Infrared Camera Spatial Calibration for Long-Distance Accuracy
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Solution Overview
Problem
Existing photogrammetric measurement systems, including infrared cameras, suffer from distortion due to lens geometry, which affects long-distance measurements, and conventional calibration methods are impractical for outdoor applications due to the need for large, flat calibration targets and issues with thermal bleeding in IR cameras.
Innovation Solution
A method for spatial calibration using a plurality of calibration points, such as halogen lamps, surveyed at a desired distance from the camera, allowing for accurate determination of camera calibration parameters through image processing and surveying equipment, suitable for long-distance focus settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration methods using large flat target boards are used, then measurement accuracy is improved, but the method becomes impractical for long-distance outdoor applications due to the size and flatness requirements of the target board
Solution Approach 1:
The invention divides the calibration target into multiple discrete calibration points distributed across a large area rather than using a single large flat board. Each calibration point can be independently positioned and surveyed, allowing the calibration setup to span long distances while avoiding the need for a single large flat surface.
Solution Approach 2:
The invention transitions from a 2D flat calibration board to a 3D distributed arrangement of calibration points in space. This allows calibration points to be positioned at various distances and elevations, enabling long-distance outdoor calibration without requiring a large flat surface.
2Measurement precision
If checkerboard patterns are used for IR camera calibration, then spatial calibration can be performed, but thermal bleeding in hot areas creates radial distortion patterns that make corner location difficult
Solution Approach 1:
The invention replaces the checkerboard pattern with calibration points that have distinct thermal or visual signatures. For IR cameras, this could be points with specific thermal properties that create clear, non-bleeding patterns in the infrared spectrum, eliminating the thermal bleeding problem while maintaining detectability.
3Reliability
If focus distance is set to long distance for outdoor applications, then distant objects appear sharply in focus, but conventional laboratory calibration methods become infeasible due to the required target size and distance
Solution Approach 1:
The calibration target is segmented into multiple discrete points that can be distributed over long distances, matching the long focus distance of the camera. This allows calibration to be performed at the actual operating distance without requiring a large flat board that would be impractical to deploy.
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
Enables high-fidelity, accurate long-distance measurements by correcting for radial and tangential distortions, applicable to infrared and visible light camera systems, improving real-world measurement precision.
Implementation Method 1
spatial calibration of an infrared (IR) camera system
Implementation Method 2
providing a precise and symmetric signature suitable for calibration of a mid-wave IR camera systems
Data Source
AI summary
A method for spatial calibration of an infrared (IR) camera allows for a large calibration area thereby providing high fidelity results for accurate long-distance measurement. Halogen lamps capable of being surveyed are spread over a relatively wide area to serve as calibration points for the infrared camera. The halogen lamps provide a precise and symmetric signature suitable for mid-wave IR cameras. An accurate model is developed for the radial and tangential distortion of the camera system. Likewise, values for the intrinsic parameters (focal lengths and optional skew coefficient) are measured to improve real-world measurements made using images recorded from a calibrated camera system.