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Tire/Road noise is a dominant contribution to a vehicle interior noise. In this paper, we present the process we developed to support automotive OEMs with road noise engineering during vehicle design and development. The process uses blocked forces identified from measurements performed on a single tire installed on a test stand. The forces are then combined with vehicle level transfer functions to predict the sound at the driver ears. The results are imported in a driving simulator for NVH to allow for auralization and sound quality evaluations. The process can be applied from the very early stages of the vehicle development using CAE simulation results and allows to evaluate the vehicle road noise performance long before the first prototype is available.

The global cost of corrosion imposes a significant burden on society, with safety and environmental consequences in addition to its direct impact. One challenge to its management is that the process of corrosion is complex, and common experimental techniques provide only limited information. The neutral salt spray test, a standardized test used for the evaluation of the corrosion resistance of steels and coatings, creates an aggressive environment not suitable for many analytical methods. Here, we report the first use of in situ Raman spectroscopy to detect the formation, growth, and evolution of corrosion products on metal surfaces, monitoring a mild steel plate in alternating salt fog and dry atmospheric conditions over a period of eight days to identify and track key corrosion products. Assisted by multivariate curve resolution alternating least squares (MCR-ALS) analysis and online weighing of the sample, we found the chemical conversion of iron hydroxides to oxides takes much longer than the physical drying of the corroded surface. Together, these results pave the way for real-time online observation of corrosion inside a salt fog chamber to obtain chemically relevant information with a single, compact apparatus.

The sol–gel process is an effective method for the preparation of homogeneous structured nanomaterials whose physico-chemical properties strongly depend on the experimental conditions applied. The control of a three-component reaction with silanes showing multiple reaction sites revealed the need for an analytical tool that allows a rapid response to ongoing transformations in the reaction mixture. Herein, we describe the implementation of near-infrared (NIR) spectroscopy based on compact, mechanically robust, and cost-efficient micro-optomechanical system technology in the sol–gel process of three silanes with a total of nine reaction sites. The NIR-spectroscopically controlled reaction yields a long-time stable product with reproducible quality, fulfilling the demanding requirements for further use in coating processes. 1H nuclear magnetic resonance measurements are used as reference values for the calibration of a partial least squares (PLS) regression model. The precise prediction of the desired parameters from collected NIR spectroscopy data acquired during the sol–gel reaction proves the applicability of the calibrated PLS regression model. The determined shelf-life and further processing tests verify the high quality of the sol–gel and the produced highly cross-linked polysilane. Osterreichische Forschungsforderungsgesellschaft 864703 Version of record

In this article, we demonstrate a promising inline near-infrared measurement scheme for 24/7 biofilm monitoring based on cost-effective microelectromechanical system-based spectrometer technology. The shown near-infrared spectral data, acquired at a beer-canning line during a representative time span of 10 days, are analyzed by means of principal component analysis and the performance of the monitoring system and its capability to identify biofilms on its sensor surface are investigated by comparing spectral response with results of offline polymerase chain reaction measurements of smear samples. Correlations between presence of a biofilm and its thickness with scores on PC1 and PC2, respectively, were observed.

The objective of this research was to quantitate the amount of wood loss that occurs during the processing of freshly harvested fir roundwood into sawlogs. The influence of the felling damages and various growth defects, e.g., curvature, taper, and forked growth, were taken into consideration. The causes of wood loss and wood volume reduction during the three primary operations of this processing chain, under the considered limited conditions, were established. The greatest wood volume reduction recorded was an 11% decrease, which was caused by the crosscutting of the stems into shorter logs. Additional wood volume reductions were due to the selection (grading) of the sawable logs and to debarking (7% and 6%, respectively). Some recommendations, in terms of industrial applicability, i.e., methods to reduce the amount of wood loss, were also formulated.

