Time-of-Flight Camera Interference Detection and Frequency Adjustment
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Solution Overview
Problem
Time-of-flight cameras with overlapping fields of view often experience interference, leading to false depth profiles due to reflections from other cameras, which is difficult to detect and resolve, especially when frequency and time slot assignments are not properly coordinated.
Innovation Solution
The system captures depth imaging data, calculates depth noise ratios, and graphs these ratios to identify interference patterns, allowing for the detection of interfering cameras and reconfiguration of their operation frequencies or time slots to minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If multiple time-of-flight cameras operate with overlapping fields of view using the same modulation frequency and time slots, then device complexity is reduced and ease of operation is improved, but interference occurs causing false depth profiles and measurement precision deteriorates
Solution Approach 1:
The patent assigns different modulation frequencies to different time-of-flight cameras operating in overlapping fields of view. By changing the frequency parameter of the illuminators, each camera operates at a unique frequency (e.g., 20 MHz, 40 MHz, 80 MHz), allowing simultaneous operation without interference while maintaining ease of operation and ensuring measurement precision.
2Measurement precision
If discrete modulation frequencies are assigned to each time-of-flight camera to eliminate interference, then measurement precision is improved, but device complexity increases and ease of operation deteriorates
Solution Approach 1:
The patent implements a centralized controller that manages multiple time-of-flight cameras, assigning modulation frequencies and sequencing time slots automatically. This universal control system handles the complexity of frequency assignment and camera coordination, allowing individual cameras to operate simply while ensuring measurement precision through systematic frequency management.
3Measurement precision
If time slots and modulation frequencies are carefully assigned to each time-of-flight camera, then interference is eliminated improving measurement precision, but the system complexity increases and setup time increases
Solution Approach 1:
The patent implements automatic frequency assignment and time slot sequencing that occurs during system initialization. The controller pre-configures each camera's modulation frequency and operational timing before depth imaging begins, eliminating the need for manual configuration and reducing setup time while ensuring measurement precision through proper frequency assignment.
4Measurement precision
If a sensor of one time-of-flight camera is exposed only when its own illuminator is active, then interference from other cameras is eliminated improving measurement precision, but the imaging speed decreases
Solution Approach 1:
The patent implements periodic modulation of illuminators at different frequencies, with sensors exposed during their assigned time slots. Each camera's illuminator operates periodically at its unique frequency, and sensors are exposed during corresponding time windows. This periodic operation allows multiple cameras to capture depth images simultaneously at high speeds while maintaining measurement precision through frequency-based interference elimination.
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
Effectively detects and mitigates depth interference between time-of-flight cameras by identifying interfering devices and adjusting their operation parameters, ensuring accurate depth imaging data without shutting down cameras unless necessary.
Implementation Method 1
illuminating a scene using a light source (e.g., a modulated source of light at any wavelength or frequency, such as infrared) and capturing light that is reflected from various points of the scene
Implementation Method 2
a discrete modulation frequency may be assigned to each of the time-of-flight cameras that are mounted at a scene with overlapping fields of view, and the times at which such cameras operate illuminators to illuminate scenes and expose sensors to capture reflected light from such scenes may be sequenced
Data Source
AI summary
Discrete frequencies and time slots of operation are assigned to each of a plurality of time-of-flight cameras. Where two time-of-flight cameras having overlapping fields of view, whether the time-of-flight cameras are operating at the same frequency or time slot is determined by calculating ratios of zero-value pixels to total numbers of pixels for each depth image captured by the time-of-flight cameras over a selected interval. If the time-of-flight cameras operate at the same frequency or time slot, a plot of the ratios of depth images captured using one time-of-flight camera is erratically sinusoidal. Another time-of-flight camera causing the interference may be identified among time-of-flight cameras operating at the frequency or time slot, based on areas of interest that overlap with the time-of-flight camera, or based on a time at which the time-of-flight cameras began capturing depth images, as compared to a time at which the interference is observed.