Thermal Imaging Applications Research Articles

Plasmonic Photovoltaic Effect of an Original 2D Electron Gas System and Application in Mid‐Infrared Imaging

AbstractOwing to their consistently emerging applications in modern photonics, highly sensitive and rapid mid‐infrared (MIR) photodetectors, operating at high temperatures, are of great significance. Herein, a novel PbTe/Ge heterostructure is introduced. Notably, the discovery of a 2D electron gas (2DEG) system on the surface of the PbTe layer is experimentally identified for the first time. A high‐performance PbTe/Ge heterostructure MIR photodetector utilizing a plasmonic photovoltaic effect is developed by employing asymmetric electrodes. The photodetecting device demonstrates an exceptionally high detectivity of 1.1 × 1011 Jones along with a short response time of 15 ns at room temperature. Additionally, the proposed plasmonic photovoltaic mechanism of the device is investigated and mainly ascribed to the propagating plasmons, generated by the coupling of the 2DEG with incident MIR photons. Moreover, a linear detector array (LDA) of PbTe/Ge is demonstrated for a thermal imaging application, which exhibits promising high‐quality real‐time imaging via the 2D photodetector arrays on Ge‐based integrated circuits. This work opens up a new way for the development of next‐generation, advanced MIR photonic devices and integrated photonic systems.

From sunburn detection to optimal cooling: A review of recent applications of thermal imaging to improve preharvest and postharvest handling of fruit and vegetables

Fruit and vegetables (FV) are susceptible to adverse physiological and biochemical changes due to temperature abuse during preharvest and postharvest handling. Rapid, reliable, and non-invasive technologies such as infrared (IR) cameras are new, cost-effective tools that can record temperature profiles of FV in real-time. In this article, the basic principles of thermal imaging (TI) technology and its recent applications in preharvest and postharvest handling of FV as a temperature monitoring tool are concisely highlighted. Detection of preharvest and postharvest quality of FV (wetness, immaturity, bruise, etc.) based on thermal images are also summarized. Additionally, different modeling and simulation methods, including statistical modeling, computer simulation, machine learning (MLR), and deep learning (DLR), are briefly introduced into the preharvest and postharvest handling of FV, and applications of TI technique as a temperature validation tool in these methods are also discussed. This review article summarized that non-contact TI technique exhibits great potential to monitor temperature profiles on the field and during the postharvest handling of FV in real-time. Quality attributes, such as sunburn, immaturity, and bruises in FV, can be detected by using thermal images. Therefore, yields can be increased in the field, and food losses reduced during the postharvest handling of FV using TI technology. Furthermore, TI technology is an effective validation tool for simulation studies of foods. Future research should focus on developing low-cost TI systems and integrating multiple imaging techniques to facilitate the decision-making process in the FV industry.

Dual-band and spectrally selective infrared absorbers based on hybrid gold-graphene metasurfaces

In this paper, we propose a dual-band and spectrally selective infrared (IR) absorber based on a hybrid structure comprising a patterned graphene monolayer and cross-shaped gold resonators within a metasurface. Rooted in full-wave numerical simulations, our study shows that the fundamental absorption mode of the gold metasurface hybridizes with the graphene pattern, leading to a second absorptive mode whose properties depend on graphene’s electrical properties and physical geometry. Specifically, the central operation band of the absorber is defined by the gold resonators whereas the relative absorption level and spectral separation between the two modes can be controlled by graphene’s chemical potential and its pattern, respectively. We analyze this platform using coupled-mode theory to understand the coupling mechanism between these modes and to elucidate the emergence and tuning of the dual band response. The proposed dual-band device can operate at different bands across the IR spectrum and may open new possibilities for tailored sensing applications in spectroscopy, thermal imaging, and environmental monitoring.

Application of Thermal Imaging for Assessing Desiccation Stress Memory in Sugarcane and Sorghum Cultivars

Application of Thermal Imaging for Assessing Desiccation Stress Memory in Sugarcane and Sorghum Cultivars

Experimental and theoretical heat transmission through a skin phantom using a Ruby IR therapeutic lamp.

