Proceedings Volume 9485

Thermosense: Thermal Infrared Applications XXXVII

Proceedings Volume 9485

Thermosense: Thermal Infrared Applications XXXVII

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Volume Details

Date Published: 10 June 2015
Contents: 11 Sessions, 50 Papers, 0 Presentations
Conference: SPIE Sensing Technology + Applications 2015
Volume Number: 9485

Table of Contents


Table of Contents

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  • Front Matter Volume 9485
  • Aerospace Applications
  • Building Materials and Infrastructure Applications I
  • Building Materials and Infrastructure Applications II
  • Detector and Sensory System Development
  • NDT and Signal Processing
  • NDT and Materials Evaluation I
  • Manufacturing and Processing Industries
  • NDT and Materials Evaluation II
  • Detection of Gas and Leaks
  • Biological/Medical Applications
Front Matter Volume 9485
Front Matter Volume 9485
This PDF file contains the front matter associated with SPIE Proceedings Volume 9485 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.
Aerospace Applications
Real time fatigue damage growth assessment of a composite three-stringer panel using passive thermography
Joseph N. Zalameda, Eric R. Burke, Michael R. Horne, et al.
Fatigue testing of advanced composite structures is critical to validate both structural designs and damage prediction models. In-situ inspection methods are necessary to track damage onset and growth as a function of load cycles. Passive thermography is a large area, noncontact inspection technique that is used to detect composite damage onset and growth in real time as a function of fatigue cycles. The thermal images are acquired in synchronicity to the applied compressive load using a dual infrared camera acquisition system for full (front and back) coverage. Image processing algorithms are investigated to increase defect contrast areas. The thermal results are compared to non-immersion ultrasound inspections and acoustic emission data.
Nondestructive evaluation of aircraft coatings with infrared diffuse reflectance spectra
Hans G. Korth, Kody A. Wilson, Kevin C Gross, et al.
Aircraft coatings degrade over time, but aging can be difficult to detect before failure and delamination. We present a method to evaluate aircraft coatings in situ using infrared diffuse reflectance spectra. This method can detect and classify coating degradation much earlier than visual inspection. The method has been tested on two different types of coatings that were artificially aged in an autoclave. Spectra were measured using a hand-held diffuse reflectance infrared Fourier transform spectrometer (DRIFTS). One set of 72 samples can be classified as either aged or unaged with 100% accuracy. A second sample set contained samples that had been artificially aged for 0, 24, 48 or 96 hours. Several classification methods are compared, with accuracy better than 98% possible.
Comparative evaluation of aerospace composites using thermography and ultrasonic NDT techniques
P. Theodorakeas, N. P. Avdelidis, I. Hatziioannidis, et al.
In the present research work a study was carried out evaluating the applicability of two NDT techniques, this of Transient Thermography (TT) and Ultrasonic Testing (UT) for the inspection of different types of composite materials (i.e. laminated CFRPs, laminated hybrid FRPs and sandwiched panels). The composite structures were consisted of a variety of artificial defects, while inspection was performed through different testing configurations. In particular, transient thermography was implemented through the monitoring of the surface transient cooling after flash heating the samples and ultrasonic testing was applied using both a conventional single element probe (immersion technique) and a linear phased array transducer consisted of 128 elements. The main objective of this work was to compare the applicability and effectiveness of the two techniques in aerospace composites inspection as well as to evaluate the accuracy produced regarding the quantitative characterisation of the detected features. The obtained results showed that all the defects were revealed by either transient thermography or ultrasonic testing, whilst thermographic inspection can display the acquired results in a more rapid manner. On the other hand UT testing can provide efficient results for deeper probing requiring however longer inspection times. In other words, the acquired data and the respective analyses highlighted the different capability of each testing configuration, to detect defects and to gain knowledge for the interior of the structures.
A new approach on JPSS VIIRS BCS and SVS PRT calibration
Tung R. Wang, Steve Marschke, Michael Borroto, et al.
A set of calibrated platinum resistance thermometers (PRT’s) was used to monitor the temperature of a Blackbody Calibration Source (BCS) and Space View Source (SVS). BCS is Ground Support Equipment (GSE) used to validate the emissive band calibration of Visible Infrared Imaging Radiometer Suite (VIIRS) of the Joint Polar Satellite System (JPSS). Another GSE, the SVS was used as an optical simulator to provide zero radiance sources for all VIIRS bands. The required PRT temperature 1 uncertainty is less than 0.030K. A process was developed to calibrate the PRTs in its thermal block by selecting a single thermal bath fluid that is compatible with spaceflight, is easy to clean and supported the entire temperature range. The process involves thermal cycling the PRTs that are installed in an aluminum housing using RTV566A prior to calibration. The PRTs were calibrated thermal cycled again and then calibrated once more to verify repeatability. Once completed these PRTs were installed on both the BCS and SVS. The PRT calibration uncertainty was estimated and deemed sufficient to support the effective temperature requirements for the operating temperature range of the BCS and SVS.
Integration of infrared and optical imaging techniques for the nondestructive inspection of aeronautic parts
F. López, S. Sfarra, C. Ibarra-Castanedo, et al.
This work focuses in the implementation of infrared and optical imaging techniques for the inspection of aeronautics parts. To this aim, a helicopter blade with known defects is inspected with four different techniques: long pulse thermography, pulsed thermography, digital speckle photography (DSP) and holographic interferometry (HI). The first two techniques belongs to the group of infrared imaging techniques, which are based on the analysis of the infrared thermal patterns in order to detect internal anomalies in the material; whilst the last two (DSP and HI) corresponds to the optical imaging techniques which make use of visible light to measure the material response to an applied stress. Both techniques were applied using the active approach, i.e. an external stimulation is applied in order to produce a gradient in either, the thermal and/or displacement field of the material. The results are then compared in order to evaluate the advantages and limitations of each technique.
Building Materials and Infrastructure Applications I
Practical identification of moisture sources in building assemblies using infrared thermography
Water, in its various phases, in any environment other than desert (hot or cold) conditions, is the single most destructive element that causes deterioration of materials and failure of building assemblies. It is the key element present in the formation of mold and fungi that lead to indoor air quality problems. Water is the primary element that needs to be managed in buildings to ensure human comfort, health and safety. Under the right thermodynamic conditions the detection of moisture in its various states is possible through the use of infrared thermography for a large variety of building assemblies and materials. The difficulty is that moisture is transient and mobile from one environment to another via air movement, vapor pressure or phase change. Building materials and enclosures provide both repositories and barriers to this moisture movement. In real life steady state conditions do not exist for moisture within building materials and enclosures. Thus the detection of moisture is in a constant state of transition. Sometimes you will see it and sometimes you will not. Understanding the limitations at the time of inspection will go a long way to mitigating unsatisfied clients or difficult litigation.

Moisture detection can be observed by IRT via three physical mechanisms; latent heat absorption or release during phase change; a change in conductive heat transfer; and a change in thermal capacitance. Complicating the three methodologies is the factor of variable temperature differentials and variable mass air flow on, through and around surfaces being inspected. Building enclosures come in variable assembly types and are designed to perform differently in different environmental regions. Sources for moisture accumulation will vary for different environmental conditions. Detection methodologies will change for each assembly type in different ambient environments.

