Talk about the application principle of epidemic prevention and control products

2020-12-14 11:45:33 fandoukeji

Talk about the application principle of epidemic prevention and control products




Because fever is one of the symptoms of new coronary pneumonia infection, temperature screening has become the main method of epidemic surveillance in public areas. Based on the theory that "the thermal radiation emitted by the human body is relatively stable and can be'segmented' from the surrounding environment within a certain range", many domestic start-up companies have begun to develop AI infrared temperature measurement products, and infrared temperature measurement has begun to experiment with AI-related faces. Combining with part recognition algorithms.


It is reported that AI infrared temperature measurement first finds the test area through the AI face recognition camera and maps it to the thermal imaging camera; then, the temperature of this area is taken out and the actual body surface temperature is given through a certain compensation algorithm. The principle of thermal imaging is to collect infrared electromagnetic waves emitted by the human body, and then present the energy intensity of the infrared electromagnetic waves with a pseudo-color heat map. However, the propagation of infrared electromagnetic waves in the air will be absorbed by gases such as carbon dioxide, causing energy attenuation, resulting in temperature measurement errors, which is why thermal imaging is susceptible to environmental interference in temperature measurement accuracy.



In response to the problem of thermal imaging temperature measurement accuracy, many companies have added blackbody, which can greatly improve the temperature measurement accuracy. The biggest feature of the black body is that it can absorb all external electromagnetic radiation without any reflection. Therefore, the black body is generally used for the calibration and verification of radiation thermometers to thermal imaging, etc., and the calibration temperature of the black body is detected by the thermal imaging. The obtained blackbody temperature is compared to calibrate the temperature measurement result, thereby reducing the interference of the environment on the thermal imaging temperature measurement accuracy, thereby improving the temperature measurement accuracy.


A black body has a characteristic. The larger its effective radiating surface, the larger its heat capacity. The temperature is easier to maintain a stable state in different environments, and it is easier to ensure heat balance. At the same time, due to the sight distance problem, the farther the black body is from the temperature measurement target, the larger the radiation surface is required. If the radiating surface of the black body is too small, the black body cannot be clearly seen in the thermal imaging screen for the temperature measurement target at a distance, and it is difficult to calibrate the black body temperature. Therefore, the larger the effective radiating surface of the black body, the more conducive to accurate temperature measurement at a longer distance. Technicians generally set the black body within the thermal imaging field of view, and the black body temperature measurement distance is consistent with the camera temperature measurement distance, so that the temperature measurement accuracy can be guaranteed to the greatest extent and the black body high precision effect can be truly exerted. If the difference between the black body temperature measurement distance and the camera temperature measurement distance is too large, there will be blind spots in temperature measurement, that is, in the same video screen, the temperature measurement results of people at a distance are too large, and the rate of false alarms and false alarms is high. So even if the black body is used, it is useless, and the temperature measurement effect is greatly reduced. It is impossible to quickly check people with a body temperature ≥37.3℃ in the first time, leaving hidden dangers in the epidemic prevention and control work.


With the development of the coronavirus, using drones equipped with special sensors to monitor people has also become a new way. The DJI region has recently begun to try to screen suspicious patients through "drone plus infrared". It is understood that due to its portability, high flight stability, thermal imaging lens and megaphone accessories, the DJI Yu 2 industry dual-light version is used by many communities and road checkpoints for remote body temperature detection. The dual-optical version of the Yu 2 industry has been verified by software and hardware debugging and different scenarios. It can meet the non-contact screening requirements of various personnel such as non-local personnel at highway intersections and high-level isolation personnel in communities at a distance of 2-3 meters. Once the temperature is found The abnormal individual will display the abnormal temperature on the screen of the drone remote control to remind the on-site staff to check further, which is safe and efficient.


However, the DJI Yu 2 industry dual-light version was originally designed for industrial scenes and is more sensitive to the difference between the measurement target and the ambient temperature. However, when measuring such a fine absolute temperature as the body temperature, the accuracy is prone to be insufficient, and sometimes the error reaches 4 degrees to 5 degrees, which cannot meet the needs of outdoor body temperature screening.


During this period, some well-known domestic technology research and development companies have devoted themselves to the development and production of epidemic prevention and control products. For a time, orders for such products at home and abroad soared. These high-tech human body temperature measurements are commonly used in various scenarios such as transportation hubs, hospitals, corporate parks, communities, schools, prisons, etc., and contribute indelibly to the fight against the epidemic.