Substrate-Guide Optical Device Using Anisotropic Reflecting Surfaces
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Solution Overview
Problem
Conventional compact optical modules for displays, such as head-mounted and head-up displays, face limitations in achieving a wide field-of-view (FOV) and large eye-motion-box, leading to bulkiness, sensitivity to movement, and high chromatic dispersion, which restricts their practicality and performance.
Innovation Solution
The design incorporates a light-transmitting substrate with anisotropic reflecting surfaces that utilize total internal reflection and selectively reflecting surfaces to couple light waves, allowing for a compact and efficient optical system with a wide FOV and large eye-motion-box, enabling the use of compact display sources and wide spectral sources, including white light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional free-space optical modules are used to achieve wide field-of-view, then the field-of-view increases, but the device becomes larger, heavier and bulkier
Solution Approach 1:
The patent transitions from conventional free-space optical path to a substrate-guided waveguide optical element, utilizing total internal reflection within the substrate to guide light waves. This dimensional change in light propagation path enables wide field-of-view while maintaining compact device size, as the light is confined and guided within the thin substrate rather than requiring large free-space optical components
Solution Approach 2:
The patent replaces conventional mechanical optical components (lenses, mirrors in free space) with a substrate-guided waveguide system that uses total internal reflection to guide and manipulate light waves. This substitution eliminates the need for bulky mechanical optical components while achieving the same or better optical performance in a compact form factor
2Adaptability or versatility
If conventional optical designs are used to increase field-of-view, then the field-of-view expands, but the eye-motion-box becomes very small and the system becomes sensitive to movement
Solution Approach 1:
The patent employs an array of selectively reflecting surfaces with different orientations distributed across the substrate. Each surface is optimized for specific viewing angles, with reflectivity characteristics tailored to local angular requirements. This local optimization enables wide field-of-view while maintaining large eye-motion-box, as different regions of the substrate handle different angular ranges efficiently
Solution Approach 2:
The patent divides the reflecting surface into multiple discrete selectively reflecting surfaces, each oriented at different angles. This segmentation allows each surface element to be optimized for specific viewing directions, collectively providing wide field-of-view and large eye-motion-box while reducing sensitivity to small movements through the distributed array configuration
3Illumination intensity
If conventional HUD designs are used to illuminate the combiner surface, then the entire combiner is illuminated, but the system becomes bulky and requires considerable installation space
Solution Approach 1:
The patent uses a substrate-guided waveguide configuration where light is coupled into the substrate and guided to the combiner surface through total internal reflection. This enables compact illumination of the entire combiner surface from a small display source positioned near the substrate, eliminating the need for large offset display sources and bulky optical paths required in conventional HUD designs
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 results in a compact, high-quality optical system that accommodates large eye movements, reduces chromatic dispersion, and supports wide spectral sources, enhancing the viewing experience in displays like head-mounted and head-up displays, as well as mobile devices, by providing a large virtual image with improved image quality and reduced physical size.
Implementation Method 1
optical means for coupling light waves into said substrate by total internal reflection
Implementation Method 2
at least one of said partially reflecting surfaces is anisotropic
Data Source
AI summary
An optical device including a light waves-transmitting substrate having two major surfaces and edges, has optical means for coupling light into the substrate by total internal reflection, and a plurality of partially reflecting surfaces (22a, 22b) carried by the substrate. The partially reflecting surfaces (22a, 22b) are parallel to each other and are not parallel to any of the edges of the substrate. One or more of the partially reflecting surfaces (22a, 22b) is an anisotropic surface.