Avalanche Diode Time-of-Flight Detection for Ambient Light Noise
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Solution Overview
Problem
Existing optical distance detection devices face challenges in accurately calculating object distance due to noise caused by ambient light, which degrades detection accuracy and introduces ambiguity in distance measurement.
Innovation Solution
The device employs an avalanche diode with a light source and counters to differentiate between light source signals and ambient light by counting electrical pulses during specific exposure intervals, allowing for the calculation of time-of-flight and subsequent object distance while eliminating ambient light noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single photon avalanche diode is used to detect reflected light in weak light environment, then detection sensitivity is improved, but ambient light causes avalanche events that trigger noises and degrade detection accuracy
Solution Approach 1:
The detection process is divided into multiple time intervals: a first time interval for detecting reflected light signals, a second time interval for detecting ambient light signals, and a third time interval for another reflected light signal. By segmenting the detection in time domains, the system can differentiate between ambient light noise and actual reflected light signals, thereby improving detection accuracy while maintaining sensitivity to weak light environments.
2Adaptability or versatility
If ambient light intensity varies alternatively, then the detection environment becomes more complex, but this causes detection results to be affected and degraded
Solution Approach 1:
The system employs periodic detection cycles with alternating time intervals: detecting reflected light during first and third intervals, detecting ambient light during the second interval, and repeating this pattern. This periodic action allows the system to adapt to varying ambient light conditions by continuously sampling and comparing signals across multiple cycles, thereby maintaining detection accuracy despite environmental variations.
3Measurement precision
If time-of-flight technique is used to calculate object distance, then distance measurement capability is improved, but ambient light interference introduces ambiguity in distance measurement
Solution Approach 1:
The system uses ambient light detection as an intermediary step to eliminate noise before performing time-of-flight calculation. By detecting ambient light signals in the second time interval and using this information to subtract or filter ambient light components from the reflected light signals detected in the first and third intervals, the system removes the intermediary noise factor that causes measurement ambiguity, thereby improving distance measurement accuracy.
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 effectively reduces ambient light influence, improving detection accuracy and reducing distance ambiguity by directly calculating time-of-flight using count ratios and converting them into object distance measurements.
Implementation Method 1
When a photon is received by the SPAD, an avalanche current is triggered in response that one photon is detected.
Implementation Method 2
an avalanche current is triggered in response that one photon is detected. The pulse caused by the avalanche current is considered an event.
Data Source
AI summary
There is provided a detection device including a light source, an avalanche diode, a first counter, a second counter and a processor. The light source emits light within a first interval, and is turned off within a second interval, a third interval and a fourth interval. The avalanche diode detects photons corresponding to the first interval, second, third and fourth intervals to trigger avalanche events. The first counter performs up-counting on the avalanche events in the first interval and performs down-counting on the avalanche events in the third interval to generate a first count value. The second counter performs up-counting on the avalanche events in the second interval and performs down-counting on the avalanche events in the fourth interval to generate a second count value. The processor calculates a time-of-flight according to the first count value and the second count value.