A skin phantom model was developed and characterized to study the interaction of infrared radiation during photothermal therapy. The phantom consists of a platinum silicone matrix with polyethylene oxide containing encapsulated sodium alginate to mimic the concentration of water in human skin. The specific heat and thermal conductivity of each component were experimentally measured. A theoretical model was built with heat transfer equations to simulate the temperature distribution. The experimental results and numerical simulations show that the interaction phenomenon with infrared radiation is superficial, concentrating mostly in the epidermis and part of the dermis. This successfully replicates the actual thermal behaviour of the skin during photothermal therapy. The developed phantom adequately represents the thermal properties and response to infrared radiation of the skin, allowing its use as a surrogate model in thermal imaging and diagnostic applications.

Thermal imaging study of Sm2+ doped SrB4O7 based on time-resolved technology.

Thermal imaging materials with high sensitivity and the ability to reflect real-time temperature play an important role in research areas such as biotechnology and electronic engineering. However, the temperature sensitivity and temporal resolution of the current materials are not suitable for the complicated detection situation. In this paper, we introduce a thermal imaging material - SrB4O7:5%Sm2+ - with high temperature sensitivity. Furthermore, by applying a time resolving technique based on an intensified charge-coupled device, the sensitivity and temporal resolution are greatly promoted. The good temperature sensitivity (9.67% K-1 at 533 K), the high spatial resolution (2.7 μm) and the fast detection time (<1 s) suggest its considerable potential for real-time thermal imaging applications. The results of temperature distribution on a printed circuit board show that the as-prepared material will be greatly beneficial for thermal imaging applications.

A Review of Modern Thermal Imaging Sensor Technology and Applications for Autonomous Aerial Navigation

A Review of Modern Thermal Imaging Sensor Technology and Applications for Autonomous Aerial Navigation

Thermal imaging for cancer detection

Problem: There is a need for effective and non-invasive techniques for early cancer detection to improve treatment outcomes and patient care. Motivation: This research explores the potential of thermal imaging as a non-invasive technique for cancer detection. Aim: The aim of this study is to investigate thermal imaging as a valuable tool for early cancer detection and its potential to enhance treatment outcomes and patient care. Methodology: The paper discusses the principles of thermal imaging, its advantages and limitations, and its application to various types of cancer. It also presents a review of recent studies in the field. Main results: The findings suggest that thermal imaging holds promise as a valuable tool for early cancer detection. Further impact of those results: The potential application of thermal imaging in cancer detection could lead to improved treatment outcomes and enhance overall patient care. The article also highlights the challenges and future prospects of thermal imaging in this domain.

Application of thermal imaging combined with machine learning for detecting the deterioration of the cassava root

Freshness is an important parameter that is indexed in the quality assessment of commercial cassava tubers. Cassava tubers that are not fresh have reduced starch content. Therefore, in this study, we aimed to develop a new approach to detect cassava root deterioration levels using thermal imaging with machine learning (ML). An underlying assumption was that nonfresh cassava roots may have fermentation inside that causes a difference in the inner temperature of the tuber. This creates the opportunity for the deterioration level to be measured using thermal imaging. The features (pixel intensity and temperature) that were extracted from the region of interest (ROI) in the form of tuber thermal images were analyzed with ML. Linear discriminant analysis (LDA), k-nearest neighbor (kNN), support vector machine (SVM), decision tree, and ensemble classifiers were applied to establish the optimal classification modeling algorithms. The highest accuracy model was developed from thermal images of cassava roots captured in a darkroom under a control temperature of 25 °C in the measurement chamber. The LDA, SVM, and ensemble classifiers gave the best overall performance for the discrimination of cassava root deterioration levels, with an accuracy of 86.7%. Interestingly, under uncontrolled environmental conditions, the combination of thermal imaging plus ML gave results that were of lower accuracy but still acceptable. Thus, our work revealed that thermal imaging coupled with ML was a promising method for the nondestructive evaluation of cassava root deterioration levels.

