Multi-Wavelength Smoke Detection with Ambient Light Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Smoke detectors with external sampling volumes face challenges in distinguishing smoke particles from ambient light and nuisance particles, leading to false alarms or missed responses due to difficulties in isolating signals and distinguishing particle types.
Innovation Solution
A smoke detector employing a proximity sensor with light emitters and detectors that emit and measure light at different wavelengths, combined with an ambient-light sensor, to differentiate between smoke and nuisance particles by analyzing the scattering behavior and ambient light corrections, allowing for accurate identification of smoke particles and obstructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single wavelength of light is used for smoke detection, then the device complexity is reduced, but the ability to distinguish smoke particles from nuisance particles and ambient light deteriorates
Solution Approach 1:
The detection system is segmented into multiple independent light sources emitting at different wavelengths (e.g., 850nm and 1550nm), with each wavelength providing distinct scattering information. This segmentation allows the system to differentiate between particle types based on their wavelength-dependent scattering characteristics without requiring a single overly complex detection mechanism.
Solution Approach 2:
The system transitions from single-wavelength detection to multi-wavelength detection, adding a spectral dimension to the measurement space. By measuring light scattering at multiple wavelengths, the system creates a more comprehensive characterization of particles, enabling differentiation between smoke, nuisance particles, and ambient light sources through their unique spectral scattering signatures.
2Device complexity
If ambient light correction is not implemented, then the device complexity is reduced, but false alarms increase due to inability to isolate smoke signals from ambient light
Solution Approach 1:
An ambient light sensor acts as an intermediary component that specifically measures ambient light levels without being exposed to the emitted detection wavelengths. This intermediary sensor provides separate ambient light measurements that are then used to correct the main detection channel, effectively isolating the smoke scattering signal from ambient light interference through differential measurement.
Solution Approach 2:
The system implements feedback by continuously monitoring ambient light levels and using this information to dynamically adjust and correct the smoke detection signals. The ambient light measurements feed back into the signal processing algorithm, which subtracts or compensates for ambient light contributions, thereby maintaining accurate smoke detection despite varying ambient light conditions.
3Loss of time
If external sampling volume is used, then the response time is improved, but the ability to isolate smoke signals from ambient light and nuisance particles deteriorates
Solution Approach 1:
The system changes the parameter of light wavelength by using multiple discrete wavelengths for detection. Different particle types exhibit characteristic scattering patterns across wavelengths, with smoke particles showing distinct scattering ratios compared to nuisance particles. By measuring and comparing scattering at multiple wavelengths, the system can isolate smoke signals even in the external sampling volume where ambient light and nuisance particles are present.
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 significantly reduces false alarms and response delays by accurately distinguishing smoke particles from nuisance particles and ambient light, enhancing the detection efficiency and reliability of smoke detectors with external sampling volumes.
Implementation Method 1
a first measurement of light including a first wavelength originating outside the housing is acquired while emitting light of approximately the first wavelength with at least one said light emitter... a second measurement of light including a second wavelength originating outside the housing is acquired while emitting light of approximately the second wavelength with at least one said light emitter
Implementation Method 2
an ambient light level outside of the housing is detected... The second measurement of light including the first wavelength is corrected based on (i) the detected ambient light level
Data Source
AI summary
In accordance with certain embodiments, a smoke detector determines the presence of smoke particles outside its housing based on measurements of light detected at different wavelengths and corrected based on an ambient light level.