Automatic liquid-crystal light shutter
First Claim
1. An automatic light-responsive light shutter comprising:
- light shutter means responsive to application of a control signal at a first level for passing light therethrough along a first path and responsive to application of said control signal at a second level for highly attenuating light passing therethrough along said first path;
first light responsive means for sensing intensity of direct light which strikes said light shutter means generally along said first path;
second light responsive means for sensing intensity of side light which strikes said light shutter means generally perpendicular to said first path;
circuit means for providing a comparison signal at a level which is a function of the relative intensities of direct and side light sensed at said first and second light responsive means, respectively; and
control means responsive to said comparison signal for applying said control signal to said light shutter means at said first level when said comparison signal level is within a first predetermined range of levels, and for applying said control signal to said light shutter means at said second level when the comparison signal level is within a second predetermined range of levels, said first and second predetermined ranges of levels being substantially adjacent one another.
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Abstract
An automatic liquid-crystal light shutter includes a NAND gate integrated circuit and a pair of RC oscillators operating in cooperation with two solar cells which experience internal resistance changes in response to received light. The changes in the internal resistance of the two solar cells results in a comparison signal which is applied to each of two NAND gates along with respective oppositely faced oscillator signals. When the NAND gate output signals are of different potential, the shutter passes light with little or no attenuation. If the NAND gate output signals are of the same potential, the liquid-crystal shutter becomes highly attentuated or unpassable for light. As a result, the automatic liquid-crystal shutter automatically passes low intensity light but attenuates or blocks high intensity light.
428 Citations
15 Claims
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1. An automatic light-responsive light shutter comprising:
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light shutter means responsive to application of a control signal at a first level for passing light therethrough along a first path and responsive to application of said control signal at a second level for highly attenuating light passing therethrough along said first path; first light responsive means for sensing intensity of direct light which strikes said light shutter means generally along said first path; second light responsive means for sensing intensity of side light which strikes said light shutter means generally perpendicular to said first path; circuit means for providing a comparison signal at a level which is a function of the relative intensities of direct and side light sensed at said first and second light responsive means, respectively; and control means responsive to said comparison signal for applying said control signal to said light shutter means at said first level when said comparison signal level is within a first predetermined range of levels, and for applying said control signal to said light shutter means at said second level when the comparison signal level is within a second predetermined range of levels, said first and second predetermined ranges of levels being substantially adjacent one another. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. The method of controlling visible light attenuation through a liquid-crystal panel, said method comprising the steps of:
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sensing intensity of direct light impinging generally perpendicularly on said panel; sensing intensity of side light directed towards that panel generally perpendicular to said direct light; comparing the sensed direct light and side light intensities; passing light through said panel with relatively little attenuation when the sensed side light intensity is approximately the same as or greater than sensed direct light intensity and when the sensed direct light intensity is below a predetermined intensity; and attenuating passage of light through said panel when the sensed direct light intensity is substantially greater than the sensed side light intensity.
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Specification