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US4909607A
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Addressing liquid crystal cells
Assignee: Nortel Networks Ltd
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Filing: 1987-03-31
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Granted: 1990-03-20
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Expires: 2007-03-31
Abstract
Abstract A method of addressing a matrix addressed ferroelectric liquid crystal cell is described that uses parallel entry of balanced bipolar data pulses on one set of electrodes to co-operate with serial entry of unipolar strobe pulses on the other set of electrodes. The polarity of the strobe pulses is periodically reversed to maintain charge balance in the long term.
Inventors
- 👤 Peter W. Ross
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 08:50
CPC Classifications
G; G09; G09G; G09G3/00; G09G3/20; G09G3/34; G09G3/36; G09G3/3611; G09G3/3622; G09G3/3629; G09G2310/00; G09G2310/06; G09G2310/065
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
198 words
A method of addressing a matrix-array type liquid crystal cell with a ferroelectric liquid crystal layer whose pixels are defined by the areas of overlap between the members of a first set of electrodes on one side of the liquid crystal layer and the members of a second set on the other side of the layer, in which method the pixels are selectively addressed on a line-by-line basis by the application of unipolar strobing pulses serially to the members of the first set of electrodes while charge balanced bipolar data pulses are applied in parallel to the members of the second set, the positive going parts of the bipolar data pulses being synchronised with a strobe pulse for one data significance and the negative going parts being synchronized with the strobe pulse for the other data significance, wherein the pixels of both data significance are set into their correct states by said line-by-line addressing by first setting the pixels of one data significance into their correct state using unipolar strobe pulses of one polarity type and then setting the pixels of the other data significance into their correct state using unipolar strobe pulses of the opposite polarity type.
Claim 2
Independent Claim
198 words
A method of addressing a matrix-array type liquid crystal cell with a ferroelectric liquid crystal layer whose pixels are defined by the areas of overlap between the members of a first set of electrodes on one side of the liquid crystal layer and the members of a second set on the other side of the layer, in which method the pixels are selectively addressed on a line-by-line basis by the application of unipolar strobing pulses serially to the members of the first set of electrodes while charge balanced bipolar data pulses are applied in parallel to the members of the second set, the positive going parts of the bipolar data pulses being synchronised with a strobe pulse for one data significance and the negative going parts being synchronized with the strobe pulse for the other data significance, wherein the pixels of both data significance are set into their correct states by said line-by-line addressing by first setting the pixels of one data significance into their correct state using unipolar strobe pulses of one polarity type and then setting the pixels of the other data significance into their correct state using unipolar strobe pulses of the opposite polarity type.
Claim 3
Dependent Claim
46 words
A method as claimed in claim 1, wherein in respect of each member of said first set of electrodes the polarity of each unipolar strobe pulse applied to that member is the opposite of that of the immediately preceding unipolar strobe pulse applied to that member.
Claim 4
Dependent Claim
23 words
A method as claimed in claim 1, wherein a gap separates the positive and negative going portions of each balanced bipolar data pulse.
Claim 5
Dependent Claim
19 words
A method as claimed in claim 1, wherein a gap always precedes or follows each balanced bipolar data pulse.
Claim 6
Dependent Claim
37 words
A method as claimed in claim 1, wherein the positive and negative going portions of each balanced bipolar data pulse are asymmetric, one part having m times the amplitude of the other and 1/m th the duration.
Claim 7
Dependent Claim
23 words
A method as claimed in claim 5, wherein a gap separates the positive and negative going portions of each balanced bipolar data pulse.
Claim 8
Dependent Claim
19 words
A method as claimed in claim 5, wherein a gap always precedes or follows each balanced bipolar data pulse.
Claim 9
Dependent Claim
23 words
A method as claimed in claim 7, wherein a gap separates the positive and negative going portions of each balanced bipolar data pulse.
Claim 10
Dependent Claim
34 words
A method as claimed in claim 1, wherein a gap separates the positive and negative going portions of each balanced bipolar data pulse and a gap always precedes or follows each such data pulse.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-03-19 | 1993-09-18 | 1994-03-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-03-19 | 1997-09-18 | 1998-03-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-03-19 | 2001-09-18 | 2002-03-20 | $7700.00 | Window Closed / Lapsed |