Dual-Wavelength Time-of-Flight Sensing for Ambient Light Robustness
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Solution Overview
Problem
Conventional Time-of-Flight (ToF) systems face challenges with ambient light robustness and color dependency due to single-wavelength operation, leading to reduced signal-to-noise ratio (SNR), inaccurate depth measurement, and ambiguity in distance estimation, particularly in scenarios like FaceID where materials have varying reflectivity.
Innovation Solution
A ToF system and method utilizing a light source that emits light at two wavelengths, one in the near-infrared (NIR) and one in the short-wave infrared (SWIR) range, combined with a sensor capable of detecting and generating separate time-of-flight data for each wavelength, to enhance SNR and resolve ambiguity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-wavelength light source is used in a ToF system, then the device complexity is reduced, but the ambient light robustness deteriorates and the signal-to-noise ratio decreases
Solution Approach 1:
The patent combines multiple light sources emitting at different wavelengths (e.g., 850 nm and 940 nm) into a single integrated illumination system. This merging approach enhances ambient light robustness by providing multiple wavelength channels that can differentiate between active illumination and passive ambient light, thereby improving reliability without proportionally increasing device complexity.
Solution Approach 2:
The light source system is designed to emit multiple wavelengths simultaneously, making it multi-functional in terms of wavelength coverage. This universal light source can operate across different wavelength bands, improving adaptability to various lighting conditions and enhancing ambient light rejection capabilities while maintaining a unified hardware structure.
2Device complexity
If a single-wavelength light source is used in a ToF system, then the device complexity is reduced, but the signal-to-noise ratio deteriorates
Solution Approach 1:
The patent combines multiple light sources emitting at different wavelengths (e.g., 850 nm and 940 nm) into a single integrated illumination system. This merging approach enhances ambient light robustness by providing multiple wavelength channels that can differentiate between active illumination and passive ambient light, thereby improving reliability without proportionally increasing device complexity.
Solution Approach 2:
The system changes the wavelength parameter of the light source to emit at multiple discrete wavelengths. By varying the wavelength parameter across different light sources, the system improves signal-to-noise ratio through wavelength-based discrimination of active illumination from ambient light, while the integrated control maintains manageable device complexity.
3Device complexity
If a single-wavelength light source is used in a ToF system, then the device complexity is reduced, but the depth measurement accuracy deteriorates due to material reflectivity variations
Solution Approach 1:
The system changes the wavelength parameter of the light source to emit at multiple discrete wavelengths. By varying the wavelength parameter across different light sources, the system improves signal-to-noise ratio through wavelength-based discrimination of active illumination from ambient light, while the integrated control maintains manageable device complexity.
Solution Approach 2:
The patent applies different wavelengths to different measurement scenarios, recognizing that materials have varying reflectivity characteristics at different wavelengths. By selecting appropriate wavelengths for different materials or conditions, the system optimizes depth measurement accuracy locally for each measurement context while maintaining a unified multi-wavelength hardware platform.
4Device complexity
If a single-wavelength light source is used in a ToF system, then the device complexity is reduced, but the distance estimation accuracy deteriorates due to ambiguity
Solution Approach 1:
The system changes the wavelength parameter of the light source to emit at multiple discrete wavelengths. By varying the wavelength parameter across different light sources, the system improves signal-to-noise ratio through wavelength-based discrimination of active illumination from ambient light, while the integrated control maintains manageable device complexity.
Solution Approach 2:
The patent segments the distance measurement problem into multiple wavelength-based measurement channels. By using multiple wavelengths with different propagation characteristics and material interactions, the system resolves distance estimation ambiguity through multi-channel data fusion, improving accuracy without requiring a single overly complex measurement system.
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 dual-wavelength approach improves ambient light robustness, increases SNR, and enhances depth measurement accuracy by addressing material reflectivity variations, thereby improving the performance and precision of ToF systems.
Implementation Method 1
a light source configured to emit first light rays at a first wavelength and second light rays at a second wavelength to an object
Implementation Method 2
a time-of-flight sensor configured to detect the first light rays at the first wavelength and the second light rays at the second wavelength, and to generate first time-of-flight data associated with the detected first light rays and second time-of-flight data associated with the detected second light rays
Data Source
AI summary
A Time-of-Flight system having a light source which emits first light rays at a first wavelength and second light rays at a second wavelength to an object, the second wavelength being larger than the first wavelength, and a time-of-flight sensor which detects the first light rays at the first wavelength and the second light rays at the second wavelength, and generates first time-of-flight data associated with the detected first light rays and second time-of-flight data associated with the detected second light rays.