Proximity Sensor Photodiode Segmentation for Distance Accuracy
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Solution Overview
Problem
Proximity sensors face challenges in differentiating between objects at very short and long distances, leading to incorrect switching of display screens, as they often fail to accurately determine the proximity of objects, especially when an object is close or far from the sensor.
Innovation Solution
A proximity sensing device is designed with a light source, a first photodiode, and a second photodiode separated by a separator, utilizing a selecting circuit to compare signals from both photodiodes and select the appropriate signal based on their difference, with the processing device generating a proximity-detection signal to accurately differentiate between close and far objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single photodiode is used to detect reflected light, then the device structure is simple, but the ability to differentiate between very close and far objects is poor
Solution Approach 1:
The single photodiode is segmented into multiple photodiodes (first photodiode and second photodiode) with different positions and functions. The first photodiode detects reflected light from objects at any distance, while the second photodiode specifically detects light from very close objects. This segmentation enables the system to differentiate between very close and far objects by comparing signals from the two photodiodes, thereby improving proximity detection accuracy without excessive complexity.
2Volume of moving object
If the light source and photodiode are placed close together, then the device size is reduced, but the ability to detect objects at different distances is compromised
Solution Approach 1:
Instead of increasing the distance between the light source and photodiode along the optical axis to improve distance differentiation, the invention uses the spatial dimension by placing two photodiodes at different lateral positions. The first photodiode is positioned to receive reflected light at a standard angle, while the second photodiode is positioned to receive light from very close objects. This dimensional approach allows compact housing volume while maintaining the ability to detect objects at different distances through spatial signal differentiation.
3Speed
If signal processing is simplified to improve response time, then the processing speed increases, but the accuracy of proximity detection decreases
Solution Approach 1:
The system performs preliminary action by continuously monitoring the signal from the second photodiode and comparing it with the signal from the first photodiode. When the second photodiode detects a signal exceeding a threshold (indicating a very close object), the system immediately switches to using only the first photodiode's signal for distance calculation. This preliminary detection and switching mechanism enables rapid response to close objects while maintaining accurate distance measurement through selective signal processing.
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 solution effectively addresses the issue of differentiating between very close and far objects, ensuring accurate switching of display screens by generating a detection signal that is higher at short distances than at long distances, preventing erroneous screen activation.
Implementation Method 1
The general principle of a proximity sensor lays in the emission by the source of a light beam, for example an infrared beam, being reflected by an object, and captured in return by the detector
Implementation Method 2
The detector can include one photodiode, or several photodiodes
Data Source
AI summary
A proximity sensing device includes a proximity sensor including a light source, a light detector including a first photodiode adapted to generate a first signal, and a second photodiode adapted to generate a second signal, the second photodiode and the light source being separated from the first photodiode with a separator. The proximity sensing device further includes a selecting circuit adapted to compare the first signal to the second signal, and to select a signal from the first and second signals according to the executed comparison.