Time-of-flight Camera TDMA Illumination Control
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Solution Overview
Problem
Time-of-flight cameras experience measurement errors due to crosstalk when multiple cameras illuminate the same scene simultaneously, with existing solutions like FDMA, CDMA, and Epipolar-ToF not fully addressing interference and shot noise issues, especially in dynamic scenes.
Innovation Solution
A time-of-flight camera system that uses a time-division multiple access (TDMA) scheme to determine and utilize free time slots for illumination, minimizing interference by scanning the scene to detect other cameras' illumination and adjusting its own illumination accordingly, using a processor to control the image sensor and illumination source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple ToF cameras illuminate the scene simultaneously, then depth measurements can be obtained for all pixels simultaneously, but measurement errors occur due to crosstalk between cameras
Solution Approach 1:
The patent segments the illumination time by dividing it into multiple time slots, with each camera assigned to a specific time slot. This temporal segmentation allows multiple cameras to operate without overlapping illumination, eliminating crosstalk while maintaining simultaneous depth measurement capability across all cameras.
Solution Approach 2:
The patent implements periodic illumination cycles where each camera illuminates the scene in alternating time slots. This periodic action ensures that only one camera illuminates at a time, preventing interference while maintaining continuous depth measurement capability through the cyclic rotation of illumination duties.
2Measurement precision
If FDMA or CDMA is used to reduce crosstalk, then interference effects are reduced, but shot noise suppression is not achieved and system complexity increases
Solution Approach 1:
The patent extracts the time dimension from the illumination process and uses it to separate camera operations. By taking out time as a独立的 resource for camera differentiation, the system achieves crosstalk reduction without requiring complex frequency modulation or code superposition, thereby reducing overall system complexity.
Solution Approach 2:
The patent changes the operational parameter from simultaneous illumination to sequential illumination in different time slots. This parameter change from spatial/temporal overlap to temporal separation simplifies the system by eliminating the need for complex modulation schemes while effectively reducing crosstalk and shot noise.
3Measurement precision
If EpiToF is used to reduce interference, then probability of interferences is reduced, but hardware complexity increases and performance is limited by illumination power and sensor readout time
Solution Approach 1:
The patent introduces dynamic time slot assignment where cameras can adaptively select their illumination time slots based on scene conditions and camera positions. This dynamic approach allows the system to optimize performance for different scenarios without requiring complex hardware modifications, achieving interference reduction through flexible temporal scheduling.
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 reduces measurement errors and shot noise by avoiding coincident time slots, allowing for accurate depth measurements in asynchronous multi-camera scenarios without requiring complex hardware or significant illumination power, even in dynamic environments.
Implementation Method 1
an image sensor for detecting light
Implementation Method 2
a modulated wave illumination
Data Source
AI summary
A time-of-flight camera has;an illumination source for illuminating a scene;an image sensor for detecting light; anda processor configured to:control the image sensor for scanning a scene for detecting illumination;determine a time slot for illumination of the scene, based on the scanning result of the scene; andcontrol the illumination source to illuminate the scene in the determined time slot, based on a time-division multiple access scheme.