The recent introduction of quantum cascade lasers (QCL) in infrared spectroscopic ellipsometry led to decisive improvements in measurement times and signal-to-noise ratios of this powerful analytical method. In this contribution, we present another significant enhancement leading to the first, to the best of our knowledge, diffraction-limited micro-ellisometry setup in the mid-infrared spectral range with a spatial resolution better than 13.3 µm. The fast spectral tunability of the QCL combined with phase-modulated polarization enabled simultaneous acquisition of broadband (900 cm−1–1204 cm−1) high-resolution (1 cm−1) hyperspectral Ψ, Δ-cubes in a scanning approach in reasonable time scales. The spatial resolution of the QCL micro-ellipsometer was experimentally characterized by the knife-edge method and measurements of a resolution test target. Furthermore, the hyperspectral ellipsometric investigation of a polymer multilayer cross section and the portrait window of a 200-euro bank note demonstrate the capabilities of diffraction-limited QCL micro-ellipsometry.

In this contribution, the current state of high-brightness supercontinuum generation is reviewed from the perspective of applied mid-infrared spectroscopy. The key emission properties of practical interest are discussed and quantified; potential spectroscopic scenarios are listed.

The best-possible valorization of each cut log is a priority. The aim of this research was to evaluate the potential of a solution for increasing the conversion efficiency of tapered logs, by edge-cutting the narrowest sideboards at 45° and joining them by gluing, in order to obtain usable lumber boards. The modality of obtaining the glued elements was described and the values of the density and bending properties (MOE and MOR) of these elements compared to solid wood elements taken from the same logs and the same position within each log was determined. The envisaged outcome was to determine if the bonded products are suited to be used as cores within laminated products for construction.

BackgroundThe primary aim of this study was to collect information on the surgical procedures used to implant two cochlear implant variants (non-pin and pin: Concerto and Concerto Pin from Med-El) in adults and children and to assess their medium-term stability. A secondary aim was to assess the safety of these variants, both of which permit a minimally invasive surgical protocol to be used. The pin variant has greater flexibility in positioning and fixing of the implant, with the pins ensuring implant stability; also it requires less or no drilling and no tie-down sutures.Materials and MethodsNon-pin and pin cochlear implant variants (Concerto and Concerto Pin from Med-El) were implanted in adults and children (n = 116) in 5 clinics. The different surgical techniques and methods of implant fixation were documented intraoperatively. Implant stability was subjectively assessed at first fitting and again approximately 3 and 6 months later. Safety was assessed based on the number and severity of adverse events.ResultsWith all non-pin variants suture fixation was always performed, but with the pin variant this was done for just 43% of adults and 49% of children (in the remainder, no additional fixation was performed). The study demonstrated the stability of both cochlear implant variants in children and adults, with no shifting or rocking observed. There were 33 adverse events reported during the study, 10 of which (9%) were classified as related to the device or procedure.ConclusionsImplant stability and safety can be achieved through various surgical techniques and fixation methods when implanting either the Concerto or Concerto Pin.

