Multi-sensor Proximity Sensing Using Near and Far Zone Light Sensors
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Solution Overview
Problem
Conventional proximity sensors using a single photodetector face challenges in accurately detecting objects at varying distances due to interference from reflections off optically transmissive media, leading to blind spots and the need for costly mechanical barriers to mitigate these issues.
Innovation Solution
Employing multiple optical sensors, including a near zone light sensor and a far zone light sensor positioned on a substrate, which discriminate between light reflected from objects and optically transmissive media, allowing for the detection of objects at different distances without mechanical barriers by analyzing output signals from both sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single photodetector is used to detect reflected light, then the device complexity is reduced, but measurement precision deteriorates due to interference from reflections off optically transmissive media
Solution Approach 1:
The single photodetector is segmented into multiple photodetectors (first photodetector and second photodetector) that are spatially separated. Each photodetector detects light from different zones (near zone and far zone), allowing the system to discriminate between reflections from the optically transmissive medium and reflections from objects at different distances, thereby improving measurement precision without excessive complexity
Solution Approach 2:
The solution transitions from a single detection point to multiple detection points in different spatial zones. By adding the dimensional aspect of spatial separation between near zone and far zone photodetectors, the system can distinguish between different sources of reflected light (medium vs. object) based on their spatial origin, improving detection accuracy
2Measurement precision
If mechanical barriers are added to block reflections from optically transmissive media, then measurement precision improves, but device complexity and manufacturing costs increase
Solution Approach 1:
The solution replaces mechanical barriers (physical structures to block reflections) with an optical/electronic approach using multiple photodetectors positioned in different zones. The discrimination between medium reflections and object reflections is achieved through spatial separation and signal processing rather than mechanical blocking, reducing device complexity and manufacturing costs while maintaining measurement precision
Solution Approach 2:
The multiple photodetectors act as intermediaries that sample the reflected light from different spatial zones. Instead of using mechanical barriers to block unwanted reflections, the system uses photodetectors positioned at different locations to selectively detect light from different zones, with the processor circuit then discriminating between medium and object reflections based on the pattern of signals received
3Measurement precision
If multiple photodetectors are used to detect light from different zones, then measurement precision improves, but device complexity increases
Solution Approach 1:
The detection system is segmented into distinct functional zones with dedicated photodetectors for each zone (near zone photodetector and far zone photodetector). This segmentation allows each photodetector to specialize in detecting light from its specific zone, improving measurement precision while keeping the overall structure manageable through clear functional division
Solution Approach 2:
The processor circuit performs multiple functions: it receives signals from multiple photodetectors, discriminates between reflections from the optically transmissive medium and reflections from objects, determines object presence, and generates output signals. This multi-functionality consolidates complex processing tasks into a single component, offsetting the added complexity of having multiple photodetectors
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
Enables accurate detection of objects at varying distances while avoiding the use of restrictive mechanical barriers, improving sensor performance and reducing manufacturing complexity and costs.
Implementation Method 1
receive reflected source light from the object and the optically transmissive medium
Implementation Method 2
A lens is positioned over the plurality of photodetectors to focus the source light received from the optically transmissive medium and the object on to the plurality of photodetectors
Implementation Method 3
A receiver includes a plurality of photodetectors, at least one of the plurality of photodetectors configured as a near zone light sensor and at least one of the plurality of photodetectors configured as a far zone light sensor
Data Source
AI summary
An apparatus includes a light source to generate source light through an optically transmissive medium to an object. A receiver includes a near zone light sensor and a far zone light sensor positioned on a substrate with the light source. The near zone light sensor is positioned on the substrate to, in response to the generated source light, receive reflected source light from the object and the optically transmissive medium. The far zone light sensor is positioned on the substrate to, in response to the source light, receive the reflected source light from the object and to receive a reduced quantity of the reflected source light from the optically transmissive medium compared to the near zone light sensor.