Single-Photon Depth Imaging With Adaptive Attenuation in Ambient Light
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Solution Overview
Problem
SPAD-based LiDAR systems face severe nonlinear distortions and depth errors due to ambient light, particularly in outdoor conditions, as the dead time of the detectors causes photon detection to depend on previous photons, leading to pile-up distortions that limit their performance.
Innovation Solution
A system with a light source, a single-photon detector, and an adjustable attenuation element, where the processor determines ambient light intensity and selects an appropriate attenuation factor to mitigate pile-up distortions by controlling the intensity of light perceived by the detector, allowing for precise depth estimation even in high ambient light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If SPAD-based LiDAR systems operate in high ambient light conditions, then they can function in outdoor environments, but severe pile-up distortions and depth errors occur due to detector dead time
Solution Approach 1:
The patent applies dynamics by making the attenuation factor adjustable and adaptive rather than fixed. The system dynamically modifies the attenuation level based on detected ambient light conditions, allowing it to adapt to varying outdoor environments while maintaining measurement precision. The attenuation element's transmittance can be changed in real-time to optimize performance under different lighting conditions.
Solution Approach 2:
The patent changes the physical parameter of light intensity reaching the detector by introducing an attenuation element with variable transmittance. By modifying the attenuation factor (a physical parameter ranging from 0 to 1), the system controls the amount of ambient light incident on the SPAD, thereby preventing pile-up distortions while maintaining sufficient signal strength for accurate depth measurement.
2Measurement precision
If attenuation is increased to reduce ambient light impact, then pile-up distortions are reduced, but signal strength from the laser source is also weakened
Solution Approach 1:
The patent implements feedback by using the detected ambient light intensity information to adjust the attenuation factor. The system continuously monitors the ambient light conditions and adapts the attenuation level accordingly, creating a closed-loop control system that optimizes the balance between reducing pile-up distortions and maintaining sufficient signal strength for accurate depth measurement.
Solution Approach 2:
The system dynamically adjusts the attenuation factor based on real-time ambient light measurements rather than using a fixed attenuation level. This dynamic adaptation allows the system to maintain optimal signal strength while minimizing pile-up effects under varying outdoor lighting conditions.
3Use of energy by moving object
If no attenuation is applied to maintain signal strength, then laser signal is preserved, but nonlinear distortions increase due to high incident flux from ambient light
Solution Approach 1:
The patent introduces an attenuation element as an intermediary between the ambient light source and the SPAD detector. This intermediary component selectively reduces the incident flux from ambient light while allowing the laser signal to pass through with appropriate transmission, thereby preventing nonlinear distortions in the histogram formation process while preserving the necessary signal strength for accurate depth 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
The system achieves improved precision in depth imaging by reducing pile-up distortions and maintaining signal strength, resulting in accurate depth estimates with reduced error, even in bright outdoor conditions, through adaptive attenuation techniques.
Implementation Method 1
Detectors that are capable of detecting the arrival time of an individual photon, such as single-photon avalanche diodes (SPADs)
Implementation Method 2
an attenuation element configured to provide a variable attenuation factor, wherein an intensity of light perceived by the detector corresponds to a product of the attenuation factor and an intensity of light perceived by the detector in the absence of attenuation
Data Source
AI summary
In accordance with some embodiments, systems, methods and media for single photon depth imaging with improved precision in ambient light conditions are provided. In some embodiments, the system comprises: a light source; a single photon detector; an attenuation element configured to provide a variable intensity attenuation factor; and a processor programmed to: (a)-determine an ambient light intensity associated with a scene point; (b)-select an attenuation factor based on the ambient light intensity; (c)-estimate a depth of the scene point based on a multiplicity of photon arrival times determined using the detector during a period of time during which light incident on the detector is attenuated by the selected attenuation factor and during which the light source is configured to periodically emit a pulse of light toward the scene point; (d)-repeat (a)-(c) for each of a multiplicity of scene points.