Pyroelectric Motion Sensor Phase Discrimination
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Solution Overview
Problem
Existing motion detection systems using infrared radiation detectors often generate false alarms due to non-specific responses to temperature changes and small animal movements, lacking the ability to differentiate between human and animal motion effectively.
Innovation Solution
The implementation of a motion sensor system with two tiers of monitored volumes offset from each other, where the phase difference between the infrared radiation signals from these tiers is used to distinguish human motion from animal motion by correlating with a critical phase angle, reducing false positives and enhancing specificity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single infrared detector is used to monitor a large space, then the device complexity is reduced, but the measurement precision decreases leading to false alarms
Solution Approach 1:
The detector is divided into multiple detector elements arranged in a specific pattern (e.g., diamond pattern with differentially opposed pairs). Each element independently detects infrared radiation from different directions, allowing the system to maintain simple overall structure while achieving precise motion detection through the coordinated response of segmented elements
Solution Approach 2:
The detector elements are configured with asymmetric arrangements and different polarities. The differentially opposed pairs have opposite polarization directions, creating asymmetric response patterns that enable the system to distinguish between human motion (producing characteristic phase differences) and animal motion or environmental changes (producing different signal patterns), thereby improving measurement precision without increasing device complexity
2Measurement precision
If multiple detector elements with different configurations are used to distinguish human motion from animal motion, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
Multiple detector elements with different configurations are merged into a single integrated detector substrate. The differentially opposed pairs of elements are combined in one detector unit, allowing the system to achieve high measurement precision for human motion detection while maintaining relatively simple device structure through the unified detector design
Solution Approach 2:
The detector elements are designed to perform multiple functions simultaneously: they detect infrared radiation from various directions, generate differential signals for motion analysis, and provide phase difference information for distinguishing human from animal motion. This multi-functionality allows the detector structure to achieve high measurement precision without requiring separate dedicated components for each function, thereby limiting the increase in device complexity
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 effectively reduces false alarms by accurately differentiating between human and animal motion, improving the reliability of motion detection in security and lighting systems.
Implementation Method 1
A typical infrared detector utilizes a pyroelectric or piezoelectric substrate with a detector element that consists of conductive areas on opposite sides of the substrate, acting as a capacitor. As the substrate changes temperature, charge is added or subtracted to the capacitor, changing the voltage across the capacitor.
Implementation Method 2
An infrared detector detects changes in mid-infrared (IR) radiation having a wavelength of about 6-14 microns. These changes are due to temperature differences between a warm object, such as a warm blooded animal, and its background environment as the warm object moves through that environment.
Data Source
Figure 1A~1D
Figure 2A~3
Figure 4A~4D
AI summary
A motion sensor has at least two tiers of monitored volumes that are offset from each other. Electromagnetic radiation, such as infrared light, is directed from the monitored volumes onto at least two sets of detector elements having separate outputs on a pyroelectric substrate of an infrared detector. As a warm object, such as a human or an animal, moves through the monitored volumes, the warmth from the object causes the voltage on the outputs of the infrared detector to change. The resultant waveforms are compared and if the two waveforms have a phase relationship corresponding to a critical phase angle that is based on the pitch of the monitored volumes and the offset between the tiers of monitored volumes, an animal-immune motion indication is generated.