Proximity Sensor Polarizer Structure for Cover Reflection Isolation
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Solution Overview
Problem
Proximity sensors face challenges due to small reflections from protective covers overwhelming the photodetector, leading to false readings and reduced accuracy in detecting objects.
Innovation Solution
The implementation of a polarizer structure that blocks light reflections from the cover while allowing light from objects to reach the photodetector, using a configuration of layers and windows to control the angle of incident light and minimize cross-talk, allowing for the comparison of signals to differentiate between object reflections and cover reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective cover is added to shield the sensor from environmental damage, then the reliability of the sensor is improved, but cross-talk from cover reflections increases and measurement precision deteriorates
Solution Approach 1:
A polarizing beam splitter is introduced as an intermediary optical element between the cover and the photodetector. This beam splitter separates light based on polarization: it transmits light reflected from objects (which maintains or has specific polarization) while blocking light reflected from the cover (which has different polarization characteristics). This intermediary component effectively filters out the harmful cover reflections without compromising the protective function of the cover, thus resolving the contradiction between reliability and measurement precision.
2Device complexity
If the photodetector is positioned close to the cover for compact design, then device complexity is reduced, but cross-talk from reflections increases and measurement precision deteriorates
Solution Approach 1:
The polarizing beam splitter serves as a mediator that enables close positioning of the photodetector to the cover while maintaining measurement precision. By filtering polarized reflections from the cover, the beam splitter allows the photodetector to be placed in close proximity without being overwhelmed by reflection noise, thus achieving both compact design and accurate measurement.
Solution Approach 2:
The optical system is designed with different polarization characteristics for different light paths. Light reflected from objects has different polarization properties compared to light reflected from the cover. By exploiting this local quality difference through the polarizing beam splitter, the system can distinguish between desired signal and unwanted reflection even when the photodetector is close to the cover.
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 solution effectively reduces cross-talk and enhances the accuracy of proximity detection by isolating light reflections from the cover, allowing for precise detection of objects even when they are close to the sensor.
Implementation Method 1
The implementation of a polarizer structure that blocks light reflections from the cover while allowing light from objects to reach the photodetector, using a configuration of layers and windows to control the angle of incident light and minimize cross-talk
Implementation Method 2
The photodetector of a proximity sensor includes a number of photosensitive pixels. Proximity sensing (e.g., detecting a presence or proximity of an object near the sensor) involves transmitting light via the light source and then receiving light that reflects off an object-to-be-detected at the photodetector
Data Source
AI summary
An optical sensor, optical system, and proximity sensor are disclosed. An illustrative proximity sensor is disclosed to include a light source, a photodetector including a photo-sensitive area that receives incident light and converts the received incident light into an electrical signal, and a plurality of polarization layers stacked on the photodetector that limit light from becoming received incident light for the photo-sensitive area to light traveling toward the photodetector along a predetermined path.