Thermal Imaging System Research Articles

Enzyme-modulated photothermal immunoassay of chloramphenicol residues in milk and egg using a self-calibrated thermal imager

Highly sensitive and accurate detection of chloramphenicol is of paramount importance for food safety. Herein, an enzyme-modulated photothermal immunosensor that uses a self-calibrated thermal imaging system (SCTIS) as signal read-out was developed for detecting chloramphenicol. In this immunosensor, alkaline phosphatase was used as a modulator of the photothermal conversion. It could hydrolyze the substrate into ascorbic acid, thereby reducing oxidized 3,3′,5,5′-tetramethylbenzidine, which exhibited a near-infrared laser-driven photothermal effect. For precise temperature measurement, the SCTIS was designed by using the temperature compensation of a ceramic chip to enable real-time self-calibration of the temperature. This SCTIS-based immunosensor could detect chloramphenicol with a LOD of 9 pg/mL in 2 h, and relative standard derivations from 3.95% to 13.58%. The average recoveries in milk and egg samples ranged from 76% to 114%. This versatile sensing strategy can detect various targets by altering recognition elements, thus has wide applicability in food safety testing and monitoring.

A temperature-controlled mid-wave infrared polarization radiation source with adjustable degree of linear polarization

This paper proposes a temperature-controlled mid-wave infrared polarization radiation source with adjustable degree of linear polarization (DoLP), referred to as TMPSD, which will be useful for the polarization performance measurements of the thermal polarization imaging systems. The main parts of the TMPSD are a standard blackbody source, a variable temperature cell holder and a mid-wave infrared polarizer placed in it. The experimental results show that when the temperature range of the blackbody source changes between 20 °C and 100 °C, and that of the polarizer between −120 °C and 20 °C, the DoLP of the radiation emitted from the TMPSD is 0.2683–0.9072 in the 3.0–5.2 μm bandwidth. The TMPSD exhibiting the large dynamic range and high accuracy can be readily adjusted. It is expected that the proposed TMPSD will effectively improve the quantitative accuracy of infrared polarization imaging systems during performance calibration and testing of mid-wave infrared polarization imaging systems.

A Complete YOLO-Based Ship Detection Method for Thermal Infrared Remote Sensing Images under Complex Backgrounds

The automatic ship detection method for thermal infrared remote sensing images (TIRSIs) is of great significance due to its broad applicability in maritime security, port management, and target searching, especially at night. Most ship detection algorithms utilize manual features to detect visible image blocks which are accurately cut, and they are limited by illumination, clouds, and atmospheric strong waves in practical applications. In this paper, a complete YOLO-based ship detection method (CYSDM) for TIRSIs under complex backgrounds is proposed. In addition, thermal infrared ship datasets were made using the SDGSAT-1 thermal imaging system. First, in order to avoid the loss of texture characteristics during large-scale deep convolution, the TIRSIs with the resolution of 30 m were up-sampled to 10 m via bicubic interpolation method. Then, complete ships with similar characteristics were selected and marked in the middle of the river, the bay, and the sea. To enrich the datasets, the gray value stretching module was also added. Finally, the improved YOLOv5 s model was used to detect the ship candidate area quickly. To reduce intra-class variation, the 4.23–7.53 aspect ratios of ships were manually selected during labeling, and 8–10.5 μm ship datasets were constructed. Test results show that the precision of the CYSDM is 98.68%, which is 9.07% higher than that of the YOLOv5s algorithm. CYSDM provides an effective reference for large-scale, all-day ship detection.