Fabrication and Evaluation of Chalcogenide-glass Diffractive-aspheric Lenses Used in Thermal Imaging Applications

Fabrication and Evaluation of Chalcogenide-glass Diffractive-aspheric Lenses Used in Thermal Imaging Applications

Polarization- and angle-insensitive broadband long wavelength infrared absorber based on coplanar four-sized resonators.

In many potential applications, there is a high demand for long wavelength infrared (LWIR) absorbers characterized by a compact configuration, broad operational bandwidth, high absorption efficiency, and polarization- and angle-insensitive characteristics. In this study, we design and demonstrate a high-performance broadband LWIR absorber based on coplanar four-sized resonators, consisting of arrays of titanium (Ti) disks with different diameters supported by a continuous zinc selenide (ZnSe) layer and by a Ti film acting as a back-reflector. Particle swarm optimization (PSO) is employed to optimize the complicated geometry parameters, and the final optimized device exhibits near-unity absorption (∼96.7%) across the entire operational bandwidth (8 µm∼14 µm) under unpolarized normal incidence, benefiting from the impedance-matching condition and the multiple surface plasmon resonances of this configuration. Furthermore, the proposed absorber is insensitive to the angle of incidence due to the localized surface plasmon resonances supported by these four-sized resonators, and is insensitive to the state of polarization thanks to the highly symmetric feature of the circular pattern. The measured absorption of the fabricated sample exhibits a relatively high coincidence with the simulation, with an average absorption of 88.9% ranging from 8 µm to 14 µm. The proposed absorber, which can be easily integrated into a standardized micro/nano manufacture process for cost-effective large-scale production, provides a feasible solution for improving optical performance in thermal emitter, infrared detection, and imaging applications. Furthermore, the generalized design principle employing the optimized method opens up new avenues for realizing target absorption, reflection, and transmission based on more complicated structure configurations.

Synergetic application of thermal imaging and CCD imaging techniques to detect mutton adulteration based on data-level fusion and deep residual network

To improve the performance of single thermal imaging and single CCD imaging in detecting unknown adulterated meat samples, these two imaging techniques combined with a deep residual network were synergistically applied to detect mutton adulteration. Considering the importance of spatial and detailed information in improving stability and accuracy, three data-level fusion methods, namely, colour image stitching, grey image stitching and grey channel stacking, were proposed for the fusion of thermal images and CCD images. Classification and prediction models were further developed based on fusion images. The results showed that the models with colour image stitching achieved the best performance. For the external validation set, the accuracy of the best classification model in discriminating five categories was 99.30%. In predicting pork proportions, the R2, RMSE, RPD and RER of the best prediction model were 0.9717, 0.0238, 7.8696 and 21.28, respectively. The best prediction model for duck proportions had a R2 of 0.9616, RMSE of 0.0277, RPD of 5.1015, and RER of 14.44. Therefore, the synergetic application of thermal imaging and CCD imaging can provide a novel and promising tool to detect mutton adulteration and the quality of other food items.

Broadband long-wave infrared metamaterial absorbers based on germanium resonators

The broadband metamaterial perfect absorbers over various incident angles are highly significant in long-wave infrared (LWIR) detection. Previous research on LWIR metamaterial absorbers has mainly focused on metallic resonators. Here, we propose two broadband LWIR metamaterial absorbers that use dielectric resonators instead. The germanium (Ge) resonators on the top layer excite resonance modes that control the equivalent impedance of the structure, which acts on the high-lossy Si3N4-Ti reflecting layer to assume the absorption. Firstly, we designed a three-layer structure of Ge-Si3N4-Ti, which achieved a broadband absorption with an average absorptivity of 93.1 % in the 8–12 μm range. The absorption ratio of metal can be effectively reduced by replacing the metal. Then, to further enhance the absorptivity, we inserted a Si3N4 layer into the Ge layer, increasing the 90 % absorption bandwidth to 7.96–14.16 μm and the average absorptivity in 8–14 μm to 96.5 %. Compared to metamaterial absorbers based on metallic resonators, dielectric resonators with a large feature size make fabricating easier. Our proposed metamaterial absorber provides ultra-wideband absorption covering the LWIR range. In addition, it is insensitive to the incident angle, making it a potential candidate for thermal imaging and broadband thermal emission applications.

