| 摘要 |
1,219,840. Light modulators. RCA CORPORATION. 13 Sept., 1968 [14 Sept., 1967 (2)], No. 43724/68. Heading H4F. [Also in Division G5] To reduce the time required for a nematic liquid crystal cell to change from its transparent state to its light scattering state in response to repetitive voltage pulses of relatively short duration, a number of such pulses being required to cause the liquid crystal to scatter light to an extent which is a function of the amplitude of the pulses, the internal resistance of the cell is increased prior to the application of the repetitive pulses. To increase the internal resistance of the cell the number of free current carriers present in the liquid crystal is reduced by applying either a continuous direct voltage bias (Figs. 8 and 9, not shown) or a continuing train of voltage pulses (Figs. 10-12, not shown) to the cell at a level lower than the voltage threshold for dynamic scattering of the cell. By increasing the internal resistance it is found that the number of excitation pulses necessary to effect a substantial amount of light scattering is reduced, i.e. the " turn-on " time for the cell is reduced. In addition, the cell exhibits a larger scattering effect and is thus brighter. The liquid crystal cells may be arranged in a matrix to form a television type display, and in every frame interval a row of cells is simultaneously " addressed," i.e. have their internal resistances increased, while pulses having amplitudes corresponding to the video information of respective elements of the row are applied to the cells. |
