Thermal Camera Calibration Target With Emissivity Contrast
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Solution Overview
Problem
Conventional calibration patterns, such as black and white checkerboards, are insufficient for thermal cameras as they do not exhibit sufficient temperature differences, making it difficult to detect intensity variations and accurately calibrate the cameras.
Innovation Solution
A calibration target with a pattern featuring materials of different thermal emissivities, such as alternating squares with distinct emissivity values or infrared light sources, is used to create a visible infrared image for accurate calibration of thermal cameras, allowing for the determination of intrinsic and extrinsic parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional black and white checkerboard pattern is used for calibration, then the pattern is easily visible to electro-optical cameras, but the pattern does not exhibit sufficient temperature differences for thermal camera detection
Solution Approach 1:
The patent changes the physical parameter of the calibration pattern from reflectivity-based (black and white colors visible to electro-optical cameras) to emissivity-based (different thermal radiation properties visible to thermal cameras). This allows the same checkerboard geometry to be effective for both electro-optical and thermal camera calibration by modifying the material properties rather than the geometric structure.
Solution Approach 2:
The calibration pattern uses composite materials with different thermal emissivities arranged in a checkerboard configuration. Each square of the checkerboard is made from materials specifically selected to have contrasting emissivity values, enabling thermal camera detection while maintaining the familiar geometric pattern structure.
2Measurement precision
If materials with different thermal emissivities are used in the calibration pattern, then sufficient temperature differences are achieved for thermal camera detection, but the manufacturing complexity increases
Solution Approach 1:
The calibration target is segmented into discrete squares arranged in a checkerboard pattern, where each square can be independently manufactured with a specific emissivity material. This segmentation allows for modular manufacturing approaches, where individual squares or groups of squares can be fabricated separately and then assembled into the complete calibration target.
Solution Approach 2:
Different regions (squares) of the calibration pattern have locally optimized properties - each square is made from a material with a specific emissivity value tailored to its position in the pattern. This local quality approach allows maximum contrast between adjacent squares while enabling flexible material selection for each region based on manufacturing considerations.
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 enables precise calibration of thermal cameras by providing significant temperature differences, enabling accurate measurement of real-world entities and transformation of pixel coordinates to world coordinates.
Implementation Method 1
The calibration target may have a pattern which can be seen on an infrared image captured by the camera... a checkerboard with every other square having one emissitivity and the remaining squares having a different emissitivity
Data Source
AI summary
A system for calibrating a thermal camera with a calibration target. The calibration target may have a pattern which can be seen on an infrared image captured by the camera. The pattern may be of various kinds. For example, the pattern may be a checkerboard with some, such as every other square, having one emissitivity and the remaining squares having a different emissitivity, or having infrared light sources placed at corners of the squares. A difference between the emmissitivities may be sufficient so that the checkerboard pattern appears in an infrared image captured by the camera for calibration. The calibration may aid in determining intrinsic and extrinsic parameters of the camera. The parameters may provide a basis for transforming camera pixel coordinates to a world coordinate system which allows measurement of real world entities by the thermal camera. Measurements may incorporate distances between objects, heights of objects, and so forth.