EP0479530A2
Expired / Lapsed
EP
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Ferroelectric liquid crystal devices
Assignee: BAE Systems Electronics Ltd
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Filing: 1991-09-30
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Granted: —
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Expires: 2011-09-30
Abstract
Abstract In a method of driving a ferroelectric liquid crystal display, a blanking pulse (41) of width 2t s followed, after a delay of n.t s (where n is an integer), by a writing pulse (43) of width t s and of opposite polarity to the blanking pulse are applied to successive row address lines at intervals of 2t s . Pairs of bipolar data pulses (49,50 ;52,53) of width t s are applied to column address lines so that the data pulses coincide with the blanking pulse applied to the ith row and the writing pulse applied to row i-(n+1)/2 for odd values of n and to row 1-(n+2)/2 for even values of n. The data pulse amplitude may be varied in order to obtain variable grey levels in the display.
Inventors
- 👤 Stephen Joseph Shelford Lister
- 👤 Colin Teck Hooi Yeoh
- 👤 Alan Mosley
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 17:42
CPC Classifications
G; G09; G09G; G09G3/00; G09G3/20; G09G3/34; G09G3/36; G09G3/3611; G09G3/3622; G09G3/3629; G09G3/04; G09G3/16; G09G3/18; G09G2310/00; G09G2310/02; G09G2310/0202; G09G2310/0205; G09G2310/06; G09G2310/061; G09G2310/065; G09G3/2007; G09G3/2011
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
159 words
A method of driving, in a time-division multiplex mode, a display comprising a matrix of rows and columns of ferroelectric liquid crystal elements, wherein a blanking voltage pulse (41) of amplitude V B and pulse width 2t s followed, after a delay of n x t s (where n is an integer), by a writing voltage pulse (43) of amplitude V w , of width t s and of opposite polarity to the blanking voltage pulse are applied to successive rows at intervals of 2t s ; and pairs of bipolar data pulses (49,50;52,53) of amplitude |V D | selected from a range including zero and each pulse being of pulse width t s are applied to column address lines such that said data pulses coincide with the blanking pulse for the ith row and the writing pulse applied to row i -(n+1)/2 for odd values of n and to row i - (n+2)/2 for even values of n.
Claim 2
Independent Claim
159 words
A method of driving, in a time-division multiplex mode, a display comprising a matrix of rows and columns of ferroelectric liquid crystal elements, wherein a blanking voltage pulse (41) of amplitude V B and pulse width 2t s followed, after a delay of n x t s (where n is an integer), by a writing voltage pulse (43) of amplitude V w , of width t s and of opposite polarity to the blanking voltage pulse are applied to successive rows at intervals of 2t s ; and pairs of bipolar data pulses (49,50;52,53) of amplitude |V D | selected from a range including zero and each pulse being of pulse width t s are applied to column address lines such that said data pulses coincide with the blanking pulse for the ith row and the writing pulse applied to row i -(n+1)/2 for odd values of n and to row i - (n+2)/2 for even values of n.
Claim 3
Dependent Claim
13 words
A method as claimed in Claim 1, wherein n is an odd integer.
Claim 4
Dependent Claim
17 words
A method as claimed in Claim 2, wherein n is an odd integer from one to nine.
Claim 5
Dependent Claim
13 words
A method as claimed in Claim 1, wherein n is an even integer.
Claim 6
Dependent Claim
17 words
A method as claimed in Claim 4, wherein n is an even integer from zero to ten.
Claim 7
Independent Claim
31 words
A method as claimed in any preceding claim, wherein the polarities of the blanking pulse (41) and the writing pulse (43) are reversed for alternate frames of operation of the display.
Claim 8
Dependent Claim
42 words
A method as claimed in Claim 1, wherein an offset dc voltage of magnitude V G is applied with said blanking and writing pulses such that V G = (2V B - V w )/N where N is the number of rows
Claim 9
Independent Claim
52 words
A method as claimed in any preceding claim, wherein the amplitudes V D , V B and V w of the data, blanking and writing pulses (49,50; 52,53; 41:43), respectively, are related by 4V D = 2 V B = V w for use in a bilevel display with no grey levels.
Claim 10
Independent Claim
23 words
A method as claimed in any one of Claims 1-7, wherein V D is variable such that various shades of grey are obtained.
Claim 11
Dependent Claim
15 words
A ferroelectric liquid crystal display operated by a method as claimed in any preceding claim.
Claim 12
Dependent Claim
164 words
Apparatus for driving, in a time-division multiplex mode, a display comprising a matrix of rows and columns of ferroelectric liquid crystal elements, the apparatus comprising means to apply to successive rows of said elements at intervals of 2t s a blanking voltage pulse (41) of amplitude V B and pulse widths t s and, after a delay of n x t s (where n is an integer), a writing voltage pulse (43) of amplitude V w , of width t s and of opposite polarity to the blanking voltage pulse; and means to apply to column address lines pairs of bipolar data pulses (49,50; 52,53) of amplitude |V D | selected from a range including zero and each pulse being of pulse width t s , such that said data pulses coincide with the blanking pulse for the ith row and the writing pulse applied to row i -(n+1)/2 for odd values of n and to row i -(n+2)/2 for even values of n.
Claim 13
Dependent Claim
164 words
Apparatus for driving, in a time-division multiplex mode, a display comprising a matrix of rows and columns of ferroelectric liquid crystal elements, the apparatus comprising means to apply to successive rows of said elements at intervals of 2t s a blanking voltage pulse (41) of amplitude V B and pulse widths t s and, after a delay of n x t s (where n is an integer), a writing voltage pulse (43) of amplitude V w , of width t s and of opposite polarity to the blanking voltage pulse; and means to apply to column address lines pairs of bipolar data pulses (49,50; 52,53) of amplitude |V D | selected from a range including zero and each pulse being of pulse width t s , such that said data pulses coincide with the blanking pulse for the ith row and the writing pulse applied to row i -(n+1)/2 for odd values of n and to row i -(n+2)/2 for even values of n.
Claim 14
Dependent Claim
46 words
Apparatus as claimed in Claim 11, comprising means to apply to said ith row with said blanking and writing pulses an offset dc voltage of magnitude V G such that V G = (2V B - V w )/N where N is the number of rows
Claim 15
Dependent Claim
35 words
Apparatus as claimed in Claim 11, wherein the means to apply said blanking pulse and said writing pulse is operative to reverse the polarities of said pulses for alternate frames of operation of the display.
References Cited (Backward Citations)
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