AR Display Waveguide Coupling With Irregular Grating Cells
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Solution Overview
Problem
Conventional augmented reality displays face challenges in manufacturing efficient diffraction gratings due to high cost and complexity, particularly when different blaze or slant angles are required for various applications, necessitating multiple grating versions.
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 grating structures, allowing asymmetrical diffraction responses to enhance light coupling into a waveguide, which can be more cost-effectively produced than blazed or slanted gratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If blazed or slanted gratings are used to improve diffractive efficiency in one diffraction order, then image brightness is maximized, but manufacturing cost and complexity increase significantly
Solution Approach 1:
The patent applies asymmetry by using irregular grating structures within unit cells that are themselves asymmetrically configured. The grating elements have varying heights, widths, and spacing patterns that create asymmetric diffraction responses, directing light preferentially into desired diffraction orders without requiring expensive blazed or slanted grating geometries. This asymmetric design at the unit cell level achieves the brightness enhancement normally associated with blazed gratings while using simpler manufacturing processes.
Solution Approach 2:
The patent implements local quality by varying the properties of grating elements at different locations within the diffractive optical element. Each unit cell contains grating elements with specific local characteristics (height, width, spacing) that are optimized for their particular position and function. This local variation in grating element properties enables precise control of diffraction efficiency across different regions and diffraction orders, achieving high brightness without uniform complex blazed structures throughout the entire device.
2Reliability
If different blaze or slant angles are required for different augmented reality display applications, then diffraction efficiency is optimized for specific uses, but the number of different grating versions increases, further complicating manufacturing
Solution Approach 1:
The patent achieves universality by designing a single diffractive optical element with irregular grating structures that can be configured to provide different diffraction efficiencies for various diffraction orders. By adjusting the parameters of the irregular grating elements within unit cells, the same basic device structure can be optimized for different applications (different wavelengths, diffraction angles, or orders) without requiring physically different grating versions. This multi-functional design reduces the need to manufacture multiple specialized grating types.
Solution Approach 2:
The patent applies parameter changes by varying the dimensions and configurations of the irregular grating elements within unit cells to optimize performance for different applications. By changing parameters such as grating element height, width, spacing, and material composition, the same fundamental device architecture can be tuned to achieve high diffraction efficiency for different wavelengths of light, different diffraction angles, or different diffraction orders. This parameter adjustment capability eliminates the need to create entirely different grating versions for each application.
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 achieves higher efficiency in desired diffraction orders, maximizing image brightness while reducing manufacturing complexity and costs, by utilizing irregular grating structures that vary in height, width, and spacing, and are readily manufactured.
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
Light from the projector is coupled into the waveguide by a diffraction grating. The projected light is totally internally reflected within the waveguide.
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.