Embedded See-Through Combiner for AR Glasses Light Efficiency
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Solution Overview
Problem
Existing AR glasses face inefficiencies in optical combiners, such as low efficiency, bulkiness, and issues like eyeglow and color non-uniformity, particularly in waveguide-based systems, which affect user experience and security.
Innovation Solution
A novel see-through optical combiner embedded within a lens unit, utilizing partially-transparent reflectors with Metasurface structures, provides high efficiency and uniform brightness by replicating the exit pupil along one dimension while maintaining lens form factor, eliminating eyeglow and rainbow effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If waveguide-based optical combiners are used, then the device can overlay virtual content, but light efficiency is low requiring brighter displays and larger batteries
Solution Approach 1:
The patent changes the optical parameters by using partially-transparent reflectors with specific reflectivity and transmissivity characteristics. These reflectors are arranged at specific angles and positions to optimize light redirection efficiency, allowing more light to reach the user's eye while maintaining a compact form factor, thereby improving light efficiency without requiring brighter displays
Solution Approach 2:
The patent employs composite optical structures combining transparent refractive index-matched materials for the combiner body with metallic or dielectric partially-transparent reflector layers. This composite approach enables efficient light manipulation while maintaining optical clarity and improving overall system light efficiency
2Reliability
If waveguide-based optical combiners are used, then virtual content can be displayed, but eyeglow and light leakage occur compromising security
Solution Approach 1:
The patent converts the potentially harmful light leakage effect into a beneficial feature by using partially-transparent reflectors that deliberately control light direction. The reflectors are designed to redirect light precisely toward the user's eye while absorbing or scattering stray light, transforming the uncontrolled light leakage problem into controlled light management that enhances security
Solution Approach 2:
The partially-transparent reflectors act as intermediary elements between the light source and the user's eye. These reflectors mediate light propagation by selectively reflecting and transmitting light, preventing direct light leakage while maintaining image quality, thus solving the security issue caused by uncontrolled light emission
3Ease of manufacture
If birdbath combiners are used, then cost is reduced, but additional optical elements make eyepieces bulkier
Solution Approach 1:
The patent merges the functions of multiple optical elements into a single integrated combiner structure. The partially-transparent reflectors are embedded within or mounted on the combiner lens itself, eliminating the need for separate curved mirrors and multiple discrete optical components. This integration reduces the overall eyepiece volume while maintaining the cost-effective manufacturing approach of birdbath designs
4Illumination intensity
If waveguide-based optical combiners are used, then virtual content can be overlaid, but color uniformity and brightness uniformity are poor
Solution Approach 1:
The patent applies local quality optimization by varying the properties of different reflectors in the array. Each partially-transparent reflector can have customized reflectivity, transmissivity, and angular characteristics tailored to its specific position in the optical path. This local customization compensates for position-dependent variations in light intensity and color, achieving uniform brightness and color across the entire field of view
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 solution achieves a significant increase in light efficiency and uniform illumination across the eyebox, reducing bulkiness and eliminating unwanted light leakage, enhancing user experience and security.
Implementation Method 1
partially-transparent reflectors arranged in a spaced-apart parallel relationship along an inner part of the lens... said partially-transparent reflectors being inclined with respect to said axis, such that said partially-transparent reflectors successively interact with the input light, and form light reflections therefrom
Implementation Method 2
each of said partially-transparent reflectors comprises a Metasurface structure having a grating pattern and being adapted to partially reflect a number N (N≥1) of predetermined discrete wavelengths
Data Source
AI summary
An optical system for use in augmented reality glasses is presented. The optical system defines an eyebox and comprises a lens unit comprising an integral structure formed by a lens and a see-through optical combiner embedded inside the lens being located in an inner part of the lens and enclosed by opposite lens segments of front and rear parts of the lens. The combiner comprises partially-transparent reflectors arranged in a spaced-apart relationship along the inner part and exposed to interaction with input light propagating along a first axis through the inner part of the lens and being indicative of image being projected with a certain exit pupil. The reflectors are inclined with respect to the first axis, to successively interact with the input light and form light reflections providing replication of the exit pupil along a first dimension of the eyebox while maintaining the wavefront curvature of the lens.