Waveguide Structured Light Depth Sensing for Near-Range Precision
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Solution Overview
Problem
Existing depth sensing techniques, such as Time of Flight (ToF) and patterned projections, struggle in near-range contexts due to resolution limitations, with ToF systems finding it difficult to resolve short time of flight pulses and pattern projection techniques being limited by the number of dots projected.
Innovation Solution
The use of phase-shifted interference patterns generated by waveguides with extraction features in a head-mounted display (HMD) to create high-resolution depth maps, where coherent illumination light is directed to form interference patterns that are phase-shifted by specific degrees, allowing for accurate near-range depth sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Time of Flight (ToF) technique is used to measure depth, then depth measurement capability is provided, but measurement precision deteriorates in near-range contexts due to difficulty in resolving short time of flight pulses
Solution Approach 1:
The patent replaces the temporal measurement approach of ToF with a spatial interference pattern approach. Instead of measuring time of flight, the system projects structured light patterns and captures interference fringes, converting a time-based measurement problem into a space-based optical interference problem that can be resolved with high precision using camera sensors.
Solution Approach 2:
The patent changes the measurement parameter from time domain (ToF) to spatial domain (interference pattern phase). By using phase-shifted interference patterns with different spatial frequencies, the system achieves high-resolution depth mapping in near-range where temporal resolution becomes insufficient.
2Measurement precision
If patterned projection technique is used for depth sensing, then depth mapping capability is provided, but measurement precision is limited by the number of dots projected
Solution Approach 1:
The patent transitions from discrete dot-based projection to continuous interference fringe patterns. By utilizing the phase dimension of optical interference, the system achieves continuous depth information across the entire field of view rather than relying on a finite number of projected dots, effectively adding a phase dimension to the measurement.
Solution Approach 2:
The patent uses optical interference to create multiple phase-shifted copies of the projection pattern simultaneously. By capturing multiple interference patterns with different phase shifts (e.g., 0°, 120°, 240°), the system obtains multiple depth measurements without requiring sequential projection of different patterns, improving both resolution and efficiency.
3Measurement precision
If multiple waveguides with extraction features are used to generate phase-shifted interference patterns, then measurement precision improves for near-range depth sensing, but device complexity increases
Solution Approach 1:
The patent integrates multiple functions into the waveguide structure: the waveguides serve both as optical transmission paths and as phase modulation elements. By incorporating extraction features directly into the waveguides, the system achieves both light guidance and interference pattern generation using a single integrated component rather than separate elements.
Solution Approach 2:
The patent divides the optical structure into multiple waveguides, each responsible for generating a specific phase-shifted interference pattern. This segmentation allows independent optimization of each waveguide's extraction features while maintaining overall system functionality, and enables parallel capture of multiple phase patterns.
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 approach provides higher resolution depth mappings than traditional methods, is not limited by the number of projected dots, and can be implemented in a low-power system within a field of view, facilitating clear scene light visibility and enhanced near-range depth sensing capabilities.
Implementation Method 1
the optical structure includes a first, second, and third waveguide configured to receive coherent illumination light and direct the coherent illumination light to the eyebox area as a first light projection and a second light projection to generate a first, second, and third interference pattern
Data Source
AI summary
At least one waveguide is configured to receive coherent illumination light and direct the coherent illumination light to an object as a first light projection and second light projection. At least one interference pattern is generated by interference between the first light projection and the second light projection. A camera captures interference images of a plurality of phase-shifted interference images and a depth from an object may be determined from the phase-shifted interference images.