In Situ Analysis of Curling Defects in Powder Bed Fusion of Polyamide by Simultaneous Application of Laser Profilometry and Thermal Imaging

Additive manufacturing (AM) is one of the key technologies in the global manufacturing market within various application sectors. The unique capabilities of AM enable high structural and part complexity, low material waste, and benefits in productivity by reducing design cycles and time to market. Efficient real-time quality control is still an important challenge in AM. In this paper, a real-time and in situ approach for monitoring the process in powder bed fusion of polyamide (PBF-LB/P/PA12) is proposed using the simultaneous application of two individual sensors, enabling the overlay and direct comparison of independent output data. An industrial grade laser profilometer and a thermal infrared (IR) camera were successfully integrated into a commercial system for PBF-LB/P. Artificially created curling defects were induced in a reproducible way by the manipulation of process parameters. The radiometric data was evaluated and processed into 3D topology and profile measurements to highlight peaks and curling progression. The results measured using different powder bed conditions were contrasted with corresponding thermographic data to prove the thermal visibility of curling and the influence of inhomogeneous temperature distribution on geometrical powder surface defects. The experimental setup enables the measuring of the entire powder bed surface inside the machine, with no limitations to sub-areas. Results indicate the measurable presence of curling and related temperature influences. When curling reached maximum values, inverted warpage into the negative z-direction was detected at part center as a further effect. These results can be used for improving real-time quality control in AM.

Compact single-band and multiband terahertz plasmonic absorbers using hybrid graphene-metal resonators with switching and modulation capability

THz thermal and single-pixel imaging need compact tunable absorbers with features like high modulation depth and multi bandwidth in the case of multispectral imaging. Here we are going to propose compact switchable absorbers based on a hybrid graphene-metal resonator that is designed through a genetic algorithm and numerical method. The proposed absorbers have a thickness as small as λmax/120 and can acquire perfect modulation depth. The special shape of the proposed resonator helps to gather 6 resonance bands in a very compact unit-cell. A theoretical formula is proposed to predict the resonance frequencies of the absorber based on Fabry-Perot concepts and graphene-metal plasmons. The role of local and propagating surface plasmon and their hybridization in the absorption mechanism is clarified. The modulation capabilities and tunability of the absorbers are analyzed. The absorbers work very well in a wide range of incident angles. Based on numerical analysis the hybrid resonators were capable of suppressing parasitic resonance modes making the designed absorbers ideal for emitter applications. The proposed absorbers have applications in THz thermal imaging, modulators, and emitters.

Ca4(PO4)2O:Eu2+, Eu3+ phosphor enabled sundry spectral range sub-K optical thermometry

Herein, we report on the luminescence and thermometric properties of Ca4(PO4)2O:Eu. The photoluminescence emission exhibited blue and red bands from Eu2+ and yellow and red lines from Eu3+. The multiple-emission features allowed a study of the thermometric properties in the different spectral ranges, namely, blue-green, yellow, red and near-infrared, using the luminescence intensity ratio method. The average temperature sensitivities of 1.76, 0.1, 0.11 and 0.11%/°C (in the temperature range of 30–60 °C) were obtained from the 425 to 525 nm, 560 to 580 nm, 615 to 635 nm, and 635 to 900 nm spectral ranges, respectively. The lifetime method produced high-temperature sensitivities of 1.96%/°C and 1.77%/°C in the 20–60 °C from the 700 to 455 nm bands, respectively. This suggests that this material could be applied in low-temperature thermal imaging applications such as thermal convection and biological processes.

