Patent ID: 7884781

Claim:
A method of correcting video data signals for addressing an active matrix display device, the device comprising a power line ( 10 ) arranged to supply current to n electroluminescent display elements ( 11 ), the current supplied to each element being controllable by a respective drive transistor ( 20 ), each drive transistor being addressable by video data signals and having an electrical characteristic parameter X, the method comprising the steps of: (i)—storing an X value for each drive transistor; (ii)—receiving a set of video data signals, each having a value v d , said video data signals corresponding to an image to be displayed; (iii)—determining from the stored X values and the received v d values an expected current through the power line i p using a model which relates the power line current to the v d and X values of the drive transistors; (iv)—measuring the current i m through the power line when the drive transistors are each addressed with the received set of video data signals; (v)—calculating the difference, g, between the expected current i p and the measured current i m ; (vi)—repeating steps (ii) to (v) for at least n−1 further sets of video data signals; (vii)—calculating an X value for each transistor using the calculated g values; (viii)—replacing the stored X values with the calculated X values; and (ix)—correcting subsequent video data signals in accordance with the stored X values.