ToF Sensing Correlation Shaping for Glare-Resistant Distance Measurement
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Solution Overview
Problem
ToF cameras experience glare effects and pixel saturation due to strong light sources, which affect neighboring pixels and measurement accuracy, especially in far-range applications.
Innovation Solution
Performing multiple ToF measurements using a specific modulation frequency to generate periodic correlation functions with increasing amplitude over distance, reducing sensitivity to close proximity light and avoiding glare and saturation by adjusting the correlation function shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If strong light sources are used for far range measurements, then measurement range is extended, but glare effects and pixel saturation occur
Solution Approach 1:
The patent applies parameter changes by using multiple modulation frequencies instead of a single frequency. The system performs ToF measurements at different modulation frequencies (e.g., first frequency f1 and second frequency f2), where each frequency provides different correlation function characteristics. By combining measurements from multiple frequencies, the system extends the effective measurement range while avoiding the harmful effects that would occur if a single high-power light source were used at one frequency alone.
Solution Approach 2:
The patent utilizes periodic action through the use of periodic correlation functions that arise from modulated light sources. The correlation functions exhibit periodic behavior with increasing amplitude over distance, and by performing measurements at multiple periodic modulation frequencies, the system can determine distances beyond the range limitations of any single frequency while maintaining accuracy and avoiding saturation effects.
2Measurement precision
If multiple modulation frequencies are used to extend measurement range, then distance determination accuracy is improved, but measurement time increases
Solution Approach 1:
The patent applies preliminary action by performing ToF measurements at multiple modulation frequencies in sequence rather than simultaneously. The system first performs measurements at a first modulation frequency to obtain initial distance information, then performs additional measurements at a second modulation frequency. This sequential approach allows the system to establish baseline measurements that can be combined with subsequent measurements, improving overall accuracy while managing total measurement time more efficiently than if all measurements had to be performed with equal weighting.
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
Improves ToF sensing by reducing glare effects and pixel saturation, enabling accurate distance determination while maintaining measurement precision over varying distances.
Implementation Method 1
Time-of-Flight (ToF) cameras measure distance by emitting near infrared light
Implementation Method 2
A respective correlation function of each of the plurality of first ToF measurements is periodic and exhibits an increasing amplitude over distance within a measurement range of the ToF sensor
Data Source
AI summary
A method for Time-of-Flight (ToF) sensing of a scene is provided. The method includes performing, by a ToF sensor, a plurality of first ToF measurements using a first modulation frequency to obtain first measurement values. A respective correlation function of each of the plurality of first ToF measurements is periodic and exhibits an increasing amplitude over distance within a measurement range of the ToF sensor. The method additionally includes determining a distance to an object in the scene based on the first measurement values.