| 摘要 |
This invention provides chromaticity compensation for color filters having nematic liquid crystal tuning elements, as well as fast-transition tuning units for use in combination with chromaticity compensation. The filters of this invention have two stages formed by three linear polarizers in series, as least two of which are color polarizers. Within each stage is a tuning unit comprising a nematic liquid crystal cell switchable between a first state wherein the polarization of light is orthogonally transformed and a second state wherein the polarization is unchanged. In the first state the liquid crystal cell chromaticity introduces significant distortion to the filter stage, but in the second state it does not. Chromaticity compensation is achieved in this invention by optimizing the use of the undistorted normal states and by judicious choice of the design wavelengths of the liquid crystal cells. This invention further provides compound tuning units, for use in the chromaticity compensating filter, that allow the use of fast unenergized-to-energized transitions in switching between three primary colors. A first embodiment of the compound tuning unit uses a half-wave bias retarder oriented at ±45° in combination with the nematic liquid crystal cell. A second embodiment of the compound tuning unit uses two nematic liquid crystal cells. A third embodiment of the compound tuning unit uses a half-wave bias retarder oriented at about ±67° or ±23° in combination with the nematic liquid crystal cell.
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