Hyperspectral Instrument Characterization Using Fabry-Perot Etalon
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Solution Overview
Problem
Current methods for characterizing the spectral response function of hyperspectral instruments are limited, particularly in providing monochromatic energy across a wide range of wavelengths, leading to inefficient characterization of performance parameters like spectral smile, keystone distortion, and MTF.
Innovation Solution
A system using a Fabry-Perot etalon in combination with a radiation source, where energy is collimated and passed through the etalon to produce a set of equally spaced transmission lines, allowing simultaneous characterization of multiple wavelengths and spatial scanning to obtain performance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser sources are used to provide monochromatic energy, then spectral line precision is improved, but wavelength coverage and measurement efficiency deteriorate because only one wavelength can be provided at a time
Solution Approach 1:
The continuous spectrum from the broadband source is segmented into multiple discrete wavelength lines by the Fabry-Perot etalon. The etalon acts as a spectral filter that transmits only specific wavelengths according to its resonance condition, creating a comb-like spectrum with precisely spaced lines. This allows simultaneous measurement at multiple wavelengths while maintaining the precision benefits of monochromatic sources.
Solution Approach 2:
The Fabry-Perot etalon produces a periodic transmission spectrum with equally spaced wavelength lines. By scanning the etalon spacing or tilting angle, the entire comb spectrum can be swept across the detector array, enabling systematic characterization of the instrument's spectral response function across the full wavelength range through periodic sampling.
2Measurement precision
If lasers are used as point sources, then spectral purity is improved, but spatial coverage deteriorates because only one pixel is illuminated at a time
Solution Approach 1:
The solution transitions from one-dimensional sequential pixel illumination (single point source) to two-dimensional simultaneous illumination by spatially distributing the Fabry-Perot etalon's comb spectrum across the entire detector array. Each spatial location on the detector receives illumination from the same spectral comb, enabling parallel measurement across all pixels while maintaining spectral purity.
3Productivity
If Fourier transform spectrometer is used to provide full spectrum simultaneously, then wavelength coverage is improved, but data processing complexity and signal-to-noise ratio deteriorate
Solution Approach 1:
Instead of using the full Fourier transform approach that processes the entire spectrum simultaneously, the invention extracts specific discrete wavelength lines from the broadband source using the Fabry-Perot etalon. This selective extraction simplifies the data processing requirements while maintaining comprehensive wavelength coverage, as the etalon's transmission peaks provide naturally separated spectral channels that map directly to detector pixels.
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 efficient and accurate characterization of hyperspectral instruments by providing multiple discrete wavelengths simultaneously, simplifying data processing and reducing measurement time, while allowing direct measurement of key performance parameters like spectral smile and keystone distortion.
Implementation Method 1
The test instrument includes a Fabry-Perot etalon comprising at least first and second etalon plates. The Fabry-Perot etalon is arranged to receive output from the radiation source and to provide output comprising a comb of transmission lines
Implementation Method 2
The radiation source may comprise a blackbody radiation source providing energy at a range of wavelengths
Data Source
AI summary
A method and apparatus for characterizing the spectral response function of hyperspectral electro-optical instruments or imaging spectrometers are provided. The system includes a test instrument that provides energy comprising multiple discrete wavelengths to the entrance slit of an instrument under test simultaneously. The provided energy can be scanned in the spectral dimension by changing the optical distance between the plates of a Fabry-Perot etalon incorporated into the test instrument. In addition, the energy provided to the instrument under test can be scanned in the spatial dimension by changing the location along the slit of the instrument under test at which the energy from the test instrument is provided.