AR Waveguide Grating Structure for Asymmetric Light Coupling
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Solution Overview
Problem
Conventional augmented reality displays face challenges in efficiently coupling light into waveguides due to the high cost and manufacturing difficulty of blazed or slanted gratings, which are required for different types of displays, necessitating multiple versions of these gratings.
Innovation Solution
The use of an optical device with a diffractive optical element featuring an array of structured grating elements arranged in a repeating unit cell with irregular structures, where each grating element varies in height, width, and spacing, producing an asymmetrical diffraction response to enhance light coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blazed or slanted gratings are used to couple light into the waveguide, then light coupling efficiency is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent applies asymmetry by designing grating elements with different heights within the same unit cell, creating an irregular grating structure that produces an asymmetrical diffraction response. This asymmetry in the grating element heights enables efficient coupling of light into the waveguide by directing more light into the desired diffraction order, while the periodic unit cell structure maintains manufacturability through repetition of a finite pattern.
Solution Approach 2:
The patent changes the geometric parameters of the grating elements, specifically varying the heights of different grating elements within a unit cell while maintaining their periodic arrangement. This parameter variation creates the irregular structure that achieves high diffraction efficiency without requiring complex blazed or slanted grating geometries, thus improving light coupling efficiency while maintaining ease of manufacture.
2Adaptability or versatility
If different blaze or slant angles are used for different augmented reality display types, then display performance is optimized, but the number of different grating versions required increases
Solution Approach 1:
The patent achieves universality by designing a unit cell structure containing multiple grating elements with different heights that can be repeated to create diffractive optical elements for different augmented reality display types. By adjusting the parameters within the same unit cell design framework, the same basic structure can be adapted to optimize performance for different display configurations without requiring entirely different grating versions.
Solution Approach 2:
The patent enables adaptation to different display types by changing the parameters of the grating elements within the unit cell, such as the heights of individual grating elements and their spacing, while maintaining the same fundamental irregular grating structure. This allows optimization for different augmented reality display configurations without increasing the number of fundamentally different grating versions.
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 allows for more cost-effective production of optical devices with higher efficiency in one diffraction order, maximizing brightness and reducing manufacturing complexity while maintaining effective light coupling and display quality.
Implementation Method 1
a diffractive optical element configured to couple light into the waveguide; wherein the diffractive optical element comprises an array of structured grating elements, the structured grating elements being arranged based on a repeating unit cell, wherein each unit cell comprises at least two grating elements defining an irregular grating structure such that the diffractive optical element produces an asymmetrical diffraction response
Implementation Method 2
The projected light is totally internally reflected within the waveguide. The light is then coupled out of the waveguide by another diffraction grating
Data Source
AI summary
An optical device for controlling light in an augmented reality display is provided. The optical device includes a waveguide and a diffractive optical element to couple light into the waveguide. The diffractive optical element includes an array of structured grating elements. The structured grating elements are arranged based on a repeating unit cell, each unit cell including at least two grating elements defining an irregular grating structure such that the diffractive optical element produces an asymmetrical diffraction response. Methods of manufacturing the optical device are also provided.