This paper will look at the issue of the methodologies for detection of the presence of moisture and determination of the various sources from which it accumulates in building assemblies. The end objective for IRT based moisture detection inspections is not to just identify that moisture is present but to determine its extent and source. Accurate assessment of the source(s) and root cause of the moisture is critical to the development of a permanent solution to the problem.
Evaluation of angle dependence in spectral emissivity of ceramic tiles measured by FT-IR
Ceramic tiles are widely used for building walls. False detections are caused in inspections by infrared thermography because of the infrared reflection and angle dependence of emissivity. As the first problem, ceramic tile walls are influenced from backgrounds reflection. As the second problem, in inspection for tall buildings, the camera angles are changed against the height. Thus, to reveal the relation between the emissivity and angles is needed. However, there is very little data about it. It is impossible to decrease the false detection on ceramic tile walls without resolving these problems; background reflection and angle dependence of emissivity. In this study, the angle problem was investigated. The purpose is to establish a revision method in the angle dependence of the emissivity for infrared thermography. To reveal the relation between the emissivity and angles, the spectral emissivity of a ceramic tile at various angles was measured by FT-IR and infrared thermographic instrument. These two experimental results were compared with the emissivity-angle curves from the theoretical formula. In short wavelength range, the two experimental results showed similar behavior, but they did not agree with the theoretical curve. This will be the subject of further study. In long wavelength range, the both experimental results almost obeyed the theoretical curve. This means that it is possible to revise the angle dependence of spectral emissivity, for long wavelength range.
Study of experimental parameters for IRT applications in building elements using multi-layered analytical solutions
Catarina Serra, Nuno Simões, António Tadeu
This paper compares experimental and heat transfer modeling results for thermography applications in building elements. Over the years most building envelope inspections using infrared thermography (IRT) have been focused on qualitative analysis using mostly passive thermography techniques. However, increased need for the monitorization and assessment of the energy performance and thermal behavior of buildings, along with ongoing structural safety concerns, has raised interest in quantitative studies and active IRT applications in buildings. Numerous other fields have benefited from developments in defect detection studies and from countless non-destructive testing applications. Pulse phase thermography, in which phase images are studied (instead of temperature images) using a long heating pulse have been proposed to be the most effective for Civil Engineering applications. However, the particular characteristics of building elements and materials, along with the complex nature of heat transfer phenomena, demand specific experimental procedures and processing techniques. In this paper, analytical solutions to simulate heat transfer in the frequency domain in multi-layered media are used to compute thermal wave phase results. These are compared to experimental IRT phase analysis results of experiments performed on test specimens simulating building elements with embedded defects. Crucial test parameters such as test duration and defect characteristics are changed and their influence is studied. In this way, this paper contributes to the understanding of building envelope thermal patterns using active IRT in defect detection studies and to the definition of test parameters.
Active infrared thermographic testing with distance heating
N. Ogasawara, H. Ando, C. Kobayashi, et al.
In order to efficiently inspect very wide area of concrete structure wall, an infrared thermographic testing with a distance heating was developed in this study. The researched subjects were the following three; 1. Improvement of radiant heating efficiency, 2. Development of distance heating method and 3. Development of data analysis method against nonuniformity of a heating and/or a wall absorptivity. In this paper, we focus on the first issue. In order to investigate about combinations between the spectral emissivity of radiant heater and the spectral absorptivity of concrete, three different types of radiant heater, a near infrared type, a far infrared type and blackbody type, were used to heat concrete specimens. As a results, both a blackbody type and a far infrared type, e.g. a ceramics heater and a blackbody coated heater, can heat a concrete wall more efficiently than a near infrared type, e.g. a halogen lamp heater and a xenon lamp heater. This is because the spectral absorptivity of concrete is higher in a far infrared region than in a near infrared region. We find that the efficiency of the heating process may be improved by choosing a heater whose radiation is concentrated near wavelengths at which the structure to be heated exhibits maximal absorptivity. The efficiency of the concrete heating process may be easily improved simply by covering the surface of a near infrared heater with a blackbody surface coating to mimic the radiation characteristics of a blackbody.
Building Materials and Infrastructure Applications II
Comparison of lock-in and pulse-phase thermography for defect characterization in FRP composites applied to concrete
Jeff Brown, Sai Harsha Chittineni
Thermal imaging is a well-established technique for the non-destructive evaluation of FRP composites applied to reinforced concrete. Defect characterization using IR thermography, however, remains a topic of on-going research, and there are currently no universally accepted standards for data collection or interpretation. This research involved large scale thermography inspection of two FRP strengthened bridge girders that were removed from service after approximately 10 years of service in a potentially corrosive marine environment. Trial inspections were performed on test areas where defects could be identified using sounding methods. Two procedures showed the most promise for identifying and characterizing defects: sinusoidal (lock-in style) heating with periods ranging from 5 s to 40 s and constant step heating for 30 s followed by 60 s of cooling. Both methods resulted in a series of phase images that provided insight into the depth and general nature of detected defects. This paper presents the findings of a comparison study between these two thermal imaging techniques.
Crack depth determination with inductive thermography
B. Oswald-Tranta, R. Schmidt
Castings, forgings and other steel products are nowadays usually tested with magnetic particle inspection, in order to detect surface cracks. An alternative method is active thermography with inductive heating, which is quicker, it can be well automated and as in this paper presented, even the depth of a crack can be estimated. The induced eddy current, due to its very small penetration depth in ferro-magnetic materials, flows around a surface crack, heating this selectively. The surface temperature is recorded during and after the short inductive heating pulse with an infrared camera. Using Fourier transformation the whole IR image sequence is evaluated and the phase image is processed to detect surface cracks. The level and the local distribution of the phase around a crack correspond to its depth. Analytical calculations were used to model the signal distribution around cracks with different depth and a relationship has been derived between the depth of a crack and its phase value. Additionally, also the influence of the heating pulse duration has been investigated. Samples with artificial and with natural cracks have been tested. Results are presented comparing the calculated and measured phase values depending on the crack depth. Keywords: inductive heating, eddy current, infrared
Measurement of flaw size from thermographic data
Simple methods for reducing the pulsed thermographic responses of delaminations tend to overestimate the size of the delamination, since the heat diffuses in the plane parallel to the surface. The result is a temperature profile over the delamination which is larger than the delamination size. A variational approach is presented for reducing the thermographic data to produce an estimated size for a flaw that is much closer to the true size of the delamination. The method is based on an estimate for the thermal response that is a convolution of a Gaussian kernel with the shape of the flaw. The size is determined from both the temporal and spatial thermal response of the exterior surface above the delamination and constraints on the length of the contour surrounding the delamination. Examples of the application of the technique to simulation and experimental data are presented to investigate the limitations of the technique.
Testing and evaluation of concrete structures by thermal wave imaging
Ravibabu Mulaveesala, Juned Siddiqui, Vanita Arora, et al.
Reinforced concrete structures (RCS) have budding applications in civil engineering due to their high strength, durability, sustainability and flexibility in making complex shapes. However, loss of durability of constructed structures due to premature corrosion of rebar is a major constraint. An initial stage of cracking and corrosion of rebar in concrete is not detectable by visual inspection. With a view to avoid catastrophic failure and massive repair of structures, it is essential to determine damage at low levels. Growing concern about the safety of structure due to premature deterioration has led to a significant demand for advancement of non-destructive testing and evaluation (NDT&E) techniques for monitoring and assessing health of RCS. This paper highlights a whole-field, remote, non-destructive testing and evaluation method based on infrared thermography for identifying hidden corrosion of rebar in a concrete structure. Results shown for both time and frequency domain transform techniques prove the effectiveness of the proposed approach for identification of corrosion in rebar in the concrete specimen.
Temperature measurements on solid surfaces in rack-storage fires using IR thermography
J. de Vries, N. Ren, M. Chaos