Bruise detection and classification in jujube using thermal imaging and DenseNet

AbstractJujubes (Ziziphus Mauritiana Lamk) are subjected to bruises during harvesting and post‐harvest processing, which will greatly reduce their commercial values. In this study, bruises on jujube are detected and classified based on thermal imaging and convolutional neural networks. A simple thermal imaging system is constructed that can capture thermal images speedily and clearly. Temperature difference analysis is performed on the collected thermal images and accordingly, the temperature difference of boundary in the bruised area varies between 1.72 and 3.25°C during the storage period. The temperature difference in the bruise boundary area minus the temperature difference in the center area varies between 0.4 and 1.2°C, and the degree of bruise of the jujube is evaluated through temperature difference analysis. The convolutional neural network DenseNet is adjusted to ensure suitability for classification of the thermal image data set collected in this study (the training dataset comprises 5,039 original thermal images, and the test dataset comprises 2,586 original thermal images), and the best prediction accuracy achieved is 99.5%.Practical ApplicationThis study can be used as a reference for the future development of harvest, sorting, storage, and transportation for bruise detection in jujube. Our study makes a significant contribution to the literature because the findings of this study could facilitate the development of an online thermal imaging system for bruise detection and classification in jujube in the future.

An experimental study on dynamic deformation and ignition response of a novel propellant under impact loading

Investigations on high-energy and low-vulnerability propellants can provide a guarantee for improving the power and safety of solid rocket motors. In the present study, mechanical-thermal coupled responses were recorded by a high-speed infrared thermal imaging systems. The dynamic compressive properties and damage-ignition response mechanism under high strain rates of a novel type of propellant were studied, using a split Hopkinson pressure bar apparatus. The experimental results suggested that the mechanical properties of the novel propellant, in terms of yield stress, initial compressive modulus, and ultimate stress, were greatly affected by the loaded strain rate. The stress-strain responses exhibited an initial linear elasticity region, followed by yielding, and then a subsequent strain hardening or softening stage (plateau region), which was strongly dependent on the strain rate. It was found that the yield stress and ultimate stress increased with the strain rates. Moreover, the ignition response was accentuated at higher strain rates, resulting in an earlier and more intense ignition. According to the high-speed images and the post-test SEM images, the critical strain rate for ignition is 4500 s−1. Finally, by calculating the bulk and local temperature rise (considering the friction mechanism), it is clear that the dominant ignition mechanism of the novel propellant is the friction which is macroscopically represented as viscous shear flow.

Imaging Luminescence Thermometry to 750\xa0\xb0C for the Heat Treatment of Common Engineering Alloys and Comparison with Thermal Imaging

Accurate temperature measurements are critical in manufacturing, affecting both product quality and energy consumption. At elevated temperatures, non-contact thermometers are often the only option. However, such instruments require prior knowledge of the surface emissivity, which is often unknown or difficult to determine, leading to large errors. Here we present a novel imaging luminescence thermometer based on the intensity ratio technique using magnesium fluorogermanate phosphor, with the potential to overcome this limitation. We describe measurements performed on a number of engineering alloys undergoing heat treatment at temperatures of up to 750 °C and compare these measurements against a traditional contact thermocouple and thermal imager system. Agreement between the luminescence and embedded thermocouple temperatures was found to be better than 45 °C at all temperatures. However, the thermal imager measurement on the bare metal samples, with the instrument emissivity set to 1.0, showed differences of up to 500 °C at 750 °C, a factor of 10 larger. In an effort to improve the thermal imager accuracy, its instrument emissivity was adjusted until its temperature agreed with that of the thermocouple. When measuring on the bare metal, the effective emissivity was strongly sample dependent, with mean values ranging from 0.205 to 0.784. Since the phosphor derived temperatures exhibited substantially smaller errors compared to the thermal imager, it is suggested that this method can be used to compliment the thermal imaging technique, by providing a robust mechanism for adjustment of the instrument emissivity until agreement between the thermal imager and phosphor thermometer is obtained.

