Optical Waveguide Out-Coupling Gratings With Discrete Unit Cells
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Solution Overview
Problem
Current diffractive optical waveguide designs face challenges in fabricating out-coupling areas due to complex partitioning of grating parameters, particularly depth and angle, which increases processing difficulty.
Innovation Solution
A light-guiding device with discrete distribution of out-coupling grating unit cells and a pupil-expansion turning area, allowing for controlled light energy allocation and simplified fabrication by adjusting the area size of each unit cell, and incorporating filter coatings or holographic volume gratings to manage different wavebands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If partitioned parameter design is implemented on a single out-coupling grating to achieve pupil-expansion effect, then the light transmission and directional propagation are improved, but the processing difficulty in fabrication increases significantly
Solution Approach 1:
The out-coupling grating is divided into multiple independent grating unit cells with different parameters (depth, angle, period) that are discrete distributed within the out-coupling area. Each unit cell corresponds to a specific viewing direction, allowing the complex pupil-expansion effect to be achieved through simple geometric arrangement rather than complex continuous parameter modulation, thereby significantly reducing fabrication difficulty while maintaining light transmission performance
Solution Approach 2:
The invention transitions from continuous parameter variation in a single grating structure to discrete spatial distribution of multiple unit cells with different parameters. By arranging unit cells with varying depths, angles, and periods at different spatial positions within the out-coupling area, the pupil-expansion effect is achieved through spatial dimensionality rather than continuous parameter changes, simplifying the fabrication process
2Ease of operation
If grating parameters such as depth and angle are partitioned to achieve different viewing directions, then the directional propagation of light is improved, but the fabrication complexity increases
Solution Approach 1:
The out-coupling grating is segmented into multiple independent grating unit cells, each with specific parameters (depth, angle, period) tailored for particular viewing directions. This segmentation allows each unit cell to be fabricated with simple, well-defined parameters while the collective arrangement achieves the desired directional propagation characteristics, reducing overall fabrication complexity
Solution Approach 2:
Different regions of the out-coupling area are assigned grating unit cells with locally optimized parameters (depth, angle, period) corresponding to specific viewing directions. This local quality approach allows each region to be fabricated independently with simple parameter sets, avoiding the need for complex continuous parameter variation across the entire grating structure
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 reduces fabrication complexity, enhances visual experience by controlling light energy distribution, and improves optical performance and imaging quality in head-mounted display devices.
Implementation Method 1
enabling the light to propagate via total internal reflection within the waveguide substrate to the out-coupling area
Implementation Method 2
the plurality of out-coupling grating unit cells are capable of coupling out light of one or more different wavebands
Data Source
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AI summary
Embodiments of the present disclosure provide a light-guiding device, an optical module and a head-mounted display device; wherein, the light-guiding device includes a waveguide substrate and an in-coupling area and an out-coupling area provided on the waveguide substrate; the in-coupling area is configured for coupling light into the waveguide substrate and enabling the light to propagate via total internal reflection within the waveguide substrate to the out-coupling area; the out-coupling area is configured for coupling out the light propagating thereto, and includes a plurality of out-coupling grating unit cells that are capable of coupling out light of one or more different wavebands, wherein the plurality of out-coupling grating unit cells form a discrete distribution within the out-coupling area, and wherein a gap is provided between adjacent ones of the out-coupling grating unit cells. The solution provided by the embodiments of the present disclosure can improve the optical performance of the optical waveguide.