Gauge Microbolometer Calibration Drift Detection
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Solution Overview
Problem
Microbolometer thermal imaging radiometers require frequent recalibration due to calibration drifts, which is costly and inconvenient, as current methods necessitate external blackbody calibration sources and controlled environments, making field corrections impractical.
Innovation Solution
Incorporating a gauge microbolometer that applies electrical stimulations to detect and correct calibration losses by comparing measured ohmic responsivity with a reference value, allowing for calibration adjustments without external calibration sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequent recalibration is performed using external blackbody calibration sources and controlled environments, then measurement precision is maintained, but device complexity and maintenance costs increase
Solution Approach 1:
An internal reference microbolometer is introduced as an intermediary element within the focal plane array to serve as a built-in calibration reference. This reference microbolometer remains unexposed to incoming radiation and provides a stable reference signal that enables calibration without requiring external blackbody sources, thereby maintaining measurement precision while eliminating the need for complex external calibration equipment.
Solution Approach 2:
The system performs self-calibration by using the internal reference microbolometer to continuously monitor and correct for drift in the imaging microbolometers. The calibration process is automated through processing circuits that compare the reference signal with the imaging signals and apply correction factors, allowing the radiometer to maintain calibration accuracy without external intervention or complex calibration setups.
2Measurement precision
If recalibration is performed in controlled environments with external calibration sources, then calibration accuracy is ensured, but ease of operation deteriorates due to the need for specialized equipment and environments
Solution Approach 1:
The internal reference microbolometer acts as a portable calibration reference that travels with the radiometer into the field. This eliminates the need to return to controlled laboratory environments for calibration, as the reference element provides the necessary calibration signal wherever the radiometer operates, thereby improving ease of operation while maintaining calibration accuracy.
Solution Approach 2:
The radiometer performs automatic self-calibration in the field using the internal reference microbolometer and processing circuits that continuously monitor drift and apply corrections. This eliminates the need for operators to transport external blackbody sources or return to controlled environments, making calibration as easy as normal operation while preserving measurement precision.
3Reliability
If a gauge microbolometer is added to detect calibration drift, then reliability of temperature measurements is improved, but device complexity increases due to additional components
Solution Approach 1:
The internal reference microbolometer serves multiple functions: it acts as both a calibration reference element and a drift detection sensor. By positioning it within the focal plane array but keeping it unexposed to incoming radiation, it provides a stable reference signal that simultaneously enables calibration and monitors for drift, improving reliability without requiring separate detection systems.
Solution Approach 2:
The calibration reference function and drift detection function are merged into a single internal reference microbolometer element. This eliminates the need for separate gauge microbolometers or additional detection systems, as the reference element inherently provides both calibration information and drift monitoring capability, thereby improving reliability while minimizing the increase in device complexity.
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 field detection and correction of calibration drifts, reducing maintenance costs and extending the operational time of thermal imaging radiometers before full recalibration is necessary, without the need for complex calibration setups.
Implementation Method 1
the electrical resistance of the sensor element 40 changes in response to a variation of temperature thereof, which in turn varies as a function of the amount of radiation 54 absorbed thereby
Implementation Method 2
radiation 54 impinging on the sensor element 40 of each imaging microbolometer 22 of the array increases the temperature of the sensor element 40 and causes a corresponding variation of its electrical resistance
Implementation Method 3
In the infrared portion of the electromagnetic spectrum, radiometers usually act as thermal cameras
Implementation Method 4
Microbolometers are thermal detectors capable of operating at room temperature
Data Source
AI summary
A method detects a loss of calibration of a thermal imaging radiometer including an array of imaging microbolometers and a gauge microbolometer. The detection method includes applying a first and a second electrical stimulation to the gauge microbolometer to bring it to a first and a second predetermined temperature, followed by measuring an ohmic responsivity of the gauge microbolometer that is representative of a difference between the first and second electrical stimulations. The measured ohmic responsivity is compared with a reference ohmic responsivity, such that a loss of calibration is signaled whenever the measured and reference ohmic responsivities differ by more than a predetermined threshold. A correction method includes steps of the detection method, to yield a corrected voltage response function for each imaging microbolometer. Advantageously, the methods involve probing the electrical response of the gauge microbolometer without requiring thermoregulated blackbody calibrations sources.