US5285214A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus and method for driving a ferroelectric liquid crystal device
Assignee: The General Electric Company PLC
•
Filing: 1992-04-08
•
Granted: 1994-02-08
•
Expires: 2012-04-08
Abstract
Abstract In a method of driving a matrix of ferroelectric liquid crystal devices in a TDM mode, each strobing signal comprises first and second pulses (20,21) of opposite polarities and of different amplitudes, together with a dc voltage (26) which is applied from the end of the second pulse to the beginning of the first pulse of the next strobing signal on the same strobe line to cancel the dc level which would be caused by the unequal pulses. Data ON signals applied selectively to data lines of the matrix comprise two consecutive pulses (22,23) of opposite polarities. Data OFF signals (24,25) may be the inverse of the data ON signals or may comprise a constant dc level. The combination of the two pulses with a dc level to form each strobing signal means that only two strobe pulse time slots per frame are required for addressing each strobe line, as compared with the conventional systems in which four time slots per frame are required.
Inventors
- 👤 Carolyn Bowry
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 07:21
CPC Classifications
G; G09; G09G; G09G3/00; G09G3/20; G09G3/34; G09G3/36; G09G3/3611; G09G3/3622; G09G3/3629; G09G2310/00; G09G2310/06; G09G2320/00; G09G2320/02; G09G2320/0204; G09G2320/0209
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
285 words
A method of driving a ferroelectric liquid crystal device matrix in a time-division multiplex mode, comprising the steps of: applying strobing signals cyclically to strobe lines coupled to two-state liquid crystal elements of the display; and applying data signals selectively to data lines coupled to the elements; wherein each strobing signal comprises, during each frame period, only two strobe pulse periods, during which there are a first pule of one polarity followed by a second pulse of the opposite polarity and of different amplitude and/or duration from the first pule, each strobing signal including, between successive frame periods, a dc voltage which is effective during a period between the end of the second strobe pulse of a said strobing signal and the beginning of the first strobe pulse of the next strobing signal applied to the same strobe line to substantially cancel a dc voltage level resulting from the difference between the amplitudes and/or durations of the first and second strobe pulses, and which dc voltage will not switch the liquid crystal elements during said period; wherein the data signals comprise selectively a first data signal or a second data signal, said first data signal being operative in combination with the strobing signal to set a selected liquid crystal element in a first one of its states, and said second data signal being operative in combination with the strobing signal to set the selected liquid crystal element in the other of its states; and wherein one or each of the first and second data signals comprises two consecutive pulses of opposite polarities, there being only two data pulse periods in a frame period, said data pulse periods being substantially coincident with the strobe pulse periods.
Claim 2
Independent Claim
285 words
A method of driving a ferroelectric liquid crystal device matrix in a time-division multiplex mode, comprising the steps of: applying strobing signals cyclically to strobe lines coupled to two-state liquid crystal elements of the display; and applying data signals selectively to data lines coupled to the elements; wherein each strobing signal comprises, during each frame period, only two strobe pulse periods, during which there are a first pule of one polarity followed by a second pulse of the opposite polarity and of different amplitude and/or duration from the first pule, each strobing signal including, between successive frame periods, a dc voltage which is effective during a period between the end of the second strobe pulse of a said strobing signal and the beginning of the first strobe pulse of the next strobing signal applied to the same strobe line to substantially cancel a dc voltage level resulting from the difference between the amplitudes and/or durations of the first and second strobe pulses, and which dc voltage will not switch the liquid crystal elements during said period; wherein the data signals comprise selectively a first data signal or a second data signal, said first data signal being operative in combination with the strobing signal to set a selected liquid crystal element in a first one of its states, and said second data signal being operative in combination with the strobing signal to set the selected liquid crystal element in the other of its states; and wherein one or each of the first and second data signals comprises two consecutive pulses of opposite polarities, there being only two data pulse periods in a frame period, said data pulse periods being substantially coincident with the strobe pulse periods.
Claim 3
Dependent Claim
50 words
A method as claimed in claim 1, wherein said first data signal comprises two consecutive pulses of mutually opposite polarities and of substantially equal amplitudes, and said second data signal comprises two consecutive pulses of opposite polarities to the pulses of said first data signal and of substantially equal amplitudes.
