Time of Flight Sensor Capacitor Segmentation for Ambient Light Compensation
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Solution Overview
Problem
Time of Flight (TOF) optical sensors face challenges in accurately measuring the propagation time of light pulses and calculating distance with minimal data captures, especially when dealing with long pulses of irregular shape, and are sensitive to ambient light, which affects measurement precision.
Innovation Solution
The TOF sensor device employs a photo-sensor component with multiple capacitors to store electrical energy from leading and trailing portions of reflected light pulses, along with ambient light, allowing for precise distance determination using a ratio or center of mass method, minimizing the impact of ambient light and achieving high precision with fewer data captures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional TOF sensors use single capacitor to store electrical energy from reflected light pulses, then the device complexity is low, but the measurement precision deteriorates due to inability to separately capture leading and trailing portions of irregular pulses
Solution Approach 1:
The patent divides the single capacitor into multiple capacitors (first measuring capacitor, second measuring capacitor, third measuring capacitor) to separately store electrical energy from different portions of the reflected light pulse. The first capacitor stores energy from the leading portion, the second capacitor stores energy from the trailing portion, and the third capacitor stores ambient light energy. This segmentation enables precise measurement of irregular pulse shapes while maintaining manageable device complexity through systematic architecture.
2Measurement precision
If TOF sensors capture more data points to improve measurement precision, then the measurement precision improves, but the acquisition time increases
Solution Approach 1:
The patent employs periodic switching of control signals to sequentially connect different capacitors to the photo device during the integration period. The control signals switch between capacitors at specific time intervals, allowing the system to capture multiple data points (leading portion, trailing portion, ambient light) within a single periodic cycle. This periodic action enables comprehensive data capture without extending the total acquisition time, as all measurements are completed within one measurement cycle.
3Reliability
If TOF sensors use simpler measurement methods, then the device complexity is low, but the reliability deteriorates due to sensitivity to ambient light
Solution Approach 1:
The patent introduces a third measuring capacitor as an intermediary element specifically dedicated to storing electrical energy from ambient light. This separate capacitor acts as a mediator that isolates ambient light effects from the pulse measurement capacitors. By measuring ambient light independently in the third capacitor and then compensating for it in the distance calculation, the system achieves high measurement reliability without requiring complex real-time filtering or processing methods.
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 accurate distance measurement with short acquisition and response times, maintaining high precision even with irregularly shaped pulses and compensating for ambient light, thus enhancing the reliability of TOF sensors in various applications.
Implementation Method 1
a photo device configured to generate electrical energy in proportion to a quantity of received light
Data Source
AI summary
A time of flight sensor device is provided that is capable of generating accurate information relating to propagation time of emitted light pulses using a small number of measurements or data captures. By generating pulse time of flight information using a relatively small number of measurement cycles, object distance information can be generated more quickly, resulting in faster sensor response times. Embodiments of the time of flight sensor can also minimize or eliminate the adverse effects of ambient light on time of flight measurement. Moreover, some embodiments execute time of flight measurement techniques that can achieve high measurement precision even when using relatively long light pulses having irregular, non-rectangular shapes.