The development of fire modeling tools capable of predicting large-scale fire phenomena is of great value to the fire science community. To this end, FM Global has developed an open-source CFD fire simulation code, FireFOAM. The accuracy of this code relies fundamentally on high-quality experimental validation data. However, at larger scales, detailed measurements of local quantities (e.g., surface temperatures) needed for model validation are difficult to obtain. Often, the information obtained from large-scale fire tests is limited to the global heat release rates (HRR) or point temperature or heat flux measurements from embedded thermocouples or heat flux gauges, respectively. The present study addresses this limitation by introducing IR thermographic measurements in a three- and a five-tier-high rack storage scenario. IR temperatures are compared against modeled results. The tested and modeled cases represent realistic industrial warehouse fire scenarios. The rack-stored commodity consisted of corrugated paperboard boxes wrapped around a steel cubic liners, placed on top of a hardwood pallet. The global heat release rate was measured using a 20- MW fire products collector located inside FM Global’s Fire Technology Laboratory. An in-house calibrated microbolometer IR camera was used to obtain two-dimensional temperature measurements on the fuel surfaces and on the surfaces inside the flue spaces. Maximum temperatures up to 1200 K were observed on the external surfaces of the test array. Inside the flue spaces between pallet loads, temperatures up to 1400 K were measured. The modeled fire spread results match well fire spread shown in the IR thermographic images. The peak modeled surface temperatures obtained inside some of the horizontal flue spaces were ~1400K, which agreed well with the peak temperatures seen by the IR camera. The effect of the flames present between the surfaces of interest and the IR camera only contribute to about 50 K increase in measured temperature due to the limited flame emissive power with low soot concentration in the long-wave IR regime. This study shows the capability of IR cameras to obtain high resolution temperature measurements in large-scale fire scenarios, which enhances existing large-scale model validation data set.
Comparison of step heating and modulated frequency thermography for detecting bubble defects in colored acrylic glass
Hongjin Wang, Sheng-Jen Hsieh
Step heating thermography and modulated frequency thermography are two commonly used inspection methods. This research compares active step heating thermography and modulated frequency thermography for use in detecting defects with diameters of 1.98 mm to 6 mm buried at depths of 1.5 to 4 mm beneath sample surfaces. Experiments were conducted using colored acrylic samples. Step heating thermography can detect shallowly buried defects as early as 4 seconds after heating. Also, lengthening heating time allows step heating thermography to reveal differences between defects of 4 to 6 mm in diameter buried 1.5 mm to 4 mm beneath glass surface. Modulated frequency thermography provides a higher signal-to-noise ratio of 1.3 for smaller defects. Thus it can be used to detect defects with diameters as small as 1.98 mm buried 4 mm beneath the glass surface. However, this level of detection requires phase frequency to be lowered by an order of 10−3. An open problem is to develop a systematic method and/or heuristics for determining the appropriate frequency for different defect types.
Detection of pinhole defects in optical film using thermography and artificial neural network
Hongjin Wang, Sheng-Jen Hsieh, Bhavana Singh
Optical film provides anti-glare, anti-reflective, and protective features for cell phones and electronic displays such as LCD screens. Due to increased use of optical film, it is challenging for manufacturers to increase their efficiency in producing better quality films. Even a micro scratch in a high-end application of film can lead to a total failure of the display. Optical and visual methods are typically employed to detect defects, but these methods have limitations such as viewing angle artifacts and design of proper illumination source. This paper describes research to utilize artificial neural networks as a non-destructive defect detection model for predicting the presence of pinhole defects in film. An infrared camera captured the thermal response of optical film subjected to heating and cooling. Pinhole defects of various sizes (0.03mm, 0.08mm, 0.2mm, 0.4mm, 0.7mm, 1mm, 2mm, 3mm, 4mm) were investigated. Pinhole defects are one of the most common types of optical film defects. For the process of identification, thermal differences of defective and defect-free regions were investigated. An Artificial Neural Network was trained to use average absolute temperature difference and cooling rate to predict the presence of a defect. The ANN model was trained and verified using separate data sets. The ANN model was able to classify defective and non-defective samples with a 77.8% accuracy rate. The regression coefficient was 0.5874. These results suggest that artificial neural networks can be used for detecting pinhole defects.
Detector and Sensory System Development
Advances in infrared fibers
Infrared (IR) fibers that transmit radiation at wavelengths from ~ 2 μm up to ~ 25 μm, a spectrum that extends across both the mid-IR (MIR) and far-IR (FIR), has gained extensive attention concomitant with the recent availability of MIR semiconductors sources and detectors. Chalcogenide glasses (ChGs) are a leading candidate for IR fibers by virtue of their wide optical transmission windows and high nonlinearity in the IR region. After extensive studies since the 1960s, the development and applications of ChG IR fibers are primarily hindered by their unfavorable mechanical properties. Here, we summarize our recent advances in low-cost, robust multimaterial ChG IR fibers with broad transmission windows and low optical losses, based on our multimaterial fiber preforms produced by several fabrication methodologies. Hundreds of meters of fibers are thermally drawn in an ambient atmosphere with desired step-index structure from a macroscopic multimaterial preform that contains few grams of ChG. These simple and efficient processes overcome many of the traditional obstacles, and therefore enable rapid production in an industrial setting.
Logarithmic InGaAs detectors with global shutter and active dark current reduction
Yang Ni, Bogdan Arion, Christian Bouvier, et al.
In this paper, we present newly developed logarithmic InGaAs detectors with global shuttering and also an active dark current reduction technique to ensure ambient temperature operation without TEC for industrial applications. The newly released detectors come with both VGA (15um pitch) and QVGA (25um pitch) resolutions, giving the possibility to use lens less than 1-inch size. The logarithmic response is obtained by using solar-cell mode InGaAs photodiodes. The VGA and QVGA ROICs have 3 analog memories inside each pixel which permit, except the classic ITR, IWR and CDS modes, a new differential imaging mode which can be a useful feature in active imaging systems. The photodiode frontend circuit, in pure voltage mode, is made with non-inverting amplifier instead of CTIA. The reason of this choice is that the exposure time can be shortened without need of excessive power consumption as in CTIA front-end. We think that this arrangement associated with true CDS could match the noise performance of CTIA based one. VGA and QVGA ROICs have been designed and manufactured by using 0.18um 1P4M CMOS process. Both ROIC have been tested with success and match the design targets. The first batch of both detectors is under fabrication and will be presented during the conference.
The fabrication of sub-micron size cesium iodide x-ray scintillator
Chien Wan Hun, Po Chun Chen, Ker Jer Huang, et al.
The cesium iodide (CsI) scintillator can converts incident X-ray into visible light with very high conversion efficiency of optical photons. The incident energy, response time, film thickness, sample size, and spatial resolution require in engineering and medical applications are difference. A smooth and flat surface and single crystal structure of CsI enhance the X-ray to visible light conversion. However, the regular CsI is soft and extremely hygroscopic; it is very difficult to polish to obtain a smooth and optical flat plane. In order to obtain a good quality of CsI scintillator for X-ray application we used an ordering channel as template and formed sub-micron CsI wire in the template. The fabrication process including: (1) Ordering structure of nano or sub-micron channels were made by an anodization method; (2) fill CsI scintillated film on the channel by CsI solution, (3) fill CsI melt into the channel formation single crystal of sub-micron crystalline scintillator after solidification. The non-vacuum processes of anodization and solidication methods were used for the sub-micron CsI scintillator column formation that is cost down the scintillator fabrication. In addition, through the fabrication method, the ordering structure scintillator of scintillator can be made by anodic treatment and die casting technology with low cost and rapid production; moreover, the film oxidized metal tubes of the tubular template can be further manufactured to nano tubes by adjusting electrolyte composition, electrolysis voltage, and processing time of anodic treatment, and the aperture size, the thickness and the vessel density of the nano tube can be controlled and ranged from 10 nm to 500 nm, 0.1 μm to 1000 μm, and hundred million to thousand billion tube/cm2, respectively.
Swap intensified WDR CMOS module for I2/LWIR fusion
Yang Ni, Vincent Noguier
The combination of high resolution visible-near-infrared low light sensor and moderate resolution uncooled thermal sensor provides an efficient way for multi-task night vision. Tremendous progress has been made on uncooled thermal sensors (a-Si, VOx, etc.). It’s possible to make a miniature uncooled thermal camera module in a tiny 1cm3 cube with <1W power consumption. For silicon based solid-state low light CCD/CMOS sensors have observed also a constant progress in terms of readout noise, dark current, resolution and frame rate. In contrast to thermal sensing which is intrinsic day&night operational, the silicon based solid-state sensors are not yet capable to do the night vision performance required by defense and critical surveillance applications. Readout noise, dark current are 2 major obstacles. The low dynamic range at high sensitivity mode of silicon sensors is also an important limiting factor, which leads to recognition failure due to local or global saturations & blooming. In this context, the image intensifier based solution is still attractive for the following reasons: 1) high gain and ultra-low dark current; 2) wide dynamic range and 3) ultra-low power consumption. With high electron gain and ultra low dark current of image intensifier, the only requirement on the silicon image pickup device are resolution, dynamic range and power consumption. In this paper, we present a SWAP intensified Wide Dynamic Range CMOS module for night vision applications, especially for I2/LWIR fusion. This module is based on a dedicated CMOS image sensor using solar-cell mode photodiode logarithmic pixel design which covers a huge dynamic range (> 140dB) without saturation and blooming. The ultra-wide dynamic range image from this new generation logarithmic sensor can be used directly without any image processing and provide an instant light accommodation. The complete module is slightly bigger than a simple ANVIS format I2 tube with <500mW power consumption.
Highly sensitive arrayed indium-antimony nanowires for infrared detection
