Airborne Infrared Spectrometer With Filter Array
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Airborne infrared spectrometers face reliability issues due to mechanical vibrations, which cause equipment malfunction and spectral instability, and circular variable filters limit spectral scanning capabilities by only allowing continuous changes, skewing measurements from non-uniform spectral bands.
Innovation Solution
A background subtracted spectrometer with a filter array comprising linear variable filters and bandpass filters, coupled to a focal plane array, replaces the circular variable filter, allowing electronic spectral scanning and conductive cooling with liquid nitrogen to enhance thermal stability and signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a circular variable filter is used for spectral scanning, then spectral measurements can be obtained, but mechanical vibrations cause equipment malfunction and spectral instability
Solution Approach 1:
The patent replaces the mechanical circular variable filter with a fixed filter array consisting of multiple discrete spectral band filters. This eliminates moving parts that are susceptible to mechanical vibrations, thereby resolving the contradiction between obtaining spectral measurements and maintaining equipment reliability under vibrational stress.
Solution Approach 2:
The continuous spectral scanning function is segmented into discrete spectral bands, each covered by a separate filter element in the filter array. This segmentation allows the system to capture multiple spectral bands simultaneously without requiring mechanical movement, thus improving reliability while maintaining spectral measurement capability.
2Measurement precision
If a circular variable filter is used, then spectral scanning can be performed, but spectral stability deteriorates due to target position changes in field-of-view
Solution Approach 1:
The mechanical circular variable filter is replaced with a fixed filter array, eliminating the spectral shift problem that occurs when target position changes in the field-of-view. Each filter element maintains a fixed spectral response independent of target position, thereby improving spectral stability while preserving measurement accuracy.
3Productivity
If a circular variable filter is used for spectral scanning, then continuous spectral changes can be achieved, but rapid increasing or decreasing radiation sources skew measurements
Solution Approach 1:
The continuous spectral scanning approach is replaced with a segmented filter array that captures multiple discrete spectral bands simultaneously. This allows rapid data collection across widely spaced spectral bands without the skewing effect caused by rapidly changing radiation sources, as all bands are measured at the same moment rather than sequentially.
Solution Approach 2:
The system uses periodic modulation (chopping) to alternately admit background radiation and target radiation to the detector. This periodic action enables background subtraction to improve signal-to-noise ratio while maintaining the ability to rapidly sample multiple spectral bands, resolving the contradiction between data collection speed and measurement accuracy.
4Adaptability or versatility
If a circular variable filter is used, then spectral scanning can be performed, but the system becomes complex with additional components
Solution Approach 1:
The single circular variable filter is replaced with a segmented filter array where each segment corresponds to a specific spectral band. This segmentation provides adaptability for selecting different spectral bands while simplifying the overall system by eliminating the mechanical scanning mechanism, relay lens, and associated control systems.
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 improved spectral stability, sensitivity, and field-of-view uniformity, reducing equipment failures and enabling rapid data collection across widely spaced spectral bands.
Implementation Method 1
a linear variable filter adapted to selectively pass a first spectral band for wavelengths in the range from about 1.5 to about 3.0 μm
Implementation Method 2
a first bandpass filter adapted to selectively pass a second spectral band for wavelengths in the range from about 2.0 to 2.5 μm; and a second bandpass filter adapted to selectively pass a third spectral band for wavelengths in the range from about 3.5 to 3.9 μm
Implementation Method 3
a detector comprising a focal plane array configured to receive the plurality of different spectral bands of infrared radiation simultaneously transmitted through the filter array, the detector being configured to generate one or more electrical signals indicative of infrared radiation intensity
Implementation Method 4
a dewar containing liquid nitrogen, wherein the filter array and the detector may be conductively cooled by the liquid nitrogen
Data Source
AI summary
A background subtracted spectrometer for airborne infrared radiometry. The background subtracted spectrometer may comprise: a filter array, a detector, and a dewar containing liquid nitrogen. The filter array may be configured to selectively pass different spectral bands of infrared radiation. The filter array may comprise: at least one linear variable filter and a plurality of bandpass filters. The detector may comprise a focal plane array configured to receive the different spectral bands of infrared radiation simultaneously transmitted through the filter array. The detector may generate one or more electrical signals indicative of infrared radiation intensity as a function of wavelength. The filter array may be coupled to the focal plane array of the detector, and the filter array and detector may be conductively cooled by the liquid nitrogen to improve signal-to-noise ratio and spectral measurements. The background subtracted spectrometer preferably lacks a circular variable filter and relay lens.