Spectral imaging has many applications, from methane detection using satellites to disease detection on crops. However, spectral cameras remain a costly solution ranging from 10 thousand to 100 thousand euros for the hardware alone. Here, we present a low-cost multispectral camera (LC-MSC) with 64 LEDs in eight different colors and a monochrome camera with a hardware cost of 340 euros. Our prototype reproduces spectra accurately when compared to a reference spectrometer to within the spectral width of the LEDs used and the ±1σ variation over the surface of ceramic reference tiles. The mean absolute difference in reflectance is an overestimate of 0.03 for the LC-MSC as compared to a spectrometer, due to the spectral shape of the tiles. In environmental light levels of 0.5 W m−2 (bright artificial indoor lighting) our approach shows an increase in noise, but still faithfully reproduces discrete reflectance spectra over 400 nm–1000 nm. Our approach is limited in its application by LED bandwidth and availability of specific LED wavelengths. However, unlike with conventional spectral cameras, the pixel pitch of the camera itself is not limited, providing higher image resolution than typical high-end multi- and hyperspectral cameras. For sample conditions where LED illumination bands provide suitable spectral information, our LC-MSC is an interesting low-cost alternative approach to spectral imaging.
MULTIFILE
We live in a world of glowing rectangles. Our devices emit a bluish light, akin to that from the cerulean sky. Even when they sleep, computers softly pulse tiny LEDs on and off, making their presence known through light. And where they were once uniformly black and dark gray, devices are now white, shiny, and reflective: they add light not just by emitting it, but by reflecting it. The airbrushed aluminium of Macintosh computers has a luminous flux that ranks higher on light meters than pure, snowy white.
MULTIFILE
An interview with HU researcher Beverly Pasian on smart cities, projects and urban life.
LINK
LINK
The transmission of constant-envelope orthogonal frequency division multiplexing (CE-OFDM) signals, based on electrical phase modulation, was shown to improve the tolerance to noise and the nonlinearity introduced by light-emitting diodes (LEDs) in visible light communication (VLC) systems. This allows the application of larger signal amplitudes despite the LED-nonlinearities and, thus, data transmission over larger distances. The performance of a 9.51 Mb/s CE-OFDM based system, with 16-QAM subcarrier mapping in a bandwidth of 5 MHz, was compared to the efficiency of a conventional OFDM system. The error vector magnitude (EVM) was reduced from 17.5% to 10% (which is below the FEC limit), an improvement around 43%, when the CE-OFDM scheme was applied in the VLC link of 6 m. A good performance was achieved by the CE-OFDM based VLC system in a link of 8 m, when 4-QAM was used as subcarrier mapping.
DOCUMENT
Electrification of transportation, communication, working and living continues worldwide. Televisions, telephones, servers are an important part of everyday life. These loads and most sustainable sources as well, have one thing in common: Direct Current. The Dutch research and educational programme ‘DC – road to its full potential’ studies the impact of feeding these appliances from a DC grid. An improvement in energy efficiency is expected, other benefits are unknown and practical considerations are needed to come to a proper comparison with an AC grid. This paper starts with a brief introduction of the programme and its first stages. These stages encompass firstly the commissioning, selection and implementation of a safe and user friendly testing facility, to compare performance of domestic appliances when powered with AC and DC. Secondly, the relationship between the DC-testing facility and existing modeling and simulation assignments is explained. Thirdly, first results are discussed in a broad sense. An improved energy efficiency of 3% to 5% is already demonstrated for domestic appliances. That opens up questions for the performance of a domestic DC system as a whole. The paper then ends with proposed minor changes in the programme and guidelines for future projects. These changes encompass further studying of domestic appliances for product-development purposes, leaving less means for new and costly high-power testing facilities. Possible gains are 1) material and component savings 2) simpler and cheaper exteriors 3) stable and safe in-house infrastructure 4) whilst combined with local sustainable generation. That is the road ahead. 10.1109/DUE.2014.6827758
DOCUMENT
The conductive textile grid is a large-scale (226 x 115 cm) multi-layer demonstrator exhibiting different conductive textile materials with certain outputs (such as LEDs, thermo-chromic ink and shape memory alloy) can be connected onto a base conductive fabric. Various conductive materials such as knitted patches, woven patches and 3D woven patches are attached on to the 2D base conductive fabric using different connectors. The objective is to determine the best way to electrically connect the various conductive textile patches, providing smooth transfer of current in each of the conductive patches of the base conductive fabric. The functioning of the outputs proved the transfer of electricity from the base fabric onto the conductive patches activating the outputs. The demonstrator constructed on semi-industrial scale has unique features and each of the components can be implemented integrally to develop different products of Smart textiles. Paper written by the Smart Functional Materials chair of Saxion for and accepted by the Autex Conference 2013 (22-24 May 2013, Dresden, Germany).
