Stacked Waveguide Display In-Couplers Angular Color Separation
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Solution Overview
Problem
Existing waveguide-based diffractive displays face inefficiencies in color separation and coupling due to polarization sensitivity limitations and complex light projection arrangements, leading to suboptimal image resolution and brightness in multicolor displays.
Innovation Solution
A waveguide display element with a stacked structure featuring different in-couplers for each layer, each comprising a thin low refractive index intermediate layer and a grating, allowing for angular separation of primary colors using laser light at distinct angles of incidence, thereby preventing cross-coupling and enhancing color control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If polarization-sensitive in-coupling gratings are used for color separation, then color separation is achieved, but coupling efficiency is low and brightness is reduced
Solution Approach 1:
The patent changes the working parameters by using laser light with short wavelength bands that enable different input angles for the same output angle. This allows the system to operate in a parameter regime where angle-sensitive coupling becomes effective, replacing the polarization-sensitive approach and achieving both high coupling efficiency and brightness simultaneously.
Solution Approach 2:
The patent introduces angular selectivity dynamics to the in-coupling gratings. By designing gratings that are sensitive to input angles rather than polarization, the system dynamically separates colors based on their incident angles. This dynamic approach allows precise control over which wavelengths are coupled into which waveguide layers, maximizing coupling efficiency and brightness.
2Ease of manufacture
If laterally separated in-coupling regions are used for different wavelength bands, then color separation is achieved, but the light projection arrangement becomes complex
Solution Approach 1:
The patent transitions from lateral separation (2D plane separation) to angular separation (adding the angle dimension). By using different incident angles to couple different wavelengths into the same waveguide stack, the system eliminates the need for complex lateral positioning and alignment of multiple in-coupling regions, greatly simplifying the light projection arrangement while maintaining effective color separation.
3Manufacturing precision
If wide bandwidth illumination is used, then all color components can be guided, but input and output angles must be the same causing image resolution loss
Solution Approach 1:
The patent changes the illumination parameters by using laser light with short wavelength bands instead of wide bandwidth illumination. This parameter change enables the system to achieve both wavelength diversity (guiding multiple color components) and angle separation (different input angles for same output angle), thereby maintaining image resolution while guiding multiple wavelength bands simultaneously through the waveguide stack.
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
This solution improves color separation efficiency, increases brightness, reduces power consumption, and simplifies manufacturing by allowing better control over color diffraction and reducing striping in out-coupling, compared to prior methods.
Implementation Method 1
Light can be coupled to a waveguide, redirected therein and coupled out of the waveguide using diffraction gratings
Implementation Method 2
the waveguide comprises a plurality of layers stacked on top of each other and each layer is designed to guide a different wavelength band
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
The invention relates to a waveguide display element comprising a plurality of waveguide layers (12A-C) stacked on top of each other and an in-coupler (16A-C) associated with each waveguide layer (12A-C) for coupling light within a predefined wavelength band into the waveguide layer (12A-C). Each of the in-couplers (16A-C) comprise an intermediate layer (14A-C) arranged on the waveguide layer (12A-C), the intermediate layer (14A-C) having intermediate layer properties, and an in-coupling grating (16A-C) arranged on the intermediate layer (14A-C), the grating having grating properties. The combination of intermediate layer (14A-C) properties and grating (16A-C) properties of each in-coupler is different with respect to other in-couplers.