Effectiveness of surface-based detection methods for vessel strike mitigation of North Atlantic right whales

Increasing commercial and recreational use of the world’s oceans has led to growing concerns about vessel and marine mammal encounters. For endangered species such as the North Atlantic right whale Eubalaena glacialis, reducing the number of vessel strikes is key to improving their protection. In this study, we developed an agent-based model to assess the efficacy of thermal imaging systems as a surface-based whale detection method for vessel strike mitigation. We found that the detection range of such systems is the determining factor for their efficacy and needs to be chosen according to vessel characteristics, such as speed and maneuverability. Furthermore, we found that combining large-scale (e.g. protected zones) and small-scale (e.g. on-board detection systems) mitigation strategies increases protection. Finally, technological improvements are needed to achieve reliable detection ranges beyond what is currently possible so that fast and poorly maneuverable vessels such as ultra-large container ships could benefit from on-board detection systems.

Fully absorbing one-dimensional photonic crystal

We investigated the resonant absorption capacity of a one-dimensional photonic crystal, the relationship between the resonant frequency and the width of its absorption band, and the composition and thickness of the layers forming it. Frequency oscillations of radiation reflection from 2.5-layer semimetal-dielectric-metal film structures caused by interference on the film thickness were studied. We measured the infrared reflection spectra of Bi87Sb13 film samples on mirror-smooth substrates with a reflective metal (Al, Ti) layer and a dielectric layer MgF2+LiF or SiO2+Si3N4). We have developed samples that absorb up to 99.5% of radiation at maximum and integrally up to 60% of resonant thermal radiation. The composition of structures for interfacing with silicon technologies and constructing matrices of sensitive bolometric receivers has been optimized. We have proposed the implementation of active selective thermal imaging systems with matching the source and receiver of radiation simultaneously in frequency and frequency band. The analogy of the absorbing properties of film structures and the properties of human eye cells was shown. Keywords: bismuth, film, IR, interference, eye color sensitivity.

Evaluating the thermal characteristics of laser powder bed fusion

• Dynamic temperature behaviour around the melt pool during the PBF-LB/M was evaluated. • Temperature distribution was influenced by morphological changes of metal powder. • Laser beam incident was characterized by direct heating and heat conduction. • Dynamic temperature behaviour provided a direct explanation for the cooling rate. This study investigates the dynamic temperature behaviour around a melt pool in metal-based powder bed fusion using a laser beam (PBF-LB/M) to clarify the influence of the associated morphological changes of the metal powder experimentally. Gas-atomized 18Ni (300-grade) maraging steel powders were processed by PBF-LB/M while high-speed photography with a two-colour radiometric thermal imaging system that was employed to correlate the temperature with melt pool behaviour. In addition, the cooling rate of the melt pool was measured directly using the dynamic temperature distribution. The temperature distribution of the melt pool was influenced by the morphological changes of the metal powder induced by physical and thermal interactions, and the melt pool exhibited an asymmetric temperature distribution in the direction parallel to the laser scan. The significant factors were droplet cohesion at low melt pool temperatures, remaining heat energy from previous laser beam irradiation, and the heat conduction inside the melt pool. The laser beam incident on the metal powder was primarily characterized by two modes: direct heating induced by laser beam irradiation and heat conduction through the single track, droplets, and substrate. In addition, the dynamic temperature behaviour provided a direct explanation for the cooling rate, the values of which ranged from 0.1 to 0.9 × 10 6 K/s owing to the self-cooling induced by PBF-LB/M.

Полностью поглощающий одномерный фотонный кристалл

We investigated the resonant absorption capacity of a one-dimensional photonic crystal, the relationship between the resonant frequency and the width of its absorption band, and the composition and thickness of the layers forming it. Frequency oscillations of radiation reflection from 2.5-layer semimetal-dielectric-metal film structures caused by interference on the film thickness were studied. We measured the infrared reflection spectra of Bi87Sb13 film samples on mirror-smooth substrates with a reflective metal (Al, Ti) layer and a dielectric layer (MgF2+LiF or SiO2+Si3N4). We have developed samples that absorb up to 99.5% of radiation at maximum and integrally up to 60% of resonant thermal radiation. The composition of structures for interfacing with silicon technologies and constructing matrices of sensitive bolometric receivers has been optimized. We have proposed the implementation of active selective thermal imaging systems with matching the source and receiver of radiation simultaneously in frequency and frequency band. The analogy of the absorbing properties of film structures and the properties of human eye cells was shown.

