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(11) | EP 0 875 881 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Active matrix light modulators, use of an active matrix light modulator, and display |
| (57) An active matrix light modulator, such as a thresholdless antiferroelectric active
matrix liquid crystal display, comprises an active matrix of control elements 18 disposed
at intersections of data lines 22 and scan lines 20, and an array 10 of pixels which
are selectively addressable by data and scan signals applied to the control elements
18 by a data driver 12 and a scan driver 14. Such addressing is controlled so that
a voltage is applied to each pixel during a corresponding addressing frame by the
application of data and scan signals to an associated one of the control elements
18 in order to select the optical level of the pixel for each frame, and bipolar switching
is applied to control the voltage applied to the pixel during successive subframes
such that, when one optical level is selected for the frame, a positive voltage is
applied to the pixel during one subframe of the frame and a negative voltage of equal
magnitude but opposite polarity is applied to the pixel during another subframe of
the frame and, when another optical level is selected for the frame, an intermediate
voltage (preferably zero voltage) is applied to the pixel during both of the subframes
of the frame, so as to provide DC balancing within the frame. The required grey level
within each frame is accurately reproduced and is substantially independent of the
previous state of the pixel. The use of such modulators to reduce the effects of asymmetrical
optical performance and colour-sequential displays are also disclosed. |