In this contribution we present results on non-destructive chemical imaging in the mid-infrared (MIR) region of well-defined biofilms formed by Pseudomonas simiae. Biofilms were grown on stainless steel slides using a static biofilm model (incubation lasted for seven days at 10 °C, with repetitive medium changes). The MIR spectra correlate with fundamental molecular vibrations and are therefore characteristic for chemical composition and structure [1, 2]. Besides a brief insight into the systematic of how the investigated biofilms were grown the main focus will be on MIR spectroscopic measurements including dynamic observation of drying processes of bacteria, as well as spatially resolved scans of the steel plates with an MIR microscope. The obtained hyperspectral chemical images of biofilms were analyzed by various spectroscopic data analysis techniques. Furthermore, the dynamic spectroscopic observation of the drying process of planktonic Pseudomonas simiae cultures in nutrient solution gave insight in dynamic variances in certain functional chemical groups of the bacteria. These variances have also been observed in biofilm samples and may correlate with vitality. The MIR chemical images, where each pixel is composed of an entire MIR spectrum (4000-400 cm-1) provide detailed information of the investigated biofilms such as their composition and spatial structure. The overlay with conventional microscope images relates spectroscopic to visual data, both laterally resolved in the µm-range, over a scan area of up to 10 x 40 mm². The variation of the vibrational bands was screened, revealing high and low variance bands, to identify certain spectral regions suitable for classification of the investigated biofilm samples. Characteristic spectral bands were found and related to data from literature. Furthermore, differences in the spatial distribution of proteins and carbohydrates as part of the bacteria and extracellular polymeric substances were clearly identified. Acknowledgment: This work was created within a research project of the des Austrian Competence Centre for Feed and Food Quality, Safety and Innovation (FFoQSI). The COMET-K1 competence centre FFoQSI is funded by the Austrian ministries BMVIT, BMDW and the Austrian provinces Niederoesterreich, Upper Austria and Vienna within the scope of COMET -Competence Centers for Excellent Technologies. The programme COMET is handled by the Austrian Research Promotion Agency FFG. References:[1] Andreas Schwaighofer, Markus Brandstetter and Bernhard Lendl , “Quantum cascade lasers (QCLs) in biomedical spectroscopy”, Chem. Soc. Rev. 46, 5903-5924 (2017)[2] Jakob Kilgus, Gregor Langer, Kristina Duswald, Robert Zimmerleiter, Ivan Zorin, Thomas Berer, and Markus Brandstetter, "Diffraction limited mid-infrared reflectance microspectroscopy with a supercontinuum laser," Opt. Express 26, 30644-30654 (2018)

The physico-chemical properties of Melamine Formaldehyde (MF) based thermosets are largely influenced by the degree of polymerization (DP) in the underlying resin. On-line supervision of the turbidity point by means of vibrational spectroscopy has recently emerged as a promising technique to monitor the DP of MF resins. However, spectroscopic determination of the DP relies on chemometric models, which are usually sensitive to drifts caused by instrumental and/or sample associated changes occurring over time. In order to detect the time point when drifts start causing prediction bias, we here explore a universal drift detector based on a faded version of the Page-Hinkley (PH) statistic, which we test in three data streams from an industrial MF resin production process. We employ committee disagreement (CD), computed as the variance of model predictions from an ensemble of partial least squares (PLS) models, as a measure for sample-wise prediction uncertainty and use the PH statistic to detect hanges in this quantity. We further explore supervised and unsupervised strategies for (semi-)automatic model adaptation upon detection of a drift. For the former, manual reference measurements are requested whenever statistical thresholds on Hotelling’s $T^2$ and/or Q-Residuals are violated. Models are subsequently re-calibrated using weighted partial least squares in order to increase the influence of newer samples, which increases the flexibility when adapting to new (drifted) states. Unsupervised model adaptation is carried out exploiting the dual antecedent-consequent structure of a recently developed fuzzy systems variant of PLS termed FLEXFIS-PLS. In particular, antecedent parts are updated while maintaining the internal structure of the local linear predictors (i.e. the consequents). We found improved drift detection capability of the CD compared to Hotelling’s $T^2$ and Q-Residuals when used in combination with the proposed PH test. Furthermore, we found that active selection of samples by active learning (AL) used for subsequent model adaptation is advantageous compared to passive (random) selection in case that a drift leads to persistent prediction bias allowing more rapid adaptation at lower reference measurement rates. Fully unsupervised adaptation using FLEXFIS-PLS could improve predictive accuracy significantly for light drifts but was not able to fully compensate for prediction bias in case of significant lack of fit w.r.t. the latent variable space.