Commissioning of the hypertriton binding energy measurement at MAMI

A high-precision hypernuclear experiment has been commissioned at the Mainz Microtron (MAMI) to determine the hypertriton Λ binding energy via decay-pion spectroscopy. The method has been successfully pioneered with 4ΛH studies in the last decade. The experiment makes use of a novel high luminosity lithium target with a length of 45mm while being only 0.75mm thick to keep momentum smearing of the decay pions low. The target-to-beam alignment as well as the observation of the deposited heat is achieved with a newly developed thermal imaging system. Together with a precise beam energy determination via the undulator light interference method a recalibration of the magnetic spectrometers will be done to obtain a statistical and systematic error of about 20 keV. The experiment started in the summer of 2022 and initial optimization studies for luminosity and data quality are presented.

Latest Advances in Common Signal Processing of Pulsed Thermography for Enhanced Detectability: A Review

Non-destructive testing (NDT) is a broad group of testing and analysis techniques used in science and industry to evaluate the properties of a material, structure, or system for characteristic defects and discontinuities without causing damage. Recently, infrared thermography is one of the most promising technologies as it can inspect a large area quickly using a non-contact and non-destructive method. Moreover, thermography testing has proved to be a valuable approach for non-destructive testing and evaluation of structural stability of materials. Pulsed thermography is one of the active thermography technologies that utilizes external energy heating. However, due to the non-uniform heating, lateral heat diffusion, environmental noise, and limited parameters of the thermal imaging system, there are some difficulties in detecting and characterizing defects. In order to improve this limitation, various signal processing techniques have been developed through many previous studies. This review presents the latest advances and exhaustive summary of representative signal processing techniques used in pulsed thermography according to physical principles and thermal excitation sources. First, the basic concept of infrared thermography non-destructive testing is introduced. Next, the principle of conventional pulsed thermography and signal processing technologies for non-destructive testing are reviewed. Then, we review advances and recent advances in each signal processing. Finally, the latest research trends are reviewed.

A Comparative Study on the Recording of Temperature by Thermo- Graphic Camera, Thermal Gun and Digital Clinical Thermometer in a Tertiary Hospital of Nepal.

Body Temperature is one of the most common and an important sign of health and disease. Considering the need of keeping physical distance, newer methods have evolved such as; thermal imaging systems which have been used by several countries during epidemics. Therefore, the present study was conducted to compare body temperatures obtained with thermo graphic camera and commercially available thermal gun with reference to standard digital clinical thermometer. The study was comparative analytical in nature and quantitative method was used to collect data. Temperatures in degrees Fahrenheit were taken simultaneously using the three different thermometers in 101 patients at the outpatient fever screening clinic at Tribhuvan University Teaching Hospital, Kathmandu. The Bland Altman statistical test was used to assess the concordance by the 95% limits of agreement. The thermo-graphic camera gave concordance (limits of agreement-0.0360 to 0.0440 °F) with standard digital clinical thermometer. Similarly, commercially available thermal gun gave the concordance (limits of agreement 0.0042 to 0.1293 °F) with standard digital clinical thermometer. The results of the present study show that both thermo-graphic camera and thermal gun were found to be concordant compared to digital clinical thermometer. Therefore, it could be a preferable option for the screening of fever in mass number of individuals as part of an initial check at entry points.

