Waveguide Grating Alignment for Display Light Coupling
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Solution Overview
Problem
Existing display devices with slab waveguides face image quality degradation due to misalignment of diffraction grating lines, requiring complex and costly manufacturing processes involving reflective edges to redirect light correctly.
Innovation Solution
A waveguide design where the input diffraction grating is positioned wholly within the geographical area of the intermediate grating, with grating vectors oriented in different directions, eliminating the need for reflective edges by directly coupling light through the waveguide, and using a method to deposit and cure fluid material to form continuous diffraction gratings on the waveguide surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressing or stamping both the first and second gratings as different parts of one general grating structure having one common orientation of grating lines throughout, then the possibility of misaligned grating lines between first and second diffraction gratings is reduced, but a highly reflective surface must be provided along parts of an edge of the slab waveguide to redirect light, requiring polishing to a very flat surface which is difficult to achieve and expensive to produce
Solution Approach 1:
The patent extracts and removes the complex reflective surface structure from the waveguide system. Instead of providing highly reflective surfaces along waveguide edges to redirect light between gratings, the invention uses a compact grating arrangement where the input grating is positioned within the footprint of the intermediate grating, eliminating the need for additional reflective surfaces and their associated manufacturing complexity.
Solution Approach 2:
The patent merges the functions of multiple gratings into a compact integrated structure. The input diffraction grating is positioned within the geographical area of the intermediate diffraction grating, allowing both gratings to be optically coupled through the waveguide without requiring separate reflective surfaces. This integration simplifies the overall device structure while maintaining precise alignment.
2Reliability
If providing a highly reflective surface along parts of an edge of the slab waveguide to redirect light from the first grating to the second grating, then light can be redirected at the required angle of incidence, but the reflective surface must be manufactured to a very high optical standard with polishing to a very flat surface which is difficult to achieve and expensive to produce
Solution Approach 1:
The patent removes the highly reflective surface component from the system entirely. By positioning the input diffraction grating within the footprint of the intermediate diffraction grating and using their respective grating vectors to redirect light, the invention eliminates the need for additional reflective surfaces and their associated manufacturing challenges.
Solution Approach 2:
The patent replaces the mechanical/optical system of reflective surfaces with a diffractive system. Instead of using reflective surfaces to redirect light, the invention uses the diffraction capability of the gratings themselves, specifically the grating vectors of the input and intermediate gratings, to achieve the required light redirection at the appropriate angles of incidence.
3Adaptability or versatility
If using separate diffraction gratings for light input, expansion in first dimension, and expansion in second dimension, then the light can be processed through successive functions, but misalignment between the orientation of grating lines in the first (input) grating and the second grating results in misalignment of light output from the second grating relative to the orientation of the grating lines of the third (output) grating, degrading image quality
Solution Approach 1:
The patent applies local quality by positioning the input diffraction grating specifically within the geographical area of the intermediate diffraction grating. This localized positioning, combined with appropriate orientation of grating vectors, ensures that light diffracted by the input grating is correctly directed to and expanded by the intermediate grating, maintaining proper alignment throughout the optical path.
Solution Approach 2:
The patent uses the spatial dimension by positioning the input grating within the footprint of the intermediate grating rather than separating them in a linear arrangement. This two-dimensional positioning strategy, along with orienting grating vectors in different directions, enables correct light redirection and expansion in multiple dimensions while maintaining alignment with the output grating.
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 enhances image quality by reducing light loss and manufacturing complexity, making the waveguide production more efficient and cost-effective while maintaining image clarity and resolution.
Implementation Method 1
an input diffraction grating arranged to receive light and diffract the received light along the optical waveguide part for guiding thereby
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
the material of the intermediate diffraction grating covers all of those parts of the surface of the optical waveguide part at one side thereof via which the received light is guided by total internal reflection from the input diffraction grating to the intermediate diffraction grating
Data Source
Figure 1A
Figure 1B
Figure 2A~2C
AI summary
A waveguide for a display apparatus comprising a planar optical waveguide part (20) for guiding light to be displayed, an input diffraction grating (21) to diffract received light (7) along the optical waveguide part for guiding thereby, an intermediate diffraction grating (22) to receive diffracted light from the input diffraction grating and to expand the received light in a first dimension by diffraction (8), and an output diffraction grating (23) to receive the expanded light and to output the received expanded light (10) from the optical waveguide part by diffraction for display. The input diffraction grating is positioned so as to be 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.