Waveguide Display Structure for Low-Loss Diffractive Coupling
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Solution Overview
Problem
Waveguide-based display devices face challenges in reducing optical losses related to light coupling, particularly due to the complexity introduced by polarization-dependent in-coupling structures and polarization-altering elements.
Innovation Solution
The use of a waveguide structure with a diffractive in-coupling element and overlapping diffractive out-coupling elements, such as surface-relief and volume holographic diffraction gratings, to facilitate light coupling and exit pupil expansion while minimizing optical losses and increasing mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If polarization-dependent in-coupling structures and polarization-altering elements are used to reduce optical losses, then optical in-coupling losses are reduced, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the polarization-dependent in-coupling structures and polarization-altering elements from the optical system. By removing these complex components, the invention achieves a simpler device architecture while maintaining low optical losses through the waveguide thickness constraint that ensures efficient total internal reflection without requiring polarization control.
Solution Approach 2:
Instead of using complex polarization-dependent structures to manage light coupling, the patent inverts the approach by constraining the waveguide thickness to be less than one-tenth of the in-coupling region width. This geometric constraint naturally optimizes light coupling efficiency through total internal reflection without requiring polarization-dependent elements, thereby simplifying the overall device structure.
2Stability of the object's composition
If waveguide thickness is increased to improve mechanical stability, then mechanical stability increases, but optical properties are impaired
Solution Approach 1:
The patent identifies the critical parameter relationship between waveguide thickness and in-coupling region width. By establishing that the waveguide thickness must be less than one-tenth of the in-coupling region width, the invention optimizes both mechanical stability and optical properties simultaneously. This parameter constraint ensures efficient light coupling while maintaining sufficient mechanical integrity without requiring excessive thickness.
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 configuration reduces optical in-coupling losses and enhances mechanical stability without impairing optical properties, enabling high-quality image formation and reducing spatial intensity variations.
Implementation Method 1
an in-coupling structure (1200) for coupling an optical beam (1201) into the waveguide (1100)
Implementation Method 2
waveguide (1100), comprising a first face (1110) extending along a base plane (1111), a second face (1120) opposite the first face (1110), and an in-coupling region (1112) on the first face (1110)
Implementation Method 3
an out-coupling structure (1300) configured to perform exit pupil expansion and to couple light from the optical beam (1201) out of the waveguide (1100)
Data Source
Figure 1~2
Figure 3~4
AI summary
A display structure (1000), comprising a waveguide (1100) comprising a first face (1110), a second face (1120) opposite the first face (1110), and an in- coupling region (1112) on the first face (1110); an in-coupling structure (1200) for coupling an optical beam (1201) into the waveguide (1100) via the in-coupling region (1112); and an out-coupling structure (1300) configured to perform exit pupil expansion by pupil replication and to couple light from the optical beam (1201) out of the wave- guide (1100). The in-coupling region (1112) has a maximum width, Wmax; the waveguide (1100) has a thickness, T, greater than 0.25 × Wmax; and the out-coupling structure (1300) comprises a diffractive first out-coupling element (1310) and a diffractive second out- coupling element (1320) at least partly laterally overlapping the first out-coupling element (1310).