Infrared Sensor Pixel Matrix In Situ Calibration
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Solution Overview
Problem
Infrared imaging devices face challenges in maintaining image quality over time due to varying spatial non-uniformities in matrix sensors, which are not correctly corrected by factory-calibrated gain tables.
Innovation Solution
An in situ calibration process for updating the gain table of matrix sensors in infrared imaging devices, allowing for correction of pixel disparities and aging effects without dismantling the sensor. This involves acquiring images of black screens and partially reflected radiation at different temperatures, and processing these images to update the gain table.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If factory calibration gain tables are used, then initial image quality is improved, but image quality deteriorates over time due to pixel aging and spatial non-uniformity variations
Solution Approach 1:
The patent performs preliminary calibration actions by acquiring reference images at known temperatures (black body at temperature T1 and reflected pixel matrix at temperature T2) before actual imaging. These preliminary measurements allow calculation of correction factors that compensate for pixel aging and spatial non-uniformities, enabling the gain table to be updated and maintained throughout the sensor's operational life without physical recalibration.
2Measurement precision
If scanning systems with external black bodies are used for recalibration, then gain table can be updated, but device complexity and cost increase
Solution Approach 1:
The patent makes the optical system multi-functional by enabling it to serve both as an imager for acquiring scenes and as a calibration device. The same optical path and pixel matrix used for normal imaging operations are utilized to acquire calibration reference images at different temperatures. This eliminates the need for separate external black bodies and scanning mechanisms, reducing device complexity while maintaining gain table update capability.
Solution Approach 2:
The sensor performs self-calibration by using its own pixel matrix to acquire reference images at known temperatures. The system leverages its existing components (optical system, pixel array, and processing unit) to generate the calibration data needed for gain table updates, eliminating dependency on external calibration equipment and reducing overall system complexity.
3Measurement precision
If dedicated calibration benches are used, then sensor can be recalibrated, but disassembly is required and operational time is lost
Solution Approach 1:
The patent enables continuous calibration operations by acquiring reference images during normal sensor operation or in between imaging tasks. The calibration process does not require sensor disassembly or removal from service, allowing calibration activities to continue seamlessly. The processing unit continuously updates the gain table using newly acquired reference data, maintaining calibration accuracy without interrupting operational availability.
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 in situ calibration process effectively updates the gain table to account for pixel aging and variations, improving image quality and extending the lifespan of infrared imaging devices without the need for complex and costly recalibration systems.
Implementation Method 1
acquisition by the pixel matrix of a first sequence of images of the radiation from a black screen corresponding to a scene at a first temperature; acquisition by the pixel matrix of a second sequence of images of the radiation from the partially reflected pixel matrix corresponding to a scene at a second temperature
Data Source
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AI summary
The invention relates to a method for in situ calibration of a pixel array of an infrared sensor, said infrared sensor comprising: an optical system (2); and a pixel array (3) disposed in the focal plane (4) of the optical system (2), said optical system (2) allowing radiation to be focused on the pixel array (3). The method comprises the following steps carried out in a processing unit (7) connected to the infrared sensor, with the pixel array being characterised by a pixel gain table: acquisition (E2) by the pixel array of a first sequence of images of the radiation from a black screen (CN) corresponding to a scene at a first temperature; acquisition (E4) by the pixel array of a second sequence of images of the partially reflected radiation from the pixel array corresponding to a scene at a second temperature; processing (E5, E6, E7, E8, E9) of the first and second image sequences such as to update the gain table by calculating a correction representative of the aging and response of the pixels of the pixel array.