Thermopile Infrared Detector with Negative Feedback for Static Object Detection
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Solution Overview
Problem
Conventional PIR-based presence detection systems are limited in detecting stationary objects and require complex designs to determine direction of movement and number of objects, often resulting in false alarms and inefficiencies.
Innovation Solution
A detection device using thermopile sensors and a processing unit that generates contrast values by comparing sensor signals to reference values, applying negative feedback, and determining object presence, capable of detecting both static and moving heat-emitting objects without the need for Fresnel lenses or timers, and can adapt to environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PIR sensors are used for presence detection, then the system can detect moving heat-generating objects, but it cannot reliably detect stationary objects and requires complex additional components (Fresnel lenses, timers, multiple sensing elements) to determine direction and count objects
Solution Approach 1:
The patent replaces the mechanical/optical system of Fresnel lenses and multiple spaced sensing elements with a single thermopile sensor combined with digital signal processing. The thermopile sensor directly converts infrared radiation into electrical signals, eliminating the need for mechanical focusing components and complex optical arrangements.
Solution Approach 2:
The system uses the natural thermal radiation properties of objects and the inherent characteristics of the thermopile sensor to automatically distinguish between stationary and moving objects. The differential measurement technique self-adjusts to compensate for environmental changes, eliminating the need for manual calibration or complex reference systems.
2Reliability
If PIR sensors with voltage bucking configuration are used, then the system becomes insensitive to environmental temperature changes, but it requires multiple sensing elements and complex readout circuits to achieve this insensitivity
Solution Approach 1:
The patent extracts the temperature sensitivity issue from the sensor system by using the thermopile sensor's inherent ability to measure absolute temperature differences. Instead of requiring multiple sensors to cancel out environmental effects, the single thermopile sensor directly measures the temperature difference between the detected object and the ambient environment, automatically achieving environmental insensitivity.
Solution Approach 2:
The system changes the measurement parameter from detecting absolute infrared radiation levels to detecting temperature differences. The thermopile sensor naturally outputs signals proportional to temperature differences, and the processing unit uses this differential measurement to automatically compensate for environmental temperature variations without requiring complex circuitry.
3Measurement precision
If conventional PIR detection methods are used, then the system can detect moving objects, but it produces false alarms and cannot accurately determine the number and direction of objects
Solution Approach 1:
The patent implements feedback through differential measurement, where the thermopile sensor continuously compares the infrared radiation from the detected object with the ambient background radiation. The processing unit analyzes the differential signal to determine object presence, direction, and count, providing feedback that distinguishes true detections from environmental variations and eliminates false alarms.
Solution Approach 2:
The system dynamically adapts to changing environmental conditions by continuously measuring the background infrared radiation and subtracting it from the total received signal. This dynamic background subtraction allows the system to accurately detect objects regardless of environmental changes, improving reliability and reducing false alarms.
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 provides robust and efficient presence detection, distinguishing between immobile heat sources and mobile objects, reducing false alarms and enabling accurate counting and direction determination of objects, while being compact and requiring minimal user adjustments.
Implementation Method 1
at least one infrared radiation sensing element adapted for generating a sensor signal related to a quantity of infrared radiation received from within the surveillance area
Implementation Method 2
sensors for detecting infrared radiation emitted by these objects
Implementation Method 3
generating a contrast value by comparing the obtained sensor signal to a reference value
Implementation Method 4
adjusting the reference value such that negative feedback is applied to the contrast value
Data Source
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AI summary
The present invention relates to a detection device (10) and a method for detecting a presence of an object (9) in a surveillance area (8). The device (10) comprises at least one infrared radiation sensing element (11) each adapted for generating a sensor signal related to a quantity of infrared radiation received from within the surveillance area (8) by the infrared radiation sensing element (11), a processing unit (12) and an output means (13) for outputting a determined presence of the object (9) and/or a property derived therefrom. The processing unit (12) is adapted for: obtaining the at least one sensor signal; generating at least one contrast value by comparing the at least one sensor signal to at least one reference value; determining the presence of the object (9) by evaluating a condition on said at least one contrast value; and adjusting the at least one reference value such that negative feedback is applied to the at least one contrast value.