We present a mid-infrared spectroscopic system based on a spectral-coding approach enabled by a modified digital micromirror device (DMD). A supercontinuum source offering a confined mid-infrared laser beam is employed to perform gas measurements with this system. The performance, flexibility, and programmability enabled by the DMD is experimentally demonstrated by gas-cell measurements (CO2, CH4, N2O, NO2 and CO). Full spectra are acquired in 14 ms at 10 nm spectral resolution and in 3.5 ms at 40 nm spectral resolution. Further, we employ the system for stand-off open-path spatially resolved CO2 measurements that fully exploit the laser emission properties – the bright and highly-collimated supercontinuum beam is scanned by a galvo mirror over a retroreflector array at a scalable remote distance. The measurement concept models a passing gas emitter under lab conditions; time and spatially resolved CO2 absorbance gas-plume images in the mid-infrared range are obtained.

Supercontinuum sources are all-fiber pulsed laser-driven systems that provide high power spectral densities within ultra-broadband spectral ranges. The tailored process of generating broadband, bright, and spectrally flat supercontinua -- through a complex interplay of linear and non-linear processes -- has been recently pushed further towards longer wavelengths and has evolved enough to enter the field of mid-infrared (mid-IR) spectroscopy. In this work, we review the current state and perspectives of this technology that offers laser-like emission properties and instantaneous broadband spectral coverage comparable to thermal emitters. We aim to go beyond a literature review. Thus, we first discuss the basic principles of supercontinuum sources and then provide an experimental part focusing on the quantification and analysis of intrinsic emission properties such as typical power spectral densities, brightness levels, spectral stability, and beam quality (to the best of the authors' knowledge, the M2 factor for a mid-IR supercontinuum source is characterized for the first time). On this basis, we identify key competitive advantages of these alternative emitters for mid-IR spectroscopy over state-of-the-art technologies such as thermal sources or quantum cascade lasers. The specific features of supercontinuum radiation open up prospects of improving well-established techniques in mid-IR spectroscopy and trigger developments of novel analytical methods and instrumentation. The review concludes with a structured summary of recent advances and applications in various routine mid-IR spectroscopy scenarios that have benefited from the use of supercontinuum sources., Comment: 34 pages, 13 figures

Recent developments in mid-infrared (MIR) spectroscopic ellipsometry enabled by quantum cascade lasers (QCLs) have resulted in a drastic improvement in signal-to-noise ratio compared to conventional thermal emitter based instrumentation. Thus, it was possible to reduce the acquisition time for high-resolution broadband ellipsometric spectra from multiple hours to less than 1 s. This opens up new possibilities for real-time in-situ ellipsometry in polymer processing. To highlight these evolving capabilities, we demonstrate the benefits of a QCL based MIR ellipsometer by investigating single and multilayered polymer films. The molecular structure and reorientation of a 2.5 µm thin biaxially oriented polyethylene terephthalate film is monitored during a stretching process lasting 24.5 s to illustrate the perspective of ellipsometric measurements in dynamic processes. In addition, a polyethylene/ethylene vinyl alcohol/polyethylene multilayer film is investigated at a continuously varying angle of incidence (0∘– 50∘) in 17.2 s, highlighting an unprecedented sample throughput for the technique of varying angle spectroscopic ellipsometry in the MIR spectral range. The obtained results underline the superior spectral and temporal resolution of QCL ellipsometry and qualify this technique as a suitable method for advanced in-situ monitoring in polymer processing.

Mid-infrared (MIR) supercontinuum (SC) lasers are an attractive new option in the field of IR spectroscopy, especially for standoff detection. Supercontinuum radiation unites high brightness, high spatial coherence, and broadband spectral coverage, thereby surpassing thermal IR sources and challenging quantum cascade lasers. The employed SC source operates in the spectral region of 1.2–4.6 µm, filling the spectral gap where quantum cascade lasers lack broader availability. In this work, the SC radiation was recorded by compact Fabry–Pérot filter spectrometers ideally suited for sensitive standoff detection with real-time capability. The noise performance of the setup and measurements of different substances at standoff distances are presented, e.g., of different paints on a metal surface and an explosive precursor. Furthermore, the real-time capability of the setup is demonstrated by monitoring the evaporation of liquid 2-propanol.

