respectively. According to the invention both pictures are analyzed for similarities and the common part for a pair of corresponding pixels is determined. Sub-field code words for the left/right picture are determined having a part for the specific left/right sub-fields and a part for the common sub-fields. The common sub-fields are positioned at the end of each left/right field for the left/right picture so that the phosphor lag effect is no longer visible.

Abstract: The present invention relates to a coding method intended to improve the performance of GCC coding based on the temporal centre of gravity of displayed video codes. According to the invention, the number of video levels that can be selected in order to implement the GCC coding is increased by increasing the number of subfields in the video level display frame. This increase in the number of subfields is made possible by simultaneously addressing the cells of at least two adjacent rows of the PDP during at least two subfields of the video image display frame.

Abstract: With the new plasma display panel technology new kinds of artifacts can occur in video pictures. These artifacts are commonly described as dynamic false contour effect, since they correspond to disturbances of grey levels and colors in the form of an apparition of colored edges in the picture when the observation point on the PDP screen moves. According to the invention such an artifact is compensated by analyzing the motion in the pictures assigning to each block of a picture a corresponding motion vector and performing a re-coding step in which a sub-field code word entry of a current pixel are calculated. For this purpose the motion vector is defined to point from a pixel in a previous picture to a pixel in the current picture. The sub-field code word entries for a current pixel (P8) are determined by dragging sub-field entries of the pixels lying on the motion vector trajectory.

Abstract: A universal Power Timing Controller (PTC) unit intended for controlling the image memory and the line power boards of a Plasma Display Panel (PDP) is discribed. The PTC is responsible for generating control signals for the power boards of the PDP in order that they produce the correct waveforms (e.g. priming, erasing, addressing, sustaining . . . ) to be applied on the lines of cells of the PDP and control signals for the image memory of the PDP. According to the invention, the PTC has a fully programmable structure. The PTC comprises programmable memories or LUTs (look-up tables) in which the data defining the display mode of the panel and data defining elementary control signals required by the line power boards for processing operations associated to each phase period of the frame are stored.

Abstract: The present invention relates to a method for processing video signals for display on a display panel comprising a matrix array of cells which could only be “ON” or “OFF”, wherein the time duration of a video field is divided into N sub-fields during which the cells can be activated, each sub-field comprising at least an addressing period and a sustaining period, the duration of which corresponding to the weight associated with said sub-field, said method comprising at least a priming period, characterized in that the position of the priming period is determined as follows: determination of a sustain threshold value D for a given addressing speed and panel technology, calculation of the number of sustain pulses in each sub-field n, n being such that 1?n?N, if the number of sustain pulses is above or equal to D, addition of a priming pulse before at least the sub-field n+1. This method is mainly applicable to plasma display panel.

Abstract: When the observation point on a PDP screen moves, artifacts will be introduced which are commonly described as “dynamic false contour”. A simple way to reduce this effect requires the use of more sub-fields at the expense of panel brightness. A first idea called Bit-Line-Repeat (BLR) makes it possible to exchange vertical resolution with addressing time in order to dispose of more sub-fields for the same brightness. Nevertheless, such a solution introduces some vertical artifacts mostly during movement. Therefore, before the step of sub-field encoding a vertically filtering of the picture divided into pixel blocks is performed, wherein each block includes at least one pixel in horizontal direction and a number of pixels corresponding to the number of common lines in vertical direction. The effect of the pre-filtering step is that the difference of brightness values within each pixel block is limited to a predetermined value.

Abstract: A method and apparatus for processing video pictures for dynamic false contour effect compensation is provided wherein the video picture consists of pixels having at least one color component (RGB) the color component values being digitally coded with a digital code word, hereinafter called sub-field code word (SF-R, SF-G, F-B). To each bit of a sub-field code word (SF-R, SF-G, SF-B) a certain duration is assigned hereinafter called a sub-field, during which a color component of the pixel can be activated for light generation. The digital code words have n bits, characterized in that among a set p possible video levels for the at least one color component (RGB) a sub-set of m video levels with n<m<p is selected, which is used for light generation.

Abstract: The present invention relates to a method and an apparatus for processing video pictures especially for dynamic false contour effect and dithering noise compensation. The main idea of this invention is to divide the picture to be displayed in areas of at least two types, for example low video gradient areas and high video gradient areas, to allocate a different set of GCC (for Gravity Center Coding) code words to each type of area, the set allocated to a type of area being dedicated to reduce false contours and dithering noise in the area of this type, and to encode the video levels of each area of the picture to be displayed with the allocated set of GCC code words. In this manner, the reduction of false contour effects and dithering noise in the picture is optimized area by area.

Abstract: The present invention relates to a method of displaying a video image on a digital display device and particularly on a plasma display panel. According to the invention, the cells of the device change state at most once during the image display period and the subscans of this display period are of two types. The subscans of the first type address two adjacent rows of the panel simultaneously and the subscans of the second type address each row of cells of the panel individually. In certain cases, the grey level delivered to the cells is modified before display. For two neighbouring cells sharing the same subscans of the second type and displaying the grey levels A and B, one of the grey levels, A or B, is modified if the first subscan for which one of the cells changes state is a subscan of the first type.

Abstract: Video pictures have different picture formats so that sidebars are displayed on the display device. Consequently, burning effects are different between used and unused areas of the screen. Therefore, the unused areas of the display device are driven with a signal which is varied in accordance with the video signal. Preferably, at least a part of the active area of the screen is analysed and a medium value of such analysed area is used for driving the unused areas. As a result, the burning effect affects the used and unused areas equally and the sidebars are less disturbing since they are adapted to the video picture.

Abstract: The luminous elements of the three colours red, green and blue of a plasma video display have different time responses. Therefore, a coloured trail/edge appears behind and in front of the edges of a moving object. In order to reduce the disturbing character of such coloured trails/edges, correcting the video data for blue and red phosphor elements to compensate for the different time responses discolour them. Then only a discoloured trail/edge appears which is less disturbing.