Po-Chun Chen, Chien-Chon Chen, Shih-Hsun Chen, et al.
The objective of this study is to achieve a high sensitive infrared detector by fabricating highly ordered array of indium-antimony (In-Sb) nanowires which is a semiconductor material. The approach is to investigate an infrared detector with arrayed nanowires which can transport signals in one dimension to obtain high efficiency and sensitivity compared with In-Sb by using traditional thin film fabrications. This research expects to provide an infrared detector by fabricating III-V alloy nanowires to highly improve the resolution of infrared signal. To develop scaled-up functional devices, highly ordered nanowire arrays are essential building blocks. Many candidate materials (metals, alloys, oxides and semiconductors) have been studied for various potential applications in nanotechnology and have shown some promising results. The solid metallic nanowires have been exploited for a wide range of applications to take the advantages of their large length/diameter aspect ratio. Further development to synthesize nanowires efficiently at lower cost is the direction for manufacturing next generation nanodevices. In this study, various diameters of ordering nanowires, from 10 nm to 500 nm, were fabricated and evaluated the performance of the sensitivity of infrared detection. Moreover, a 1 inch plate, which can be regarded as a device, with nanowires array was fabricated by designing a new type of processing chamber.
Computational methods for improving thermal imaging for consumer devices
In consumer imaging, the spatial resolution of thermal microbolometer arrays is limited by the large physical size of the individual detector elements. This also limits the number of pixels per image. If thermal sensors are to find a place in consumer imaging, as the newly released FLIR One would suggest, this resolution issue must be addressed. Our work focuses on improving the output quality of low resolution thermal cameras through computational means. The method we propose utilises sub-pixel shifts and temporal variations in the scene, using information from thermal and visible channels. Results from simulations and lab experiments are presented.
NDT and Signal Processing
Pulsed thermal NDT in tables, figures, and formulas
Several reviews and summary papers describing the history and the current status of pulsed thermal nondestructive testing (TNDT have been published recently. However, some of the theoretical possibilities cannot easily be implemented in practical applications. This paper contains useful tables and formulas that are illustrated with typical IR thermograms to provide a general overlook of pulsed TNDT.
Advances in thermographic signal reconstruction
Since its introduction in 2001, the Thermographic Signal Reconstruction (TSR) method has emerged as one of the most widely used methods for enhancement and analysis of thermographic sequences, with applications extending beyond industrial NDT into biomedical research, art restoration and botany. The basic TSR process, in which a noise reduced replica of each pixel time history is created, yields improvement over unprocessed image data that is sufficient for many applications. However, examination of the resulting logarithmic time derivatives of each TSR pixel replica provides significant insight into the physical mechanisms underlying the active thermography process. The deterministic and invariant properties of the derivatives have enabled the successful implementation of automated defect recognition and measurement systems. Unlike most approaches to analysis of thermography data, TSR does not depend on flawbackground contrast, so that it can also be applied to characterization and measurement of thermal properties of flaw-free samples. We present a summary of recent advances in TSR, a review of the underlying theory and examples of its implementation.
Principal component analysis of thermographic data
Principal Component Analysis (PCA) has been shown effective for reducing thermographic NDE data. While a reliable technique for enhancing the visibility of defects in thermal data, PCA can be computationally intense and time consuming when applied to the large data sets typical in thermography. Additionally, PCA can experience problems when very large defects are present (defects that dominate the field-of-view), since the calculation of the eigenvectors is now governed by the presence of the defect, not the "good" material. To increase the processing speed and to minimize the negative effects of large defects, an alternative method of PCA is being pursued where a fixed set of eigenvectors, generated from an analytic model of the thermal response of the material under examination, is used to process the thermal data from composite materials. This method has been applied for characterization of flaws.
Review of pulsed phase thermography
Pulsed phase thermography (PPT) was proposed in 1996 to enhance results from pulsed thermography experiments. PPT can be thought as the link between pulsed thermography (PT) and lock-in thermography (LT), since it provides phase delay (and amplitude) data (as in LT) from a PT configuration. PPT theory as well as some experimental investigations has been addressed in detail in previous works. In this paper, we review the basic theory and thee experimental aspects behind PPT and we discuss the latest developments.
A novel data processing algorithm in thermal property measurement and defect detection by using one-sided active infrared thermography
V. P. Vavilov, V. V. Shiryaev, A. O. Chulkov
The proposed algorithm is based on the analysis of an artificial front-surface pixel-based function which includes temperature and time. This function experiences certain extremums, and the corresponding times can be used for determining thermal diffusivity by the formula similar to the known Parker expression. In thermal NDT, such approach being applied to defect areas, provides diffusivity variations which can be used for the evaluation of defect severity in a particular specimen. In this study, both the theoretical basis and the some experimental implementations of the proposed data processing algorithm have been explored to illustrate its validity in thermal properties measurement and thermal NDT, including thermal tomography.
Signal and image processing techniques for testing and evaluation of glass fibre reinforced polymers
Ravibabu Mulaveesala, Vanita Arora, Juned A. Siddiqui, et al.
Glass Fibre Reinforced polymer (GFRP) composites are being used in a wide range of application areas since these materials are less affected by corrosive environmental conditions and provide longer life with less maintenance. However, there are still some concerns about reinforced polymers, such as the presence of surface and sub-surface defects which influence their in service applications. To detect these defects, InfraRed Thermographic (IRT) methods show their potential usage for Non-Destructive Testing and Evaluation (NDT&E) of composite materials due to their inherent testing capabilities such as remote, whole field, quantitative and qualitative to detect surface and sub-surface defects. Thermal NDT&E is broadly categorized into passive or active approach. In passive approach, the test sample's temperature distribution is monitored in the absence of any external heat stimulus at ambient conditions. However, this may not provide ample thermal contrast to detect the defects located at deeper depths. In order to detect deeper defects inside the test specimen, an active thermography is preferred. This can be carried out by applying an external heat stimulus, to induce enough thermal contrast over the test object. The thermal gradients appear over the material during the active heating due to the changes in thermal properties of defective and sound region leading to the detection of subsurface defects. This present work highlights a spectral reshaping by introducing a Gaussian window on the captured thermal profile in a frequency modulated thermal wave imaging and named as Gaussian Windowed Frequency Modulated Thermal Wave Imaging (GWFMTWI) technique. Further various multi-transform techniques (time and frequency domain based) have been introduced in order to test sub-surface defect detection capabilities in chosen GFRP sample. Comparison has been made with the non-stationary linear frequency modulated thermal wave imaging technique in terms of depth scanning capability. Results obtained from GWFMTWI clearly show better detection potential with improved test resolution and sensitivity.
NDT and Materials Evaluation I
Infrared thermography and ultrasound C-scan for non-destructive evaluation of 3D carbon fiber materials: a comparative study
Hai Zhang, Marc Genest, Francois Robitaille, et al.
3D Carbon fiber polymer matrix composites (3D CF PMCs) are increasingly used for aircraft construction due to their exceptional stiffness and strength-to-mass ratios. However, defects are common in the 3D combining areas and are challenging to inspect. In this paper, Stitching is used to decrease these defects, but causes some new types of defects. Infrared NDT (non-destructive testing) and ultrasound NDT are used. In particular, a micro-laser line thermography technique (micro-LLT) and a micro-laser spot thermography (micro-LST) with locked-in technique are used to detect the micro-defects. In addition, a comparative study is conducted by using pulsed thermography (PT), vibrothermography (VT). In order to confirm the types of the defects, microscopic inspection is carried out before NDT work, after sectioning and polishing a small part of the sample..
Characterization of phononic heterostructures by infrared thermography
This work deals with the development of a new class of metamaterials based on phononic composite structures that can offer vibration protection in a wide range of applications. Such phononic heterostructures is a class of phononic crystals that exhibit spectral gaps with lattice constants of a few orders of magnitude smaller than the relevant acoustic wavelength. The design of a phononic composite metamaterial is based on the formation of omnidirectional frequency gaps. This is very much relevant to the dimensionality of a finite slab of the crystal. In this respect, two dimensional structures are used to cut off acoustic waves. In this study, different infrared thermography techniques were used in order to assess the phononic structure’s geometry, as well as to determine the thermal properties of the metamaterial.
Superimpose methods for uncooled infrared camera applied to the micro-scale thermal characterization of composite materials
Junko Morikawa
The mobile type apparatus for a quantitative micro-scale thermography using a micro-bolometer was developed based on our original techniques such as an achromatic lens design to capture a micro-scale image in long-wave infrared, a video signal superimposing for the real time emissivity correction, and a pseudo acceleration of a timeframe. The total size of the instrument was designed as it was put in the 17 cm x 28 cm x 26 cm size carrying box.

