Waveguide Display with Hexagonal Grating for Uniform AR Projection
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Solution Overview
Problem
Existing waveguides in augmented reality (AR) glasses face challenges in achieving both uniform image projection and high optical efficiency when using laser projectors, with prior designs either compromising on uniformity or efficiency.
Innovation Solution
A display component comprising a waveguide with an in-coupling structure, an exit pupil expansion structure, and an out-coupling structure, utilizing diffractive gratings to manage beam propagation and coupling, allowing for efficient and uniform image projection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional waveguide designs are used to achieve uniform image projection, then image uniformity is improved, but optical efficiency deteriorates
Solution Approach 1:
The waveguide is divided into multiple functional zones with different diffractive grating configurations. The exit pupil expansion structure segments the guided propagation domain into multiple k-space domains, allowing different regions to be optimized for different functions (uniformity vs. efficiency), thereby resolving the contradiction between image uniformity and optical efficiency
Solution Approach 2:
Different portions of the waveguide are assigned different local properties through varying diffractive grating parameters. The in-coupling structure, exit pupil expansion structure, and out-coupling structure each have locally optimized grating configurations tailored to their specific functional requirements, enabling simultaneous achievement of uniformity and efficiency
2Loss of energy
If conventional waveguide designs are used to achieve high optical efficiency, then optical efficiency is improved, but image uniformity deteriorates
Solution Approach 1:
The invention transitions from conventional single-domain waveguide operation to multi-domain k-space operation. By utilizing multiple domains in k-space through the exit pupil expansion structure, the system achieves both high optical efficiency (through effective beam guidance) and improved uniformity (through distributed beam paths across multiple domains)
3Volume of moving object
If laser projectors are used in small form factor AR glasses, then device miniaturization is achieved, but image uniformity and optical efficiency cannot be simultaneously optimized
Solution Approach 1:
The diffractive grating structures serve multiple functions simultaneously: they act as in-coupling elements, exit pupil expansion elements, and out-coupling elements. This multi-functionality allows the compact waveguide to achieve both miniaturization and optimized image quality without requiring separate structures for each function
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 enhances optical efficiency and uniformity of image projection in AR glasses by effectively guiding and expanding beams through the waveguide, reducing optical losses and bright stripe artifacts.
Implementation Method 1
an in-coupling structure configured to couple a set of input beams into the waveguide as a first set of in-coupled beams associated with a first set of in-coupled k vectors lying in a first domain in k-space
Implementation Method 2
an exit pupil expansion structure comprising a diffractive grating and configured to receive the first set of in-coupled beams and to diffract the first set of in-coupled beams in a first plurality of directions in k-space to form three sets of guided beams associated with three sets of k vectors lying in a first set of three domains within the annular guided propagation domain
Implementation Method 3
an out-coupling structure configured to receive, from the exit pupil expansion structure, a first diffracted set of beams associated with a diffracted set of k vectors lying in at least one of the domains in the first set of three domains, and to out-couple the first diffracted set of beams from the waveguide as a set of output beams
Implementation Method 4
three sets of guided beams associated with three sets of k vectors lying in a first set of three domains within the annular guided propagation domain
Data Source
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Figure 4
AI summary
According to an embodiment, a display component (100) comprises a waveguide (104), an in-coupling structure (101) configured to couple a set of input beams (901) into the waveguide (104) as a first set of in-coupled beams (110) associated with a first set of in-coupled k vectors (204_1) lying in a first domain (205_1) in k-space; an exit pupil expansion structure (102) comprising a hexagonal diffractive grating and configured to diffract the first set of in-coupled-beams (110) in a first plurality of directions (206) in k-space to form three sets of guided beams associated with three sets of k vectors (204_1, 204_2, 204_3) lying in a first set of three domains (205_1, 205_2, 205_3); an out-coupling structure (103) configured to receive a first diffracted set of beams (111) associated with a diffracted set of k-vectors lying in at least one of the domains in the first set of three domains (205_1, 205_2, 205_3), and to out-couple the first diffracted set of beams (111) from the waveguide (104).