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US4048628A
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Method and apparatus for erasing scattering in storage-type liquid crystals by frequency sweeping
Assignee: Raytheon Co
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Filing: 1976-07-28
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Granted: 1977-09-13
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Expires: 1996-07-28
Abstract
Abstract Methods and apparatus for erasing the stored scattering image in storage-type liquid crystal light valves. Erasure is accomplished by applying a signal from an erasing signal source across the liquid crystal cell where the signal is a voltage which is swept over the audio frequency range of 1 KHZ through 20 KHZ. In another embodiment, the erasing signal source supplies a precursor signal which has an initial frequency below the frequency threshold for scattering. This low frequency signal is maintained for a brief period of time to excite the entire liquid crystal cell into a uniform scattering state. The erasing signal is then swept over the audio frequency spectrum of 1 KHZ through 20 KHZ to cause the cell to return to the non-scattered, translucent state.
Inventors
- 👤 Donald D. Boswell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 07:40
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/13; G02F1/133; G02F1/13306; G02F1/135; G02F1/137; G02F1/13756
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
52 words
An improved storage-type liquid crystal cell comprising a storage-type liquid crystal layer and imaging means for causing emulsive storage scattering to occur in selected regions of the liquid crystal cell, the improvement comprising means for applying a swept frequency erasing signal across at least one selected region of the liquid crystal layer.
Claim 2
Dependent Claim
52 words
An improved storage-type liquid crystal cell comprising a storage-type liquid crystal layer and imaging means for causing emulsive storage scattering to occur in selected regions of the liquid crystal cell, the improvement comprising means for applying a swept frequency erasing signal across at least one selected region of the liquid crystal layer.
Claim 3
Dependent Claim
93 words
The storage-type liquid crystal cell of claim 1 wherein said means for applying a swept frequency swept signal comprises: a. a first electrode interposed on one side of the liquid crystal layer; b. a second electrode interposed on the opposite side of the liquid crystal layer, said first and second electrodes in electric field influencing relationship with said liquid crystal layer; and c. a swept frequency erasing signal source coupled to said first and second conductors to provide an image erasing signal between said first and second electrodes in said liquid crystal cell.
Claim 4
Dependent Claim
49 words
The storage-type liquid crystal cell of claim 1 wherein said swept frequency erasing signal has an rms amplitude threshold of the liquid crystal layer and a variable frequency in the audio frequency range which sweeps continuously from a first frequency to a second frequency higher than said first frequency.
Claim 5
Dependent Claim
84 words
The storage-type liquid crystal cell of claim 1 wherein said swept frequency erasing signal has a rms amplitude above the amplitude threshold of the liquid crystal layer and a variable frequency in the audio frequency range which comprises: a. a precursor signal having a frequency below the frequency threshold of the liquid crystal layer to generate uniform scattering across the liquid crystal layer, and b. an erase signal which sweeps continuously from a first frequency to a second frequency higher than said first frequency.
Claim 6
Independent Claim
94 words
A method for causing transformation from the scattered to the non-scattered state in a storage-type liquid crystal cell having a storage-type liquid crystal layer comprising the step of applying a swept frequency erasing signal across the liquid crystal device said signal having a rms amplitude above the amplitude threshold of the liquid crystal layer and a variable frequency in the audio frequency range which sweeps continuously from a first frequency to a second frequency high than said first frequency wherein said second frequency is above the maximum scattering frequency of the liquid crystal cell.
Claim 7
Independent Claim
94 words
A method for causing transformation from the scattered to the non-scattered state in a storage-type liquid crystal cell having a storage-type liquid crystal layer comprising the step of applying a swept frequency erasing signal across the liquid crystal device said signal having a rms amplitude above the amplitude threshold of the liquid crystal layer and a variable frequency in the audio frequency range which sweeps continuously from a first frequency to a second frequency high than said first frequency wherein said second frequency is above the maximum scattering frequency of the liquid crystal cell.
Claim 8
Independent Claim
120 words
The method for causing transformation from the scattered to non-scattered state in a storage-type liquid crystal cell having a storage-type liquid crystal layer said method comprising the steps of: a. applying a precursor signal having an amplitude above the amplitude threshold of the liquid crystal cell at a frequency below the frequency maximum scattering, and b. secondly, applying an erasing signal across the liquid crystal device said signal having a rms amplitude above the amplitude threshold of the liquid crystal layer and variable frequency in the audio frequency range which sweeps continuously from a first frequency to a second frequency higher than said first frequency wherein said second frequency is above the maximum scattering frequency of the liquid crystal cell.
Claim 9
Independent Claim
120 words
The method for causing transformation from the scattered to non-scattered state in a storage-type liquid crystal cell having a storage-type liquid crystal layer said method comprising the steps of: a. applying a precursor signal having an amplitude above the amplitude threshold of the liquid crystal cell at a frequency below the frequency maximum scattering, and b. secondly, applying an erasing signal across the liquid crystal device said signal having a rms amplitude above the amplitude threshold of the liquid crystal layer and variable frequency in the audio frequency range which sweeps continuously from a first frequency to a second frequency higher than said first frequency wherein said second frequency is above the maximum scattering frequency of the liquid crystal cell.
Claim 10
Dependent Claim
36 words
The method of claim 6 wherein the precursor signal is applied for a duration of time sufficient to cause uniform scattering throughout the region of the liquid crystal cell to which the precursor signal is applied.
Claim 11
Dependent Claim
21 words
The method of claim 6 wherein the first frequency is about 1 KHZ and the second frequency is about 20 KHZ.
Claim 12
Dependent Claim
23 words
The method of claim 6 wherein the frequency of the precursor signal is substantially equal to said first frequency of the erasing signal.
References Cited (Backward Citations)
US3655269A
Cited
US3921162A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-09-12 | 1981-03-14 | 1981-09-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-09-12 | 1985-03-14 | 1985-09-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-09-12 | 1989-03-14 | 1989-09-13 | $7700.00 | Window Closed / Lapsed |