Infrared Camera Flat Field Correction via Segmented Calibration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing thermal imaging systems face performance degradation due to non-uniform responses among infrared detectors and out-of-field infrared radiation from mechanical components, which conventional calibration techniques fail to fully correct.
Innovation Solution
An infrared camera system that includes a focal plane array, memory for storing supplemental flat field correction values, and a processor to estimate temperature differences and apply scale factors to these values to adjust thermal image data for non-uniformities across the optical path, thereby correcting for distortions caused by components like lenses and mounting hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a shutter is inserted into the optical path close to the FPA to reduce shutter size, then the infrared camera becomes more compact, but the thermal non-uniformity of the shutter's paddle and out-of-field infrared radiation from other optical path components cannot be corrected
Solution Approach 1:
The flat field correction is divided into two segments: primary correction for the region between shutter and FPA, and supplemental correction for the region between lens and shutter. This segmentation allows each correction to be optimized for its specific optical path segment, resolving the contradiction between compact shutter design and comprehensive thermal uniformity correction.
Solution Approach 2:
The supplemental flat field correction values are determined in advance during manufacturing and stored in memory. During operation, these pre-calculated correction values are retrieved and applied based on detected temperature differences, eliminating the need for real-time recalibration and maintaining accuracy in a compact design.
2Measurement precision
If conventional shutter calibration is used to correct FPA response non-uniformity, then calibration for the region between shutter and FPA is achieved, but non-uniformities from the lens and other components in front of the shutter remain uncorrected
Solution Approach 1:
The optical path is segmented into two correction zones: the primary flat field correction addresses the shutter-to-FPA region, while the supplemental correction addresses the lens-to-shutter region. This dual-segment approach ensures comprehensive correction across the entire optical path, improving radiometric accuracy without sacrificing FPA response uniformity.
Solution Approach 2:
The supplemental flat field correction values act as an intermediary correction layer that bridges the gap between the primary shutter-based calibration and the actual thermal conditions in the lens-to-shutter region. These correction values mediate the uncorrected non-uniformities, allowing accurate radiometric measurement while maintaining FPA calibration.
3Device complexity
If the shutter is positioned close to the FPA to minimize size, then device compactness is improved, but correction for out-of-field infrared radiation from components like lenses and mounting hardware becomes ineffective
Solution Approach 1:
The supplemental flat field correction values serve as an intermediary computational layer that compensates for out-of-field infrared radiation from lens and mounting hardware. By calculating and applying these correction values based on temperature differences, the system neutralizes harmful thermal effects without requiring physical separation between components.
Solution Approach 2:
Instead of using mechanical means (increasing physical distance between components) to reduce out-of-field radiation effects, the invention substitutes a computational approach. The supplemental correction values are calculated from temperature differences and applied digitally to compensate for thermal non-uniformities, replacing mechanical separation with algorithmic correction.
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
This approach enhances the accuracy of thermal images by effectively addressing non-uniformities across the entire optical path, reducing radiometric distortion and the need for frequent recalibration, while improving the reliability of camera components.
Implementation Method 1
infrared radiation passing through an optical path of the infrared camera is received by infrared detectors of the FPA, which provide thermal image data for pixels of a two-dimensional image
Implementation Method 2
estimate a temperature difference between the FPA and a component of the infrared camera that is in proximity to a first optical path of the infrared camera
Data Source
AI summary
Various techniques are provided to perform flat field correction for infrared cameras. In one example, a method of calibrating an infrared camera includes calibrating a focal plane array (FPA) of the infrared camera to an external scene to determine a set of flat field correction values associated with a first optical path from the external scene to the FPA. The method also includes estimating a temperature difference between the FPA and a component of the infrared camera that is in proximity to the first optical path. The method also includes determining supplemental flat field correction values based on, at least in part, the first set of flat field correction values, where the supplemental flat field correction values are adjusted based on the estimated temperature difference before being applied to thermal image data obtained with the infrared camera. The method also includes storing the supplemental flat field correction values.