Searched for: author:"Wolffenbuttel, R.F."
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Wolffenbuttel, R.F. (author), Wolffenbuttel Hosli, T.M. (author)
Apps have been used for providing additional user functionality on demand to the smartphone. Several highly promising medical apps have been introduced that rely on the build-in camera. However, some of these apps fall short of the expectations, due to the inherent limitation of the camera to operation in the visible spectral range. The more...
journal article 2016
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Costa, C.G. (author), Gomes, J.M. (author), Wolffenbuttel, R.F. (author), Correia, J.H. (author)
Medical imaging is an important part of diagnosis. The procedure should provide valuable information for diagnosis and, at the same time, should be minimally invasive for the patient. Therefore, when performing endoscopic imaging, a system with reduced dimensions is crucial. The performance of imaging systems, used in several diagnosis...
journal article 2016
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Ayerden, N.P. (author), Ghaderi, M. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author)
The design, fabrication and characterization of a highly integrated optical gas sensor is presented. The gas cell takes up most of the space in a microspectrometer and is the only component that has so far not been miniaturized. Using the tapered resonator cavity of a linear variable optical filter as a gas cell enables ultimate miniaturization,...
conference paper 2015
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Ghaderi, M. (author), Ayerden, N.P. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author)
The design and CMOS-compatible fabrication of airgap-based optical filters in a surface micromachining process with sacrificial release using thevapour phase is presented. An airgap-dielectric layer combination offers a higher refractive index contrast, as compared to the conventional all-dielectriclayer based filters, which results in a higher...
conference paper 2015
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Ghaderi, M. (author), Ayerden, N.P. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author)
In CMOS-compatible optical filter designs, SiO2 is often used as the low-index material, limiting the optical contrast (nHi/nLo) to about 2. Using the air as low-index material improves the optical contrast by about 50%, thus increasing the reflectivity and bandwidth at a given design complexity. The design and fabrication of a 4-layered air...
journal article 2014
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Silva, M.F. (author), Rodrigues, J.A. (author), Oliveira, M.J. (author), Fernandes, A.R. (author), Pereira, S. (author), Costa, C.G. (author), Ghaderi, M. (author), Ayerden, P. (author), Goncalves, L.M. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author), Correia, J.H. (author)
This paper presents the design, fabrication and characterization of two Fabry Perot type optical filters (415 nm and 540 nm) for enabling Narrow Band Imaging (NBI) in medical devices (MD). The two-colour illumination should satisfy a highly specific optical design, which is composed of a thin-film optical filter stack of titanium dioxide (TiO2)...
journal article 2014
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Ayerden, N.P. (author), Ghaderi, M. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author)
A set-up for optical gas composition measurement based on absorption spectroscopy is composed of a white light source, a gas cell and a spectrometer. The Fabry-Perot optical filter is suitable for miniaturization of this system, as it is composed of only two reflectors with a transparent layer in-between. Varying the width of this optical...
journal article 2014
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Emadi, A. (author), Wu, H. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author)
This paper presents the design, fabrication and characterization of Infra-Red (IR) Linear Variable Optical Filter (LVOF)-based micro-spectrometers. Two LVOF microspectrometer designs have been realized: one for operating in the 1400 nm to 2500 nm wavelength range and another between 3000 nm and 5000 nm. The IR LVOFs have been fabricated in an IC...
journal article 2013
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Dias, R.A. (author), Cretu, E. (author), Wolffenbuttel, R.F. (author), Rocha, L.A. (author)
The pull-in time of electrostatically actuated parallel-plate microstructures enables the realization of a high-sensitivity accelerometer that uses time measurement as the transduction mechanism. The key feature is the existence of a metastable region that dominates pull-in behavior, thus making pull-in time very sensitive to external...
journal article 2012
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Dias, R.A. (author), Macedo, P.J. (author), Silva, H.D. (author), Wolffenbuttel, R.F. (author), Cretu, E. (author), Rocha, L.A. (author)
A high-resolution, high dynamic range capacitive accelerometer based on pull-in time measurement is described in this paper. The high sensitivity of pull-in time can be used to implement high performance accelerometers, but non-linearity and low dynamic range compromise device performance. A closed-loop approach using an electrostatic actuation...