Fourier transform infrared (FT-IR) spectrometers have been the dominant technology in the field of mid-infrared (mid-IR) spectroscopy for decades. Supercontinuum laser sources operating in the mid-IR spectral region now offer the potential to enrich the field of FT-IR spectroscopy due to their distinctive properties, such as high-brightness, broadband spectral coverage and enhanced stability. In our contribution, we introduce this advanced light source as a replacement for conventional thermal emitters. Furthermore, an approach to efficient coupling of pulsed mid-IR supercontinuum sources to FT-IR spectrometers is proposed and considered in detail. The experimental part is devoted to pulse-to-pulse energy fluctuations of the applied supercontinuum laser, performance of the system, as well as the noise and long-term stability. Comparative measurements performed with a conventional FT-IR instrument equipped with a thermal emitter illustrate that similar noise levels can be achieved with the supercontinuum-based system. The analytical performance of the supercontinuum-based FT-IR spectrometer was tested for a concentration series of aqueous formaldehyde solutions in a liquid flow cell (500 µm path length) and compared with the conventional FT-IR (130 µm path length). The results show a four-times-enhanced detection limit due to the extended path length enabled by the high brightness of the laser. In conclusion, FT-IR spectrometers equipped with novel broadband mid-IR supercontinuum lasers could outperform traditional systems providing superior performance, e.g., interaction path lengths formerly unattainable, while maintaining low noise levels known from highly stable thermal emitters.

Optical coherence tomography (OCT) is a high-resolution three-dimensional imaging technique that enables non-destructive measurements of surface and subsurface microstructures. Recent developments of OCT operating in the mid-infrared (MIR) range (around 4 {\mu}m) lifted fundamental scattering limitations and initiated applied material research in formerly inaccessible fields. The MIR spectral region, however, is also of great interest for spectroscopy and hyperspectral imaging, which allow highly selective and sensitive chemical studies of materials. In this contribution, we introduce an OCT system (dual-band, central wavelengths of 2 {\mu}m m and 4 {\mu}m) combined with MIR spectroscopy that is implemented as a raster scanning chemical imaging modality. The fully-integrated and cost-effective optical instrument is based on a single supercontinuum laser source (emission spectrum spanning from 1.1 {\mu}m to 4.4 {\mu}m). Capabilities of the in-situ correlative measurements are experimentally demonstrated by obtaining complex multidimensional material data, comprising morphological and chemical information, from a multi-layered composite ceramic-polymer specimen., Comment: 12 pages, 9 figures

Miniature spectrometers based on microelectromechanical systems (MEMS) are a compact, cost-efficient and rugged alternative to conventional infrared spectrometers. Different practical applications of this emerging technology are presented to demonstrate its applicability in industrial process monitoring.

Novel types of supercontinuum sources radiating in the infrared (IR) spectral region provide ultra-broadband spectral coverage and maintain distinctive laser-like properties of emission such as brightness, spatial coherence and high power. Being a perfectly suitable light source for mid-infrared optical coherence tomography (OCT) and spectroscopy, supercontinuum sources initiated a significant amount of recent developments in these fields and promise to be a gamechanging factor in the nearest future. In this paper, we exhibit a simple, optimized and relatively cost-effective system operating in near and mid-infrared ranges and combining OCT and co-registered IR spectroscopy. The performance of the OCT modality of the setup is evaluated with respect to the sensitivity and roll-off. Due to reduced scattering inherited with the new spectral window, we achieve the enhancement in the penetration depth in artificial paintings, ceramics and pottery. Furthermore, the hyperspectral data is used to supplement structural information and access to the chemical composition of the sample. The gained results reveal the potential of the multimodal system for non-destructive testing, art and cultural objects diagnosis.

