Aperture-Controlled Photoelectric Sensor FOV Overlap
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Solution Overview
Problem
Retro-reflective photoelectric sensors face limitations in detection range due to the 'white card effect,' where reflective materials incorrectly indicate no obstruction, leading to false sensing events and reduced effective range, especially in environments with scattering or reflective surfaces.
Innovation Solution
A photoelectric sensor system with adjustable aperture modules that control the field of view overlap between the transmitter and receiver, allowing for customizable apertures to minimize false positives, increase detection range, and maintain alignment under disturbances, featuring a registration/alignment pin for precise orientation and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the minimum sensor threshold is increased to reduce false positives from reflective materials, then the reliability of obstruction detection is improved, but the maximum detection range is reduced
Solution Approach 1:
The patent applies local quality by using multiple detectors with different field-of-view characteristics. Specifically, a first detector with a narrower field-of-view is used to detect obstructions at longer ranges with higher reliability, while a second detector with a wider field-of-view detects obstructions at closer ranges. This allows the system to maintain high detection reliability across the entire detection range without compromising maximum range, as each detector operates in its optimal performance zone.
2Reliability
If the field of view overlap between transmitter and receiver is increased to improve detection of reflective materials, then the resistance to white card effect is improved, but the detection range is reduced
Solution Approach 1:
The patent applies segmentation by dividing the detection task between multiple detectors with different field-of-view overlaps. The first detector is configured with a specific field-of-view overlap optimized for detecting reflective materials at longer ranges, while the second detector has a different field-of-view overlap optimized for closer ranges. This segmentation allows the system to maintain resistance to white card effect across the entire detection range without sacrificing maximum range, as each detector handles the detection in its optimal range zone.
3Device complexity
If a single detector configuration is used to simplify the system, then the device complexity is reduced, but the ability to detect obstructions at various ranges and conditions is compromised
Solution Approach 1:
The patent applies universality by designing a sensor system where multiple detectors serve different functional roles within a single integrated apparatus. The first detector with narrower field-of-view functions as a long-range obstruction detector, while the second detector with wider field-of-view functions as a close-range detector. This multi-functionality allows the system to maintain versatility across various detection ranges and conditions while keeping the overall device complexity manageable through integrated design and shared optical components.
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 system enhances resistance to the 'white card effect,' increases maximum sensor range, and maintains reliable signal detection in diverse environmental conditions, including dense smoke or humidity, while being robust against displacement disturbances.
Implementation Method 1
A photoelectric sensor system includes an emitter having an emitter optical axis and a nominal emitter field of view (FOV), the emitter being configured to generate an optical signal directed along an incident optical path from the emitter to a retro-reflective substrate
Implementation Method 2
a retro-reflective substrate operable to redirect a portion of light from the incident optical path to a reflected optical path
Implementation Method 3
An aperture and focal length of an optical system may determine the cone angle of a bundle of rays that are emitted or are accepted by an optical system
Implementation Method 4
a photodetector mounted adjacent to and offset from the emitter, the photodetector having a photodetector optical axis and a nominal photodetector field of view (FOV), the photodetector being configured to receive at least a portion of the generated optical signal reflected by the retro-reflective substrate
Data Source
AI summary
Apparatus and associated methods relate to a photoelectric sensor system having a transmitter and a receiver, and at least one aperture module configured to modify a nominal field of view (FOV) of the transmitter and/or receiver, such that an overlap between the transmitter and receiver FOVs is controlled. In an illustrative example, the aperture module may be a plate having respective receiver and transmitter apertures. The transmitter and/or receiver apertures may be aligned or slightly offset from respective transmitter and receiver optical axes. The transmitter and/or receiver apertures may have a specific size/shape/position that produces a custom predetermined FOV overlap. At least one registration/alignment pin may extend through the aperture plate, a baffle, and a lens module to control orientation. The photoelectric sensor system may advantageously (1) be more resistant to the “white card effect,” (2) increase maximum sensor range, and (3) control the shape/size/overlap of the FOVs.