Diffractive Waveguide Grating Merging for AR Field of View
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Solution Overview
Problem
Existing augmented reality display systems face challenges in providing wide-screen views due to the need for multiple diffraction gratings, which occupy significant space, cause scattering, and are not suitable for color displays.
Innovation Solution
An optical device with a waveguide featuring an input diffractive optical element and two overlaid diffractive optical elements that achieve two-dimensional expansion and output coupling of light, reducing the number of diffraction interactions and allowing for more efficient use of space, improved contrast, and compatibility with color displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If multiple diffraction gratings are used to achieve wide-screen views, then the field of view is expanded, but the device occupies significant space and causes scattering
Solution Approach 1:
The patent combines multiple diffraction gratings into a single integrated diffractive optical element that performs both beam expansion and output coupling functions. This merging reduces the number of separate components from multiple gratings to one unified element, thereby reducing device complexity and space occupation while maintaining the wide-screen field of view capability
Solution Approach 2:
The single diffractive optical element is designed to perform multiple functions simultaneously: it acts as both the beam expansion grating and the output coupling grating. This multi-functionality eliminates the need for separate gratings, reducing the overall device complexity while achieving the same optical performance
2Area of moving object
If multiple diffraction gratings are used, then beam expansion is achieved, but scattering increases and contrast deteriorates
Solution Approach 1:
By merging the beam expansion and output coupling functions into a single diffractive optical element, the patent reduces the number of diffraction interfaces from multiple gratings to one. This reduction in interfaces minimizes the cumulative scattering effects that occur at each grating boundary, thereby improving image contrast while maintaining beam expansion
3Length of moving object
If traditional waveguide design is used, then light coupling is achieved, but physical expansion of image is limited
Solution Approach 1:
The patent employs a photonic crystal structure that enables light propagation and manipulation in three-dimensional space within the waveguide. This dimensional approach allows the light to undergo multiple reflections and expansions in different directions, physically expanding the image size beyond the constraints of traditional two-dimensional waveguide designs without proportionally increasing the waveguide volume
4Ease of operation
If conventional optical elements are used, then light manipulation is achieved, but manufacturing cost increases
Solution Approach 1:
The patent utilizes the photonic crystal's bandgap properties and refractive index variations to achieve light manipulation. By changing the structural parameters of the photonic crystal (such as hole size, spacing, and arrangement), the optical properties can be tuned to achieve the desired beam expansion and coupling effects, eliminating the need for expensive conventional optical elements while maintaining optical control
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 enables efficient two-dimensional expansion and output coupling within a smaller space, improving optical characteristics and reducing manufacturing costs, while maintaining performance across various wavelengths for color displays.
Implementation Method 1
an input diffractive optical element and two overlaid diffractive optical elements arranged to receive input light and diffract the input light in use
Implementation Method 2
The captured light can travel within the waveguide by total internal reflection towards a second grating
Data Source
AI summary
An optical device is disclosed for expanding input light in two dimensions in an augmented reality display. The device comprises a waveguide (12) and three linear diffraction grat-ings H0, H1, H2. An incident beam from a projector illuminates an input grating H0 with polychromatic light, and the light is coupled into the waveguide (12). The other two gratings H1, H2 are overlaid on top of one another. Light can be diffracted by one grating H1 into a first diffracted order and towards the other grating H2 which can couple the light out of the waveguide (12) towards a viewer. In another arrangement the crossed gratings H1, H2 may be replaced by a photonic crystal (19) having a regular array of pillars (20) which create a number effective diffraction gratings.