Waveguide Surface Relief Grating Formation with Reusable Molds
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Solution Overview
Problem
Electronic devices with displays, such as virtual and augmented reality headsets, face challenges in designing components that are both aesthetically pleasing and provide desired optical performance without being bulky.
Innovation Solution
The use of a waveguide system incorporating a surface relief grating (SRG) structure that couples image light into and out of the waveguide efficiently, utilizing a reusable mold formed with a flexible substrate and high-index material to create ridges for optimal optical efficiency, and varying trough and ridge thicknesses for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional display components are used, then optical performance can be achieved, but the device becomes bulky and unsightly
Solution Approach 1:
The SRG structure is integrated directly into the waveguide substrate, nesting the grating functionality within the waveguide structure itself rather than using separate external components. This integration eliminates bulkiness while maintaining optical performance.
Solution Approach 2:
The patent transitions from conventional planar display structures to a three-dimensional waveguide structure with vertically extended SRG features. The ridges and troughs extend in the vertical dimension, enabling optical coupling and image expansion within a compact footprint.
2Reliability
If SRG structure with high-index material is used, then optical efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The mold is prepared in advance with the desired ridge and trough patterns before the high-index material is deposited. This preliminary molding action simplifies the subsequent deposition process and ensures consistent SRG structure formation across multiple manufacturing steps.
Solution Approach 2:
A low-index resin layer is used as an intermediary during the nanoimprinting process to form the mold structure. This resin layer facilitates the transfer of the grating pattern to the high-index material through conformal deposition, simplifying the manufacturing of complex SRG structures.
3Ease of manufacture
If nanoimprinting is performed on low-index resin, then SRG mold is formed, but additional deposition steps are required
Solution Approach 1:
The conformal deposition of high-index material continuously follows the nanoimprinted mold structure, creating a seamless transition from mold formation to final SRG structure. This continuous process eliminates the need for separate patterning steps and maintains manufacturing efficiency.
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 SRG structure enhances optical efficiency and reduces bulkiness while maintaining aesthetic appeal, providing seamless image display without visible gaps between components.
Implementation Method 1
The input coupler may couple image light into the waveguide
Implementation Method 2
The image light may propagate down the waveguide via total internal reflection
Implementation Method 3
The SRG structure may perform a cross-coupling operation in which the SRG structure expands the image light in a direction perpendicular to the direction of propagation
Implementation Method 4
The SRG structure may also perform an output coupling operation in which the SRG structure couples the expanded image light out of the waveguide and towards an eye box
Data Source
AI summary
An electronic device may have a display system. The display system may include a waveguide, an input coupler, and a surface relief grating (SRG) structure. There are various ways to form a SRG structure. In one example, nanoimprinting may be performed on a low-index resin to form a mold for a subsequent deposition of high-index material. The high-index material conforms to the mold to form ridges for the SRG structure. A reusable mold may be formed with a plurality of ridges on a flexible substrate and coated by an anti-stick coating. The reusable mold may be coated with a high-index material that is attached to a glass substrate and cured to form a wafer-level SRG structure with high-index ridges on a glass substrate. The wafer-level SRG structure is subsequently diced. SRG structures may also be formed that include varying trough thicknesses, varying ridge thicknesses, and/or a sloped substrate.