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Many non-destructive optical testing methods are currently used for material research, providing various information about material parameters. At RECENDT, a multimodal experimental setup has been designed that combines terahertz (THz) spectroscopy, optical coherence tomography (OCT), infrared (IR), and Raman spectroscopy with a tensile test stage. This setup aims to gather material information such as crystallinity and optical parameters of high-density polyethylene (HDPE) during a tensile test. The setup compares common IR and Raman spectroscopy and the less common optical methods THz and OCT. Complementarity is achieved through different frequency ranges and measurement approaches, resulting in different measured optical material parameters and depths. During tensile testing, HDPE samples with varying crystallinity were analysed, and the determined optical parameters such as refractive index, birefringence, scattering coefficient of decay, and penetration depth can be correlated with the change in crystallinity. These findings demonstrate that the optical methods and their outcomes can be interconnected. With further optimization of the experimental setup, it would be possible to observe the alignment of fibres in fibre composite panels and the stress distribution of polymers effectively. This opens interesting possibilities for polymer characterization in the future, including quality control during moulding processes and material testing.

Abstract In this contribution, we demonstrate a wide-field hyperspectral mid-infrared (MIR) microscope based on multidimensional single-pixel imaging (SPI). The microscope employs a high brightness MIR supercontinuum source for broadband (1.55 $$\upmu \hbox {m}$$ μ m –4.5 $$\upmu \hbox {m}$$ μ m ) sample illumination. Hyperspectral imaging capability is achieved by a single micro-opto-electro-mechanical digital micromirror device (DMD), which provides both spatial and spectral differentiation. For that purpose the operational spectral bandwidth of the DMD was significantly extended into the MIR spectral region. In the presented design, the DMD fulfills two essential tasks. On the one hand, as standard for the SPI approach, the DMD sequentially masks captured scenes enabling diffraction-limited imaging in the tens of millisecond time-regime. On the other hand, the diffraction at the micromirrors leads to dispersion of the projected field and thus allows for wavelength selection without the application of additional dispersive optical elements, such as gratings or prisms. In the experimental part, first of all, the imaging and spectral capabilities of the hyperspectral microscope are characterized. The spatial and spectral resolution is assessed by means of test targets and linear variable filters, respectively. At a wavelength of 4.15 $$\upmu \hbox {m}$$ μ m a spatial resolution of 4.92 $$\upmu \hbox {m}$$ μ m is achieved with a native spectral resolution better than 118.1 nm. Further, a post-processing method for drastic enhancement of the spectral resolution is proposed and discussed. The performance of the MIR hyperspectral microsopce is demonstrated for label-free chemical imaging and examination of polymer compounds and red blood cells. The acquisition and reconstruction of Hadamard sampled 64 $$\times$$ × 64 images is achieved in 450 ms and 162 ms, respectively. Thus, combined with an unprecedented intrinsic flexibiliy gained by a tunable field of view and adjustable spatial resolution, the demonstrated design drastically improves the sample throughput in MIR chemical and biomedical imaging.

A rugged handheld sensor for rapid in-field classification of cannabis samples based on their THC content using ultra-compact near-infrared spectrometer technology is presented. The device is designed for use by the Austrian authorities to discriminate between legal and illegal cannabis samples directly at the place of intervention. Hence, the sensor allows direct measurement through commonly encountered transparent plastic packaging made from polypropylene or polyethylene without any sample preparation. The measurement time is below 20 s. Measured spectral data are evaluated using partial least squares discriminant analysis directly on the device’s hardware, eliminating the need for internet connectivity for cloud computing. The classification result is visually indicated directly on the sensor via a colored LED. Validation of the sensor is performed on an independent data set acquired by non-expert users after a short introduction. Despite the challenging setting, the achieved classification accuracy is higher than 80%. Therefore, the handheld sensor has the potential to reduce the number of unnecessarily confiscated legal cannabis samples, which would lead to significant monetary savings for the authorities.