Claim 4
Dependent Claim
38 words
A method as claimed in claim 1, wherein said first data signal comprises a constant dc level, and said second data signal comprises two consecutive pulses of polarities opposite to those of the pulses of the strobing signal.
Claim 5
Dependent Claim
37 words
A method as claimed in claim 1, wherein said first data signal comprises two consecutive pulses of the same polarities as the pulses of the strobing signal, and said second data signal comprises a constant dc level.
Claim 6
Dependent Claim
23 words
A method as claimed in claim 1, wherein said first and second pulses of the strobing signal are of mutually different time durations.
Claim 7
Dependent Claim
27 words
A method as claimed in claim 1, wherein each first and second data signal comprises two pulses of mutually opposite polarities and of mutually different time durations.
Claim 8
Dependent Claim
32 words
A method as claimed in claim 1, wherein the strobing signal and/or each first and second data signal comprises two pulses of mutually opposite polarities separated by a period of zero voltage.
Claim 9
Dependent Claim
23 words
A method as claimed in claim 1, wherein a relatively high-frequency ac voltage is superimposed on the strobing signal and/or the data signal.
Claim 10
Dependent Claim
284 words
Apparatus for driving a ferroelectric liquid crystal device matrix in a time-division multiplex mode, comprising the steps of: applying strobing signals cyclically to strobe lines coupled to two-state liquid crystal elements of the display; and applying data signals selectively to data lines coupled to the elements; wherein each strobing signal comprises, during each frame period, only two strobe pulse periods, during which there are a first pulse of one polarity followed by a second pulse of the opposite polarity and of different amplitude and/or duration from the first pulse, each strobing signal including, between successive frame periods, a dc voltage which is effective during a period between the end of the second strobe pulse of a said strobing signal and the beginning of the first strobe pulse of the next strobing signal applied to the same strobe line to substantially cancel a dc voltage level resulting from the difference between the amplitudes and/or durations of the first and second strobe pulses, and which dc voltage will not switch the liquid crystal elements during said period; wherein the data signals comprise selectively a first data signal or a second data signal, said first data signal being operative in combination with the strobing signal to set a selected liquid crystal element in a first one of its states, and said second data signal being operative in combination with the strobing signal to set the selected liquid crystal element in the other of its states; and wherein one of each of the first and second data signals comprises two consecutive pulses of opposite polarities, there being only two data pulse periods in a frame period, said data pulse periods being substantially coincident with the strobe pulse periods.
Claim 11
Dependent Claim
284 words
Apparatus for driving a ferroelectric liquid crystal device matrix in a time-division multiplex mode, comprising the steps of: applying strobing signals cyclically to strobe lines coupled to two-state liquid crystal elements of the display; and applying data signals selectively to data lines coupled to the elements; wherein each strobing signal comprises, during each frame period, only two strobe pulse periods, during which there are a first pulse of one polarity followed by a second pulse of the opposite polarity and of different amplitude and/or duration from the first pulse, each strobing signal including, between successive frame periods, a dc voltage which is effective during a period between the end of the second strobe pulse of a said strobing signal and the beginning of the first strobe pulse of the next strobing signal applied to the same strobe line to substantially cancel a dc voltage level resulting from the difference between the amplitudes and/or durations of the first and second strobe pulses, and which dc voltage will not switch the liquid crystal elements during said period; wherein the data signals comprise selectively a first data signal or a second data signal, said first data signal being operative in combination with the strobing signal to set a selected liquid crystal element in a first one of its states, and said second data signal being operative in combination with the strobing signal to set the selected liquid crystal element in the other of its states; and wherein one of each of the first and second data signals comprises two consecutive pulses of opposite polarities, there being only two data pulse periods in a frame period, said data pulse periods being substantially coincident with the strobe pulse periods.
References Cited (Backward Citations)
US3995942A
Cited
US4508429A
Cited
US4681404A
Cited
US4705345A
Cited
EP0229647A2
Cited
US4830467A
Cited
US4909607A
Cited
JPS62257131A
Cited
JPS63249130A
Cited
JPS6472819A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-02-07 | 1997-08-09 | 1998-02-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-02-07 | 2001-08-09 | 2002-02-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-02-07 | 2005-08-09 | 2006-02-08 | $7700.00 | Window Closed / Lapsed |