Output Coupling Surface Treatment for Smartglass Image Quality
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Solution Overview
Problem
Optical systems in smartglasses face challenges in maintaining high imaging quality due to manufacturing difficulties in achieving precise alignment and surface quality of Fresnel segments, leading to issues like loss of contrast, double images, and aberrations, especially when using partly transparent layers for see-through functionality.
Innovation Solution
The optical system selectively surface-treats areas of the output coupling arrangement to control light output, applying reflecting layers to predefined portions for optimal imaging while reducing intensity in other areas, and using refractive index-matched layers to minimize reflections and stray light, thereby enhancing transparency and reducing aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a free-form Fresnel surface with one or more segments is used for output coupling, then the optical imaging quality depends very strongly on the surface trueness and quality, but manufacturing precision and alignment are difficult to achieve, leading to loss of contrast, double images, and aberrations
Solution Approach 1:
The patent changes the surface treatment parameters of the output coupling arrangement by applying different optical coatings (reflecting layers, anti-reflective layers, transparent layers) to different areas. This allows optimization of light output intensity and direction without requiring ultra-precise Fresnel segment manufacturing, thereby resolving the contradiction between imaging quality and manufacturing ease
Solution Approach 2:
The patent applies different surface treatments to different local areas of the output coupling arrangement. Specifically, the first area receives a reflecting layer for enhanced light output, while the second area receives an anti-reflective layer for reduced stray light. This local differentiation allows the system to achieve high imaging quality without requiring uniform ultra-precise manufacturing across the entire Fresnel surface
2Reliability
If a partly transparent layer is applied to the output coupling arrangement for see-through functionality, then transparency is improved, but imaging quality deteriorates due to unwanted light components reaching the eye
Solution Approach 1:
The patent divides the output coupling arrangement into different areas with different surface treatments. The first area has a reflecting layer that enhances light output toward the eye, while the second area has an anti-reflective layer that prevents stray light from reaching the eye. This local differentiation maintains see-through functionality while eliminating harmful light components
Solution Approach 2:
The patent converts the potentially harmful effect of the transparent layer (which allows unwanted light to pass through) into a benefit by selectively applying anti-reflective coating to specific areas. The transparent layer becomes beneficial because it allows desired light to pass while the coated areas block unwanted light, transforming a harmful effect into a useful one
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 improves imaging quality by reducing unwanted light components and aberrations, maintaining high contrast and clarity of the virtual image while ensuring see-through functionality, even with manufacturing tolerances and material properties.
Implementation Method 1
the output coupling of the light propagating in the light guide is realized by way of a reflection at a free-form Fresnel surface with one (e.g., free-form mirror) or more segments
Implementation Method 2
using refractive index-matched layers to minimize reflections and stray light
Data Source
AI summary
An optical system for generating a virtual image of a source image provided on an image generator includes a surface of an output coupling that is exposed to a light beam path that is surface-treated such that the light beam path is coupled out from an optical waveguide toward the eye from first partial regions of the surface of the output coupling. In second partial regions of the surface of the output coupling, said second partial regions being different from the first partial regions, said light beam path is coupled out from the optical waveguide toward the eye at most with reduced intensity, or not at all.