Double-Sided Imaging Light Guide Diffractive Optics
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Solution Overview
Problem
Conventional optical light guides for head-mounted displays face challenges in separating color channels effectively, leading to cross-talk and color shifts, which are difficult to correct and result in thicker, heavier devices with reduced brightness and image quality.
Innovation Solution
A double-sided beam expander design within a single waveguide substrate, utilizing in-coupling and out-coupling diffractive optics with oriented grating vectors, separates color channels by angle and distance to minimize cross-talk, allowing for efficient pupil expansion without increasing device thickness or weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple waveguides are stacked together to separate color channels, then color channel separation is improved, but device thickness increases
Solution Approach 1:
The patent transitions from a vertical stacking approach (multiple waveguides stacked together) to a horizontal multiplexing approach within a single waveguide substrate. By using multiple diffractive optics at different positions and orientations within the same plane, the system achieves color channel separation without increasing thickness, instead utilizing the lateral dimension and angular separation to differentiate color channels.
Solution Approach 2:
The patent segments the color channel separation function across multiple diffractive optics (in-coupling and out-coupling gratings) positioned at different locations and orientations within a single waveguide substrate. Each diffractive optic handles specific color channels through angular selectivity, dividing the color separation task across multiple components rather than requiring separate waveguides.
2Reliability
If multiple waveguides are stacked together to separate color channels, then color channel separation is improved, but device weight increases
Solution Approach 1:
The patent merges multiple color channel processing functions into a single waveguide substrate by integrating multiple diffractive optics (in-coupling and out-coupling gratings for different color channels) within the same substrate. This consolidation eliminates the need for separate waveguides, thereby reducing overall device weight while maintaining effective color channel separation.
3Reliability
If multiple waveguides are stacked together to separate color channels, then color channel separation is improved, but brightness is reduced
Solution Approach 1:
The patent combines multiple color channel paths within a single waveguide substrate, eliminating the light loss that occurs when stacking multiple waveguides. By using a unified substrate with strategically positioned diffractive optics, the system maintains higher light throughput and brightness while achieving effective color channel separation through angular and spatial multiplexing.
4Adaptability or versatility
If conventional light guide mechanisms are used, then pupil expansion capability is provided, but device thickness increases
Solution Approach 1:
The patent achieves pupil expansion through angular multiplexing and lateral positioning of diffractive optics within a single waveguide substrate, rather than through vertical stacking. By utilizing different angles and positions of in-coupling and out-coupling gratings, the system expands the exit pupil in the lateral dimension while maintaining a thin profile.
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 effectively reduces color channel crosstalk and improves color quality by separating color channels within a single waveguide substrate, maintaining image quality and reducing device bulk.
Implementation Method 1
A first in-coupling diffractive optic directs a first set of the image-bearing light beams into the waveguide along a first path
Implementation Method 2
A first turning diffractive optic disposed along the first path expands the image-bearing light beams of the first set in a first dimension
Implementation Method 3
The first out-coupling diffractive optic further expands the image-bearing light beams of the first set in a second dimension and directs the further expanded image-bearing light beams of the first set from the waveguide toward the eyebox
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
An imaging light guide has waveguide for conveying image-bearing light beams from an image source to an eyebox within which a virtual image can be viewed. First and seccond in-coupling diffractive optics direct first and second sets of the image-bearing light beams into the waveguide along different first and second paths. First and second turning diffractive optics disposed along the respective paths expand the image-bearing light beams of the first and second sets in a first dimension and direct the expanded image-bearing light beams of the first and second sets to first and second out-coupling diffractive optics. The first and second out-coupling diffractive optics further expand the image-bearing light beams of the two sets in a second dimension and direct the further expanded image-bearing light beams of the two sets from the waveguide toward the eyebox.