Infrared Radiometry Research Articles

Novel Grey Body for Accurate Radiometric Measurements.

This study presents an original approach on how to generate a radiator with an emissivity less than one by using a conventional blackbody and a screen with a defined area density of holes. This is needed for the calibration of infrared (IR) radiometry, which is a very useful form of temperature measurement in industrial, scientific, and medical applications. One of the major sources of errors in IR radiometry is the emissivity of the surface being measured. Emissivity is a physically well-defined parameter, but in real experiments, it may be influenced by many factors: surface texture, spectral properties, oxidation, and aging of surfaces. While commercial blackbodies are prevalent, the much-needed grey bodies with a known emissivity are unavailable. This work describes a methodology for how to calibrate radiometers in the lab or in the factory or FAB using the "screen approach" and a novel thermal sensor dubbed Digital TMOS. The fundamental physics required to appreciate the reported methodology is reviewed. The linearity in emissivity of the Digital TMOS is demonstrated. The study describes in detail how to obtain the perforated screen as well as how to do the calibration.

Radiometric calibration algorithm for high dynamic range infrared imaging system

The infrared imaging system with high dynamic range is one of the most prime candidates in the area of quantitative infrared radiometry and thermometry applications. As the foundation of the measurement processes, radiometric calibration is the inception procedure which will be studied emphatically in this paper. Conventional radiometric calibration algorithm is not suitable for high dynamic range infrared imaging systems that requires the flexibility of adjusting the integration time and transmittance according to characteristics of the detected target. Unfortunately, fixed calibration coefficients will inevitably arouse the deterioration of the calibration accuracy in the case of variable integration time or the transmittance. For the purpose of solving above issues, effects of integration time and transmittance on calibration are analyzed in detail. A modified calibration algorithm considering the integration time and transmittance is proposed to compensate the calibration error caused by the change of these two factors. Experiments confirm that the accuracy of the proposed calibration algorithm can reach about 1 % under the conditions of varying integration time and transmittance, which is effectively applicable to high dynamic range infrared imaging applications.

Obtaining Cloud Base Height and Phase From Thermal Infrared Radiometry Using a Deep Learning Algorithm

Obtaining Cloud Base Height and Phase From Thermal Infrared Radiometry Using a Deep Learning Algorithm

Using ground-based thermal imagery to estimate debris thickness over glacial ice: fieldwork considerations to improve the effectiveness

AbstractDebris-covered glaciers are an important component of the mountain cryosphere and influence the hydrological contribution of glacierized basins to downstream rivers. This study examines the potential to make estimates of debris thickness, a critical variable to calculate the sub-debris melt, using ground-based thermal infrared radiometry (TIR) images. Over four days in August 2019, a ground-based, time-lapse TIR digital imaging radiometer recorded sequential thermal imagery of a debris-covered region of Peyto Glacier, Canadian Rockies, in conjunction with 44 manual excavations of debris thickness ranging from 10 to 110 cm, and concurrent meteorological observations. Inferring the correlation between measured debris thickness and TIR surface temperature as a base, the effectiveness of linear and exponential regression models for debris thickness estimation from surface temperature was explored. Optimal model performance (R2 of 0.7, RMSE of 10.3 cm) was obtained with a linear model applied to measurements taken on clear nights just before sunrise, but strong model performances were also obtained under complete cloud cover during daytime or nighttime with an exponential model. This work presents insights into the use of surface temperature and TIR observations to estimate debris thickness and gain knowledge of the state of debris-covered glacial ice and its potential hydrological contribution.

Herschel-PACS photometry of the five major moons of Uranus

Aims.We aim to determine far-infrared fluxes at 70, 100, and 160μm for the five major Uranus satellites, Titania, Oberon, Umbriel, Ariel, and Miranda. Our study is based on the available calibration observations at wavelengths taken with the PACS photometer aboard theHerschelSpace Observatory.Methods.The bright image of Uranus was subtracted using a scaled Uranus point spread function (PSF) reference established from all maps of each wavelength in an iterative process removing the superimposed moons. The photometry of the satellites was performed using PSF photometry. Thermophysical models of the icy moons were fitted to the photometry of each measurement epoch and auxiliary data at shorter wavelengths.Results.The best-fit thermophysical models provide constraints for important properties of the moons, such as surface roughness and thermal inertia. We present the first thermal infrared radiometry longward of 50μm for the four largest Uranian moons, Titania, Oberon, Umbriel, and Ariel, at epochs with equator-on illumination. Due to this inclination geometry, heat transport took place to the night side so that thermal inertia played a role, allowing us to constrain that parameter. Also, we found some indication for differences in the thermal properties of leading and trailing hemispheres. The total combined flux contribution of the four major moons relative to Uranus is 5.7 × 10−3, 4.8 × 10−3, and 3.4 × 10−3at 70, 100, and 160μm, respectively. We therefore precisely specify the systematic error of the Uranus flux by its moons when Uranus is used as a far-infrared prime flux calibrator. Miranda is considerably fainter and always close to Uranus, impeding reliable photometry.Conclusions.We successfully demonstrate an image processing technique for PACS photometer data that allows us to remove a bright central source and reconstruct point source fluxes on the order of 10−3of the central source as close as ≈3 × the half width at half maximum of the PSF. We established improved thermophysical models of the five major Uranus satellites. Our derived thermal inertia values resemble those of trans-neptunian object (TNO) dwarf planets, Pluto and Haumea, more than those of smaller TNOs and Centaurs at heliocentric distances of about 30 AU.