The video signal synthesizer enabled to record a direct digital signal of monitoring temperature or positioning data. The encoded digital signal data embedded in each image was decoded to read out. The protocol to encode/decode the measured data was originally defined. The mixed signals of IR camera and the imposed data were applied to the pixel by pixel emissivity corrections and the pseudo-acceleration of the periodical thermal phenomena. Because the emissivity of industrial materials and biological tissues were usually inhomogeneous, it has the different temperature dependence on each pixel. The time-scale resolution for the periodic thermal event was improved with the algorithm for “pseudoacceleration”. It contributes to reduce the noise by integrating the multiple image data, keeping a time resolution.

The anisotropic thermal properties of some composite materials such as thermal insulating materials of cellular plastics and the biometric composite materials were analyzed using these techniques.
A numerical approach for testing and evaluation of mild steel material by thermal wave imaging
Ravibabu Mulaveesala, Geetika Dua, Juned A. Siddiqui, et al.
Among the widely used active infrared non-destructive testing and evaluation methods, coded thermal wave imaging modalities have proved to be an efficient testing and evaluation methods for characterization of various solid materials. These techniques makes use of relatively low peak power heat sources in a moderate time compared with the conventional pulsed based and sinusoidal modulated thermographic approaches respectively. This present work introduces a 11-bit Barker coded thermal wave imaging approach for characterization of mild steel sample having flat bottom holes as defects. Capabilities of the proposed approach has been studied on a mild steel sample containing flat bottom holes as sub-surface defects located at different depths and it has been modeled using a finite element method. Results show the defect detection capabilities of the proposed 11-bit Barker coded excitation scheme as a promising testing and evaluation method to detect the subsurface defects.
Characterization of nuclear graphite elastic properties using laser ultrasonic methods
Fan W. Zeng, Karen Han, Lauren R. Olasov, et al.
Laser ultrasonic methods have been used to characterize the elastic behaviors of commercially-available and legacy nuclear graphites. Since ultrasonic techniques are sensitive to various aspects of graphite microstructure including preferred grain orientation, microcrack orientation and porosity, laser ultrasonics is a candidate technique for monitoring graphite degradation and structural integrity in environments expected in high-temperature, gas-cooled nuclear reactors. Aspects of materials texture can be assessed by studying ultrasonic wavespeeds as a function of propagation direction and polarization. Shear wave birefringence measurements, in particular, can be used to evaluate elastic anisotropy. In this work, laser ultrasonic measurements of graphite moduli have been made to provide insight into the relationship between the microstructures and the macroscopic stiffnesses of these materials. In particular, laser ultrasonic measurements have been made using laser line sources to produce shear waves with specific polarizations. By varying the line orientation relative to the sample, shear wave birefringence measurements have been recorded. Results from shear wave birefringence measurements show that an isostatically molded graphite, such as PCIB, behaves isotropically, while an extruded graphite, such as H-451, displays significant ultrasonic texture. Graphites have complicated microstructures that depend on the manufacturing processes used, and ultrasonic texture in these materials could originate from grain orientation and preferred microcrack alignment. Effects on material isotropy due to service related microstructural changes are possible and the ultimate aim of this work is to determine the degree to which these changes can be assessed nondestructively using laser ultrasonics measurements.
Thermal diffusivity estimation with quantitative pulsed phase thermography
J. E. Ospina-Borras, Juan F. Florez-Ospina, H. D. Benitez-Restrepo, et al.
Quantitative Pulsed Phase Thermography (PPT) has been only used to estimate defect parameters such as depth and thermal resistance. Here, we propose a thermal quadrupole based method that extends quantitative pulsed phase thermography. This approach estimates thermal diffusivity by solving a inversion problem based on non-linear squares estimation. This approach is tested with pulsed thermography data acquired from a composite sample. We compare our results with another technique established in time domain. The proposed quantitative analysis with PPT provides estimates of thermal diffusivity close to those obtained with the time domain approach. This estimation requires only the a priori knowledge of sample thickness.
Manufacturing and Processing Industries
IR-based spot weld NDT in automotive applications
Jian Chen, Zhili Feng
Today’s auto industry primarily relies on destructive teardown evaluation to ensure the quality of the resistance spot welds (RSWs) due to their criticality in crash resistance and performance of vehicles. The destructive teardown evaluation is labor intensive and costly. The very nature of the destructive test means only a few selected welds will be sampled for quality. Most of the welds in a car are never checked. There are significant costs and risks associated with reworking and scrapping the defective welded parts made between the teardown tests.

