Thermal Camera In-Situ Calibration for Drift-Stable Building Surveys
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Solution Overview
Problem
Thermal cameras face challenges in maintaining stable temperature measurements due to environmental changes and temporal drift, making on-site calibration time-consuming and difficult, especially when surveying multiple buildings over extended periods.
Innovation Solution
A method for in-situ calibration of thermal cameras involves acquiring and comparing thermal images while the camera and object move relative to each other, identifying identical sections, and determining correlation and correction values to account for detector signal variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal camera calibration is performed in a laboratory by the manufacturer, then initial measurement accuracy is achieved, but the calibration cannot guarantee permanently stable temperature measurements due to environmental changes and drift
Solution Approach 1:
The thermal camera performs self-calibration in the field by using its own detector signals and identified object sections as reference. The system automatically determines correlation and correction values without external intervention, allowing it to self-correct drift and environmental effects during actual measurements.
Solution Approach 2:
The method uses feedback by comparing detector signals from identical object sections captured at different times and positions. The system continuously monitors measurement consistency and automatically adjusts calibration parameters based on the detected variations, creating a closed-loop correction mechanism.
2Reliability
If frequent calibration of the thermal camera is performed during the measurement process, then drift is corrected and measurement consistency is maintained, but the calibration process becomes very time-consuming
Solution Approach 1:
The thermal camera autonomously performs calibration using its own measurement data and identified reference sections. This eliminates the need for time-consuming manual calibration procedures with external equipment, as the system self-corrects using information already captured during normal operation.
Solution Approach 2:
The method extracts calibration information from ordinary measurement data by identifying stable reference sections within the measured scene. Instead of requiring separate calibration procedures with external standards, the system extracts the necessary reference signals from the actual measurement environment itself.
3Productivity
If the thermal camera is used to survey a large number of buildings over a relatively long period, then comprehensive energy performance data is collected, but drift occurs making it difficult to obtain comparable results
Solution Approach 1:
The calibration method using identified object sections is universally applicable across different measurement scenarios and locations. The same self-calibration approach works for all buildings surveyed, allowing consistent correction of drift effects throughout the entire measurement campaign regardless of environmental variations.
Solution Approach 2:
The self-calibration process operates continuously throughout the measurement campaign, automatically correcting drift as it occurs rather than requiring intermittent manual calibration stops. This maintains measurement comparability throughout the entire survey period without interrupting the productive workflow.
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 reduces calibration time and accounts for drift, ensuring accurate and consistent temperature measurements across multiple thermal images.
Implementation Method 1
The detector system, in particular, consists of a matrix of individual detectors (a so-called focal plane array) that convert thermal radiation flux into an electrical signal.
Implementation Method 2
The atmosphere, as well as the lenses and filters, absorb a small portion of the radiation.
Implementation Method 3
both the detectors and the thermal camera housing itself emit thermal radiation, which also strikes the detectors and adds to the radiation—and thus also the electrical signal—through the observed area.
Data Source
Figure 1~2
AI summary
Method for in-situ calibration of a thermal camera (1) with a detector system (7) with multiple detectors (7a-f) comprising the following steps: a) recording a thermal image of an object (10) with the thermal camera (1), b) generating a relative movement of the thermal camera (1) and the object (10), c) recording another thermal image of the object (10) or a part of the object (10) with the thermal camera (1), d) evaluating the recorded thermal images, identifying at least one identical section (12) of the object (10) present in the thermal images, e) identifying the detector (7a-f) that recorded the identified identical section (12) in the respective thermal image and determining the detector signal of the respective identified detector (7a-f) for the respective thermal image, and f) determining correlation and/or correction values from the detector signals, wherein before step a) or after step c), d),or e) a characterization of the thermal camera (1) is carried out.