Scientific Research—Calibration Steps of Infrared Thermal Imaging Camera to Improve Temperature Measurement Accuracy

Calibration Steps of Infrared Thermal Imaging Camera to Improve Temperature Measurement Accuracy

   Compared with refrigerated thermal imaging systems, uncooled infrared thermal imaging systems have many advantages such as no need for cooling, small size, simple operation, high performance, and low price. They are widely used in many fields such as aerospace, military, industry, and medicine. Value. The emissivity of the human body can reach above 0.99, which is a good infrared radiator. The lesions of various organs are usually accompanied by a local temperature increase or decrease, and these temperature informations can be detected by infrared thermal imaging cameras through heat conduction to the body surface. The infrared temperature image detected by the infrared thermal imager can intuitively show the temperature details of each part of the human body. The application of medical thermal imaging technology in clinical diagnosis can not only diagnose some diseases on the body surface or close to the body surface, but also play a good role in diagnosing diseases of deep organs. In order to accurately diagnose the disease information of the body, medical infrared thermal imaging cameras are required to accurately measure the body temperature. This puts forward higher requirements for the temperature measurement accuracy of the infrared thermal imager. Therefore, strict temperature calibration of the thermal imaging camera must be carried out.

   Infrared thermal imager temperature calibration technology is based on the relationship between the temperature of the reference black body source and the digital output of the infrared thermal imager to establish a thermal imager output and temperature curve. The smaller the temperature calibration interval of the reference black body source, the calibration is more points, the more accurate the temperature measurement. For uncooled infrared thermal imaging cameras, as the ambient temperature and absorption of infrared radiation increase, a more serious temperature drift phenomenon will occur, which will affect the response characteristics of the infrared detector, which will affect the temperature measurement accuracy to a certain extent. In order to improve the human body temperature measurement accuracy of uncooled infrared thermal imaging cameras, it is necessary to analyze the impact of temperature drift on temperature measurement and find a method to correct drift noise

   A lot of research has been done on the influence of detector temperature on the temperature measurement of uncooled thermal imaging cameras. It is believed that for uncooled thermal imaging cameras, the temperature drift of the detector has a great impact on temperature measurement. This study is aimed at the uncooled infrared focal plane imaging system. Taking the temperature of the detector into account on the temperature measurement of the infrared camera, a complete temperature calibration process is given, and the calibration algorithm is implemented in software to realize the detector High-precision radiation temperature measurement at different working temperatures.

Figure 1. Infrared thermal imaging camera to measure human body temperature.

   The temperature calibration experiment steps are as follows: 1. Place the infrared detector in the self-made temperature control box, and aim the lens of the uncooled infrared thermal imager at the radiation window of the standard black body source; 2. Adjust the temperature of the temperature control box to a certain temperature point, then Adjust the temperature of the standard blackbody source to the test temperature point, wait until the temperature of the temperature control box and the temperature of the standard blackbody source are stable, use the dedicated temperature measurement software on the PC to measure the temperature of the detector; 3. When the temperature of the detector is stable, measure this time The detector output count value D; 4. Adjust the standard black body source temperature to the next test temperature point, measure the detector temperature and the detector output count value.

   For uncooled thermal imaging cameras, the influence of the temperature drift of the detector on the measurement results cannot be ignored. Therefore, when using an uncooled thermal imaging camera, you should first calibrate it under the influence of the working temperature of the detector. The calibration method eliminates the influence of the temperature drift of the detector on the human body temperature measurement of the uncooled infrared focal plane thermal imager, and improves the temperature measurement accuracy.