In this work, mid-infrared hyperspectral images of multilayer polymer film (MLPF) cross sections are acquired with a high-speed quantum cascade laser (QCL) based mid-infrared microscope and analyzed using different data analysis techniques. The investigated MLPF is a polypropylene (PP) and ethylene-vinyl alcohol co-polymer (EVOH) composite commonly used for food packaging due to its outstanding barrier characteristics. Pure band integration of supposedly selective absorption bands for the two constituents of the MLPF is compared to principal component analysis (PCA) and multivariate curve resolution (MCR) algorithms regarding the ability to spatially resolve the differently composed areas in the MLPF. While both pure band integration and PCA are strongly affected by common physical artifacts in the spectral data, such as sample tilt, scattering or interference effects, MCR managed to give a clear picture of the composition of the MLPF, which matches the actual situation given by the manufacturing process. The obtained results can guide the way to the application of high-performance mid-infrared spectroscopic instrumentation for spatially resolved polymer analysis by meaningful interpretation of hyperspectral image data.

Abstract Background The study analyses clinical characteristics of histologically defined head and neck (H&N) lymphoma to raise the awareness of ENT specialists to the leading symptoms. Method From 2003 to 2011, all patients with histologically defined H&N lymphoma from our clinic were evaluated. Results This study identified 221 patients with H&N lymphoma comprising 193 non-Hodgkin lymphomas (NHL) and 28 Hodgkin lymphomas (HL). Among NHL there were 77 indolent (iNHL), 110 aggressive (aNHL), six highly aggressive NHL and further 28 HL. Patients with highly aggressive NHL and HL were significantly younger (p

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.

In this contribution, we present a high-speed, multiplex, grating spectrometer based on a spectral coding approach that is founded on principles of compressive sensing. The spectrometer employs a single-pixel InGaAs detector to measure the signals encoded by an amplitude spatial light modulator (digital micromirror device, DMD). This approach leads to a speed advantage and multiplex sensitivity advantage atypical for standard dispersive systems. Exploiting the 18.2 kHz pattern rate of the DMD, we demonstrated 4.2 ms acquisition times for full spectra with a bandwidth of 450 nm (5250–4300 cm−1; 1.9–2.33 µm). Due to the programmability of the DMD, spectral regions of interest can be chosen freely, thus reducing acquisition times further, down to the sub-millisecond regime. The adjustable resolving power of the system accessed by means of computer simulations is discussed, quantified for different measurement modes, and verified by comparison with a state-of-the-art Fourier-transform infrared spectrometer. We show measurements of characteristic polymer absorption bands in different operation regimes of the spectrometer. The theoretical multiplex advantage of 8 was experimentally verified by comparison of the noise behavior of the spectral coding approach and a standard line-scan approach.

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 contribution, we demonstrate the realization and application of a low-cost, flexible, small and fast hyperspectral imaging approach operating in the midinfrared fingerprint region where most molecules exhibit their fundamental vibrations. Following this approach, the recording of chemical images of macroscopic-sized samples at standoff distances in reflection geometry is possible. The optical setup is based on spectral identification by means of a MEMS-based Fabry-Pérot interferometer combined with 2D-snapshot spatial resolution using a bolometer camera. Results show the successful spatially resolved (resolution below 500 µm) chemical identification of different samples deposited on a metal surface (FOV = 6 × 5 cm) at a working distance of 35 cm.

A room temperature operated pulsed external-cavity (EC) quantum cascade laser (QCL) was used for mid-infrared (mid-IR) transmission measurements of glucose and lactate in aqueous solution. The high spectral power density of the EC-QCL (ranging from 1–350 mW) over a wide tuning range (1030–1230 cm−1) allowed transmission measurements through optical paths of 130 μm and more. This is a significant improvement in terms of robustness of the measurement setup, especially when samples containing cells or other particles, as is the case for biofluids, are to be analyzed. The broad tuning range furthermore permitted multi-analyte detection based on multivariate calibrations. Promising results on the simultaneous determination of glucose (c= 0–800 mg dL−1) and sodium-lactate (c= 0–224 mg dL−1) in aqueous solutions in the presence of the interferents maltose and xylose are reported. A partial least squares (PLS) calibration model was calculated which was able to predict the glucose concentration with a root mean square error of prediction (RMSEP) of 9.4 mg dL−1, as proved by external validation. Due to their small size and room temperature operation, EC-QCLs offer an attractive alternative regarding the way mid-IR measurements are carried out. This may be of special importance for new reagent-free bedside monitoring systems. [ABSTRACT FROM AUTHOR]