A Practical Validation of Uncooled Thermal Imagers for Small RPAS

Uncooled thermal imaging sensors in the LWIR (7.5 μm to 14 μm) have recently been developed for use with small RPAS. This study derives a new thermal imaging validation methodology via the use of a blackbody source (indoors) and real-world field conditions (outdoors). We have demonstrated this method with three popular LWIR cameras by DJI (Zenmuse XT-R, Zenmuse XT2 and, the M2EA) operated by three different popular DJI RPAS platforms (Matrice 600 Pro, M300 RTK and, the Mavic 2 Enterprise Advanced). Results from the blackbody work show that each camera has a highly linearized response (R2 > 0.99) in the temperature range 5–40 °C as well as a small (<2 °C) temperature bias that is less than the stated accuracy of the cameras. Field validation was accomplished by imaging vegetation and concrete targets (outdoors and at night), that were instrumented with surface temperature sensors. Environmental parameters (air temperature, humidity, pressure and, wind and gusting) were measured for several hours prior to imaging data collection and found to either not be a factor, or were constant, during the ~30 min data collection period. In-field results from imagery at five heights between 10 m and 50 m show absolute temperature retrievals of the concrete and two vegetation sites were within the specifications of the cameras. The methodology has been developed with consideration of active RPAS operational requirements.

IMPROVEMENT OF INFORMATIVITY OF COMBINED DIFFERENT-RANGE IMAGES IN MEDICAL DIAGNOSTICS

Задача повышения качества результатов медицинской диагностики и удобства их интерпретации является актуальной на современном этапе развития биомедицинской инженерии. Особый интерес представляют методы визуализации, применимые при диагностике онкологических заболеваний. Повышать достоверность медицинской диагностики таких патологических состояний предлагается посредством совмещения разнодиапазонных изображений, в частности сканов в инфракрасном и видимом диапазонах длин волн. Предлагается методика, в которой два изображения конкретного биообъекта, полученные от датчиков, работающих в разных частотных диапазонах, имеющие одинаковые пространственные параметры и сформированные с общего ракурса, сводятся в общее изображение чересстрочно. Новизна предлагаемой методики заключается в том, что после совмещения изображений производится взаимная передача заданных частей каждого пикселя соседним пикселям по вертикали. В полученном изображении каждый пиксель содержит информацию оптического и инфракрасного изображений в заданных пропорциях. Показано, что предлагаемая методика обеспечивает увеличение информативности в полученном изображении в шесть раз относительно исходных изображений. Предлагаемая методика совмещения разнодиапазонных изображений может быть применена в различных прикладных областях In the medical diagnostics of diseases, it is necessary to obtain the most reliable information in order to obtain the correct diagnosis and, as a result, the correct treatment for the patient. One of the methods of diagnostic studies of oncological diseases of a near-surface nature is to obtain infrared images. It is possible to increase the reliability of information by combining images obtained from thermal imagers, as well as from television video cameras. In this paper, we propose a technique in which two images of a particular object obtained from sensors operating in different frequency ranges, having the same spatial parameters, and formed from the same angle, are interlaced into a common image. The novelty of the proposed method lies in the fact that after combining the images, the specified parts of each pixel are mutually transmitted to the neighboring pixels vertically. In the resulting image, each pixel contains information of optical and infrared images in appropriate proportions. It is shown that the proposed method provides an increase in information content in the resulting image six times relative to the original image. The proposed technique for combining multi-range images can be applied in various areas

