Infrared Motion Sensor Using Non-Uniform Thermal Target
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Solution Overview
Problem
Conventional passive infrared (PIR) motion sensors face challenges in accurately controlling detection range and are affected by varying temperature and environmental conditions, leading to inconsistent performance in monitoring human-sized objects.
Innovation Solution
A defined target infrared motion sensor system that includes an IR sensor with a target emitting a non-uniform pattern of IR radiation, allowing the processor to compare sensor output signals with a target signature signal to detect deviations and accurately monitor for objects within the monitored volume, using either spatially or temporally non-uniform targets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional passive infrared sensors are used to monitor long-range volumes, then the detection range is extended, but the detection accuracy and control over detection range deteriorate due to varying temperature and environmental conditions
Solution Approach 1:
A target object is introduced as an intermediary between the sensor and the environment. The target has controlled thermal properties that create a distinctive IR signature, serving as a reference mediator that allows the sensor to distinguish between environmental variations and actual intrusions, thereby maintaining accuracy over long detection ranges
Solution Approach 2:
The system changes the thermal parameters of the target object to create a non-uniform temperature distribution or temporal temperature variation. This creates a distinctive IR radiation pattern that serves as a recognizable signature, allowing the sensor to differentiate between the target and background environmental variations, thus improving detection precision while maintaining extended range
2Volume of stationary object
If conventional passive infrared sensors monitor large volumes, then the coverage area is increased, but the ability to accurately identify human-sized objects deteriorates due to background interference
Solution Approach 1:
The target object acts as an intermediary reference within the monitored volume. By establishing a known thermal signature from the target, the system creates a baseline for comparison that enables accurate identification of human-sized objects against the background, even when monitoring large volumes
Solution Approach 2:
The system applies local quality by creating a non-uniform temperature distribution in specific regions of the monitored volume through the target object. This localized thermal characteristic creates a distinctive IR signature that can be differentiated from uniform background radiation, improving object identification accuracy across large monitoring areas
3Measurement precision
If active beam sensors are used with small monitored volumes, then detection precision for small objects is improved, but the monitored volume becomes too small for practical human-sized object detection
Solution Approach 1:
The system transitions from monitoring only spatial position to monitoring temporal temperature variations as an additional dimension. By detecting changes in temperature over time at the target location, the system can identify human-sized objects crossing the monitored area while maintaining a larger effective monitoring volume, thus resolving the contradiction between precision and volume
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 provides a controlled detection range and improved accuracy in identifying human intrusions by utilizing a processor to verify the presence of a target and detect deviations, reducing false alarms and enhancing security monitoring.
Implementation Method 1
a target positioned within the field of view of the sensor which emits a non-uniform pattern of IR radiation
Implementation Method 2
an infrared (IR) detector which is generally responsive to mid-IR light in the 6-14 micron wavelength range. The detector, in turn, provides an electrical signal responsive to changes in the effective blackbody temperature
Data Source
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AI summary
An infrared motion sensor system has an infrared (IR) sensor having a predetermined field of view, a target positioned within the field of view of the sensor which emits a spatially or temporally non-uniform pattern of IR radiation, and a processor which receives an output signal from the IR sensor, compares the received output signal to a signature temperature profile signal corresponding to the non-uniform pattern of IR radiation emitted by the target, and detects deviation of the sensor output signal from the signature temperature profile signal, indicating intervention of an object in a monitored volume between the target and sensor. The size of the target may be of the order of human size.