Split Optical Power Head-Worn Display for Finite-Distance XR Images
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Solution Overview
Problem
Existing head-worn displays present extended reality images at an infinite distance, causing eye strain and discomfort due to constant focus switching between the image and the real world.
Innovation Solution
A head-worn display system with an optical path that splits optical power application between a light engine and a lightguide, presenting the XR image at a predetermined finite distance using a combination of components without additional thickness or weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If collimated light is used to present XR images at an infinite distance, then the optical path is simple, but the user experiences eye fatigue and discomfort due to constant focus switching
Solution Approach 1:
The optical power application is segmented between two distinct components: the light engine (with its lens) and the lightguide. The light engine applies a first optical power to converge light to a virtual image, while the lightguide applies a second optical power to redirect this converging light. This segmentation allows each component to perform a specific function, achieving finite distance image presentation without requiring a single complex optical element.
Solution Approach 2:
The patent merges the optical power application functions of the light engine and lightguide to work together as an integrated system. The light engine's lens and the lightguide's diffractive/reflective structures combine their optical powers to achieve the desired finite distance focus, creating a unified optical path that presents XR images at a comfortable viewing distance.
2Object-affected harmful factors
If additional optical components are added to present images at a finite distance, then eye fatigue is reduced, but the device thickness and weight increase
Solution Approach 1:
The lightguide is designed to perform multiple functions: it acts as both the light transmission medium and the optical element that applies the second optical power. The diffractive or reflective structures within the lightguide simultaneously guide light propagation and provide the necessary optical convergence, eliminating the need for separate dedicated optical components and reducing overall device weight.
Solution Approach 2:
The optical structures are nested within the lightguide body itself. The diffractive or reflective structures are integrated into the lightguide material, with the light engine positioned within or adjacent to the lightguide assembly. This nested configuration minimizes the overall volume and weight of the device while achieving the required optical functionality.
3Device complexity
If the light engine applies all optical power to converge light, then the lightguide structure is simple, but the image cannot be presented at a finite distance
Solution Approach 1:
The optical power application is segmented between the light engine and lightguide. The light engine applies a first optical power to converge light to a virtual image location, while the lightguide applies a second optical power to redirect this converging light toward the user's eye. This segmentation enables precise control over the final image distance by distributing the optical power requirements across two components.
Solution Approach 2:
The system controls the optical power parameters of both the light engine and lightguide to achieve the desired finite distance focus. By adjusting the optical power values and their distribution between the two components, the system can precisely control the virtual image distance and present XR content at comfortable viewing distances.
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
Reduces eye fatigue, headaches, and nausea by allowing the user to maintain focus at a consistent distance, while maintaining image quality and avoiding bulkiness.
Implementation Method 1
a lightguide configured to direct the light from the light engine to an eye of a user using total internal reflection
Implementation Method 2
a lens configured to apply an optical power to the light from the light engine such that the light represents an extended reality image displayed at a predetermined finite distance from a user
Data Source
AI summary
A head-worn display (HWD) is configured to present an extended reality (XR) image to a user at a predetermined finite distance. To this end, the HWD includes an optical path having a first component configured to apply a first optical power to light representing the XR image emitted from a light engine. Further, the optical path includes a second component, different from the first component, configured to apply a second optical power to the light having the first optical power applied. Additionally, the optical path is configured to present the light having the first and second optical powers applied to the user such that the XP image is presented to the user at a finite distances based on the first and second optical powers.