POSSIBILITY USING THERMOGRAPHIC CONTROL METHOD TO DETECT CRACKS IN REINFORCED CONCRETE STRUCTURES

The article presents the study results of the possibility of using thermographic non-destructive testing to search for cracks in reinforced concrete structures. The basis of non-destructive thermal control is the registration of changes in the thermal field that occurs when the thermodynamic equilibrium of object with the environment is disturbed, which appears on the surface, and the nature of which allows obtaining the necessary information. The thermal control method is based on the interaction of the object's thermal field with thermodynamic sensitive elements (thermocouple, photodetector, liquid crystal element, bolometer), which convert the field parameters (intensity, temperature gradient, contrast, radiance) into an electrical signal of the recording device. As a result of the experiment, it was confirmed that the thermographic control method can be used when examining reinforced concrete structures for a qualitative assessment of hidden defects and damages. Thermal imagers with different resolution of the IR image matrix, an infrared thermo hygrometer, and a luxmeter were used as measuring instruments for the experiment. During the experiment, no fundamental difference in the use of thermal imagers with different types of IR matrices was revealed. When using the more accurate Flir E8 thermal imager, the thermogram had a clearer definition of the surface temperature compared to the Flir C2. This feature can be useful for quantifying defects, for example, the depth and size of a crack under a layer of paint, but fundamentally, for high-quality detection of defects and damage, the use of more accurate equipment is not a prerequisite. The authors conclude that the method of thermographic control can be used when examining reinforced concrete structures for a qualitative assessment of the presence of cracks.

Experimental studies of the energy dissipation processes at the tops of fatigue cracks in the elements of bridge structures

In the article, the authors investigated the possibility of using the thermal control method for diagnosing fatigue cracks in the metal superstructure, determined the necessary parameters for that control method. The studies were conducted during cantilevered steel samples fatigue tests simulating the superstructure beam wall operation, reinforced with stiffening ribs. To carry out the experiments were developed a test setup and a loading procedure at the various intensity of exposure. An electric motor with eccentrics is used as a loading device. The sample surface heating was recorded by thermal imagers with 0.03 K and 0.05 K temperature sensitivities and 60 frames/s and 9 frames/s shooting speed, respectively. Was confirmed the possibility of determining crack presence before its emergence to the surface namely at the stage of its initiation, and also were determined the self-heating zone dimensions at the tip of a crack. The conducting a laboratory experiment technique on the dissipative processes study in the metal superstructure elements is described.

Automated Detection of Animals in Low-Resolution Airborne Thermal Imagery

Detecting animals to estimate abundance can be difficult, particularly when the habitat is dense or the target animals are fossorial. The recent surge in the use of thermal imagers in ecology and their use in animal detections can increase the accuracy of population estimates and improve the subsequent implementation of management programs. However, the use of thermal imagers results in many hours of captured flight videos which require manual review for confirmation of species detection and identification. Therefore, the perceived cost and efficiency trade-off often restricts the use of these systems. Additionally, for many off-the-shelf systems, the exported imagery can be quite low resolution (<9 Hz), increasing the difficulty of using automated detections algorithms to streamline the review process. This paper presents an animal species detection system that utilises the cost-effectiveness of these lower resolution thermal imagers while harnessing the power of transfer learning and an enhanced small object detection algorithm. We have proposed a distant object detection algorithm named Distant-YOLO (D-YOLO) that utilises YOLO (You Only Look Once) and improves its training and structure for the automated detection of target objects in thermal imagery. We trained our system on thermal imaging data of rabbits, their active warrens, feral pigs, and kangaroos collected by thermal imaging researchers in New South Wales and Western Australia. This work will enhance the visual analysis of animal species while performing well on low, medium and high-resolution thermal imagery.

