Freeform Volume Grating Light Guide Illuminance Control
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Solution Overview
Problem
Conventional light guide display systems lack control over spatial and angular illuminance distribution at the output side, resulting in poor visual effects and inability to provide uniform or pre-configured non-uniform illuminance profiles, which are desirable for enhanced user experience in augmented and virtual reality applications.
Innovation Solution
Incorporating a freeform volume grating with predetermined spectral and angular Bragg selectivity variations in the light guide display system, allowing for controlled spatial and angular illuminance distribution by diffracting light via Bragg diffraction, thereby optimizing the light guide's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional light guide display system is used, then the system structure is simple, but the spatial and angular illuminance distribution at the output side cannot be controlled, resulting in poor visual effects
Solution Approach 1:
The patent applies parameter changes by varying the grating period, orientation, and depth of the volume grating to control the diffraction of guided light. By changing these parameters spatially, the system achieves controlled spatial and angular illuminance distribution at the output side, transforming uniform guided light into a desired non-uniform output profile.
Solution Approach 2:
The patent implements local quality by creating a volume grating with spatially varying properties throughout the light guide. Different regions of the light guide contain gratings with different periods, orientations, and depths, allowing each local region to contribute to a specific aspect of the overall illuminance distribution pattern, enabling precise control over the output light profile.
2Illumination intensity
If conventional light guide systems are used, then the manufacturing process is simple, but the ability to provide uniform or pre-configured non-uniform illuminance profiles is lacking
Solution Approach 1:
The patent applies preliminary action by pre-configuring the volume grating parameters during the manufacturing process to achieve the desired illuminance profile. The grating structure is designed and fabricated in advance with specific spatial variations that will produce the target uniform or non-uniform illuminance distribution at the output, eliminating the need for post-manufacturing adjustments.
Solution Approach 2:
The patent uses parameter changes in the grating structure to control illuminance profile uniformity. By adjusting the grating period, orientation, and depth as functions of position within the light guide, the system can produce either uniform or deliberately non-uniform illuminance profiles at the output side, providing design flexibility.
3Illumination intensity
If no volume grating is used, then the device complexity is low, but the light intensity uniformity and effective pupil expansion are insufficient
Solution Approach 1:
The patent applies parameter changes by designing the volume grating with spatially varying grating period, orientation, and depth. These parameter variations control the diffraction efficiency and angular distribution of light at different positions, achieving uniform light intensity output across the exit pupil while expanding the effective viewing area.
Solution Approach 2:
The patent replaces mechanical or optical components that would traditionally be used to control light distribution with a diffractive volume grating structure. Instead of using movable parts or complex optical assemblies, the system uses a static refractive index modulation pattern to achieve light control, reducing mechanical complexity.
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 enables uniform or pre-configured spatial and angular illuminance distributions, improving the visual experience by enhancing light intensity uniformity and expanding the effective pupil, thus addressing the limitations of conventional systems.
Implementation Method 1
a volume grating disposed at a portion of the light guide and configured to diffract a light via Bragg diffraction
Data Source
AI summary
A device is provided. The device includes a light guide coupled with an in-coupling element at an input portion of the light guide and an out-coupling element at an output portion of the light guide. The device also includes a volume grating disposed at a portion of the light guide and configured to diffract a light via Bragg diffraction. The volume grating is configured with at least one of a predetermined spectral Bragg selectivity variation or a predetermined angular Bragg selectivity variation along one or more dimensions in a film plane of the volume grating.