Liquid-crystal variable retarder using liquid crystal cells of differing thicknesses
AssigneePalo Alto Research Center Incorporated
InventorAlex Hegyi
Life of this patent
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Abstract
A liquid-crystal variable retarder has first and second liquid-crystal cells with respective first and second thicknesses, the second thickness being less than the first thickness. A feedback sensor provides a feedback signal indicative of a retardance of the liquid-crystal variable retarder. A controller is coupled to the feedback sensor and the first and second liquid-crystal cells. The controller is operable to apply a first signal to the first liquid-crystal cell based on a target retardance trajectory and a feedforward control model. The controller applies a second signal to the second liquid-crystal cell based on the feedback signal and the target retardance trajectory.
Claims21
An apparatus comprising:
- a liquid-crystal variable retarder comprising:
- a first liquid-crystal cell having a first thickness;
- and
- a second liquid-crystal cell having a second thickness that is less than the first thickness;
- a feedback sensor providing a feedback signal indicative of a retardance of the liquid-crystal variable retarder;
- and
- a controller coupled to the feedback sensor and the first and second liquid-crystal cells, the controller operable to:
- apply a first signal to the first liquid-crystal cell based on a target retardance trajectory and a feedforward control model;
- and
- apply a second signal to the second liquid-crystal cell based on the feedback signal and the target retardance trajectory.
An apparatus comprising:
- a liquid-crystal variable retarder having a first maximum retardance;
- a liquid-crystal waveplate having a second maximum retardance that is less than the first maximum retardance, the liquid-crystal waveplate oriented relative to the liquid-crystal variable retarder such that the liquid-crystal waveplate, in a first state, has a minimal retardance that opposes a retardance of the liquid-crystal variable retarder;
- and
- a controller coupled to the liquid-crystal waveplate, the controller operable to switch the liquid-crystal waveplate from the first state to a second state, wherein the liquid-crystal waveplate, in the second state, has the second maximum retardance.
A method, comprising:
- receiving a temperature signal indicative of a temperature of a liquid-crystal variable retarder, the liquid-crystal variable retarder comprising a first liquid-crystal cell having a first thickness and a second liquid-crystal cell having a second thickness that is less than the first thickness;
- applying a first signal to the first liquid-crystal cell based on a target retardance trajectory and an output of a feedforward control model of the liquid-crystal variable retarder, a parameter of the feedforward control model being modified based on the temperature signal;
- receiving a retardance feedback signal from the liquid-crystal variable retarder;
- and
- varying a second signal applied to the second liquid-crystal cell responsive to the retardance feedback signal;
Dependencies are inferred from the claim text.