IR thermography as a non-destructive testing (NDT) tool has its distinct advantage — its non-intrusive and non-contact nature. This makes the IR based NDT especially attractive for the highly automated assembly lines. IR for weld quality inspection has been explored in the past, mostly limited to the offline post-processing manner in a laboratory environment. No online real-time RSW inspection using IR thermography has been reported. Typically for postprocessing inspection, a short-pulse heating via xenon flash lamp light (in a few milliseconds) is applied to the surface of a spot weld. However, applications in the auto industry have been unsuccessful, largely due to a critical drawback that cannot be implemented in the high-volume production line – the prerequisite of painting the weld surface to eliminate surface reflection and other environmental interference. This is due to the low signal-to-noise ratio resulting from the low/unknown surface emissivity and the very small temperature changes (typically on the order of 0.1°C) induced by the flash lamp method.

An integrated approach consisting of innovations in both data analysis algorithms and hardware apparatus that effectively solved the key technical barriers for IR NDT. The system can be used for both real-time (during welding) and post-processing inspections (after welds have been made). First, we developed a special IR thermal image processing method that utilizes the relative IR intensity change, so that the influence of surface reflection and environment interference can be reduced. Second, for the post-processing inspection, a special induction heater is used to replace the flash lamp, resulting in temperature changes on the order of 10°C. As a result, the signal-to-noise ratio increased by several orders of magnitudes with no surface painting needed, and the inspection results are more accurate and reliable. For real-time inspection, the heat from welding (with temperature exceeding 1000°C) was utilized. Third, “thermal signatures” were identified to uniquely correlate to different weld quality attributes through computational modeling of heat transfer and extensive testing of specially designed ranges of welding conditions. Novel IR image analysis algorithms that automatically and intelligently identify the “thermal signatures” from the IR images and positively determine the weld quality in less than a second were developed.
Laser beam welding quality monitoring system based in high-speed (10 kHz) uncooled MWIR imaging sensors
Rodrigo Linares, German Vergara, Raúl Gutiérrez, et al.
The combination of flexibility, productivity, precision and zero-defect manufacturing in future laser-based equipment are a major challenge that faces this enabling technology. New sensors for online monitoring and real-time control of laserbased processes are necessary for improving products quality and increasing manufacture yields. New approaches to fully automate processes towards zero-defect manufacturing demand smarter heads where lasers, optics, actuators, sensors and electronics will be integrated in a unique compact and affordable device.

Many defects arising in laser-based manufacturing processes come from instabilities in the dynamics of the laser process. Temperature and heat dynamics are key parameters to be monitored. Low cost infrared imagers with high-speed of response will constitute the next generation of sensors to be implemented in future monitoring and control systems for laser-based processes, capable to provide simultaneous information about heat dynamics and spatial distribution.

