Multi-Band Flame Detector with Notch Filters
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Solution Overview
Problem
Traditional flame detectors are limited in their ability to detect flames outside the specific infrared optical band they are designed for, failing to distinguish between hydrocarbon and hydrogen-based flames, leading to false negatives and false positives from hot objects.
Innovation Solution
A multiple band flame detector design featuring an array of infrared detectors with a band reject structure that rejects light in the 2.7-4.4 µm range, using a combination of windows and notch filters to selectively pass wavelengths corresponding to hydrocarbon and hydrogen flames, while rejecting interfering radiation from hot objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bandpass filter is used to detect flames in one infrared optical band, then detection accuracy for that specific flame type is improved, but the ability to detect other flame types is lost
Solution Approach 1:
The detector is divided into multiple independent detection channels, each equipped with a bandpass filter tuned to a specific infrared wavelength range corresponding to different flame types. This segmentation allows each channel to specialize in detecting particular flame characteristics while the overall system maintains versatility across multiple flame types.
Solution Approach 2:
The detector system is designed to perform multiple detection functions simultaneously by incorporating several detector elements with different spectral response characteristics. Each element can detect different flame types (hydrocarbon, hydrogen, alcohol-based), making the single device universal for detecting multiple flame types without requiring separate detectors.
2Device complexity
If a single bandpass filter is used for flame detection, then device complexity is reduced, but false positives from hot objects increase
Solution Approach 1:
The detection system is segmented into multiple wavelength bands, each monitored by dedicated detector elements. This segmentation allows the system to distinguish between the spectral signature of actual flames and the thermal radiation from hot objects, reducing false positives while maintaining a relatively simple overall structure.
Solution Approach 2:
Bandpass filters serve as intermediary components that selectively transmit only specific wavelength ranges to the detector elements. These filters act as mediators between the incoming radiation and the detectors, blocking interfering radiation from hot objects while allowing flame-specific wavelengths to pass through, thereby reducing false positives.
3Adaptability or versatility
If multiple detector elements with different spectral responses are used, then flame type detection capability is improved, but device complexity increases
Solution Approach 1:
Multiple detector elements with different spectral responses are merged into a single integrated detector assembly. Each element is equipped with appropriate bandpass filters and optical elements, and all components are combined in one compact device housing, allowing simultaneous detection of multiple flame types without requiring multiple separate detector systems.
Solution Approach 2:
The detector system is designed as a universal multi-functional device where each detector element contributes to a broader detection capability. By integrating elements with different spectral responses (sensitive to hydrocarbon flames, hydrogen flames, alcohol-based flames, etc.), the system achieves universal flame type detection while maintaining a unified device structure rather than requiring separate specialized detectors.
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
Enables accurate detection of multiple flame sources with reduced false positives from hot bodies, maintaining a wide field of view and accommodating wavelength shifts due to non-orthogonal light incidence, thereby improving detection accuracy and reliability.
Implementation Method 1
A multiple band flame detector design featuring an array of infrared detectors with a band reject structure that rejects light in the 2.7-4.4 µm range
Implementation Method 2
using a combination of windows and notch filters to selectively pass wavelengths corresponding to hydrocarbon and hydrogen flames
Implementation Method 3
A multiple band flame detector design featuring an array of infrared detectors
Data Source
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AI summary
A flame detector (100) includes an infrared detector (110) and a first window (120) covering the infrared detector. A second window (125) is positioned in front of the first window. The flame detector is adapted to reject light having a wavelength below approximately 2 µm and to reject light having a wavelength above approximately 6µm, allowing detection of flame from multiple sources. In variations, the windows in combination with the infrared detector may provide the rejection or a band pass filter (130) provides the rejection. Still further variations utilize notch filters or a band reject filter to provide notches of light to the infrared detector corresponding to the wavelength of different flame sources to be detected.