Influence of Atmosphere on Calibration of Radiation Thermometers

Current process of calibrating radiation thermometers, including thermal imagers, relies on measurement comparison with the temperature of a black body at a set distance. Over time, errors have been detected in calibrations of some radiation thermometers, which were correlated with moisture levels. In this study, effects of atmospheric air on thermal transmission were evaluated by the means of simulations using best available resources of the corresponding datasets. Sources of spectral transmissivity of air were listed, and transmissivity data was obtained from the HITRAN molecular absorption database. Transmissivity data of molecular species was compiled for usual atmospheric composition, including naturally occurring isotopologs. Final influence of spectral transmissivity was evaluated for spectral sensitivities of radiation thermometers in use, and total transmissivity and expected errors were presented for variable humidity and measured temperature. Results reveal that spectral range of measurements greatly influences susceptibility of instruments to atmospheric interference. In particular, great influence on measurements is evident for the high-temperature radiation pyrometer in the spectral range of 2–2.7 µm, which is in use in our laboratory as a traceable reference for high-temperature calibrations. Regarding the calibration process, a requirement arose for matching the humidity parameters during the temperature reference transfer to the lower tiers in the chain of traceability. Narrowing of the permitted range of humidity during the calibration, monitoring, and listing of atmospheric parameters in calibration certificates is necessary, for at least this thermometer and possibly for other thermometers as well.

Effects of NaB2O4:Mn2+ and Ba2Li2Si2O7:Sn3+,Mn2+ phosphors and remote structure organizations on the white light-emitting diodes with quantum dots and phosphors

In order to increase the optical features of white light-emitting diodes (WLEDs), quantum dots (QDs) and phosphor materials have been proposed because of outstanding performance. The configuration of WLEDs with QDs layer and phosphor-silicone layer suggested placing these components separately to limit light loss, and enhance consistency at contact surface of QDs. In this research, the effects of QDs and phosphor on the performance of WLEDs are concluded through experiments. The emitted light and PL spectra were examined thoroughly, and infrared thermal imagers were applied to simulate the heat generation of an actual WLED device. The results show that with the configuration of 60 mA energy source, WLEDs which has the QDs-on-phosphor form attained luminous efficiency (LE) of 110 lm/W, with color rendering index (CRI) of Ra=92 and R9=80, whereas the WLEDs which has the phosphor-on-QDs form only has 68 lm/W in LE, Ra=57 and R9=24. Furthermore, WLEDs which has the QDs-on-phosphor form has less high temperature generated at the components’ conjunction in comparison to the counterpart, the peak generated heat in QDs-on-phosphor WLEDs is also lower and the heating capacity gap between 2 structures can go up to 12.3°C.

Investigation of the Centers of Endogenous Fires at the Rock Dumps of the Coal Enterprises

The formed rock dumps of sections, mines and washing plants are composed of carbonaceous rocks and are capable of spontaneous combustion when the required amount of air is supplied. The conducted studies evaluated the efficiency of detecting a center of spontaneous combustion at the rock dumps of sections by measuring the temperature of rocks in the wells with a depth of 2.5 m, drilled at the distance of 20 m from each other, according to the current normative documents. For the landfill, a dump site with a long-existing center of spontaneous combustion was selected. The experiment showed the impossibility of drilling wells on the slopes of the dumps, as well as the need for casing the wells with pipes along the entire length. The temperature of rocks in the wells at a depth of 2.5 m varied from 69 to 773 °C. It was found that in the heated zone there are sharp temperature drops in the rocks, which cannot be detected with an interval between the measurement points equal to 20 m. With such a distance between the control wells, the places with a diameter of 1–10 m may remain undetected at the initial stage of spontaneous combustion. Measurements showed that in all the wells the rock temperature increases with depth. At the same time, the recommended well depth of 2.5 m does not allow determining the size of the heated zone deep into the rock dump. The upper layer of rocks above the center of spontaneous combustion exceeds the ambient temperature, so remote temperature measuring devices can be used to detect endogenous fires in the rock dumps. The use of thermal imagers installed on the unmanned aerial vehicles will significantly reduce the cost of detecting spontaneous combustion centers on the rock dumps and increase the efficiency of detecting fire centers not only on the dump sites, but on the slopes of the dump side and in other hard-to-reach places. Moreover, with a decrease in the atmospheric air temperature, the efficiency of remote thermal photography does not decrease. To clarify the parameters of the center of endogenous fires, it is advisable to use the temperature measurement of rocks with a contact thermometer at a depth of 0.5 m.