Steam sterilization is a standard tool in the field of healthcare and medical equipment as it is economical, effective, and reliable. Considering the increase of antibiotic resistance and the challenge in sterilizing narrow tubes used for keyhole surgery, a safe process control is required. To achieve this, a full understanding of the local dynamics of the sterilization process inside the sterilizer is crucial. In this paper, water condensation under high temperature and high pressure, focusing on sterilization conditions, is qualitatively analyzed. An infrared sensor system was designed supplied by two LEDs, at a steam-absorbing and a non-absorbing wavelength, respectively. The local water vapor concentration was directly detected by evaluating the absorbance of infrared light as it passes through steam. Based on the absorbance monitored by this optical sensor, the condition of the steam was classified with respect to saturation and the onset of condensation. For typical sterilization cycles, differences as well as identical behavior between the local sensor measurements and the global results calculated from the temperature and pressure sensors are discussed.

In this paper, a hierarchical iterative control algorithm is proposed to optimally balance grid load (both voltage drop and current load) while meeting consumers power demand. The proposed control architecture is based on the assumption that a certain proportion of the consumers can predict their consumption profile and adapt their control strategies to fulfill power consumption constraints. It is assumed that a simplified model of the power grid and a prediction based on historical data for the consumption profile of passive consumers are available. Based on the consumers’ consumption profile predictions, the controller proposes constraints for predictively controlled buildings (PCBs) at critical times, so that these consumers can adapt their consumption strategies in advance. The control algorithm also deals with the case of noncompliant consumers. It has low-communication requirements and consumer information is only shared with the hierarchical controller. The method is verified by simulations of an existing power grid with two PCBs. For this purpose, a grid linearization method and a model predictive controller for a building are suggested.

Model predictive control (MPC) is highly suitable for building heating and cooling control because it exploits disturbance predictions, obeys constraints, and enables optimal building operation in terms of user comfort and energy efficiency. This work presents a highly efficient nonlinear modular MPC concept. It optimally controls both, heating and cooling activities in a low-energy office building simultaneously. Relevant system nonlinearities are considered through a nonlinear prediction model, an LTI MPC optimization step, and an efficient mixed-integer mapping to setpoint temperatures in the building. The involved optimization problems are efficiently solvable and enable realtime control, and the controller structure allows for retrofitting and can directly be incorporated into the existing building control infrastructure. A clear formulation of thermal user comfort and energy efficiency allows straightforward tuning. Excellent control performance and robustness are observed in detailed co-simulation studies, significantly outperforming a classical rule-based reference control law. Possible approaches to analyze robust stability of the controlled system are discussed and related to results of robust TS-fuzzy system analysis.

Real-time measurements and adjustments of critical process parameters are essential for the precise control of fermentation processes and thus for increasing both quality and yield of the desired product. However, the measurement of some crucial process parameters such as biomass, product, and product precursor concentrations usually requires time-consuming offline laboratory analysis. In this work, we demonstrate the in-line monitoring of biomass, penicillin (PEN), and phenoxyacetic acid (POX) in a Penicillium chrysogenum fed-batch fermentation process using low-cost microspectrometer technology operating in the near-infrared (NIR). In particular, NIR reflection spectra were taken directly through the glass wall of the bioreactor, which eliminates the need for an expensive NIR immersion probe. Furthermore, the risk of contaminations in the reactor is significantly reduced, as no direct contact with the investigated medium is required. NIR spectra were acquired using two sensor modules covering the spectral ranges 1350–1650 nm and 1550–1950 nm. Based on offline reference analytics, partial least squares (PLS) regression models were established for biomass, PEN, and POX either using data from both sensors separately or jointly. The established PLS models were tested on an independent validation fed-batch experiment. Root mean squared errors of prediction (RMSEP) were 1.61 g/L, 1.66 g/L, and 0.67 g/L for biomass, PEN, and POX, respectively, which can be considered an acceptable accuracy comparable with previously published results using standard process spectrometers with immersion probes. Altogether, the presented results underpin the potential of low-cost microspectrometer technology in real-time bioprocess monitoring applications © 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Mid-infrared hyperspectral imaging is advanced by the application of novel supercontinuum laser technology enabling short acquisition times and high SNR. Diffraction limited microscopic as well as macroscopic measurements at standoff distances are presented.

