SWIR Radiance Ratio Ice Detection for Aircraft
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Solution Overview
Problem
Current systems for detecting ice and icing conditions on surfaces, particularly for ground-based and airborne vehicles, face challenges in accurately distinguishing between ice and other dielectric materials, leading to false reports and inadequate safety measures.
Innovation Solution
A multi-spectral measurement system using shortwave infrared (SWIR) cameras with filters at specific spectral bands (2.05-2.15 µm and 2.20-2.30 µm) to differentiate between liquid water and ice by measuring radiance ratios, providing accurate detection and size estimation of supercooled liquid water droplets and ice particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If polarization measurement is used to detect slippery ice on surfaces, then detection capability is improved, but false reporting occurs because other dielectric materials (wet/oily surfaces) also polarize light
Solution Approach 1:
The patent changes the detection parameter from polarization measurement to multi-spectral radiance measurement. By measuring radiance at multiple spectral bands (including SWIR regions where ice has distinctive absorption features), the system can differentiate ice from other dielectric materials based on their unique spectral signatures, thereby maintaining detection capability while eliminating false alarms from wet or oily surfaces.
Solution Approach 2:
The patent introduces spectral radiance ratios as an intermediary measurement approach. Instead of directly measuring polarization, the system uses radiance ratios between different spectral bands as a mediator to indirectly identify ice presence. This intermediary approach provides more specific information about the material properties, enabling discrimination between ice and other reflective surfaces.
2Device complexity
If temperature-based detection is used to warn of freezing conditions, then simplicity is maintained, but accuracy deteriorates because air temperature near freezing does not indicate surface ice presence
Solution Approach 1:
The patent replaces the thermal-based detection mechanism (temperature sensing) with an optical measurement mechanism (radiance measurement). By substituting thermal sensing with optical spectroscopy, the system can directly detect the physical presence of ice on surfaces rather than inferring it from ambient temperature, providing accurate surface condition information while maintaining practical system complexity through the use of standard optical sensors.
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 system effectively detects ice and supercooled water droplets on surfaces and in the airspace, enhancing safety by providing early warnings and reducing false alerts, thus preventing accidents and ensuring reliable detection before hazardous conditions occur.
Implementation Method 1
A multi-spectral measurement system using shortwave infrared (SWIR) cameras with filters at specific spectral bands (2.05-2.15 µm and 2.20-2.30 µm) to differentiate between liquid water and ice by measuring radiance ratios
Implementation Method 2
capable of detecting supercooled water droplets that freeze when impacting the surfaces of airborne vehicles, such as aircrafts, Unmanned Air Vehicles (UAVs) and other objects of interest
Data Source
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AI summary
A system for detecting ice or supercooled large droplets within an area of interest having a detection system measuring radiance or reflectance of the area of interest when exposed to shortwave infrared radiation having a wavelength in the range of about 2.05 μm to about 2.30 μm. The detection system measures the radiance or reflectance in a first band having a wavelength in the range of about 2.05 μm to about 2.15 μm and outputting a first band signal, and further measures the radiance or reflectance in a second band having a wavelength in the range of about 2.15 μm to about 2.30 μm and outputting a second band signal. A processing unit determines a ratio of the first band signal and the second band signal and compares the ratio to a predetermined critical ratio and outputs a determination signal indicating presence of ice or supercooled water droplets.