Waveguide Grating Overlap Eliminates Reflective Edge
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Solution Overview
Problem
Prior art display devices with slab waveguides require a highly reflective surface for aligning diffraction gratings, which is difficult to manufacture and expensive, leading to image quality degradation due to potential misalignment of grating lines.
Innovation Solution
A waveguide design where the input diffraction grating is positioned wholly within the geographical area of the intermediate diffraction grating, with grating vectors oriented in different directions, eliminating the need for a reflective edge by using a continuous material for the intermediate diffraction grating that covers the surface via which light is guided by total internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a highly reflective surface is provided along parts of an edge of the slab waveguide to redirect light from the first grating to the second grating, then light alignment between gratings is improved, but manufacturing complexity and cost increase due to the difficulty of polishing the reflective surface to very high optical standards
Solution Approach 1:
The invention extracts and removes the problematic reflective surface from the waveguide structure. Instead of providing a reflective surface along the edge to redirect light, the patent positions the input diffraction grating within the geographical area of the intermediate diffraction grating, allowing light to travel directly through the waveguide without requiring edge reflection. This eliminates the manufacturing complexity associated with creating and maintaining highly polished reflective surfaces while preserving the optical alignment function.
Solution Approach 2:
The invention changes the spatial arrangement from a linear sequence requiring edge reflection to a overlapping two-dimensional configuration. By positioning the input grating within the geographical area of the intermediate grating and allowing light propagation in different spatial dimensions, the design eliminates the need for reflective surfaces while maintaining proper light redirection and alignment between gratings.
2Manufacturing precision
If the input diffraction grating and intermediate diffraction grating are positioned with proper alignment, then image quality is improved, but the device complexity increases due to the need for precise positioning and orientation control
Solution Approach 1:
The invention merges the input diffraction grating and intermediate diffraction grating into a unified overlapping configuration where the input grating is positioned within the geographical area of the intermediate grating. This merging eliminates the need for separate alignment mechanisms and complex positioning structures, as the overlapping arrangement inherently provides the necessary optical coupling and alignment while simplifying the overall device structure.
3Speed
If a reflective surface is used to redirect light between gratings, then light direction control is improved, but light loss and scattering increase due to imperfections in the reflective surface
Solution Approach 1:
The invention extracts and eliminates the reflective surface from the optical path. By positioning the input grating within the intermediate grating's geographical area and allowing direct light propagation through the waveguide, the design removes the source of light loss and scattering associated with reflective surfaces. Light direction is controlled through the diffraction grating geometry and waveguide structure rather than reflection, preserving light energy while maintaining directional control.
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 design simplifies manufacturing, reduces costs, and enhances image quality by eliminating light loss and scattering, resulting in improved image brightness and contrast.
Implementation Method 1
an input diffraction grating arranged to receive light and diffract the received light along the optical waveguide part for guiding
Implementation Method 2
an intermediate diffraction grating optically coupled to the input diffraction grating via the optical waveguide part and arranged to receive diffracted light from the input diffraction grating and to expand the received light in a first dimension by diffraction
Implementation Method 3
an output diffraction grating optically coupled to the intermediate diffraction grating via the optical waveguide part and arranged to receive the expanded light and to output the received expanded light from the optical waveguide part by diffraction for display
Implementation Method 4
a planar optical waveguide part for guiding light to be displayed
Data Source
Figure 1A
Figure 1B
Figure 2A~2C
AI summary
A method for manufacturing a waveguide for a display apparatus comprising providing a planar optical waveguide part (20), depositing upon the optical waveguide part a fluid material (11) curable to form an optically transparent solid, impressing (30) upon the fluid material an impression defining an input diffraction grating region, an intermediate diffraction grating region and an output diffraction grating region wherein the fluid material of the intermediate diffraction grating region is continuous with the fluid material of at least the input diffraction grating region, curing (45) the impressed fluid material to solidify said impression. The physical location of the input diffraction grating is located wholly within the geographical area of the intermediate grating, and the grating vectors of the input diffraction grating and the intermediate diffraction grating are oriented in different respective directions.