Device for emissivity estimation in LWIR range

The paper deals with the influence of emissivity on infrared measurements (Tab. 1; Fig. 1-3) and presents the developed device for emissivity estimation (Fig. 4). There is comparison shown between the reference emissivity values measured with thermal camera (Fig. 5) and estimated with the developed device (Tab. 2). Obtained results are in good agreement for three examined samples with emissivity ranging from 0.1 to 0.95

Background light suppression lock-in method for multispectral measurements with near-infrared LED spotlight illumination

The paper deals with illumination issues in multispectral imaging and presents the lock-in approach for background light suppression. There is comparison shown between the results obtained with differential approach and lock-in approach without sweep and with sweep. Obtained results prove the good performance of background suppression with the proposed lock-in approach

Hyperspectral LWIR measurements with imaging diffraction grating spectrometer and uncooled thermal camera

This paper demonstrates how to perform hyperspectral infrared measurements with uncooled thermal camera and imaging spectrometer. Such thermal cameras are sensitive to wavelengths in the range of 7 – 14 µm (LWIR). There is a description of a diffraction grating based spectrometer with Czerny-Turner optical configuration. To perform hyperspectral acquisition of thermograms it is required to have the camera synchronized with spectrometer, so that recorded frames correspond to known wavelengths. For this purpose the dedicated software was developed and it is also described in this paper, with its operation algorithm. There is a problem of thermal camera drift, and this paper proposes the solution to deal with it. Moreover a description how to obtain transmission plot and exemplary results is presented with the description of measurement rig. In addition, noise related issues are covered and discussed

Correction of microbolometer detector temperature drift (offset)

W pracy przedstawiono nową metodę wyznaczania dryftu temperaturowe-go (ang. offset) mikrobolometrycznych kamer termowizyjnych bez ko-nieczności stosowania migawki, która przesłania obserwowaną scenę. Zamiast migawki zastosowano półprzezroczystą przysłonę, która zmienia poziom energii docierającej do detektora. Metoda zakłada, że w czasie korekcji dryftu temperaturowego kamera "patrzy" na nieruchomy obiekt.In this paper a new method of temperature drift compensation of microbolometer detectors is presented. Thermal cameras with such detectors are commonly used thanks to relatively low price, small dimensions and no requirement for cooling the detector. Regardless of the microbolometer type, there is a problem of detector temperature drift which is non-uniform over the detector surface. The problem is a result of very high thermal sensitivity of the microbolometer structure which is susceptible to heat coming from surrounding electronics. The most commonly used approach to deal with the problem of temperature drift is use of a mechanical shutter which periodically blocks the observation of scene for the time necessary to perform the correction. The principle of the presented method is based on using an aperture introduced periodically between the detector and the observed scene instead of the shutter. The detector response to the scene radiation with and without the aperture is recorded. Using equation (4), one can calculate the real amount of scene radiation, irrespective of the offset value introduced by the microbolometer temperature drift (equation (5)). This method enables a thermal camera to perform a live offset correction without using a shutter and without interruption of scene observation. Besides of theoretical information about the new method, chosen quantitative results of experiments realized at the Institute of Electronics, Technical University of Lodz are given (Figs. 4 and 5)

Influence of infrared emitter on efficiency of gain correction in microbolometer detectors

Artykuł porusza problem korekcji współczynników wzmocnienia matryc mikrobolometrycznych w kamerach termowizyjnych przy użyciu promienników podczerwieni. Przedstawiona metoda nie wymaga używania dwóch modeli ciał doskonale czarnych. Nowością jest porównanie efektów uzyskiwanych przy użyciu dużego (pierścieniowego) i małego (punktowego) promiennika podczerwieni. Wskazano możliwość wystąpienia artefaktów w macierzy wyznaczanej przy użyciu małego promiennika, oraz stwierdzono ich brak podczas stosowania dużego promiennika.The paper describes the problem of correcting microbolometer gain coefficients in thermal cameras. There is presented the reference approach (Section 2) which requires to record thermograms of two blackbody model surfaces in different temperatures [1, 2, 3]. The authors propose a different method (Section 3) [4, 5], which is based on using an infrared emitter built into the thermal camera (Fig. 2). The novelty in this paper is analysis of the dependence between the emitter size and correction efficiency. In particular, the comparison of small, spotlight emitter (Fig. 1a) and larger, toroidal one (Fig. 1b) is provided. For qualitative comparison of correction results, the matrices of the calculated gain correction factors are shown in Fig. 3. One may notice some artifacts in Fig. 3c (obtained with the small emitter). The quantitative analysis (namely, the calculated values of the root mean square error for centre regions of matrices) confirms the presence of artifacts. Also the histograms of the calculated matrices (Fig. 4) are in coherence with the above observations. The conclusion is that a large emitter is better for determination of gain correction factors with the proposed method (root mean square error was about 0,0096 in this particular case). In case of a small emitter the unwanted point artifacts may occur

