Proximity Sensor Integration Circuit for Ambient Light Rejection
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Solution Overview
Problem
Traditional proximity sensors face interference from ambient light, leading to inaccurate detection of object proximity due to varying light intensities during turn-on and turn-off intervals, causing false positives when subtracting ambient light interference.
Innovation Solution
The proximity sensor design involves a light source that is turned on and off multiple times during a measurement interval, with shorter intervals, allowing the optical sensing element to generate both turn-on and turn-off currents, which are integrated and compared to a threshold, effectively reducing ambient light interference by counting comparison signals during these intervals to generate accurate sensing values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light source is turned on and off once during a measurement interval to eliminate ambient light interference, then the ambient light interference can be subtracted, but the ambient light intensity may change between turn-on and turn-off intervals causing false positives
Solution Approach 1:
The patent divides the measurement process into multiple turn-on and turn-off intervals instead of using a single pair of intervals. By segmenting the measurement into multiple cycles, the system captures ambient light variations more accurately and uses statistical processing to eliminate false positives while maintaining the ability to subtract ambient light interference.
2Measurement precision
If the light source is turned on and off multiple times with shorter intervals, then the difference in ambient light intensity between intervals is minimized, but the measurement time interval increases
Solution Approach 1:
The patent employs periodic turn-on and turn-off actions of the light source multiple times during the measurement interval. This periodic action allows the system to capture reflected light and subtract ambient light interference at multiple points, minimizing the impact of ambient light variations while maintaining a reasonable overall measurement time through efficient cycling.
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 reduces ambient light interference, enhancing the accuracy of proximity detection by minimizing the difference in ambient light intensities between turn-on and turn-off intervals, thereby improving the sensor's ability to accurately determine object proximity.
Implementation Method 1
The optical sensing element 121 senses the reflected light L′ and the ambient light to generate a current Iph
Data Source
AI summary
A proximity sensor includes a light source, an optical sensing element, and an integration circuit. The light source is turned on and off several times during a measurement time interval. When the light source is turned on and off, the optical sensing element senses the surrounding light to generate a first current and a second current, respectively. The integration circuit integrates the first current and the second current to generate a first integration signal and a second integration signal respectively for determining whether an object is approaching. When the light source is turned on, the present second integration signal is stored, and a stored first integration signal is used as a starting value to integrate the first current. When the light source is turned off, the present first integration signal is stored, and the stored second integration signal is used as a starting value to integrate the second current.