Patent ID: 7800559

Claim:
Method 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 elements is based on the intensity of picture signals supplied to the luminous element and the power level and/or contrast for each picture is controlled by adjusting the intensity of the picture signals to be supplied to each luminous element, and wherein the intensity of the picture signals to be supplied to the luminous elements is based on a plurality of analog reference signals characterized in that the power level and/or contrast is controlled by adjusting the intensity of the said analog reference signals based on an average power level of said picture and wherein a non linear transformation is applied to the reference levels and an inverse transformation is applied to the picture signal for using instead of reference levels below a predetermined value, said predetermined value or a value above said predetermined value for said analog reference signals to avoid reference levels having a value between zero and the predetermined value and to adapt further reference levels related to a certain percentage of white surface in the picture to avoid precision errors when the picture load is high and to provide continuously increasing gray levels; wherein the display device is an organic light emitting display.