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AssigneeThomson Licensing
InventorsCarlos Correa, S?eacute;bastien Weitbruch, Harald Roth
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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.
Method for power level control in a display device having a plurality of elements corresponding to the colour components of pixels of a picture, wherein the time duration of a video frame or video field is divided into a plurality of sub-fields during which the luminous elements can be activated for light output with small sustain pulses corresponding to a sub-field code word which is used for brightness control, wherein a set of power level modes is provided for sub-field coding, wherein the method includes further the steps of determining a value (PL) which is characteristic for the power level of a video picture and selecting a corresponding power level mode for the sub-field coding, characterized in that two power level modes differ from each other by one or both of the following parameters:
Apparatus for power level control in a display device having a plurality of elements corresponding to the colour components of pixels of a picture, wherein a control unit (21) is provided that divides the time duration of a video frame or video field into a plurality of sub-fields during which the luminous elements can be activated for light output with small sustain pulses corresponding to a sub-field code word which is used for brightness control, wherein said apparatus has included a picture power measuring circuit (20), and a sub-field coding unit (23) and wherein a table of power level modes (27) is stored in the control unit (21) for sub-field coding, wherein the picture power measuring circuit (20) determines a value (PL) which is characteristic for the power level of a video picture and the control unit (21) selects a corresponding power level mode for the sub-field coding, characterized in that upon switching from one power level mode to another the control unit (21) provides sustain pulses with one or both of the following characteristics changed compared to the previous power level mode:
Dependencies are inferred from the claim text.