Method and apparatus for erasing scattering in storage-type liquid crystals by frequency sweeping
AssigneeHughes Aircraft Company
InventorDonald D. Boswell
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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.
Claims9
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.
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.
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.
Dependencies are inferred from the claim text.