Drive method for twisted nematic liquid crystal shutters for stereoscopic and other applications
First Claim
1. A method for driving a shutter including a twisted nematic liquid crystal cell, between a low voltage state in which a low peak-to-peak voltage signal is applied to the cell, and a shuttering state in which a high peak-to-peak voltage signal is applied to the cell, said method including the steps of:
- (a) applying a first one of the low peak-to-peak voltage signal and the high peak-to-peak voltage signal to the cell;
(b) then, applying a transition signal to the cell for a transition period, where the transition signal has an envelope whose amplitude varies monotonically over the transition period; and
(c) then, applying the other of the low peak-to-peak voltage signal and the high peak-to-peak voltage signal to the cell.
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Abstract
A method for overcoming optical artifacts which are an intrinsic part of the performance of twisted nematic liquid crystal shutter devices. When power is shut off from a conventional shutter device of this type, the device exhibits a brief periodic flickering called "bounce". When the power is turned on, the device exhibits a similar flickering effect, known as "stumble." When a pair of such devices are used as lenses in a stereoscopic selection apparatus, these artifacts, which contribute nothing to the device'"'"'s performance, are obtrusive and disturbing to the user. By carefully controlling the voltage to each shutter in accordance with the invention while turning the shutter on or off, these artifacts are eliminated or substantially reduced.
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Citations
23 Claims
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1. A method for driving a shutter including a twisted nematic liquid crystal cell, between a low voltage state in which a low peak-to-peak voltage signal is applied to the cell, and a shuttering state in which a high peak-to-peak voltage signal is applied to the cell, said method including the steps of:
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(a) applying a first one of the low peak-to-peak voltage signal and the high peak-to-peak voltage signal to the cell; (b) then, applying a transition signal to the cell for a transition period, where the transition signal has an envelope whose amplitude varies monotonically over the transition period; and (c) then, applying the other of the low peak-to-peak voltage signal and the high peak-to-peak voltage signal to the cell. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for driving a twisted nematic liquid crystal shutter apparatus from a shuttering state in which a high voltage signal is applied to the apparatus, to a low voltage state in which a low voltage signal is applied to the apparatus, in a manner substantially reducing bounce artifacts that would result from a sudden transition from the shuttering state to the low voltage state, said method including the steps of:
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(a) applying the high voltage signal to a twisted nematic liquid crystal cell within the apparatus, wherein the high voltage signal has a high peak-to-peak voltage; and (b) then, applying the low voltage signal to the twisted nematic liquid crystal cell, wherein the low voltage signal has a low peak-to-peak voltage. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for driving a twisted nematic liquid crystal shutter apparatus from a transmissive state in which a low voltage signal in which a low voltage signal is applied to the apparatus, to a shuttering state in which a high voltage signal is applied to the apparatus, in a manner substantially reducing stumble artifacts that would result from a sudden transition to the shuttering state from the transmissive state, said method including the steps of:
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(a) applying the low voltage signal to a twisted nematic liquid crystal cell within the apparatus, wherein the low voltage signal has a low peak-to-peak voltage; and (b) then, applying the high voltage signal to the twisted nematic liquid crystal cell, wherein the high voltage signal has a high peak-to-peak voltage. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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Specification