Producers of pharmaceuticals have to guarantee the quality of their products. Therefore, substantial efforts are invested in process monitoring and control. However, crucial parameters, such as the nutrient and product precursor concentrations often require time-consuming analysis of a sample. Infrared (IR) spectroscopy is a promising measurement technique for the online quantification of multianalyte solutions, such as fermentation broths. Besides the high investment cost of devices, chemometric models often are not fully transferable and provide noisy estimates which need to be treated before further usage. To increase robustness and accuracy of these measurements they can be combined with kinetics models under the usage of a state observation algorithms, such as Kalman- or Particle filters. In this work, we present a unique combination of a transferable mechanistic process description with the real-time information derived from near and mid IR spectroscopy leading to stable, smooth and accurate state estimates. IR spectra were collected in Penicillium chrysogenum fed-batch processes. PLS models were trained for the prediction of nitrogen, product and product precursor concentrations, which were used as inputs for the state observer. The resulting probabilistic estimates provide a good basis for automatic control.

In this paper we present a multimodal OCT imaging system operating in the NIR and MIR spectral region. NIR/MIR Supercontinuum source based multimodal OCT provides new insights in scattering .materials. The system combines the modality of OCT and spectroscopy and enables a structural and specific characterization of different ceramics, polymers or composites.

We introduce a compressive sensing based approach for single pixel hyperspectral chemical imaging in a broad spectral range in the near-infrared. Fully integrated MEMS based Fabry-Pérot tunable filter spectrometers and a digital micro-mirror device were employed to achieve spectral and spatial resolution, respectively. The available spectral range from 1500 to 2200 nm covers molecular overtone vibrations enabling chemical identification. Hyperspectral images of different adhesives deposited on a textile were recorded revealing their chemical composition. Furthermore, spectrally resolved near-infrared images with compression rates up to 90% are presented. The approach of single pixel imaging illustrates a promising technology for the infrared spectral range superior to conventionally used costly focal plane arrays.

Recent developments and commercial availability of low-noise and bright infrared (IR) supercontinuum sources initiated intensive applied research in the last few years. Covering a significant part of near- and mid-infrared spectral ranges, supercontinuum radiation opened up unique possibilities and alternatives for the well-established imaging technique of optical coherence tomography (OCT). In this contribution, we demonstrate the development, performance, and maturity of a cost-efficient dual-band Fourier-domain IR OCT system (2 µm and 4 µm central wavelengths). The proposed OCT setup is elegantly employing a single supercontinuum source and a pyroelectric linear array. We discuss adapted application-oriented approaches to signal acquisition and post-processing when thermal detectors are applied in interferometers. In the experimental part, the efficiency of the dual-band detection is evaluated. Practical results and direct comparisons of the OCT system operating within the employed sub-bands are exhibited and discussed. Furthermore, we introduce the 2 µm OCT sub-system as an affordable alternative for art diagnosis; therefore, high resolution and sensitive measurements of the painting mock-ups are presented. Finally, potentials of the dual-band detection are demonstrated for lithography-based manufactured industrial ceramics.

Chemical mapping was demonstrated with a mid-infrared (MIR) microspectroscopy setup based on a supercontinuum source (SC) emitting in the spectral range from 1.55 to 4.5 µm and a MEMS-based Fabry-Perot filter spectrometer. Diffraction limited spatial resolution in reflection geometry was achieved. A multilayer film consisting of different polymers and mixtures thereof was measured and results were compared to those gained with a conventional FTIR microscope equipped with a thermal MIR source. Results show that compared to thermal sources, the application of the SC source results in higher signal-to-noise ratios together with better spatial resolution and faster scanning. Furthermore, diffraction limited imaging of red blood cells was demonstrated for the first time in the MIR spectral region in reflection mode. The distinctive characteristics of the MIR spectral region in conjunction with the high brightness, spatial coherence and broadband nature of supercontinuum radiation show the potential for improving infrared microscopy significantly.

