Waveguide Display Substrate Thickness Bias for Uniform Light Propagation
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Solution Overview
Problem
Unintended thickness variations in waveguide display substrates lead to image quality issues such as color non-uniformity and luminance variations, which are exacerbated as thickness variations approach zero, due to random shape differences and path length discrepancies affecting light propagation.
Innovation Solution
Implementing a biased total thickness variation (TTV) with a consistent thickness shape, characterized by a combination of wedge and dome components, controlled through Zernike polynomial coefficients, to minimize part-to-part variations and enhance luminance and color uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional manufacturing processes are used for waveguide display substrates, then production cost and complexity are reduced, but thickness variations and image quality deteriorate
Solution Approach 1:
The patent applies preliminary action by pre-compensating for expected thickness variations during the molding process. A thickness compensation pattern is integrated into the master mold, which proactively counteracts known deformation tendencies of the molding process, thereby achieving ultra-low TTV without requiring complex post-processing steps.
Solution Approach 2:
The patent employs parameter changes by systematically adjusting multiple molding parameters including injection pressure, temperature profiles, and mold design features. These parameter optimizations enable precise control over polymer固化过程中的收缩和变形, achieving consistent thickness uniformity across large substrate areas.
2Reliability
If thickness variations are reduced to improve image quality, then luminance and color uniformity improve, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by implementing spatially varying thickness compensation patterns tailored to specific regions of the substrate. The compensation pattern is not uniform but rather locally optimized based on the expected deformation behavior in different areas, allowing precise control of thickness uniformity across the entire large-area substrate.
Solution Approach 2:
The patent employs feedback mechanisms through iterative measurement and adjustment of the compensation pattern. Prototype substrates are manufactured, measured for actual thickness variations, and the compensation pattern is refined based on this feedback data, progressively achieving the target TTV specifications.
3Area of stationary object
If large area substrates are manufactured, then display field of view increases, but thickness variations and image quality worsen
Solution Approach 1:
The patent applies segmentation by dividing the large substrate area into multiple zones, each with its own optimized compensation parameters. This allows the complex deformation behavior across large areas to be managed through localized control strategies, maintaining thickness uniformity even as substrate area increases.
Solution Approach 2:
The patent addresses the two-dimensional challenge of large area uniformity by introducing a third dimension through controlled thickness variation compensation. The compensation pattern operates in the thickness dimension to counteract the spreading of variations across the large planar area, enabling FOV expansion without sacrificing image quality.
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 biased TTV approach improves image quality by ensuring consistent light propagation and reduced variations, resulting in enhanced luminance and color uniformity across waveguide displays.
Implementation Method 1
waveguide display substrates, each waveguide display substrate having a cylindrical portion having a diameter and a planar surface, a curved portion opposite the planar surface defining a nonlinear change in thickness across the substrate
Data Source
AI summary
A plurality of waveguide display substrates, each waveguide display substrate having a cylindrical portion having a diameter and a planar surface, a curved portion opposite the planar surface defining a nonlinear change in thickness across the substrate and having a maximum height D with respect to the cylindrical portion, and a wedge portion between the cylindrical portion and the curved portion defining a linear change in thickness across the substrate and having a maximum height W with respect to the cylindrical portion. A target maximum height Dt of the curved portion is 10−7 to 10−6 times the diameter, D is between about 70% and about 130% of Dt, and W is less than about 30% of Dt.