Sieć miniaturowych czujników termowizyjnych do wykrywania i śledzenia obiektów

This paper presents a concept and implementation of an infrared imaging sensor network for object localization and tracking. The sensor network uses multiple low-resolution (80× 80 pixels) microbolometric thermal cameras to detect, track and locate an object within the area of observation. The network uses information simultaneously acquired from multiple sensors to detect and extract additional information about object’s location. The use of thermal-imaging systems responsive to objects’ natural infrared radiation, makes the system resistant to external illumination and environmental conditions. At the same time, the use of infrared sensor requires application of specially designed, dedicated image processing techniques appropriate for this kind of sensor. The paper describes: image processing techniques, means of object localization, accuracy measurements, comparison to other known solutions and final conclusions.

Effect of length-to-diameter ratio on film cooling and heat transfer performances of simple and compound cylindrical-holes in transverse trenches with various depths

Advances in trenched-hole film cooling result in a fact that short-holes exposing in a transverse trench have a significantly large potential for application in designs of future double-wall cooled blade. In present work, combined influences of hole-length, trench-depth, compound angle and cooling air flowrate on the film effectiveness and heat transfer features of trenched-holes were discussed deeply. Film effectiveness and heat transfer coefficient were measured by an infrared thermal imaging system. Numerical simulation as an auxiliary tool was conducted to provide necessary flow details. Two typical length-to-diameter ratios of L/D = 2 and 5, three trench-depths of H = 0.5D, 0.75D and 1.0D and two compound-angles of film-hole of 0° and 45° were designed. Cooling air flowrate was controlled in a relatively large range from 0.5 to 4.0 in averaged blowing ratio (BR). The results revealed the various jet-mechanisms caused by L/D while relatively regular variations of turbulent intensity of jets. Thus, the complicated trends in film effectiveness while regular trends in heat transfer coefficient can be clearly captured. The combined influences of trends above can bring to the more undesirable thermal protections for the short-hole jet. The L/D-induced decrement in area-averaged net heat flux reduction (NHFR) can reach 60% at most. To effectively improve film coverage and NHFR, the short-holes were properly embedded in the deeper trench. And the sensitivity analysis of trench-depth to discharge coefficient showed the negligible variation below 5%. The NHFR of the shallowest trench can be improved through application of compound angle, inducing an enlarged aerodynamic loss below 10%.

Non-Contact Spirometry Using a Mobile Thermal Camera and AI Regression.

Non-contact physiological measurements have been under investigation for many years, and among these measurements is non-contact spirometry, which could provide acute and chronic pulmonary disease monitoring and diagnosis. This work presents a feasibility study for non-contact spirometry measurements using a mobile thermal imaging system. Thermal images were acquired from 19 subjects for measuring the respiration rate and the volume of inhaled and exhaled air. A mobile application was built to measure the respiration rate and export the respiration signal to a personal computer. The mobile application acquired thermal video images at a rate of nine frames/second and the OpenCV library was used for localization of the area of interest (nose and mouth). Artificial intelligence regressors were used to predict the inhalation and exhalation air volume. Several regressors were tested and four of them showed excellent performance: random forest, adaptive boosting, gradient boosting, and decision trees. The latter showed the best regression results, with an R-square value of 0.9998 and a mean square error of 0.0023. The results of this study showed that non-contact spirometry based on a thermal imaging system is feasible and provides all the basic measurements that the conventional spirometers support.

Detection of the 3D temperature characteristics of maize under water stress using thermal and RGB-D cameras

Global warming and water resource shortage greatly influence the crop growth and negatively affect the crop yield. Breeding water–stress resistant crop varieties is one of the effective ways to handle this problem. The surface temperatures of the crop are essential for assessing their water stress resistance. Thermal imaging has been widely used to acquire the crop surface temperatures. However, most studies focus on 2D measurement. A 3D thermal imaging system is designed, and a method is developed by using the thermal and RGB-D data to acquire 3D thermal information of maize under water stress conditions. First, thermal and RGB-D cameras were used to collect the thermal and color images, and depth data of maize at the jointing stage and the thermal and color images were processed to extract the edge images of maize. Second, the KAZE feature was selected to register the edge images. Testing results showed that the KAZE feature has better performance than the SURF and BRISK features in the thermal and color image registration of maize. On the basis of the thermal and color image registration, the depth data of maize were assigned with temperature values. Third, the depth data of maize were further processed with denoising, maize extraction, amplification, smoothing, and temperature correction steps to improve the data qualities. Finally, the crop water stress index and canopy–air temperature difference values of each point were calculated. The results demonstrated that the system and the proposed method can effectively detect the water stress characteristics of maize in 3D, which can be combined with the morphological traits of leaves to synthetically analyze the water stress resistance of the crop.

