Patent ID: 8207914

Claim:
A method of compensating image signals for driving an OLED display having a plurality of light-emitting elements having outputs that change with time or use, the method comprising: obtaining an initial measured or estimated first current value used by each of the respective light-emitting elements in response to known image signals at a first time before the OLED display is put into service; specifying multiple groups of light-emitting elements at a second time later than the first time; measuring total currents used by each of the specified groups in response to known image signals at the second time; comparing the measured total current used by each of the specified groups at the second time to the same specified group's total first current values to determine at least one specified group whose measured total current is sufficiently different from the same specified group's total first current values; specifying multiple smaller groups of individual light-emitting elements that are subsets of the determined specified group; measuring total currents used by each of the specified smaller groups in response to known image signals at the second time; comparing the measured total current used by each of the specified smaller groups to the same specified smaller group's total first current values to determine at least one specified smaller group whose measured total current is sufficiently different from the same specified smaller group's total first current values; forming an estimated second value of the current used by individual light-emitting elements within the determined smaller groups based on the measured total currents of the smaller groups; calculating correction values for individual light-emitting elements within the determined smaller groups based on the difference between the first and second current values; and employing the correction values to compensate image signals for the changes in the output of the light-emitting elements and produce compensated image signals.