TOF 3D Camera Distance Accuracy via Probabilistic Light Modeling
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Solution Overview
Problem
Time of flight (TOF) 3D cameras face challenges in accurately determining distances to features in a scene due to the interference of background light and multipath reflections, which affect the correlation between light pulses and exposure periods, leading to inaccurate distance measurements.
Innovation Solution
A TOF 3D camera system that uses a probabilistic model to account for the expected light registration during different exposure periods, incorporating a function Λ(t) that describes light intensity as a function of time, and integrates for multipath reflections to separate direct and indirect light contributions, allowing for more accurate distance calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional TOF measurement methods are used, then distance measurement can be performed, but measurement precision deteriorates due to background light and multipath reflections
Solution Approach 1:
The patent segments the light registration process into multiple distinct exposure periods (first exposure period and second exposure period) with different timing relative to the light pulse transmission. By separating the measurement into these segments, the system can differentiate between direct reflected light and multipath reflected light, thereby improving distance measurement accuracy despite the presence of background light and multipath reflections.
Solution Approach 2:
The patent employs periodic transmission of light pulses and corresponds each pulse with specific exposure periods. The first and second exposure periods are periodically repeated for each transmitted light pulse, allowing the system to collect multiple measurements and use probabilistic modeling to determine the most likely distance while mitigating the effects of background light and multipath reflections.
2Measurement precision
If multiple exposure periods are used to mitigate background light and multipath reflections, then distance measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent implements dynamic control of the shutter mechanism to create different exposure periods (first exposure period during which the shutter is closed, second exposure period during which the shutter is open) in response to each transmitted light pulse. This dynamic timing control allows the system to capture different aspects of light reflection without requiring additional hardware components, thereby improving measurement accuracy while limiting complexity increase.
3Reliability
If probabilistic modeling is applied to account for light registration variations, then measurement reliability improves, but computational complexity increases
Solution Approach 1:
The patent uses feedback through probabilistic modeling where the system compares the actual light registration amounts during different exposure periods with expected values based on hypothesized distances. The model iteratively determines which distance hypothesis best explains the observed light registration pattern, thereby improving measurement reliability. This feedback-based approach uses computational algorithms rather than additional hardware to achieve robust distance measurement.
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 enables the TOF 3D camera to determine distances more accurately by mitigating the impact of background light and multipath reflections, providing a probabilistic model that maximizes the likelihood of the measured light amounts, thereby improving the reliability of distance measurements.
Implementation Method 1
A pixel registers incident light by accumulating positive or negative electric charge, hereinafter also referred to as 'photocharge' provided by electron-hole pairs generated by photons in the incident light.
Implementation Method 2
A time of flight (TOF) three dimensional (3D) camera acquires distances to features in a scene that the TOF-3D camera images by determining how long it takes temporally modulated light that the camera transmits to illuminate the scene to make a 'round trip' from the camera to the features and back to the camera.
Data Source
AI summary
An embodiment of the invention provides a time of flight three-dimensional TOF-3D camera that determines distance to features in a scene responsive to amounts of light from the scene registered by pixels during different exposure periods and an experimentally determined probabilistic model of how much light the pixels are expected to register during each of the different exposure periods.