See-through Display Light Trap Stray Light Management
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Solution Overview
Problem
Head-mounted displays (HMDs) that provide a see-through view are affected by stray light, leading to reduced image sharpness and contrast, as stray light scatters or reflects within the optics, causing black areas to appear gray and compromising the see-through view.
Innovation Solution
The implementation of an optical system with a dark light trap and polarized light management, using a DLP or TIR wedge configuration to direct image light along the optical axis while diverting dark state light away, reducing stray light and enhancing contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a see-through optical system is used to provide environmental view, then transparency and see-through capability are improved, but stray light scattering and reflection increase, reducing image contrast and sharpness
Solution Approach 1:
The optical system is divided into separate functional components: a first optical element for transmitting environmental light, a second optical element for displaying digital content, and a light trap positioned between them. This segmentation allows each component to be optimized for its specific function while managing stray light through dedicated structures.
Solution Approach 2:
A light trap is introduced as an intermediary component between the first and second optical elements. This light trap absorbs stray light that would otherwise scatter or reflect between the optical elements, acting as a mediator to eliminate harmful light while preserving the see-through capability.
2Device complexity
If conventional optical elements are used without stray light management, then device complexity is reduced, but image contrast and black area depth deteriorate due to stray light
Solution Approach 1:
A light trap is introduced as an intermediary component between the first and second optical elements. This light trap absorbs stray light that would otherwise scatter or reflect between the optical elements, acting as a mediator to eliminate harmful light while preserving the see-through capability.
Solution Approach 2:
The harmful stray light is extracted and removed from the optical path using the light trap. By taking out the problematic light before it can cause degradation, the system maintains high contrast without requiring complex additional filtering or polarization components.
3Manufacturing precision
If light trap is added to manage stray light, then image contrast and sharpness are improved, but device complexity and optical path management increase
Solution Approach 1:
The optical system is divided into separate functional components: a first optical element for transmitting environmental light, a second optical element for displaying digital content, and a light trap positioned between them. This segmentation allows each component to be optimized for its specific function while managing stray light through dedicated structures.
Solution Approach 2:
The light trap serves multiple functions simultaneously: it absorbs stray light, maintains optical isolation between elements, and preserves the see-through capability. This multi-functionality reduces the need for additional separate components, managing complexity while achieving precise image quality.
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 solution improves image contrast and sharpness by effectively managing stray light, allowing for deeper blacks and higher brightness in see-through computer display systems, enhancing the user's experience by providing clearer digital and environmental overlays.
Implementation Method 1
a first optical element to transmit light from an environment to an eye of a user
Implementation Method 2
a second optical element to reflect or otherwise provide light representative of digital content to the eye of the user
Implementation Method 3
positioned between the first optical element and the second optical element to reduce stray light
Data Source
AI summary
A see-through head mounted display with controllable light blocking includes an optics module comprising a light source and image source positioned on a same side of an angled partially-reflective surface, wherein the light source projects light off the surface to the image source which reflects the light as image light to the surface which transmits the image light along a first axis. The display also includes a flat combiner positioned to reflect the image light off of a first side and simultaneously transmit incident light through the first and a second side, along an optical axis perpendicular to the first axis to provide a view of a displayed image overlaid onto a see-through view of the environment, and a controllable light blocking element arranged generally parallel to the flat combiner and in front of the second side to block light incident on the same optical axis as the image light.