Infrared Sensor Signal Processing for False Alarm Reduction
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Solution Overview
Problem
Existing motion detection systems using passive infrared sensors face challenges in distinguishing between genuine intrusion signals and parasitic heat sources, leading to false alarms and missed detections, particularly with low-amplitude signals.
Innovation Solution
A device and method employing a pyroelectric sensor with a processing unit that utilizes two distinct evaluation means to determine peak amplitude and signal variation, allowing for selective alarm generation based on adjustable criteria, thereby differentiating between intrusion and parasitic signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If signal integration method is used to reduce false alarms from short duration peaks, then false alarm rate is reduced, but low amplitude intrusion signals are rejected
Solution Approach 1:
The patent divides the signal evaluation into two separate processing chains: one for detecting threshold crossings (to identify potential intrusions) and another for integrating the signal over time (to filter false alarms). By segmenting the detection criteria into multiple independent evaluations, the system can detect low-amplitude signals through the threshold crossing method while simultaneously rejecting false alarms through the integration method, thus resolving the contradiction between detection sensitivity and false alarm rate.
2Reliability
If multiple signal sources are used to improve detection quality and reliability, then detection reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the single pyroelectric sensor perform multiple functions by implementing two different signal processing chains within the same detection device. The sensor simultaneously feeds into both a threshold crossing detection path and a signal integration path, allowing one component to serve dual detection purposes. This multi-functionality approach improves detection reliability without requiring multiple separate sensors or complex additional hardware, thus avoiding the complexity and cost increase that would result from using multiple signal sources.
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 approach enhances detection reliability by reducing false alarms and improving the detection of low-amplitude signals while maintaining system simplicity and reducing resource usage.
Implementation Method 1
an optical system divides the space to be monitored into zones and focuses on a pyroelectric sensor the variations in heat caused by the movements of people inside the protected volume. The sensor produces on its output a signal proportional to the power of infrared radiation collected
Implementation Method 2
Passive infrared (PIR) sensors and detectors, introduced in the mid-1970s
Data Source
Figure 1
Figure 2
Figure 3A~5B
AI summary
The present invention relates to a presence and/or movement detection device by infrared measurement, comprising: - at least one infrared radiation sensor (2) delivering an electrical measurement signal (EMS), - a means (3) for detection and selective triggering of a processing time window (FTT), - a processing unit (4) comprising means (5, 5') for processing the signal (EMS), as well as a means (6) for verifying intrusion or presence criteria, device (1) characterized in that the processing unit (4) comprises two distinct operational means (5 and 5') for processing the electrical measurement signal (EMS), namely, on the one hand, of the value of the peak amplitude and occurrences of exceeding threshold values and, on the other hand, of the variation of the amplitude of the electrical signal (EMS).