Multifocal Liquid Crystal Lens for AR Visual Fatigue
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Solution Overview
Problem
Current display technologies for virtual and augmented reality have fixed focal lengths, limiting them to single depth spatial imaging and causing accommodation-convergence conflicts that lead to visual fatigue and discomfort.
Innovation Solution
A multifocal lens composed of N liquid crystal panels stacked in a switchable configuration, allowing the lens to change between multiple focal lengths by altering the refractive indices of the liquid crystal layers under voltage control, enabling imaging at multiple depth spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed focal length lens is used in display technology, then the device structure is simple, but it causes accommodation-convergence conflicts leading to visual fatigue
Solution Approach 1:
The patent applies the dynamics principle by transforming the fixed focal length lens into a variable focal length lens using liquid crystal technology. The liquid crystal layers can dynamically adjust their refractive indices under voltage control, enabling the lens to switch between multiple focal lengths (e.g., first focal length when first liquid crystal layer has first refractive index, second focal length when first liquid crystal layer has second refractive index). This dynamic adjustability allows the lens to adapt to different depth spaces, resolving the accommodation-convergence conflict and reducing visual fatigue while maintaining reasonable device complexity.
Solution Approach 2:
The patent implements parameter changes by modifying the refractive index parameter of the liquid crystal layers through voltage application. When different voltages are applied to the liquid crystal layers, their refractive indices change, which directly alters the focal length of the lens. This parameter change mechanism enables smooth transition between different focal lengths, allowing the display system to present content at multiple depth spaces and eliminate visual discomfort caused by fixed focal length.
2Adaptability or versatility
If multiple lenses are stacked to achieve multiple focal lengths, then multiple depth spatial imaging is enabled, but the device complexity increases
Solution Approach 1:
The patent applies the merging principle by combining multiple liquid crystal layers with a single lens structure. Instead of using separate physical lenses for different focal lengths, the patent integrates multiple liquid crystal layers (first liquid crystal layer, second liquid crystal layer, etc.) within one lens system. By controlling the refractive indices of these layers through voltage application, the system achieves multiple focal lengths (first focal length, second focal length, etc.) and enables imaging at multiple depth spaces, thereby reducing device complexity compared to using multiple separate lenses.
Solution Approach 2:
The patent implements multi-functionality by designing a single lens structure that can perform multiple functions - imaging at different depth spaces. The liquid crystal-based lens can switch between first focal length, second focal length, and other focal lengths by adjusting the refractive indices of the liquid crystal layers. This universal lens structure replaces what would traditionally require multiple specialized lenses, enabling the system to present virtual or augmented reality content at various depth planes while maintaining a compact and simplified device architecture.
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 multifocal lens effectively alleviates visual discomfort by allowing selection of different focal lengths based on content, enabling multiple depth spatial imaging and reducing accommodation-convergence conflicts.
Implementation Method 1
The n-th liquid crystal panel may be configured to be switchable between a converging state and a non-converging state
Implementation Method 2
allowing the lens to change between multiple focal lengths by altering the refractive indices of the liquid crystal layers under voltage control
Implementation Method 3
the n-th converging element comprises an annular phase diffraction grating
Implementation Method 4
enabling imaging at multiple depth spaces
Data Source
AI summary
The present disclosure relates to a multifocal lens. The multifocal lens may include N liquid crystal panels in a stacked manner. The N liquid crystal panels may include an n-th liquid crystal panel, and the n-th liquid crystal panel may include an n-th converging element having an n-th focal length. N is a positive integer greater than or equal to 2, n is a positive integer, and 1≤n≤N. The n-th liquid crystal panel may be configured to be switchable between a converging state and a non-converging state. The N liquid crystal panels may be configured to make the multifocal lens to have switchable CN1+CN2+CN3+ . . . +CNN focal lengths, and the CN1+CN2+CN3+ . . . +CNN focal lengths are all different from one another.