Deep Learning Based Super Resolution and Classification Applications for Neonatal Thermal Images

The thermal camera systems can be used in all kinds of applications that require the detection of heat change, but thermal imaging systems are highly costly systems. In recent years, developments in the field of deep learning have increased the success by obtaining quality results compared to traditional methods. In this paper, thermal images of neonates (healthy - unhealthy) obtained from a high-resolution thermal camera were used and these images were evaluated as high resolution (ground truth) images. Later, these thermal images were downscaled at 1/2, 1/4, 1/8 ratios, and three different datasets consisting of low-resolution images in different sizes were obtained. In this way, super-resolution applications have been carried out on the deep network model developed based on generative adversarial networks (GAN) by using three different datasets. The successful performance of the results was evaluated with PSNR (peak signal to noise ratio) and SSIM (structural similarity index measure). In addition, healthy - unhealthy classification application was carried out by means of a classifier network developed based on convolutional neural networks (CNN) to evaluate the super-resolution images obtained using different datasets. The obtained results show the importance of combining medical thermal imaging with super-resolution methods.

Real‐Time Thermal Imaging based on the Simultaneous Rise and Decay Luminescence Lifetime Thermometry

The most reliable technique of remote temperature sensing considers either the rise or the decay transient of a luminescent temperature probe. Here, real‐time visible (Vis) and near‐infrared (NIR) thermal imagings based on the simultaneous measurement of the emission rise and decay of transition or lanthanide metal activator are described. A single pulse time‐gated detection method that allows the real‐time mode of the temperature measurement, the emission detection at its highest temporal intensity, and the tunability of the emission detection in terms of time delay and gate width is proposed. Cr‐ZnGaGeO4/ZnGa2O4; Er, Ho, Yb–Y2O3 and Er, Ho, Yb–β‐NaYF4 nanoparticles that display luminescence in the Vis to NIR range (450–1200 nm) with timescales varying from 10 to 100 ms are selected. Maximum relative temperature sensitivity in Vis to Vis and NIR to NIR imaging which exceeds up to a factor of two the values obtained by the standard average lifetime method is achieved. This method applies to any lifetime‐based luminescent thermometer, opening a new avenue in designing accurate and straightforward lifetime thermal imaging systems operating in the Vis to NIR range.

Porosity formation mitigation in laser powder bed fusion process using a control approach

This study deals with quality control of the laser powder bed fusion (L-PBF) process using a temperature measurement approach rather than the commonly used energy density criterion. Temperature domains corresponding to the most common porosities, namely; lack of fusion (LOF), lack of penetration (LOP), and keyhole, were determined in a range of process parameters using a thermal imaging system. A safe zone was introduced by defining a lower and an upper limit based on the critical temperatures causing transitions from LOP to defect-free and from defect-free to keyhole zones, respectively. A proportional-integral-derivative (PID) controller was used to maintain the melt pool temperature within the safe zone during the L-PBF process for Inconel 625 and avoid the formation of porosities, regardless of the initial condition selected and the scanning speed employed. In all cases, a short settling time in the order of the printing time for a few layers was required to reach the steady-state condition at which defect-free parts could be obtained. The knowledge gained from this study can pave the way for the development of new temperature-based criteria considering all process variables contributing a role in the L-PBF process.