Optical Waveguide Grating Conformal Dielectric Layer Attenuation
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Solution Overview
Problem
Optical waveguides in imaging systems, such as head-up displays, face challenges in maintaining uniform light intensity and efficiency along their length due to increasing attenuation, leading to variations in image brightness and inefficient light utilization.
Innovation Solution
A surface relief grating with a conformal dielectric layer that varies in thickness along the waveguide's length and transverse direction, increasing efficiency to compensate for attenuation and ensure uniform light output, combined with a beam splitter for optimal image formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional uniform efficiency grating is used, then the device complexity is low, but the light intensity uniformity deteriorates due to attenuation along the waveguide length
Solution Approach 1:
The patent applies local quality by varying the grating efficiency along the waveguide length according to a specific profile (e.g., linear or exponential increase). Different sections of the grating have different efficiencies, with earlier sections having lower efficiency and later sections having higher efficiency to compensate for attenuation. This non-uniform distribution of grating properties along the propagation direction ensures uniform light extraction intensity throughout the waveguide.
Solution Approach 2:
The patent implements dynamics by making the grating efficiency a variable parameter that changes continuously along the waveguide length rather than being static and uniform. The efficiency profile is designed to dynamically adapt to the attenuation characteristics, increasing efficiency in proportion to the cumulative attenuation experienced by light propagating through different sections of the waveguide.
2Loss of energy
If the grating efficiency is increased to compensate for attenuation, then the light efficiency improves, but the bandwidth deteriorates due to increased diffraction losses
Solution Approach 1:
The patent applies parameter changes by systematically varying the grating efficiency parameter along the waveguide length. The efficiency is increased in a controlled manner (linearly or exponentially) to match the attenuation profile, optimizing light extraction efficiency while managing the trade-off with bandwidth through careful parameter selection.
Solution Approach 2:
The patent uses partial action by implementing low-efficiency gratings that extract only a portion of the available light at each section, allowing the majority of light to continue propagating. This partial extraction approach, when distributed along the waveguide with increasing efficiency, achieves overall high efficiency while maintaining bandwidth, as no single section imposes excessive diffraction losses.
3Adaptability or versatility
If a low-efficiency grating is used, then the bandwidth is maintained, but the light efficiency deteriorates due to insufficient extraction
Solution Approach 1:
The patent implements continuity of useful action by distributing light extraction continuously along the entire waveguide length rather than concentrating it at specific locations. The continuous low-efficiency extraction along the propagation path accumulates to high overall efficiency while maintaining bandwidth, as light is gradually extracted throughout its journey through the waveguide.
Solution Approach 2:
The patent applies segmentation by dividing the waveguide into multiple longitudinal sections, each with progressively increasing grating efficiency. This segmentation allows the system to achieve high overall extraction efficiency through the cumulative effect of many low-efficiency sections, while each individual section maintains sufficient bandwidth.
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 solution maintains uniform light intensity along the waveguide, enhances light efficiency, and reduces the total input light required for a given brightness, addressing the issue of attenuation and improving image uniformity in waveguide-based displays.
Implementation Method 1
a surface relief grating with a conformal dielectric layer that varies in thickness along the waveguide's length... increasing efficiency to compensate for attenuation
Implementation Method 2
A conformal dielectric coating or layer is applied to the grating in a thickness which increases in the direction of propagation of the light along the waveguide
Implementation Method 3
The waveguide may comprise a beam splitter for directing propagating light towards both of said external surfaces
Data Source
Figure 1~2(c)
Figure 3(a)~4(b)
Figure 5
AI summary
An optical waveguide comprising a body of material configured for the contained propagation of light therethrough, a surface relief grating configured to receive the propagating light and at least partially to diffract or reflect it out of the waveguide, and at least one layer of dielectric material of varying thickness having a first surface and a second surface which conforms to a profiled surface of the grating so that the grating exhibits a spatial variation in efficiency dependent on the varying thickness of the dielectric material.