Waveguide Facet Overlap for Uniform Image Output
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Solution Overview
Problem
Conventional optical modules for head-mounted displays become larger, heavier, and bulkier as the desired field-of-view increases, making them impractical for compact applications, and they are sensitive to small eye movements, limiting pupil motion and image uniformity.
Innovation Solution
An optical device featuring a waveguide with a sequence of facets, including a first facet with a specific width, middle facets with a different width, and a last facet, where the facets are partially reflecting and obliquely angled, ensuring uniform reflection and image quality by managing the overlap of facet projections onto the waveguide surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional free-space optical modules are used to increase field-of-view, then the field-of-view increases, but the optical module becomes larger, heavier, and bulkier
Solution Approach 1:
The patent replaces conventional free-space optical modules with a waveguide-based optical system. The waveguide uses total internal reflection and carefully designed facet geometries to guide and reflect light, eliminating the need for bulky mechanical optical components while achieving the desired field-of-view. This substitution of mechanical optical systems with a waveguide structure directly resolves the contradiction between field-of-view and weight.
Solution Approach 2:
The patent transitions from three-dimensional free-space optical paths to a two-dimensional waveguide plane. By confining light propagation within the waveguide substrate and using internal reflection at facet surfaces, the system achieves extended field-of-view functionality in a planar, compact form factor, effectively resolving the size and weight issues associated with conventional optical modules.
2Adaptability or versatility
If conventional optical modules are used to increase field-of-view, then the field-of-view increases, but the optical module becomes larger and bulkier
Solution Approach 1:
The waveguide structure replaces bulky mechanical optical components with a compact integrated photonic device. Light is guided and reflected within the waveguide using total internal reflection at facet interfaces, eliminating the need for large free-space optical paths and associated mechanical structures, thereby reducing overall device volume while maintaining field-of-view performance.
Solution Approach 2:
The optical functionality is nested within the waveguide substrate itself. The facets are embedded within the waveguide structure, and the light propagation path is contained within the waveguide boundaries. This nesting of optical functions within a compact substrate volume directly addresses the contradiction between field-of-view and device volume.
3Ease of operation
If conventional optical modules are used, then the system can function, but the eye-motion-box is very small and the system is sensitive to small movements
Solution Approach 1:
The patent carefully controls the facet geometry parameters, including width, length, and angular orientation, to optimize the eye-motion-box. By adjusting these geometric parameters, the system achieves a larger eye-motion-box that accommodates greater pupil motion while maintaining image quality and reducing sensitivity to eye movements. This parameter optimization directly resolves the contradiction between ease of operation and system reliability.
Solution Approach 2:
Different regions of the waveguide have different facet configurations optimized for their specific functions. The facets are strategically positioned and dimensioned to create uniform light distribution across the output aperture, ensuring consistent performance across the extended eye-motion-box. This local optimization of facet properties enhances both pupil motion range and reduces sensitivity to eye movements.
4Volume of moving object
If facets are arranged in a waveguide, then compactness is achieved, but non-uniform reflection and image quality issues occur
Solution Approach 1:
The patent optimizes facet geometric parameters including width, length, and angular orientation to achieve uniform light distribution. By carefully selecting and adjusting these parameters, the system compensates for potential non-uniformities in reflection, ensuring consistent image quality across the output aperture while maintaining the compact waveguide structure.
Solution Approach 2:
The overlapping facet design ensures continuous light reflection across the waveguide output. Each facet is positioned and dimensioned to overlap with adjacent facets, creating a continuous reflective surface that eliminates gaps or discontinuities in the light distribution. This continuity ensures uniform reflection and image quality while maintaining the compact integrated 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
The solution achieves uniform reflection and improved image quality by ensuring consistent overlap of facet projections, reducing non-uniformity and sensitivity to eye movements, thus enhancing the compactness and practicality of head-mounted display systems.
Implementation Method 1
a first sequence of facets (56), including a first facet (5610), a last facet (5650), and one or more middle facets (5620, 5630, 5640) therebetween
Implementation Method 2
The display includes an array of elements (pixels) imaged to infinity by a collimating lens and transmitted into the eye of the viewer by means of a reflecting, or partially reflecting, surface acting as a combiner
Data Source
AI summary
Specific management of configuration of overlap of facets reduces non-uniformity in an image outcoupled toward a nominal point of observation. A waveguide including at least two parallel surfaces, first, middle, and last partially reflecting facets are configured such that in a geometrical projection of the facets onto one of the surfaces the facets overlap, preferably with adjacent facets overlapping and non-adjacent facets starts and ends coinciding along at least a portion of the waveguide.