journal article 2012
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Emadi, A. (author), Wu, H. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author)
In this paper the concept of a microspectrometer based on a Linear Variable Optical Filter (LVOF) for operation in the visible spectrum is presented and used in two different designs: the first is for the narrow spectral band between 610 nm and 680 nm, whereas the other is for the wider spectral band between 570 nm and 740 nm. Design...
journal article 2011
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Wu, H. (author), Vollebregt, S. (author), Emadi, A. (author), De Graaf, G. (author), Ishihara, R. (author), Wolffenbuttel, R.F. (author)
A thermopile based detector array has advantages when used for an infrared (IR) micro-spectrometer, as compared to an array of photon detector, such as flat spectral response and uncooled operation. A thermal detector requires a good absorber to achieve a high absorption coefficient in the spectral range of interest. Several solutions are...
journal article 2011
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De Graaf, G. (author), Bakker, F. (author), Wolffenbuttel, R.F. (author)
The gas sensor research presented here has a focus on the measurement of the composition of natural gas and gases from sustainable resources, such as biogas. For efficient and safe combustion, new sensor systems need to be developed to measure the composition of these new gases. In general about 6 gas components need to be measured to determine...
journal article 2011
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Dias, R.A. (author), Wolffenbuttel, R.F. (author), Cretu, E. (author), Rocha, L.A. (author)
The experimental evaluation of damping-improved parallel-plate geometries is reported in this paper. An improved damper geometry with air channels was developed to address contradictory design constraints: large sensing parallel-plate area is desirable for a significant readout capacitance as well as reduced damping coefficient. Damping...
journal article 2011
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Wu, H. (author), Emadi, A. (author), De Graaf, G. (author), Leijtens, J. (author), Wolffenbuttel, R.F. (author)
A sun sensor is usually included in a satellite for optically measuring the position relative to the sun. The accuracy of a conventional sun sensor is affected by reflected sunlight at the nearby earth atmosphere: the albedo radiation. The part of the spectrum at near IR (1.5 ?m) is not included in the albedo radiation, due to the high water...
journal article 2011
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Ferreira, D.S. (author), Mirkovic, J. (author), Wolffenbuttel, R.F. (author), Correia, J.H. (author), Feld, M.S. (author), Minas, G. (author)
A strategy for spectroscopy tissue diagnosis using a small number of wavelengths is reported. The feasibility to accurately quantify tissue information using only 16 wavelengths is demonstrated with several wavelength reduction simulations of the existing esophageal data set. These results are an important step for the development of a...
journal article 2011
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Rocha, L.A. (author), Dias, R.A. (author), Cretu, E. (author), Mol, L. (author), Wolffenbuttel, R.F. (author)
This paper describes an electro-mechanical auto-calibration technique for use in capacitive MEMS accelerometers. Auto-calibration is achieved using the combined information derived from an initial measurement of the resonance frequency and the measurement of the pull-in voltages during device operation, with an estimation of process-induced...
journal article 2011
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Emadi, A. (author), Wu, H. (author), De Graaf, G. (author), Hedsten, K. (author), Enoksson, P. (author), Correia, J.H. (author), Wolffenbuttel, R.F. (author)
This paper presents the design, fabrication and spectral measurements of an Ultra-Violet (UV) Linear Variable Optical Filter (LVOF)-based micro-spectrometer operating in the 300 nm–400 nm wavelength range. The UV LVOF has been fabricated in an IC-Compatible process using resist reflow. Characterization by passing monochromatic light through the...
journal article 2010
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Emadi, A. (author), Grabarnik, S. (author), Wu, H. (author), De Graaf, R.F. (author), Wolffenbuttel, R.F. (author)
This paper presents spectral measurements using a linear variable optical filter. A LVOF has been developed for operation in the 530 nm–720 nm spectral band and has been fabricated in an IC-compatible process. The LVOF has been mounted on a CMOS camera. A Least Mean Square algorithm has been implemented to calculate the spectrum of light from...
journal article 2010
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Wu, H. (author), Emadi, A. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author)
A thermopile-based detector array for use in a miniaturized Infrared (IR) spectrometer has been designed and fabricated using CMOS compatible MEMS technology. The emphasis is on the optimal of the detector array at the system level, while considering the thermal design, the dimensional constraints of a design on a chip and the CMOS compatibility...
conference paper 2010
Searched for: author:"Wolffenbuttel, R.F."
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