Transparent Electrostrictive Actuators for AR Eyewear
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Solution Overview
Problem
Existing electroactive ceramics used in optical devices suffer from optical scattering due to variations in refractive index, porosity, and grain boundaries, leading to degraded optical quality and performance, particularly in virtual and augmented reality applications where transparency and deformation are crucial.
Innovation Solution
The development of electrostrictive ceramics with a substantially pore-free microstructure, sandwiched between conductive electrodes, which are capacitively actuated to deform and modify optical elements, thereby reducing scattering events and enhancing optical transparency and clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electroactive ceramics are used in optical devices, then actuation function is achieved, but optical scattering occurs due to refractive index variations, porosity, and grain boundaries
Solution Approach 1:
The patent changes the microstructural parameters of the electroactive ceramic by achieving ultra-fine grain sizes (sub-100 nm to sub-50 nm) and controlling porosity to extremely low levels (<5% volume fraction). These parameter changes reduce the scale of scattering centers below the wavelength of visible light, thereby minimizing optical scattering while preserving the actuation function.
Solution Approach 2:
The patent applies local quality control by creating a highly dense microstructure with minimized porosity and refined grain boundaries in the regions where light propagation occurs. The local microstructural quality is optimized to be transparent while maintaining the bulk material's actuation properties through controlled electric field application.
2Ease of manufacture
If conventional electroactive ceramics are used, then manufacturing is easier, but optical transparency is degraded due to porosity and grain boundaries
Solution Approach 1:
The patent segments the ceramic microstructure into ultra-fine grains (sub-100 nm to sub-50 nm) that are smaller than the scattering threshold for visible light. This segmentation approach allows conventional sintering processes to be used while achieving superior optical transparency, as the fine-grained structure minimizes grain boundary scattering.
Solution Approach 2:
The patent converts the typically harmful effect of porosity into a benefit by controlling pore size and distribution at the nanoscale. The nanoscale porosity (<5% volume fraction) creates scattering centers smaller than visible light wavelengths, effectively converting what would be defect-induced scattering into a transparent microstructure that maintains manufacturability.
3Illumination intensity
If dense microstructure is achieved to reduce scattering, then optical transparency improves, but manufacturing complexity increases
Solution Approach 1:
The patent achieves dense microstructure through controlled parameter changes during sintering, specifically optimizing temperature, time, and atmosphere to achieve ultra-fine grain sizes and minimal porosity. These parameter changes are implemented within conventional sintering equipment, avoiding the need for complex manufacturing processes while achieving >95% theoretical density and sub-100 nm grain structures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves high transmissivity (>70%) and low bulk haze (<10%) in electroactive ceramics, maintaining optical clarity and stability under electric fields, improving the optical quality and performance of devices like virtual and augmented reality eyewear.
Implementation Method 1
an electrostrictive layer disposed between and abutting the primary electrode and the secondary electrode
Data Source
AI summary
An optical element includes a primary electrode, a secondary electrode overlapping at least a portion of the primary electrode, and an electrostrictive ceramic layer disposed between and abutting the primary electrode and the secondary electrode, where the electrostrictive ceramic may be characterized by a relative density of at least approximately 99%, an average grain size of at least approximately 300 nm, a transmissivity within the visible spectrum of at least approximately 70%, and bulk haze of less than approximately 10%. Optical properties of the electrostrictive ceramic may be substantially unchanged during the application of a voltage to the electrostrictive ceramic layer and the attendant actuation of the optical element.