A compact multi-bounce attenuated total reflection (ATR) probe combined with a Fabry-Perot filter spectrometer (FPFS) has been developed for detection of hydrogen peroxide used for oxidative gas scrubbing operating in the mid-infrared (MIR) spectral region. A novel MIR supercontinuum light source is employed to enhance the quantification capabilities of the sensor and is compared to a classical thermal emitter. An improvement of a factor of 4 in noise and approximately a factor of 3 in limit of detection is shown in this study allowing fast inline detection of aqueous hydrogen peroxide solutions around 0.1%.

In this work, we report mid-IR transmissionmeasurements of the protein amide I band in aqueous solution atlarge optical paths. A tunable external-cavity quantum cascade laser(EC-QCL) operated in pulsed mode at room temperature allowedone to apply a path length of up to 38 μm, which is four times largerthan that applicable with conventional FT-IR spectrometers. Tominimize temperature-induced variations caused by backgroundabsorption of the ν2-vibration of water (HOH-bending) overlappingwith the amide I region, a highly stable temperature control unitwith relative temperature stability within 0.005 °C was developed.An advanced data processing protocol was established to overcomefluctuations in the fine structure of the emission curve that areinherent to the employed EC-QCL due to its mechanical instabilities. To allow for wavenumber accuracy, a spectral calibrationmethod has been elaborated to reference the acquired IR spectra to the absolute positions of the water vapor absorption bands.Employing this setup, characteristic spectral features of five well-studied proteins exhibiting different secondary structures couldbe measured at concentrations as low as 2.5 mg mL−1. This concentration range could previously only be accessed by IRmeasurements in D2O. Mathematical evaluation of the spectral overlap and comparison of second derivative spectra confirmexcellent agreement of the QCL transmission measurements with protein spectra acquired by FT-IR spectroscopy. This provesthe potential of the applied setup to monitor secondary structure changes of proteins in aqueous solution at extended opticalpath lengths, which allow experiments in flow through configuration. Fil: Alcaraz, Mirta Raquel. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Departamento de Química. Cátedra de Química Analítica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina Fil: Schwaighofer, Andreas. Technische Universitat Wien; Austria Fil: Kristament, Christian. Technische Universitat Wien; Austria Fil: Ramer, Georg. Technische Universitat Wien; Austria Fil: Brandstetter, Markus. Technische Universitat Wien; Austria Fil: Goicoechea, Hector Casimiro. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Departamento de Química. Cátedra de Química Analítica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina Fil: Lendl, Bernhard. Technische Universitat Wien; Austria

Quantum cascade lasers (QCL) are the first room temperature semiconductor laser source for the mid-IR spectral region, triggering substantial development for the advancement of mid-IR spectroscopy. Mid-IR spectroscopy in general provides rapid, label-free and objective analysis, particularly important in the field of biomedical analysis. Due to their unique properties, QCLs offer new possibilities for development of analytical methods to enable quantification of clinically relevant concentration levels and to support medical diagnostics. Compared to FTIR spectroscopy, novel and elaborated measurement techniques can be implemented that allow miniaturized and portable instrumentation. This review illustrates the characteristics of QCLs with a particular focus on their benefits for biomedical analysis. Recent applications of QCL-based spectroscopy for analysis of a variety of clinically relevant samples including breath, urine, blood, interstitial fluid, and biopsy samples are summarized. Further potential for technical advancements is discussed in combination with future prospects for employment of QCL-based devices in routine and point-of-care diagnostics.