This work describes the result of using an innovative low-cost high-speed infrared imager based on the first quantum infrared imager monolithically integrated with Si-CMOS ROIC of the market. The sensor is able to provide low resolution images at frame rates up to 10 KHz in uncooled operation at the same cost as traditional infrared spot detectors. In order to demonstrate the capabilities of the new sensor technology, a low-cost camera was assembled on a standard production laser welding head, allowing to register melting pool images at frame rates of 10 kHz. In addition, a specific software was developed for defect detection and classification. Multiple laser welding processes were recorded with the aim to study the performance of the system and its application to the real-time monitoring of laser welding processes. During the experiments, different types of defects were produced and monitored. The classifier was fed with the experimental images obtained. Self-learning strategies were implemented with very promising results, demonstrating the feasibility of using low-cost high-speed infrared imagers in advancing towards a real-time / in-line zero-defect production systems.
Comparison of the insulation property of an innovative material and a traditional one by infrared thermography
A. Barizza, P. Bison, S. Boldrini, et al.
An innovative ceramic material has been developed as a possible substitute of the traditional rock-wool as thermal insulating material. It should be used in the future inside a machine working at a temperature greater than 200 °C. The effect of exposition to this temperature for several hours has been evaluated to check if a degradation of the insulating properties can be measured. Experiments did not show any evidence of degradation. Nonetheless the value of the thermal conductivity measured both at high and ambient temperature was not so good as expected. At the same time, the same measurements on rock-wool (the traditional choice for insulation in this machinery) revealed to be very difficult as it is not possible to prepare samples to be tested in a laser flash. To overcome this problem in the measurement of the performance at high temperature a new experiment was prepared by heating one side of the material by means of an electric heater and by looking and comparing (at least qualitatively) the temperature increase on the other side. On the purpose, two parallel-piped samples of the two rival materials, with the same thickness have been prepared and put in contact with the electric heater plate. The temperature evolution of the side facing the ambient has been measured by means of a thermographic camera for almost one hour. The experiment shows that the traditional material owns better insulation performance than the innovative one. Attention has been paid on the properties of the innovative material that, being highly hygroscopic, can maintain a low temperature during the drying process due to the very high value of the latent heat of water when changing from liquid to gas phase.
Thermographic investigation of luminescent barium borate glasses for white-LED applications
Florian Wagner, Peter W. Nolte, Franziska Steudel, et al.
A method to analyze the heat generation in luminescent barium borate glasses under continuous optical excitation is presented. The heat development is monitored by infrared thermography. Experimental surface temperature data are used as input for the differential heat equation to evaluate the volumetric heat rate from the spatial and temporal development of the temperature distribution. Having determined the volumetric heat rate in the glass, the heat generation under optical excitation can be estimated without further knowledge of optical parameters. Experiments on barium borate glasses with different doping levels are performed. For comparison, the heat generation is also estimated on the basis of optical parameters only to confirm the accuracy and validity of the presented method via infrared thermography. The experimentally determined total heat generation is in good agreement with those calculated from optical properties.
About infrared scanning of photovoltaic solar plant
T. Kauppinen, P.-E. Panouillot, S. Siikanen, et al.
The paper is discussing about infrared scanning of PV solar plants. It is important that the performance of each solar panel and cell is verified. One new possibility compared to traditional ground-based scanning (handheld camera) is the utilization of UAV (Unmanned Aerial Vehicle). In this paper results from a PV solar Plant in Western Greece are introduced. The nominal power of the solar plants were 0, 9 MW and 2 MW and they were scanned both by a ground-controlled drone and by handheld equipment. It is essential to know all the factors effecting to results and also the time of scanning is important. The results done from the drone and from ground-based scanning are compared; also results from various altitudes and time of day are discussed.

The UAV (Unmanned Aerial Vehicle/RPAS (Remote Piloted Aircraft Systems) will give an excellent opportunity to monitor various targets which are impossible or difficult to access from the ground. Compared to fixed-wing and helicopter-based platforms it will give advantages but also this technology has limitations. One limitation is the weight of the equipment and the short operational range and short flight time. Also valid procedures must be created for different solutions in the future. The most important thing, as in all infrared thermography applications, is the proper interpretation of results.
NDT and Materials Evaluation II
Three-dimensional non-destructive testing (NDT) in the infrared spectrum
Moulay A. Akhloufi, Yannis Guyon, Abdelhakim Bendada, et al.
Three-dimensional (3D) vision scanning for metrology and inspection applications is an area that knows an increasing interest in the industry. This interest is driven by the recent advances in 3D technologies, permitting to attain high precision measurements at an affordable cost. 3D vision allows for the modelling and inspection of the visible surface of objects. When it is necessary to detect subsurface defects, active infrared (IR) thermography is one of the most used tools today for non-destructive testing (NDT) of materials. Fusion of these two modalities allows the simultaneous detection of surface and subsurface defects and to visualize these defects overlaid on a 3D model of the scanned and modelled parts or their 3D computer-aided design (CAD) models. In this work, we present a framework for automatically fusing 3D data (scanned or CAD) with the infrared thermal images for an NDT process in 3D space.
Thermographic inspection of external thermal insulation systems with mechanical fixing
Nuno Simões, Inês Simões, Catarina Serra, et al.
An External Thermal Insulation Composite System (ETICS) kit may include anchors to mechanically fix the insulation product onto the wall. Using this option increases safety when compared to a simple bonded solution, however, it is more expensive and needs higher labor resources. The insulation product is then coated with rendering, which applied to the insulation material without any air gap. The rendering comprises one or more layers of coats with an embedded reinforcement. The most common multi-coat rendering system presents a base coat applied directly to the insulation product with a glass fiber mesh as reinforcement, followed by a second base coat, before a very thin coat (key coat) that prepares the surface to receive the finishing and decorative coat. The thickness of the rendering system may vary between around 5 to 10 mm. The higher thicknesses may be associated with a reinforcement composed by two layers of glass fiber mesh.

The main purpose of this work is to apply infrared thermography (IRT) techniques to 2 ETICS solution (single or double layer of glass fiber mesh) and evaluate its capability in the detection of anchors. The reliability of IRT was tested using an ETICS configuration of expanded cork boards and a rendering system with one or two layers of glass fiber mesh. An active thermography approach was performed in laboratory conditions, in transmission and reflection mode. In the reflection mode halogen lamps and air heater were employed as the thermal stimulus. Air heater was also the source used in the transmission mode tests. The resulting data was processed in both time and frequency domains. In this last approach, phase contrast images were generated and studied.
Analysis of the relative merits of the 3-5 μm and the 8-12 μm spectral bands using detected thermal contrast
Seán M. Stewart
The two most important atmospheric transmission bands in the infrared occur at 3–5μm and 8–12μm respectively. For a given infrared detector a common question that continues to be asked is, of the two spectral bands, which, if any, gives the better performance? While seemly an innocent enough question, the literature attests it has not been without controversy. Conflicting and often contradictory results have been given that tend to reflect the predilections of the proponent rather than any sort of measured consideration based on technical factors likely to affect performance. In this study an analysis designed to assess the relative merits of infrared detectors operating in the 3–5μm and 8–12μm spectral bands based on the recently defined figure of merit known as the detected thermal contrast is undertaken. The detected thermal contrast attempts to describe the overall performance of the sequence of events from the initial emission of thermal radiation at the surface of a target to the final measurable output signal seen in the detecting instrument. Under ideal limiting conditions typical of those found for many industrial and scientific applications, by considering targets whose spectral emissivities vary as a function of both wavelength and temperature, exact expressions based on the recently introduced polylogarithmic formulation of the problem are developed for both thermal and quantum detectors. It is found the 3–5μm waveband for either detector type gives better performance while differences between the two types of detectors is not as significant as one might initially expect. The work not only extends upon a number of approximate schemes that have been proposed and developed in the past where target emissivities as a function of the temperature have been used, it also challenges a number of previously reported results.
Detection of Gas and Leaks
Time-resolved multispectral imaging of combustion reaction
Alexandrine Huot, Marc-André Gagnon, Karl-Alexandre Jahjah, et al.
Thermal infrared imaging is a field of science that evolves rapidly. Scientists have used for years the simplest tool: thermal broadband cameras. This allows to perform target characterization in both the longwave (LWIR) and midwave (MWIR) infrared spectral range. Infrared thermal imaging is used for a wide range of applications, especially in the combustion domain. For example, it can be used to follow combustion reactions, in order to characterize the injection and the ignition in a combustion chamber or even to observe gases produced by a flare or smokestack. Most combustion gases such as carbon dioxide (CO2) selectively absorb/emit infrared radiation at discrete energies, i.e. over a very narrow spectral range. Therefore, temperatures derived from broadband imaging are not reliable without prior knowledge about spectral emissivity. This information is not directly available from broadband images. However, spectral information is available using spectral filters. In this work, combustion analysis was carried out using Telops MS-IR MW camera which allows multispectral imaging at a high frame rate. A motorized filter wheel allowing synchronized acquisitions on eight (8) different channels was used to provide time-resolved multispectral imaging of combustion products of a candle in which black powder has been burnt to create a burst. It was then possible to estimate the temperature by modeling spectral profile derived from information obtained with the different spectral filters. Comparison with temperatures obtained using conventional broadband imaging illustrates the benefits of time-resolved multispectral imaging for the characterization of combustion processes.
Thermal imaging of microfluidic systems as a model for investigating energy efficiency
Michael G. Mauk, Richard Y. Chiou, Dharma T. Varapula, et al.
We explore the use of a commercial thermal imaging infrared camera (7-12 micron, uncooled microbolometer array, 320 x 240 resolution) to characterize microfluidic devices with the aims of: 1) evaluating the usefulness of thermal imaging to assess various flow configurations with respect to heat transfer, and 2) developing educational laboratory projects combining rapid prototyping, thermal imaging, microfluidics, and heat transfer. We investigated concurrent and countercurrent heat exchangers, mixing streams of different temperature (cold and hot water), mixing streams yielding a heat of mixing (ethanol and water), mixing streams yielding a heat of reaction (acid-base neutralization), and freezing and heating flowing streams in channels with a Peltier module. Energy efficiency can be assessed to determine the feasibility and effectiveness of microfluidic designs. Substantial improvements in mixing and heat transfer using a magnetic stirrer are demonstrated with thermal imaging.
Gas and flame detection and identification using uncooled MWIR imaging sensors
Rodrigo Linares, Germán Vergara, Raúl Gutiérrez, et al.
Gas detectors are nowadays widely spread for safety purposes in industrial facilities. They are categorized by the type of gas they detect: combustible and/or toxic. Whereas electrochemical sensors have limited lifetime and maintenance issues, infrared sensors are reliable and free of maintenance devices used for detecting a wide variety of VOCs and inflammable gases such as hydrocarbon vapors. They usually work via a system of transmitters (light sources) which power is interfered when a gas is present in the optical path. A spectral analysis of this optical interference allows the gas detection and identification. Optical flame detectors are sensors intended to sight and respond to the presence of a flame, faster than a smoke detector or a heat detector would do. Many of these systems operate in the infrared band in order to detect the heat radiation, most of the times by comparison of three specific wavelength bands.