Infrared Laser Effect on Healthy and Ossified Costal Cartilage: The Development of Stable Load-Bearing Autoimplants.

The laser-induced stress relaxation provides new prospects to obtain stable long fragments of costal cartilage for autoimplantation avoiding the risk of spontaneous deformation and poor engraftment. However, the age-related alterations of cartilage may sufficiently influence its interaction with infrared (IR) laser radiation and disrupt the effectiveness and safety of the technique. The aim of the work is to study the influence of the structural quality of costal cartilage on its interaction with IR laser and efficiency of obtaining of curved implants for trachea surgery. Healthy costal cartilage was taken from pigs and human. Ossified costal cartilage was taken from humans of age 65 ± 7. The cartilage slices with a mean thickness of 3 mm were mechanically curved and processed to stress relaxation by laser irradiation with the wavelength 1.56 µm. The structure and mineral content were studied by X-ray microtomography and element analysis. The optical measurements included the study of the propagation of IR radiation, speckle interferometry, and IR radiometry. The aged cartilage demonstrates a high level of heterogeneity in structure and properties and decreased water content. The presence of dense inclusions consisting of amorphous calcined volumes makes the tissue more fragile and less elastic. The IR radiation propagation intensity for aged cartilage is at least twice higher than that for healthy cartilage. The thermal-induced motion of scatterers in aged cartilage is slower. X-ray microtomography showed the cartilage-like and the bone-like structures within the ossified samples. The main challenge for laser reshaping of aged cartilage is the presence of ossifications. However, the new stable curvature can be obtained with adjustment of laser power. To obtain the satisfying stable curvature of an implant the ossified volumes should be avoided The laser-induced stress-relaxation mechanism for aged cartilage can be particularly different from that of healthy tissue and the optimal laser regimes should be specified. Lasers Surg. Med. © 2020 Wiley Periodicals, Inc.

Photothermal, photocarrier, and photoluminescence phenomena in semiconductors studied using spectrally resolved modulated infrared radiometry: Physics and applications

Photothermal, photocarrier, and photoluminescence phenomena in semiconductors studied using modulated infrared (IR) radiometry are discussed. Spectrally resolved measurements are carried out using IR filters placed in front of the detector. A new approach based on modulated IR radiometry is proposed which is a valuable extension of conventional IR-spectroscopic techniques for measuring IR absorption coefficients of thick highly IR-absorbing samples and of thin films deposited on thick highly IR-absorbing substrates, as well as for the simultaneous measurement of IR absorption and photoluminescence spectra. It is also shown that spectrally resolved modulated IR radiometry measurements lead to greater accuracy than conventional approaches for estimating thermal and recombination properties of semiconductors.

On Investigations of the Optical Absorption Coefficient of Gold and Germanium Implanted Silicon with the Use of the Non-destructive Contactless Photo Thermal Infrared Radiometry

In this paper results of investigations of Au2+ and Ge+ ion-implanted silicon samples with the use of the nondestructive frequency and the space domain photo thermal infrared radiometry (PTR) method are presented. Frequency amplitude characteristics and spatial amplitude distributions of the PTR signal for the implanted silicon samples were measured and analyzed. Measurements have been performed for several wavelengths of the exciting light. The dependence of the amplitude of the PTR signal on the optical and recombination parameters of the implanted layers has been analyzed experimentally and theoretically and discussed. The objective of this work is to present the possibilities of investigations of the influence of the high energy and high dose implantation process into silicon on the optical and recombination parameters of implanted silicon with the use of the frequency and spatial domain PTR method. Observed changes in the measured signal have been explained by simultaneous changes of values of the optical absorption coefficient and carriers lifetime of implanted layers.

