Structured Light Interference Mitigation via Sampling Adjustment
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Solution Overview
Problem
Optical interference from sources like alternating current-powered lights and electronic devices impairs the recovery of structured light signals in augmented reality environments, leading to erroneous or unusable images.
Innovation Solution
An interference mitigation module identifies and mitigates optical interference by applying over- or undersampling coefficients to cameras, filtering out interfering signals, and shifting the frame start timing of projectors to avoid interference intervals, using data from an object datastore to tailor mitigation techniques to specific interference sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard sampling is used to acquire optical signals, then the acquisition process is simple and fast, but optical interference from periodic light sources causes erroneous or unusable images
Solution Approach 1:
The system performs preliminary characterization of the scene to identify periodic light sources and their frequencies before acquiring structured light signals. This advance detection allows the system to plan interference mitigation strategies, such as adjusting sampling rates or timing, to avoid capturing interference patterns, thereby ensuring reliable image quality without requiring complex real-time processing
Solution Approach 2:
The system changes sampling parameters (rate, timing, phase) based on detected interference characteristics. By dynamically adjusting these parameters, the system can avoid sampling during interference peaks or use differential sampling to cancel out periodic interference, thus improving image reliability while keeping processing complexity manageable through parameter optimization rather than structural complexity
2Measurement precision
If sampling rate is increased to capture more signal data, then signal recovery accuracy improves, but interference from periodic sources becomes more prominent
Solution Approach 1:
The system employs periodic sampling at rates specifically chosen to avoid aliasing with periodic interference sources. By understanding the interference frequency, the system can sample at rates that are not integer multiples or submultiples of the interference frequency, or use synchronous sampling techniques where the sampling phase is deliberately offset from the interference phase, thereby capturing accurate signal data while minimizing interference prominence
Solution Approach 2:
The system uses the known characteristics of periodic interference (frequency, amplitude) to its advantage by implementing differential measurement techniques. By taking multiple measurements at different phases or times and combining them mathematically, the system can cancel out the periodic interference component while preserving the structured light signal, thus converting the harmful interference into a predictable factor that can be eliminated through processing
3Reliability
If frame timing is shifted to avoid interference intervals, then interference mitigation is effective, but synchronization with other devices becomes more complex
Solution Approach 1:
The system implements a feedback mechanism where the detected interference characteristics (frequency, timing) are used to dynamically adjust the frame timing of the structured light projector and camera. This closed-loop approach ensures that the system automatically adapts to changing interference conditions while maintaining proper synchronization through coordinated timing adjustments based on real-time feedback from interference detection
Solution Approach 2:
The system employs a universal timing synchronization protocol that can accommodate both interference-avoidance requirements and standard synchronization needs. By designing a flexible timing mechanism that can operate in multiple modes (standard synchronization, interference-avoidance mode, adaptive mode), the system achieves effective interference mitigation without significantly complicating synchronization, as the same infrastructure supports both functions
Data Source
AI summary
Structured light generated by a projector may be recovered by a camera to determine three-dimensional data about a scene. The structured light signal acquired by the camera may be impaired due to interference from flickering sources of illumination such as lights, electronic displays, and so forth. This optical interference to an image acquisition system, such as a structured light system, is mitigated by modifying operation of a camera by applying a sampling coefficient to the camera's frame rate or by presenting structured light frames during times non-coincident with the interference.