Most of the present infrared gas and optical flame detectors traditionally make use of MWIR single point sensors rather than imaging sensors; this is mainly due to the lack of affordable imaging sensing technologies in this band of the infrared spectrum. However, the appearance of uncooled imaging MWIR sensors made of VPD PbSe, with spectral detection range from 1 to 5 microns, opens the possibility to incorporate these sensors into gas and flame detection systems to allow area monitoring.
Detection of seal contamination in heat-sealed food packaging based on active infrared thermography
Karlien D'huys, Wouter Saeys, Bart De Ketelaere
In the food industry packaging is often applied to protect the product from the environment, assuring quality and safety throughout shelf life if properly performed. Packaging quality depends on the material used and the closure (seal). The material is selected based on the specific needs of the food product to be wrapped. However, proper closure of the package is often harder to achieve. One problem possibly jeopardizing seal quality is the presence of food particles between the seal. Seal contamination can cause a decreased seal strength and thus an increased packaging failure risk. It can also trigger the formation of microchannels through which air and microorganisms can enter and spoil the enclosed food. Therefore, early detection and removal of seal-contaminated packages from the production chain is essential. In this work, a pulsed-type active thermography method using the heat of the sealing bars as an excitation source was studied for detecting seal contamination. The cooling profile of contaminated seals was recorded. The detection performance of four processing methods (based on a single frame, a fit of the cooling profile, pulsed phase thermography and a matched filter) was compared. High resolution digital images served as a reference to quantify contamination. The lowest detection limit (equivalent diameter of 0.63 mm) and the lowest processing time (0.42 s per sample) were obtained for the method based on a single frame. Presumably, practical limitations in the recording stage prevented the added value of active thermography to be fully reflected in this application.
Biological/Medical Applications
Observation of temperature trace, induced by changing of temperature inside the human body, on the human body skin using commercially available IR camera
Vyacheslav A. Trofimov, Vladislav V. Trofimov
As it is well-known, application of the passive THz camera for the security problems is very promising way. It allows seeing concealed object without contact with a person and this camera is non-dangerous for a person. In previous papers, we demonstrate new possibility of the passive THz camera using for a temperature difference observing on the human skin if this difference is caused by different temperatures inside the body. For proof of validity of our statement we make the similar physical experiment using the IR camera.

We show a possibility of temperature trace on human body skin, caused by changing of temperature inside the human body due to water drinking. We use as a computer code that is available for treatment of images captured by commercially available IR camera, manufactured by Flir Corp., as well as our developed computer code for computer processing of these images. Using both codes we demonstrate clearly changing of human body skin temperature induced by water drinking.

Shown phenomena are very important for the detection of forbidden samples and substances concealed inside the human body using non-destructive control without X-rays using. Early we have demonstrated such possibility using THz radiation. Carried out experiments can be used for counter-terrorism problem solving.

We developed original filters for computer processing of images captured by IR cameras. Their applications for computer processing of images results in a temperature resolution enhancing of cameras.
Mass screening for infectious disease containment and pandemic outbreaks: misconceptions
IR imaging in mass screening for the containment of pandemic disease is based on detecting a febril (fever) state in individuals.

The ability to use IR affectively for this is dependent on a good understanding of the physiology and physics related to the pathology that we are trying to screen for and is not restricted to temperature measurements alone. The radiometric thermal data processed during real-time imaging must include calibrated reference sources, thermal pattern recognition and comparative analysis between individual people being screened.

A screening test should have high ‘sensitivity’ rather than ‘specificity’ and to be effective the false negative rate must be very low. To achieve this the false positive rate will be higher by necessity and so a ‘secondary’ level of screening can be implemented to bring the false positive rate to within a manageable level by the higher ‘specificity’ secondary level of screening.
3D medical thermography device
In this paper, a novel handheld 3D medical thermography system is introduced. The proposed system consists of a thermal-infrared camera, a color camera and a depth camera rigidly attached in close proximity and mounted on an ergonomic handle. As a practitioner holding the device smoothly moves it around the human body parts, the proposed system generates and builds up a precise 3D thermogram model by incorporating information from each new measurement in real-time. The data is acquired in motion, thus it provides multiple points of view. When processed, these multiple points of view are adaptively combined by taking into account the reliability of each individual measurement which can vary due to a variety of factors such as angle of incidence, distance between the device and the subject and environmental sensor data or other factors influencing a confidence of the thermal-infrared data when captured. Finally, several case studies are presented to support the usability and performance of the proposed system.