MULTIFILE
De missie van het lectoraat Fotonica is om een bijdrage te leveren aan een gezonde wereld en een duurzame economie door het toepasbaar maken van fotonicatechnologie in de praktijk. Ook draagt het lectoraat bij aan het opleiden van professionals op het gebied van fotonica, wat een voorwaarde is om de ambities van deze groeisector waar te kunnen maken. Het fotonica-onderzoek richt zich op de toepassingsgebieden Hightech Industrie, Agri & Food, Energie & Klimaat, Gezondheid en Mobiliteit. Digitale technologie speelt in de ontwikkeling van deze gebieden een grote rol, waarbij fotonica op grote schaal wordt ingezet voor het verkrijgen van digitale data. Sleutelwoorden voor het onderzoek zijn spectroscopie, metrologie en afbeelding. Het toepassen van optische sensoren, zoals spectrometers of glasvezel-gebaseerde sensoren, speelt hierbij een centrale rol. De lijfspreuk van de natuurkundige Heike Kamerlingh Onnes ‘door meten tot weten’, aangevuld met ‘door weten tot handelen’, is dan ook een leidraad voor het lectoraat.
DOCUMENT
In this work, a feasible and low-cost approach is proposed for level measurement in multiphase systems inside tanks used for petroleum-derived oil production. The developed level sensor system consisted of light-emitting diodes (LEDs), light-dependent resistor (LDR), and a low-cost microprocessor. Two different types of oil were tested: AW460 and AW68. Linear regression (LR) was applied for 11 scenarios and showed a direct correlation between the level of oil and the sensor’s output. The measurement with AW460 oil presented a perfect linear behavior, while for AW68, a higher standard deviation was obtained justifying the occurrence of the nonlinearity in several scenarios. In order to overcome the nonlinear effect, two machine learning (ML) techniques were tested: K-nearest neighbors regression (KNNR) and multilayer perceptron (MLP) neural network regression. The highest correlation coefficient ( R2 ) and the lowest root mean squared error (RMSE) were obtained for AW68 with MLP. Therefore, MLP was used for regression (level prediction for water, oil, and emulsion) as well as classification (identify the type of oil in the reservoir) simultaneously. The suggested network exhibited a high accuracy for oil identification (99.801%) and improved linear performance in regression ( R2 = 0.9989 and RMSE = 0.065).
DOCUMENT
The age estimation of biological traces is one of the holy grails in forensic investigations. We developed a method for the age estimation of semen stains using fluorescence spectroscopy in conjunction with a stoichiometric ageing model. The model describes the degradation and generation rate of proteins and fluorescent oxidation products (FOX) over time. The previously used fluorimeter is a large benchtop device and requires system optimization for forensic applications. In situ applications have the advantage that measurements can be performed directly at the crime scene, without additional sampling or storage steps. Therefore, a portable fiber-based fluorimeter was developed, consisting of two optimized light-emitting diodes (LEDs) and two spectrometers to allow the fluorescence protein and FOX measurements. The handheld fiber can be used without touching the traces, avoiding the destruction or contamination of the trace. In this study, we have measured the ageing kinetics of semen stains over time using both our portable fluorimeter and a laboratory benchtop fluorimeter and compared their accuracies for the age estimation of semen stains. Successful age estimation was possible up to 11 days, with a mean absolute error of 1.0 days and 0.9 days for the portable and the benchtop fluorimeters, respectively. These results demonstrate the potential of using the portable fluorimeter for in situ applications.
DOCUMENT
