AR Display Waveguide Using Fresnel Mirrors for Compact Size
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Solution Overview
Problem
Current see-through displays for head-up and wearable applications face challenges in achieving compact size, high resolution, large field of view, and large eye-box while maintaining efficient light utilization and minimizing chromatic aberration and ghost images.
Innovation Solution
A compact see-through display system utilizing a projector, light pipe with in-coupling prism, folding mirrors with saw-teeth shaped prisms, and a single out-coupling waveguide, which uses telecentric optics and totally internal reflection to direct and reflect light rays efficiently, eliminating diffraction and reducing the size of the light pipe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If holographic optical elements are used to reduce display size, then compactness is improved, but light utilization efficiency deteriorates and resolution is limited
Solution Approach 1:
The patent replaces holographic optical elements with a waveguide-based optical system using total internal reflection and refraction. This substitution eliminates the need for complex holographic calculations and materials, achieving compact display size while maintaining high light utilization efficiency through straightforward optical path management.
Solution Approach 2:
The patent changes the optical parameters by using a waveguide with specific refractive index and designing coupling prisms with calculated angles. This allows the system to achieve compact size while maintaining high resolution and light efficiency, as the optical paths are precisely controlled through parameter optimization rather than relying on holographic diffraction.
2Adaptability or versatility
If diffraction surfaces are used for see-through display, then viewing capability is improved, but chromatic aberration occurs and manufacturing complexity increases
Solution Approach 1:
The patent replaces diffraction surfaces with a waveguide system based on total internal reflection and refraction. This substitution eliminates chromatic aberration inherent in diffraction while simplifying manufacturing, as the waveguide structure can be fabricated using standard optical component fabrication techniques without requiring precise diffraction grating patterns.
3Length of stationary object
If single plane mirror optics are used, then display thickness is reduced, but field of view is limited
Solution Approach 1:
The patent introduces angular surfaces at strategic locations within the waveguide to expand the field of view without increasing thickness. By carefully designing the angles of these surfaces, the system achieves a wide field of view while maintaining a thin profile, effectively utilizing three-dimensional optical path management within the constrained thickness dimension.
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
The system achieves a wide field of view over 60 degrees, a large eye-box of 15 mm, and high resolution up to 4K, fitting within compact eyewear, while avoiding chromatic aberration and ghost images, thus meeting the demands for portable and hands-free augmented reality displays.
Implementation Method 1
a prism is used for in-coupling optics to lead the light beams from the projector into the light pipe
Implementation Method 2
The surface of the light pipe receives only one direction of light beam from each of pixels in the display device
Implementation Method 3
the surfaces of the sides of the light pipe are reflective by coating or totally internal reflection
Implementation Method 4
folding mirrors with saw-teeth shaped prisms to reflect the light rays from the light pipe to the out-coupling waveguide
Implementation Method 5
the out-coupling waveguide has multiple saw-teeth shaped mirrors and reflects the rays toward the eye of a viewer
Data Source
AI summary
A projection display having an optical waveguide for a see-though display system using Fresnel mirrors is disclosed. A display using this waveguide enables high resolution, free from chroma aberration, wide viewing angle, large eye-box and very compact size.