Light-Guide Optical Element With Embedded Reflective Surfaces
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Solution Overview
Problem
Existing light-guide optical elements (LOEs) face issues with non-uniform illumination due to inactive portions of reflecting surfaces, leading to 'holes' in images, which reduce the performance of both near-eye and head-up displays.
Innovation Solution
The LOE design features light directing surfaces fully embedded within the substrate, spaced from major surfaces, with interfaces oriented at a predetermined angle, ensuring no overlap or gaps, and a method for mass production involving patterned substrates and dicing to create multiple LOEs with embedded light directing regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overlapping is set between the reflective surfaces to compensate for the inactive portions in the output aperture, then the holes in the projected augmented image are eliminated, but rays from the output scene that cross these overlapped areas suffer from double attenuations and holes are created in the external view
Solution Approach 1:
The reflective surfaces are segmented into distinct, non-overlapping regions. Each reflective surface is precisely positioned and sized to reflect light only to its intended destination, preventing any overlap with adjacent reflective surfaces. This segmentation eliminates the double attenuation problem while maintaining uniform illumination across the output aperture.
2Reliability
If the ends of the reflecting surfaces are adjacent to one another over the length of the LOE, then there is no holes in the projected augmented image, but since there is no overlap between the surfaces there is no holes in the real image of the external view
Solution Approach 1:
An intermediary layer or structure is introduced to precisely position and secure the reflective surfaces within the LOE substrate. This intermediary element ensures that the reflective surfaces are accurately positioned with their ends adjacent to one another without requiring high-precision direct positioning, thereby achieving uniform illumination while simplifying the manufacturing process.
3Ease of manufacture
If the major axis orientation of two adjacent surfaces is identical, then the alignment is simplified, but the entire second surface will be inactive
Solution Approach 1:
The major axis orientation of adjacent reflective surfaces is deliberately made asymmetric rather than identical. Each reflective surface is oriented at a specific angle relative to its neighbors, ensuring that all surfaces are active and contribute to light reflection. This asymmetric orientation prevents any surface from being completely inactive while maintaining manufacturability through precise angular positioning.
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 provides uniform illumination and improved optical performance by eliminating inactive areas, enhancing the quality of images in both near-eye and head-up displays.
Implementation Method 1
The main physical principle of the operation of LOE is that light waves are trapped inside a substrate by total internal reflections from the major surfaces of the LOE
Implementation Method 2
the light waves which are trapped inside the LOE are coupled out into the eyes of the viewer by one or more internal reflecting or partially reflecting/diffractive surfaces
Implementation Method 3
the light waves which are trapped inside the LOE are coupled out into the eyes of the viewer by one or more internal reflecting or partially reflecting/diffractive surfaces
Data Source
AI summary
An optical structure and corresponding process of manufacture for light guide optical elements (LOEs) which guide light by reflection at major surfaces. The structure further includes light directing surfaces for coupling light out of the LOE, obliquely inclined with respect to the major surfaces. The optical structure is formed from a stack of multiple optically transparent layers each of which has a surface pattern of regions configured as light directing surfaces which are arranged in an X-Z plane in a spaced-apart relationship along at least the X-axis with optically transparent regions between them. The layers are stacked along a Y-axis so that each of the surface patterns is located at an interface between two adjacent layers and the patterns of the layers are aligned with a shift of a predetermined value along one or both of the X-axis and Z-axis.