| 摘要 |
A low-cost, large-area display system having a backlight in segments each positioned to illuminate a subfield of M rows of a fast supertwisted-nematic (STN) display of N rows. Fields of Q+1 subfields are addressed by the method known as Active Addressing using orthogonal waveforms of period MT/N where T is the frame time. A subfield is addressed for Q+1 periods MT/N of the row waveforms and illuminated during the last one. Fast STNs allow Q to be small leading to a small effective multiplex ratio with improved contrast and horizontal viewing-angle range. A few additional leading and trailing rows may be addressed to overcome vertical parallax. The row drivers are periodically connected by switches that simply ground un-addressed rows. With Q+1 also a divisor of N, subfield contributions to the column waveforms can be calculated once and used Q+1 times in each frame. For example, N=240, M=16, L=4 and Q=2 provide an effective multiplex ratio of 57 and allow at least 2.2 msec for pixels to turn on when the frame rate 1/T is 60 Hz. The viewing-angle range can also be expanded by moving subfields a few rows in the scan direction and advancing the integration time to equalize the brightness of pixels illuminated by the next segment. For example, if the turn-off time is 0.76 T and the integration time is shortened to 0.33 MT/N, equalization is possible with turn-on times as large as ¾ of the turn-off time without decreasing pixel transmittance by more than 50%. Dual-scan configurations using N=240, for example, can display VGA or 480 p formats.
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