Fast Electroactive Lens Switching via Polarization Selection
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Solution Overview
Problem
Existing electroactive lenses are slow to switch optical power, taking hundreds of milliseconds, which degrades the visual experience in augmented and virtual reality applications.
Innovation Solution
A fast-switching electroactive lens system combining a polarization changer and slower focus-changing components, allowing rapid optical power transitions by switching light between orthogonal polarization states, with the polarization changer switching faster than the focus-changing lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a typical electroactive lens is used to adjust focus, then the lens can change optical power, but the switching takes hundreds of milliseconds which degrades visual experience
Solution Approach 1:
The system divides the single lens function into multiple electroactive lens elements (first and second lenses) with different polarization sensitivities. Each lens element handles a specific polarization state, allowing parallel processing of different optical paths and enabling faster effective switching by selecting which lens element is active based on input polarization.
Solution Approach 2:
The system changes the polarization state of light as a control parameter to switch between different lens elements. By using a polarization adjuster to modify the polarization angle, the system can rapidly select which lens element (and thus which optical power) is active, achieving fast switching without requiring the lens material itself to change state slowly.
2Speed
If multiple electroactive lens elements are used with different polarization sensitivities, then fast switching can be achieved, but the device complexity increases
Solution Approach 1:
Each electroactive lens element is designed to be sensitive to a specific polarization state, making it universally applicable for handling that polarization. The polarization adjuster serves multiple functions: it controls which lens element is active, adjusts focus by selecting different lens elements, and can potentially provide continuous focus adjustment by varying the polarization angle to blend between lens elements.
Solution Approach 2:
The polarization adjuster acts as an intermediary between the control system and the lens elements. Instead of directly controlling multiple lens elements, the system uses the polarization adjuster to mediate the selection process, converting electrical control signals into polarization state changes that automatically route light through the appropriate lens element.
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
Enables optical power changes in tens of milliseconds, providing seamless focus adjustments in augmented and virtual reality systems without perceptible lag.
Implementation Method 1
a dynamic polarization switcher that can switch light between those orthogonal polarization states in tens of milliseconds
Implementation Method 2
the first electroactive lens element may be configured to focus horizontally polarized light but not vertically polarized light, and the second electroactive lens element may be configured to focus vertically polarized light but not horizontally polarized light
Data Source
AI summary
A conventional liquid crystal lens switches on and off so slowly that a person can perceive the lens's gradual transition from high to low optical power. This makes a conventional liquid crystal lens unsuitable for focusing virtual images quickly in an augmented, mixed, or virtual reality system. Conversely, an inventive fast-switching electroactive lens system can switch so fast (e.g., in 35 milliseconds or less) that a person perceives its optical power to change instantaneously. The system accomplishes this fast switching with using an electroactive wave plate in series with slower liquid-crystal lenses. The wave place can be switched quickly between emitting vertically or horizontally polarized light. Each lens focuses either vertically or horizontally polarized light and transmits orthogonally polarized light. By switching between polarization states, the wave plate effectively turns one lens on and the other lens off much faster than either lens could be switched by itself.