Simultaneous measurement of infrared absorption coefficient of Carbon doped Al0.33Ga0.67As thin film and thermal boundary resistance between thin film and heavily Zn doped GaAs substrate using spectrally-resolved modulated photothermal infrared radiometry

In this paper, we investigated C doped Al0.33Ga0.67As thin film epitaxially grown on a Zn-doped GaAs substrate using spectrally resolved modulated photothermal infrared radiometry (SR-PTR). We assumed that thermal conductivity and diffusivity of the thin layer are known and estimate values of the infrared absorption coefficient of the thin layer and the thermal boundary resistance of the interface between the thin layer and the substrate. We found out that the thermal boundary resistance is two orders of magnitude greater than thermal boundary resistance of studied recently undoped AlGaAs/GaAs sample. We attribute this effect to formation of quasi 2-dimensional hole gas due to modulation doping. Finally, the infrared absorption coefficient of the thin layer decreases with increasing wavelength due to inter-valence band absorption. We found out that with increasing infrared absorption coefficient of the thin film, the sensitivity of the method for estimation of the infrared absorption coefficient increases, while the estimation error decreases.

Pedestrian detection at night time in FIR domain: Comprehensive study about temperature and brightness and new benchmark

This paper presents a novel method to detect pedestrians in the far infrared (FIR) domain at night. In existing infrared data, the brightness is distorted by the contrast of the scene, causing the performance to degrade. The radiometric temperature was introduced to cope with this issue. The temperature was unaffected by the contrast and was more stable than the brightness because of the limitation to the specific thermal range with thermoregulation. The dataset was constructed across each season and four versions of thermal infrared radiometry aggregated channel feature (TIR-ACF) are presented with normalization using the maximum temperature of humans. In these experiments, the proposed method outperformed the brightness-based baseline method by a maximum 11% on the log-averaged miss rate for seasonal variations. As a result, the physical temperature enhanced the performance and helped detect pedestrians that cannot be found using the brightness with a reduction of false positives.

Erratum: “On the infrared absorption coefficient measurement of thick heavily Zn doped GaAs using spectrally resolved modulated photothermal infrared radiometry” [J. Appl. Phys. 122, 135109 (2017)

Erratum: “On the infrared absorption coefficient measurement of thick heavily Zn doped GaAs using spectrally resolved modulated photothermal infrared radiometry” [J. Appl. Phys. <b>122</b>, 135109 (2017)

Investigation of Thermal Properties of High-Density Polyethylene/Aluminum Nanocomposites by Photothermal Infrared Radiometry

In this study, thermal properties of high-density polyethylene (HDPE) filled with nanosized Al particles (80 nm) were investigated. Samples were prepared using melt mixing method up to filler volume fraction of 29 %, followed by compression molding. By using modulated photothermal radiometry (PTR) technique, thermal diffusivity and thermal effusivity were obtained. The effective thermal conductivity of nanocomposites was calculated directly from PTR measurements and from the measurements of density, specific heat capacity (by differential scanning calorimetry) and thermal diffusivity (obtained from PTR signal amplitude and phase). It is concluded that the thermal conductivity of HDPE composites increases with increasing Al fraction and the highest effective thermal conductivity enhancement of 205 % is achieved at a filler volume fraction of 29 %. The obtained results were compared with the theoretical models and experimental data given in the literature. The results demonstrate that Agari and Uno, and Cheng and Vachon models can predict well the thermal conductivity of HDPE/Al nanocomposites in the whole range of Al fractions.

On the infrared absorption coefficient measurement of thick heavily Zn doped GaAs using spectrally resolved modulated photothermal infrared radiometry

In this paper, we report on measurements of the infrared absorption coefficient in the mid-infrared range of a heavily Zn-doped GaAs wafer using spectrally resolved modulated photothermal infrared radiometry (PTR). The method allows us to measure the infrared absorption coefficient of (i) much thicker samples as compared to the one used in Fourier Transform Infrared (FTIR) spectroscopy in transmission configuration and (ii) with non-mirror-like surfaces as would be required for measurements in the reflection configuration. From the best fits of the theoretical model to the PTR results, the values of the infrared absorption coefficient and thermal diffusivity of GaAs wafer are obtained. These values of infrared absorption coefficients are compared both with the literature values on very thin, similarly doped GaAs:Be sample and with infrared absorption coefficients calculated from FTIR specular reflectance measurements on the same sample. FTIR reflectance measurements demand additional assumptions for the evaluation of absorption coefficient and mirror-like surfaces. The results obtained from both experimental methods yield the same order of the infrared absorption coefficients. It is observed that the infrared absorption coefficient decreases with increasing wavelength because of inter-valence band transitions. However, only the infrared spectrum estimated using PTR exhibits free carrier absorption effect at a shorter wavelength as observed in previous works on very thin Be-doped GaAs samples. It is worth mentioning that the presented method is not limited to semiconductors, but can be used for other highly infrared absorbing samples. In addition, the spectrally resolved PTR measurements simultaneously provide the same values of thermal diffusivity of the GaAs wafer within estimation uncertainties thus demonstrating the reliability of the PTR method in the measurement of thermal diffusivity of such samples.

Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry

Abstract. Multiband downwelling thermal measurements of zenith sky radiance, along with cloud boundary heights, were used in a retrieval algorithm to estimate cloud optical depth and effective particle diameter of thin ice clouds in the Canadian High Arctic. Ground-based thermal infrared (IR) radiances for 150 semitransparent ice clouds cases were acquired at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80° N, 86° W). We analyzed and quantified the sensitivity of downwelling thermal radiance to several cloud parameters including optical depth, effective particle diameter and shape, water vapor content, cloud geometric thickness and cloud base altitude. A lookup table retrieval method was used to successfully extract, through an optimal estimation method, cloud optical depth up to a maximum value of 2.6 and to separate thin ice clouds into two classes: (1) TIC1 clouds characterized by small crystals (effective particle diameter ≤ 30 µm), and (2) TIC2 clouds characterized by large ice crystals (effective particle diameter &gt; 30 µm). The retrieval technique was validated using data from the Arctic High Spectral Resolution Lidar (AHSRL) and Millimeter Wave Cloud Radar (MMCR). Inversions were performed over three polar winters and results showed a significant correlation (R2 = 0.95) for cloud optical depth retrievals and an overall accuracy of 83 % for the classification of TIC1 and TIC2 clouds. A partial validation relative to an algorithm based on high spectral resolution downwelling IR radiance measurements between 8 and 21 µm was also performed. It confirms the robustness of the optical depth retrieval and the fact that the broadband thermal radiometer retrieval was sensitive to small particle (TIC1) sizes.

On measurement of the thermal diffusivity of moderate and heavily doped semiconductor samples using modulated photothermal infrared radiometry

In this work, the accuracy of the thermal diffusivity estimation in moderately and heavily doped semiconductor samples using the modulated photothermal infrared radiometry is investigated. The studies were carried out on heavily doped Si and GaAs wafers, and on moderately doped Si and recently studied GaAs and CdSe samples. It is shown, that depending on the infrared properties of the semiconductor sample, the modulated photothermal infrared radiometry signal can yield information about thermal diffusivity, (effective) infrared absorption coefficient and electronic transport parameters (recombination lifetime, carrier diffusivity and surface recombination velocities). For the heavily doped samples, the modulated photothermal infrared radiometry signal consists only of the thermal response yielding information about the (effective) infrared absorption coefficient and thermal diffusivity. The relative expanded uncertainty with 0.95 level of confidence Ur of estimating the thermal diffusivity in this case is about Ur=0.05. For moderately doped samples the modulated photothermal infrared radiometry signal consists of the thermal and of the photocarrier response. The relative expanded uncertainty with 0.95 level of confidence Ur of estimating the thermal diffusivity in this case varies between about Ur=0.10 and about Ur=0.30, depending on the existence of the maximum in the signal phase, but information about the electronic transport properties is derived. It is shown that not only infrared properties have the influence on the accuracy in estimating the thermal diffusivity of moderate doped semiconductor samples, but also the thermal, geometrical (thickness) and carrier recombination properties can play an important role.

Quantitative thermal wave phase imaging of an IR semi-transparent GaAs wafer using IR lock-in thermography

In this paper, the simultaneous measurement of out-of-plane thermal diffusivity and effective infrared absorption coefficient of an IR semi-transparent GaAs wafer using infrared lock-in thermography technique (LIT) is presented. The method relies on analysis of the generated LIT phase images recorded at different modulation frequencies, using the thermal wave model in the transmission configuration. The out-of-plane thermal diffusivity and effective infrared absorption coefficient are estimated from the best fit of the theoretical model to the experimental data. The obtained values are in good agreement with those obtained by supplementary measurement using the modulated photothermal infrared radiometry technique (PTR) in the reflection mode, and also with data reported in the literature. In addition, simple modification of the LIT experiment set up allows one to determinate the in-plane thermal diffusivity of n-GaAs wafer. It was found that in-plane and out-of-plane thermal diffusivities of the GaAs wafer are very close, as expected, within the limit of measurement errors. The results show that the LIT technique in transmission configuration can provide spatial information about both the (effective) infrared absorption coefficient and thermal diffusivity of semiconductor crystals.

