AR Display Optical Stack for Compact Mixed Reality
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Solution Overview
Problem
Existing virtual and augmented reality head-mounted displays face challenges in providing a wide field of view while maintaining compact size and addressing the visual conflict between accommodation and vergence, leading to discomfort and visual inaccuracies.
Innovation Solution
The design positions a display between the user's eye and a curved reflector, incorporating an optical stack that includes a quarter-wave plate and a reflective polarizer, allowing for multiple displays at different distances to create virtual images at varying apparent distances, and includes a liquid crystal display for real-world occlusion control, enabling a seamless mixed reality environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a curved reflector is used to achieve wide field of view, then the field of view is improved, but the device size and complexity increase
Solution Approach 1:
The patent embeds the curved reflector within the head-mounted display structure, nesting optical components within each other to achieve wide field of view while maintaining compact form factor. The reflector is positioned to work in conjunction with the display and waveguide, creating a nested optical path that expands functionality without proportionally increasing device size.
Solution Approach 2:
The patent uses a waveguide structure that directs light along a extended path, effectively adding a dimensional aspect to the optical design. This allows the field of view to be expanded in angular space while the physical footprint remains constrained, resolving the contradiction between wide field of view and compact device size.
2Ease of operation
If multiple displays at different distances are used to address accommodation-vergence conflict, then visual comfort is improved, but device complexity increases
Solution Approach 1:
The patent implements different optical paths for different regions of the field of view, with specific displays or display regions assigned to different depth planes. This local differentiation allows the system to address accommodation-vergence conflict by providing appropriate focal cues for different virtual object distances without requiring all displays to be equally complex.
Solution Approach 2:
The patent employs dynamic control of display elements, where certain displays or display regions can be selectively activated or adjusted based on the virtual content being presented. This dynamic approach allows the system to manage accommodation-vergence conflict adaptively, reducing the need for permanently active multiple displays and thereby lowering overall device complexity.
3Adaptability or versatility
If a liquid crystal display is used for real-world occlusion control, then mixed reality quality is improved, but energy consumption increases
Solution Approach 1:
The patent implements occlusion control that is activated only when needed, rather than continuously operating. The liquid crystal display elements are switched on demand to occlude the real world when virtual content requires it, and remain off otherwise. This periodic activation significantly reduces energy consumption while maintaining the capability for high-quality mixed reality experiences when required.
Solution Approach 2:
The patent applies occlusion selectively to specific regions of the field of view rather than uniformly across the entire display. The liquid crystal display elements are activated only in areas where virtual objects need to be presented, allowing the real world to remain visible in other regions. This localized approach reduces the total energy required for occlusion control while preserving mixed reality quality where needed.
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
This configuration enables a smaller, more comfortable display system with a wide field of view, effectively addressing the visual conflict and allowing for a seamless blend of virtual and real-world elements by controlling brightness and occlusion.
Implementation Method 1
The optical stack consists of a display, a quarter wave plate and a reflective polarizer
Implementation Method 2
The optical path of the pancake window device uses circular polarization based mirror bounces to generate a virtual image of the display seen from the eye side of the optics
Implementation Method 3
a curved mirror can be used to achieve short focal lengths with large diameters thus offering wide fields of view
Data Source
AI summary
Compact and low mass augmented and fully virtual head mounted display designs are disclosed. The disclosed displays employ a display located between the eye and the main optical element of the head mounted display. These designs additionally afford the ability to support augmented reality displays because the user can see both the virtual image from the display and the real world if desired. The designs use semi-transparent displays where either the display emits circularly polarized light or the displays which emits light from one surface or the view of the display directly from the eye is obscured.