Light Guide Wearable HUD Grating Uniformity and Defect Reduction
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Solution Overview
Problem
Wearable heads-up displays face challenges in achieving a slim, aesthetically appealing design while maintaining high visual quality and minimizing optical defects such as seams and diffraction of environmental light, which hinders their adoption in consumer markets.
Innovation Solution
The use of a light guide based wearable heads-up display with multiple laser light sources and a two-dimensional exit pupil expander/outcoupler, combined with surface-relief or holographic gratings, to enhance field of view and uniformity, and a contiguous photopolymer material for the incoupler, exit pupil expander, and outcoupler to reduce optical defects and improve cosmetics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If large display components are used to provide sufficient visual quality, then the visual quality is improved, but the device becomes bulkier and less aesthetically appealing
Solution Approach 1:
The optical system is segmented into multiple functional components: laser projectors for light generation, diffractive optical elements for light manipulation, and light guides for light transmission. This segmentation allows each component to be optimized independently, enabling high visual quality through precise optical control while maintaining a compact overall form factor suitable for wearable applications
Solution Approach 2:
The patent transitions from conventional two-dimensional display approaches to three-dimensional optical path manipulation using diffractive optical elements and light guides. By utilizing the third dimension (depth/optical path length), the system achieves enhanced visual quality and field of view without proportionally increasing the device's external dimensions, thus resolving the contradiction between visual quality and device bulk
2Ease of operation
If conventional laser projectors with controllable mirrors are used, then the display functionality is achieved, but the alignment precision and optical defects are worsened
Solution Approach 1:
The patent replaces mechanical mirror-based light deflection systems with diffractive optical elements that manipulate light through diffraction and interference patterns. This substitution eliminates the need for precise mechanical alignment of mirrors while maintaining display functionality, as the diffractive patterns are inherently more tolerant to manufacturing variations and do not require active mechanical control
Solution Approach 2:
The diffractive optical elements create multiple virtual images or exit pupils that replicate the display information across different spatial locations. This copying approach provides redundancy and tolerance to alignment errors, as the display functionality is maintained even if individual optical paths are not perfectly aligned, thereby improving manufacturing precision
3Area of stationary object
If multiple optical components are integrated to increase field of view, then the field of view is improved, but optical defects such as seams and diffraction increase
Solution Approach 1:
The patent employs composite optical structures combining light guide materials with integrated diffractive optical elements. This composite approach allows the different optical functions (light guidance, diffraction, outcoupling) to be integrated into a unified structure, reducing the number of discrete component interfaces that would otherwise generate seams and diffraction artifacts, thus maintaining a wide field of view while minimizing optical defects
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 approach results in a more aesthetically pleasing and functional wearable heads-up display with an increased field of view, improved uniformity, and reduced optical defects, allowing users to see both display content and their environment without the bulkiness and optical issues of previous designs.
Implementation Method 1
The optical combiner includes a first grating to receive light and to redirect the light towards an eye of a user; and a second grating immediately adjacent the first grating
Implementation Method 2
Light guides in Wearable Heads-Up Displays... A light guide can operate under the principle of total internal reflection (TIR)
Data Source
AI summary
Systems, devices, and methods for light guide based wearable heads-up displays (“WHUD”) are described. Display uniformity may be improved via incoupler double bounce uniformity or eyebox mapping. Grating cosmetic effects may be reduced. FOV may be enhanced by multiple EPEs. Bandwidth may be increased by laser wavelength offsets. The couplers may be a single contiguous photopolymer.