High Temperature Calibration of Thermal Imagers for Infrared Measurements on Military Platforms
Abstract
Calibration of thermal imaging system is not a straight forward process and hence manufacturers suggest re-calibration at factory itself. However, it is time consuming and expensive. A few research papers refer various approaches to perform low temperature calibration considering the wide requirement of low temperature measurements (typically less than 150 °C). However, no reference is available in open literature about high temperature calibration of thermal imagers. Hence, the possibility of high temperature calibration of thermal imaging systems has been explored using high temperature blackbody sources available at laboratory. With the use of neutral density filters, calibration has been performed in mid-wave (3.7 μm - 4.8 μm) and long-wave (7.7 μm - 9.5 μm) bands of imagers for IR measurements. The developed calibration has also been tested for field measurements.
- Fig. 6 Calibration curve of MWIR imager with 200 mm lens for 750 – 1600 °C dynamic range with IT: 330 µs
- Fig. 5 Calibration curve of MWIR imager with 50 mm lens for 330 – 630 °C dynamic range with IT: 2000 µs
- Fig. 4 Low and high reference temperatures taken at 30% and 70% of dynamic range respectively for performing ‘Two Point’ NUC
- Fig. 3 Photon detector response (voltage output) as a function radiant energy
- Fig. 2 Experimental setup for calibrating thermal imaging systems
- Fig. 1 Schematic of a thermal imaging system
- Fig. 7 Calibration curve of LWIR imager with 50 mm lens for 100 – 1600 °C dynamic range with IT: 120 µs
- Fig. 8 Calibration curve of LWIR imager with 200 mm lens for 100 – 1600 °C dynamic range with IT: 130 µs
- Table-1 Details of dynamic ranges and their corresponding integration times (ITs)
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