Modulated IR radiometry for determining thermal properties and basic characteristics of titanium thin films

Titanium thin films of different thicknesses were prepared by direct current magnetron sputtering to study modulated infrared (IR) radiometry as a tool for analyzing film thickness. Thickness was varied by regularly increasing the deposition time, keeping all the other deposition parameters constant. The influence of film thickness on morphological, structural, and electrical properties of the titanium coatings also was investigated. The experimental results revealed a systematic grain growth with increasing film thickness, along with enhanced film crystallinity, which led to increased electrical conductivity. Using the results obtained by modulated IR radiometry, the thickness of each thin film was calculated. These thickness values were then compared with the coating thickness measurements obtained by scanning electron microscopy. The values confirmed the reliability of modulated IR radiometry as an analysis tool for thin films and coatings, and for determining thicknesses in the micrometer range, in particular.

Influence of Rolling on the Thermal Diffusivity of Metal Alloys by Photothermal Infrared Radiometry

The thermal diffusivities of metallic foils subjected to cold-rolling processes have been studied by photothermal radiometry in a thermal transmission and reflection configuration. In this work, measurements were conducted on foils of Al, Cu, and stainless steel (V2A) that were subjected stepwise to cold-rolling process, reducing the sample of around 1 mm, as prepared, to approximately 0.1 mm. It was found that the effect of the cold-rolling is manifested as a relationship between the relative diffusivity and the relative thickness, both with respect to their corresponding initial values. This empirical relationship consists of a linear decrease of the relative diffusivity with the negative of the logarithm of the relative thickness of the sample. Within the approximation of small deformations, this behavior is consistent with linear diminishing of the thermal diffusivity with the degree of rolling. An influence of rolling on both the thermal diffusivity and effusivity was previously observed for a polycrystalline NiTi shape memory alloy with a nearly equi-atomic composition. Due to the thermal-diffusivity behavior of metal alloys due to rolling, a simple microscopic model is proposed to explain this influence upon the effective thermal parameters within the framework of a one-dimensional heat flow perpendicular to the foil surface. The model assumes the reduction of grain sizes and the consequent increase of grain interfaces during rolling as responsible for a larger effective thermal resistance. Numerical results are shown using the available polycrystalline NiTi for both the thermal-diffusivity and thermal-effusivity values.

Improved methods for measuring thermal parameters of liquid samples using photothermal infrared radiometry

High accuracy, non-contact measuring methods for finding thermal properties of liquid samples using photothermal infrared radiometry (PTR) are presented. The use of transparent windows to confine micro volume liquid samples and the implementation of front and/or back signal detection procedures helped the successful implementation of the PTR technique for measuring liquids with high proficiency. We present two configurations, the so-called back–front photothermal infrared radiometry and back photothermal infrared radiometry to find thermal diffusivity and thermal effusivity of liquid samples. Sensitivity studies and error analyses included prove the robustness of each method. As an illustration of the temperature and electric field varying studies, we have included the experimental results on a 5CB (4-cyano-4′-pentylbiphenyl) liquid crystal.

Characterisation of sputter deposited niobium and boron interlayer in the copper–diamond system

In most metal matrix composites (MMCs) interfaces are decisive but hard to manipulate. Especially copper–carbon composites can exhibit excellent mechanical and thermal properties only if the Cu/C interface is modified by an optimised interlayer. Due to the excellent thermal conductivity and mechanical stability of diamond this form of carbon is preferred as reinforcement in heat sink materials (copper–diamond composite) which are often subjected to severe thermal and mechanical loads.In the present case niobium and boron interlayers of various thicknesses were deposited on diamond and vitreous carbon substrates by magnetron sputter deposition. After the coverage of all samples by a copper film, a part of the samples was subjected to heat treatment for 30min at 800°C under high vacuum (HV) to simulate the thermal conditions during the production of the composite material by uniaxial hot pressing.De-wetting during heat treatment leads to the formation of holes or humps in the Cu coating. This effect was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). A comparison of time-of-flight secondary ion mass spectroscopy (TOF SIMS) profiles of heat treated samples with those of as deposited ones showed the influence of interdiffusion during the heating process. Diffusion behaviour and chemical composition of the interface were also studied by cross sectional transmission electron microscopy (X-TEM) investigations using focused ion beam (FIB) cut samples. The thermal contact resistance (TCR) of the interface was calculated from results obtained from modulated infrared radiometry (IR). Thin interlayers suppressed de-wetting most effectively and consequently the TCR at the Cu–diamond interface was found to decrease. Therefore they are promising candidates for optimising the Cu–diamond interface.