Bilayer Binary 2D Gratings for Waveguide Display Coupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current waveguide display systems face challenges in achieving economical manufacturing while maintaining design flexibility and improved functionality, particularly in input-coupling and output-coupling elements, which affect illuminance uniformity and field of view.
Innovation Solution
A bilayer binary surface relief grating with a pair of adjacent grating layers, where the interlayer and intralayer geometries, including relative displacement, allow for a locally tunable effective slant angle, enhancing coupling efficiency and waveguide performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional single-layer gratings with constant slant angles are used, then manufacturing is simpler, but coupling efficiency and waveguide performance are limited
Solution Approach 1:
The grating structure is divided into two separate layers (first grating layer and second grating layer), each with independently controllable geometries. This segmentation allows optimization of coupling efficiency through adjusted interlayer and intralayer configurations while maintaining manufacturability through standard fabrication processes.
Solution Approach 2:
The invention transitions from a single-layer two-dimensional grating to a bilayer three-dimensional structure. By adding the vertical dimension through a second grating layer with lateral offset, the system achieves variable effective slant angles and improved coupling efficiency without significantly complicating the manufacturing process.
2Reliability
If gratings with variable slant angles are implemented to improve coupling efficiency, then waveguide performance increases, but manufacturing complexity increases
Solution Approach 1:
The complex variable slant angle functionality is achieved by segmenting the grating into two simpler layers. Each layer can be manufactured with standard geometries, but their combined three-dimensional arrangement creates the effective variable slant angle effect, reducing individual layer complexity while maintaining overall performance.
Solution Approach 2:
Instead of creating complex variable slant angles within a single layer, the invention uses the vertical dimension by stacking two layers with lateral offsets. This dimensional approach simplifies the geometry of individual layers while achieving the desired variable slant angle effect through their spatial arrangement.
3Adaptability or versatility
If bilayer binary gratings with lateral offset are used, then effective slant angle control is improved, but manufacturing precision requirements increase
Solution Approach 1:
The lateral offset between layers is designed and predetermined during the fabrication planning stage. By establishing the offset distance in advance based on desired slant angle requirements, the manufacturing process can focus on achieving consistent reproduction of this predetermined geometry rather than requiring complex real-time alignment adjustments.
Solution Approach 2:
The invention controls the effective slant angle by changing geometric parameters (lateral offset distance, layer thickness, grating period) rather than requiring complex alignment procedures. This parameter-based control approach allows for tunable slant angles while maintaining reasonable manufacturing precision requirements through standard fabrication tolerances.
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 bilayer binary grating structure improves coupling efficiency and waveguide performance by enabling variable slant angles, making it more economical to manufacture and potentially duplicating or exceeding the performance of gratings with constant slant angles.
Implementation Method 1
surface relief gratings that are configured to couple light into and out of the waveguide
Implementation Method 2
directing a display image to a user
Data Source
AI summary
A bilayer binary 2D surface relief grating includes a primary grating layer having an array of primary grating elements, and a secondary grating layer having an array of secondary grating elements overlying the primary grating layer, where the secondary grating elements are at least partially laterally offset from the primary grating elements. A method of manufacturing such a surface relief grating includes forming a low refractive index layer over a substrate, the low refractive index layer including a primary sub-layer having an array of primary openings and a secondary sub-layer overlying the primary sub-layer and having an array of secondary openings, where the secondary openings are at least partially laterally offset from the primary openings, and forming a high refractive index layer within the primary and secondary openings.