Optical polarization switch and method of using same
First Claim
1. An optical polarization switch acting upon incident light having a polarization state along a polarization axis, comprisinga first nematic liquid crystal cell which selectively alters polarization of light passing therethrough depending upon an application of external energy to said first nematic liquid crystal cell, but which does not substantially displace the path of the light;
- a second nematic liquid crystal cell which selectively alters polarization of light passing therethrough depending upon an application of external energy to said second nematic liquid crystal cell but which does not substantially displace the path of the light, said second nematic liquid crystal cell being arranged in optical series with said first nematic liquid crystal cell;
a compensation means interposed between said first and second nematic liquid crystal cells, wherein said compensation means comprises one of an optical rotator effecting substantially 90°
rotation of the polarization state of light exiting the first nematic liquid crystal cell, an optical half-wave retarder having a slow axis oriented substantially parallel to the polarization axis of the incident light, and an optical half-wave retarder having a fast axis oriented substantially parallel to the polarization axis of the incident light.
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Abstract
An improved optical polarization switch which provides a wide field-of-view and achromatic action. Two liquid crystal cells are used and are selectively operated in a preferred embodiment to provide three distinct optical states. Interposed between the two nematic liquid crystal cells is a compensating member such as an half-wave retarder or an optical rotator. Such switches are of utility in shutter applications and in high-performance field-sequential color filters.
194 Citations
20 Claims
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1. An optical polarization switch acting upon incident light having a polarization state along a polarization axis, comprising
a first nematic liquid crystal cell which selectively alters polarization of light passing therethrough depending upon an application of external energy to said first nematic liquid crystal cell, but which does not substantially displace the path of the light; -
a second nematic liquid crystal cell which selectively alters polarization of light passing therethrough depending upon an application of external energy to said second nematic liquid crystal cell but which does not substantially displace the path of the light, said second nematic liquid crystal cell being arranged in optical series with said first nematic liquid crystal cell; a compensation means interposed between said first and second nematic liquid crystal cells, wherein said compensation means comprises one of an optical rotator effecting substantially 90°
rotation of the polarization state of light exiting the first nematic liquid crystal cell, an optical half-wave retarder having a slow axis oriented substantially parallel to the polarization axis of the incident light, and an optical half-wave retarder having a fast axis oriented substantially parallel to the polarization axis of the incident light. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for altering a polarization state of incident light having a polarization state along a polarization axis, comprising the steps of:
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(a) selectively energizing a first nematic liquid crystal cell arranged in optical series with a second nematic liquid crystal cell; (b) selectively altering the polarization state of the incident light by passing the incident light through the first nematic liquid crystal cell; (c) altering the polarization state of the light exiting from the first nematic liquid crystal cell using a compensating means comprising one of an optical rotator effecting substantially 90°
of the polarization state of light exiting the first nematic liquid crystal cell an optical half-wave retarder having a slow axis oriented substantially parallel to the polarization axis of the incident light, and an optical half-wave retarder having a fast axis oriented substantially parallel to the polarization axis of the incident disposed between the first and second nematic liquid crystal cells; and(d) selectively energizing the second nematic liquid crystal cell; (e) selectively altering polarization state of the light exiting from the compensating means using the second nematic liquid crystal cell. - View Dependent Claims (19, 20)
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Specification