Curve-Based Radiometric Calibration for Spaceborne LVF Hyperspectral Imagers
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Solution Overview
Problem
The challenge of radiometric calibration in hyperspectral imagers with programmable band selection imaging technology is exacerbated by the need for numerous radiometric correction coefficients, leading to resource-intensive data transmission, storage, and processing burdens, particularly in spaceborne systems.
Innovation Solution
A curve-based radiometric calibration method and system for spaceborne hyperspectral imagers, involving prelaunch and postlaunch calibration processes to establish and update radiometric calibration coefficients, utilizing a CMOS detector array and linear variable filter, with steps including matching, noise correction, and polynomial curve fitting to reduce resource requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional per-band measurement methods are used for radiometric calibration, then measurement precision is improved, but device complexity and resource consumption increase significantly
Solution Approach 1:
The patent merges the radiometric calibration process with the pushbroom imaging process by utilizing the imaging detector array to simultaneously perform both imaging and calibration functions. The calibration target is imaged along with the scene, and calibration coefficients are derived from the imaging data itself, combining what were previously separate operations into a unified process that reduces system complexity.
Solution Approach 2:
The imaging detector array is made multi-functional by using it for both scene imaging and radiometric calibration. The same detector array that captures spectral imagery is also used to measure the calibration target, eliminating the need for separate calibration detectors and reducing overall device complexity while maintaining calibration precision.
2Measurement precision
If per-band radiometric correction coefficients are measured for all bands, then measurement precision is improved, but loss of information and resource burden increase
Solution Approach 1:
The patent extracts only the essential calibration information needed for radiometric correction by deriving coefficients from pushbroom imaging data of a calibration target. Instead of measuring and storing all raw spectral data across hundreds of bands, the method extracts the specific radiometric correction coefficients required for accurate spectral radiance calculation, reducing data transmission and storage requirements.
Solution Approach 2:
The patent inverts the traditional calibration approach by deriving calibration coefficients from imaging data rather than requiring separate dedicated calibration measurements for each band. By using the pushbroom imaging process itself to obtain calibration information, the method reduces the data burden while maintaining measurement precision.
3Adaptability or versatility
If full-spectrum hyperspectral imaging is performed, then adaptability is improved, but device complexity and resource consumption increase
Solution Approach 1:
The patent segments the spectral range into multiple bands and performs radiometric calibration separately for each band using pushbroom imaging. This segmentation allows the system to handle full-spectrum imaging adaptability while reducing processing complexity by treating each band independently with its own calibration coefficients, rather than processing all bands simultaneously as a complete dataset.
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 method enables efficient, universal, and simplified on-orbit radiometric calibration, reducing satellite resources and providing a normalized calibration reference for hyperspectral imagers, addressing the challenges of high inter-band correlation and resource intensity.
Implementation Method 1
A linear variable filter is an optical device with its spectral properties linearly changing along with mechanical position, which can decompose incident polychromatic light into spectra corresponding to positions
Implementation Method 2
With the linear variable filter (LVF) serving as a light splitter to combine with a Complementary Metal Oxide Semiconductor (CMOS) detector array
Data Source
AI summary
The present disclosure provides a curve-based radiometric calibration method and system of a spaceborne hyperspectral imager, which belongs to the field of remote-sensing optical technologies. A new radiometric calibration coefficient curve is introduced to describe the radiometric properties of sensor response, providing the radiometric calibration coefficients of all bands of the hyperspectral camera with linear variable filter (LVF) within an imaging spectral range to match the implementation of the programmable band selection imaging technology, and thereby efficiently and simply implementing single-band imaging, integral imaging of adjacent band, imaging of randomly-selected band combination and within-spectral-range cyclic imaging. In the present disclosure, the radiometric calibration coefficient is used to cover the entire imaging spectral range of the hyperspectral camera and match the implementation of the programmable band selection imaging technology, and realizing on-orbit absolute radiometric calibration with simple flow and strong universality.