Shielded Infrared Sensor Calibration for Thermal Imaging
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Solution Overview
Problem
Existing thermal imagers face challenges with pixel-to-pixel variations in infrared sensors, requiring costly and time-consuming factory calibration and mechanical shutters that are prone to failure, increasing complexity and cost.
Innovation Solution
The use of shielded and unshielded infrared sensors to determine an average thermographic offset reference, allowing for the calculation of absolute radiometric values without relying on factory calibration or shutter-based techniques, thereby correcting for sensor variations and eliminating the need for mechanical shutters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If factory calibration is used to compensate for pixel-to-pixel variations, then measurement precision is improved, but loss of time and manufacturing cost increase
Solution Approach 1:
The patent applies preliminary action by performing calibration during the factory testing phase rather than requiring periodic field calibration. The system captures images of a uniform shutter during manufacturing, determines offset values for each sensor element once, and stores these calibration terms for ongoing use. This preliminary calibration eliminates the need for time-consuming periodic recalibration in the field.
Solution Approach 2:
The patent uses a shutter as a copy or substitute for the actual target scene during calibration. The shutter provides a uniform reference surface that replicates the conditions needed for calibration without requiring actual target objects. This copying approach enables efficient determination of offset values during factory testing.
2Measurement precision
If mechanical shutters are used to determine offset values, then measurement precision is improved, but device complexity and reliability worsen
Solution Approach 1:
The patent extracts the calibration function from the main imaging path by using a separate shutter mechanism that can be positioned in front of the sensor array only when needed for calibration. The shutter is taken out of the continuous imaging path and used periodically to capture reference images, thereby reducing its impact on overall system complexity and operational reliability.
Solution Approach 2:
The shutter serves multiple functions: it acts as a mechanical barrier to protect the sensor, provides a uniform calibration target for determining offset values, and can be used to verify sensor performance. This multi-functionality reduces the need for separate components and simplifies the overall system architecture.
3Measurement precision
If mechanical shutters are used for calibration, then offset values can be determined, but reliability decreases due to mechanical failure risk
Solution Approach 1:
The patent performs the calibration action preliminarily during factory testing when the shutter is new and reliable. By capturing calibration images and determining offset values once during manufacturing, the system eliminates the need for periodic shutter operation in the field, thereby reducing the cumulative exposure to mechanical failure risks.
Solution Approach 2:
The system uses the shutter and calibration process to self-diagnose and self-correct for sensor non-uniformity. The calibrated offset values stored in memory enable the imaging system to compensate for pixel-to-pixel variations automatically during normal operation without requiring repeated mechanical intervention.
4Measurement precision
If conventional shutter implementations are used, then calibration can be performed, but cost and weight increase
Solution Approach 1:
The patent employs a thin-film or lightweight shutter assembly rather than a bulky mechanical structure. The shutter is designed as a delicate component that can be easily positioned and removed, minimizing its weight and dimensional footprint while still providing the necessary calibration function.
Solution Approach 2:
The shutter is designed as a simple, inexpensive component that can be easily replaced if needed. Rather than investing in a complex, expensive, long-lasting mechanical shutter system, the patent uses a simpler approach that prioritizes cost-effectiveness and ease of replacement over extended service life.
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 method enables accurate determination of absolute radiometric values for each pixel, improving thermal imaging performance by reducing costs and mechanical complexity while enhancing reliability and accuracy.
Implementation Method 1
capturing a signal from a shielded infrared sensor that is substantially blocked from receiving infrared radiation from a scene
Implementation Method 2
capturing a signal from an unshielded infrared sensor configured to receive the infrared radiation from the scene
Data Source
AI summary
Various techniques are provided for using one or more shielded (e.g., blinded, blocked, and/or obscured) infrared sensors of a thermal imaging device. In one example, a method includes capturing a signal from a shielded infrared sensor that is substantially blocked from receiving infrared radiation from a scene. The method also includes capturing a signal from an unshielded infrared sensor configured to receive the infrared radiation from the scene. The method also includes determining an average thermographic offset reference for the shielded and unshielded infrared sensors based on the captured signal of the shielded infrared sensor. The method also includes determining an absolute radiometric value for the scene based on the average thermographic offset reference and the captured signal of the unshielded infrared sensor.