Electroactive Lens with Position-Dependent Pretilt Alignment
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Solution Overview
Problem
Existing electroactive lenses with liquid crystal and Fresnel lens structures suffer from double images when handling unpolarized light due to inhomogeneous liquid crystal orientation, leading to variations in refractive indices across the lens surface.
Innovation Solution
The optical device incorporates a diffractive lens structure between two substrates with a nematic liquid crystal layer, where the liquid crystals are axially aligned, and a pretilt is introduced to align them linearly in the on-state, ensuring a uniform refractive index and reducing twist angles, thereby maintaining linear polarization and filtering out double images using a polarizer or a second electroactive lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vertically aligned liquid crystals are used in electroactive lenses, then the lens can be switched between on and off states, but double images occur due to inhomogeneous liquid crystal orientation in different parts of the device
Solution Approach 1:
The patent introduces position-dependent pretilt angles in the alignment layer, where different regions of the alignment layer provide different pretilt angles to compensate for the different local lens surface inclinations. This ensures that the liquid crystal director orientation is corrected locally in each region to prevent double image formation while maintaining the switching function.
2Device complexity
If the liquid crystal director is oriented perpendicular to the substrate, then the lens structure is simple, but the orientation becomes inhomogeneous over the lens substrate due to lens surface geometry
Solution Approach 1:
The alignment layer is designed with position-dependent properties, where the pretilt angle varies across different regions of the substrate. This local variation compensates for the geometric effects of the lens surface, maintaining uniform liquid crystal orientation without requiring complex overall structural changes.
Data Source
AI summary
The present disclosure relates to an electroactive for use in eyewear, the electroactive unit comprising: an electroactive element, the electroactive element comprising a first and a second optically transparent substrate, between which at least one liquid crystal layer comprising nematic liquid crystals; and a Fresnel-lens structure are arranged, wherein a first and a second transparent electrode are formed on the first and second substrates respectively, and wherein an alignment layer is present on the first substrate and in contact with the liquid crystal layer and is configured to align the nematic liquid crystals in a first direction, and a polarization element configured for adjusting light having a polarization in a second direction perpendicular to the first direction, wherein the liquid crystals of the liquid crystal layer are in the Mauguin regime.