Sensor Apparatus Difference Signal Evaluation for False Alarm Reduction
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Solution Overview
Problem
Existing photoelectrical proximity and hazard alarms are prone to false alarms due to interference from extraneous light and reflections, which can override the detection of intended objects, leading to unreliable object recognition.
Innovation Solution
A sensor apparatus with two receiving devices and an evaluation unit that generates a difference signal between their output signals, effectively reducing interference by differentiating between intended and extraneous radiation, and allowing for independent activation of transmitting devices to enhance object detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single receiving device is used to detect scattered light from an object, then the device complexity is low, but the reliability of object detection deteriorates due to interference from extraneous light and reflections
Solution Approach 1:
The single receiving device is segmented into two receiving devices (first receiving device and second receiving device), each detecting signals through different paths. This segmentation allows the system to differentiate between intended scattered light from the target object and extraneous light through reflections, thereby improving detection reliability while managing complexity through functional division
2Measurement precision
If the receiving device is made highly sensitive to detect weak scattered light signals, then the measurement precision improves, but the susceptibility to extraneous light interference increases causing false alarms
Solution Approach 1:
The evaluation device acts as an intermediary that processes signals from both receiving devices. It calculates the difference between the first output signal and the second output signal, effectively filtering out common extraneous light interference while preserving the genuine scattered light signal from the target object, thus maintaining high measurement precision while reducing false alarms
3Area of stationary object
If the transmission radiation is increased to improve the scattered light signal strength, then the detection range extends, but the interference from reflections and extraneous light also increases
Solution Approach 1:
The system extracts the genuine scattered light signal from the total received signal by taking the difference between signals from two receiving devices. This extraction process removes the harmful reflection components and extraneous light that affect both paths equally, allowing the use of higher transmission radiation to extend detection range without proportionally increasing interference
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 significantly reduces false alarms and improves the reliability of object detection by isolating intended radiation signals from extraneous interference, enabling precise recognition of objects, including smoke detection in smoke alarms.
Implementation Method 1
at least one transmitting device (3, 5, 111, 121) for transmitting a transmission radiation
Implementation Method 2
the reception radiation comprises a scattered light which is produced by at least partial scattering of the transmission radiation at the object that is to be captured
Implementation Method 3
two receiving devices (11, 12, 112, 122) for receiving in each case a reception radiation
Data Source
AI summary
A sensor apparatus for optically detecting an object includes (a) a first emitting device, configured to emit a first emission beam, (b) a first receiving device, configured to receive a first reception beam, (c) a second receiving device, configured to receive a second reception beam, and (d) an evaluation unit connected downstream of the first receiving device and the second receiving device. The first reception beam and/or the second reception beam contains scattered light which is produced when an at least partial scattering of the first transmission beam occurs at the object. The evaluation unit is coupled to the first receiving device and the second receiving device so as to receive a difference signal between a first output signal of the first receiving device and a second output signal of the second receiving device. The sensor apparatus may be incorporated in a proximity sensor and a danger warning system.