Broadband Plasmonic Metamaterial Optical Absorber for the Visible to Near-Infrared Region

An oblique angle and polarization insensitive metamaterial absorber (MA) are highly desired for the visible and infrared optical applications like, wave energy harvesting, optical filters, and detecting thermal leaks and electrical defects. In this paper, a multi-layered MA consisting of two layers of tungsten resonators on a silicon dioxide substrate, coated with additional SiO2 materials is investigated. The unit cell size of the MA is 0.5λ × 0.5λ × 0.8λ, at the lowest wavelength. The proposed MA offers an average absorption of 92% from 400 nm to 2400 nm with stable oblique incident angles up to 45°. The structure also achieves polarization insensitivity at the entire visible and near-infrared spectrum. Moreover, the MA is found highly compatible for solar absorber applications with high y AAM1.5. The structure is also compatible for filter application in optical communication system by modifying the plasmonic nano structure. The modified structure can block the wavelengths of the visible band (450 nm to 800 nm) and transmit optical communication bands (800 to 1675 nm). These versatile absorption and filtering performance make the proposed design highly potential for solar energy harvesting, photodetection, thermal imaging, photo-trapping, and optical communications applications.

Design and Parametric Analysis of a Wide-Angle and Polarization Insensitive Ultra-Broadband Metamaterial Absorber for Visible Optical Wavelength Applications

Researchers are trying to work out how to make a broadband response metamaterial absorber (MMA). Electromagnetic (EM) waves that can pass through the atmosphere and reach the ground are most commonly used in the visible frequency range. In addition, they are used to detect faults, inspect tapped live-powered components, electrical failures, and thermal leaking hot spots. This research provides a numerical analysis of a compact split ring resonator (SRR) and circular ring resonator (CRR) based metamaterial absorber (MMA) using a three-layer substrate material configuration for wideband visible optical wavelength applications. The proposed metamaterial absorber has an overall unit cell size of 800 nm × 800 nm × 175 nm in both TE and TM mode simulations and it achieved above 80% absorbance in the visible spectrums from 450 nm to 650 nm wavelength. The proposed MA performed a maximum absorptivity of 99.99% at 557 nm. In addition, the steady absorption property has a broad range of oblique incidence angle stability. The polarization conversion ratio (PCR) is evaluated to ensure that the MMA is perfect. Both TM and TE modes can observe polarization insensitivity and wide-angle incidence angle stability with 18° bending effects. Moreover, a structural study using electric and magnetic fields was carried out to better understand the MMA's absorption properties. The observable novelty of the proposed metamaterial is compact in size compared with reference paper, and it achieves an average absorbance of 91.82% for visible optical wavelength. The proposed MMA also has bendable properties. The proposed MMA validation has been done by two numerical simulation software. The MMA has diverse applications, such as color image, wide-angle stability, substantial absorption, absolute invisible layers, thermal imaging, and magnetic resonance imaging (MRI) applications.

Применение инфракрасных изображений для обнаружения и визуализации источников радиоактивного излучения

The application of thermal images for visualization of small-sized, masked sources of radioactive radiation by the heating of objects caused by them as a result of heat release during radioactive decay is considered. The acquisition of IR images of a thermal imitator of a radioactive source is simulated. Known applications of thermal imagers for remote visualization of radioactive sources are analyzed. IR images of fragments of irradiated fuel elements are presented.

Review of Application of Thermal Imaging for Face Recognition

Recent advances in facial recognition utilizing infrared as a source are described. Recent research has concentrated on face identification using visible light, with the main issue being that the lighting on the face varies in outside circumstances. Recent studies employ infrared light as a source to produce infrared face pictures to overcome this and increase performance. This is known as a thermal face image, and it is extremely valuable in a variety of application systems. Night surveillance systems and military applications are two applications where night vision comes into picture. The choice of infrared, intensity fluctuation, and angle of incidence all play crucial roles in these applications. Keywords: Face recognition, multi spectral images, LBP, SIFT