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Control Circuit for Liquid Crystal Cells

IP.com Disclosure Number: IPCOM000074440D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Dickson, LD: AUTHOR [+2]

Abstract

Active liquid crystal cell 10 in A is preconditioned by voltage pulses VG shown in B, passed by logical OR 15. The amplitude of the preconditioning pulses is sufficient to turn cell 10 on. However, the pulse width of the preconditioning pulses is less than the turnon time of cell 10. The duty cycle of pulse generator 20, which provides the preconditioning pulses, is maintained by sensing the opacity of cell 25. Photosensor 30 is responsive to the amount of light from source 35, which is passed by cell 25. The signal from 30 is applied to amplifier 40. Differential amplifier 45 compares the output of 40 with a reference voltage VR. The output of 45 controls duty cycle adjustment circuit 50, which in turn maintains 20 at the proper duty cycle. Preconditioned cell 10 is turned on by applying a voltage signal VT to OR 15.

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Control Circuit for Liquid Crystal Cells

Active liquid crystal cell 10 in A is preconditioned by voltage pulses VG shown in B, passed by logical OR 15. The amplitude of the preconditioning pulses is sufficient to turn cell 10 on. However, the pulse width of the preconditioning pulses is less than the turnon time of cell 10. The duty cycle of pulse generator 20, which provides the preconditioning pulses, is maintained by sensing the opacity of cell 25. Photosensor 30 is responsive to the amount of light from source 35, which is passed by cell 25. The signal from 30 is applied to amplifier 40. Differential amplifier 45 compares the output of 40 with a reference voltage VR. The output of 45 controls duty cycle adjustment circuit 50, which in turn maintains 20 at the proper duty cycle. Preconditioned cell 10 is turned on by applying a voltage signal VT to OR 15. Signal VT has the same amplitude as the preconditioning pulses VG but its width together with the preconditioning pulse VG is sufficient to turn cell 10 on and in a shorter period of time than if the preconditioning pulses were absent.

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