Low-cost thermal scanner image enhancement by merging thermal and visual data

This paper demonstrates the application of different image processing techniques to process high resolution visual images and merge it with low resolution thermograms to improve its level of detail. The same idea is applied in commercially available thermal cameras (e.g. FLIR with MSX® technology). Low resolution thermograms considered in this paper were obtained from a thermal scanner with point infrared detector (Fig. 1) sensitive to long wavelength infrared spectral range. The proposed algorithms are Laplacian, Sobel operator, embossing and Gaussian differential blur (described in section 3). The authors processed 6 different thermograms to qualitatively assess obtained results. It was done in a statistical manner through a survey and revealed that both Sobel operator and embossing provided the most clear, detailed and unambiguous results (Fig. 5). Such algorithms may be applied for processing more channels in a multispectral, cost-effective system

Distributed temperature sensing in optical fibers based on Raman scattering: demodulation algorithms

Distributed temperature sensing systems (DTS) has improved over years thanks to the improvements in configurations, components and demodulation calculating algorithms. The demodulation algorithms have been improved depending on the application and the environment, in which the fiber is installed, in order to obtain accurate measurements of temperature and distance. This study discusses the conventional calculating methods and proposed algorithms for different configurations for DTS systems

Practical application research infrared by power industry

Wykorzystanie kamery termowizyjnej do oceny stanu technicznego aparatury rozdzielczej i dystrybucyjnej systemu energetycznego ma bezpośredni wpływ na zachowanie ciągłości dostaw energii elektrycznej. Szczególne warunki środowiskowe, odnoszą się bezpośrednio do sposobu interpretacji wyników pomiarów. Zaprezentowane przykłady badań termowizyjnych, obrazują mechanizmy działań stosowane w praktyce zawodowej. Uzmysławiają, że zignorowanie nawet najmniejszych nieprawidłowości może skutkować rozległą awarią systemu energetycznego. Natomiast prawidłowa weryfikacja termogramów umożliwia diagnostykę sytemu bez konieczności pozbawiania dopływu energii elektrycznej do odbiorców przemysłowych i indywidualnych.The use of a thermal imaging cameras to analyze the technical condition of the switchgear and distribution of the energy system has a direct impact on the continuity of electricity supply. Specific environmental conditions relate directly to how to interpret the results. The presented examples of research of the thermal imaging, illustrate the mechanisms of action used in professional practice. They make clear that ignoring even the smallest irregularities may result in the failure of an extensive energy systems. Whereas the correct verification of the thermal image allows diagnostics of the system without depriving voltage transmission facilities and thus without disconnecting customers

Thermal insulation tests in 15kV distribution stations

Pomiary termowizyjne są doskonałą metodą szybkiej diagnostyki systemu elektroenergetycznego, nie mniej jednak są obarczone pewnymi niedoskonałościami. Błędy popełniane w trakcie badania mogą wpłynąć na ich wynik i spowodować, że ich interpretacja nie będzie rzetelna. Oprócz typowej niepewności pomiaru wynikającej min. z przyczyn sprzętowych, zdarzają się również błędy przypadkowe, których źródło jest w ogólnym przypadku trudne do zidentyfikowania. Umiejętność ich unikania, znajomość sprzętu badawczego oraz prawidłowe rozpoznanie środowiska wykonywania pomiarów pozwalają uzyskać wiarygodne termogramy.Thermovision measurements are an excellent method of quick diagnostics of the power system, however, they are burdened with some imperfections. Mistakes made during the test can offset the results and make the interpretation of the thermograms unreliable. In addition to the typical uncertainty of measurement resulting from min. due to hardware reasons, there are also accidental errors whose origin address is diametrically opposed. The ability to avoid them, knowledge of test equipment and correct recognition of the measurement environment allow us to obtain reliable thermograms

Distributed temperature sensing in optical fibers based on Raman scattering: theory and applications

Distributed temperature sensing (DTS) based on Raman scattering in optical fibers gains more importance in several applications, due to its accuracy, immunity to electromagnetic interference and corrosion, durability, low cost and availability. DTS systems are configured differently depending on the environment of application, and uses Optical Time Domain Reflectometry (OTDR) or Optical Frequency Domain Reflectometry (OFDR) for data analyzes. This study features a theoretical background and an introduction to DTS systems’ configurations and applications