Fachbereich Ingenieur- und Naturwissenschaften
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- 3D measurement (1)
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In this work, a measurement concept based on triangulation was developed for borescopic 3D-surveying of surface defects. The integration of such measurement system into a borescope environment requires excellent space utilization. The triangulation angle, the projected pattern, the numerical apertures of the optical system, and the viewing angle were calculated using partial coherence imaging and geometric optical raytracing methods. Additionally, optical aberrations and defocus were considered by the integration of Zernike polynomial coefficients. The measurement system is able to measure objects with a size of 50 μm in all dimensions with an accuracy of ± 5 μm. To manage the issue of a low depth of field while using an optical high resolution system, a wavelength dependent aperture was integrated. Thereby, we are able to control depth of field and resolution of the optical system and can use the borescope in measurement mode with high resolution and low depth of field or in inspection mode with low resolution and higher depth of field. First measurements of a demonstrator system are in good agreement with our simulations.
In this study, we present the experimental investigations on interference patterns, such as those already reported in VIMOS-IFU, and up to now no appropriate explanation has been presented. These interference patterns are produced in multimode fibres coated with acrylate or polyimide, which is the preferred coating material for the fibres used in IFUs. Our experiments show that, under specific conditions, cladding modes interact with the coating and produce interference. Our results show that the conditions at which the fibre is held during data acquisition has an impact in the output spectrum. Altering the positioning conditions of the fibre leads to the changes into the interference pattern, therefore, fibres should be carefully manipulated in order to minimise this potential problem and improve the performance of these instruments. Finally we present a simple way of predicting and modelling this interference produced from the visible to the near infrared spectra. This model can be included in the data reduction pipeline in order to remove the interference patterns.
These results should be of interest for the optimisation of the data reduction pipelines of instruments using optical fibres. Considering these results will benefit innovations and developments of high performance fibre systems.
Fabry-Perot (FP) polymer film sensors offer high acoustic sensitivity, small element sizes, broadband frequency response and optical transmission to enable high resolution, backward mode photoacoustic (PA) imaging. Typical approaches to sensor fabrication involve the deposition of stacks of alternating dielectric materials to form interferometer mirrors, which are separated by a polymer spacer. If hygroscopic soft dielectric materials are used, a protective polymer layer is typically required. In this study, methods for the deposition of water-resistant, hard dielectric materials onto polymers were explored to improve the robustness and performance of the sensors. This involved the optimisation of the fabrication process, the optical and acoustic characterisation of the sensors, and a comparison of the frequency response with the output of an acoustic forward model. The mirrors, which were separated by a 20 μm Parylene spacer, consisted of eight double layers of Ta2O5 and SiO2 deposited onto polymer substrates using temperature-optimised electron vapour deposition. The free spectral range of the interferometer was 32 nm, its finesse FR = 91, and its visibility V = 0.72. The noise-equivalent pressure was 0.3 kPa (20 MHz bandwidth). The measured frequency response was found to be more resonant at 25 MHz compared to sensors with soft dielectric mirrors, which was also in good agreement with the output of a forward model of the sensor. The sensors were used in a PA scanner to acquire 3-D images in tissue phantoms.
3D through silicon via profile metrology based on spectroscopic reflectometry for SOI applications
(2016)
Through-silicon via (TSV) technology is a key feature for 3D circuit integration. TSVs are formed by etching a vertical via and filling them with a conductive material for creation of interconnections which go through the silicon or silicon-on-insulator (SOI) wafer. The Bosch etch process on Deep Reactive Ion Etching (DRIE) is commonly used for this purpose. The etch profile defined by the critical dimensions (CDs) at the top and at the bottom, by the depth and by the scallop size on the sidewall needs to be monitored and well controlled.
In this work a nondestructive 3D metrology of deeply-etched structures with an aspect ratio of more than 10 and patterns with lateral dimensions from 2 to 7 μm in SOI wafer is proposed. Spectroscopic reflectometry in the spectral range of 250-800 nm using a production metrology tool was applied. The depth determinations based on different algorithms are compared.
The Pearson correlation coefficient between measured and calculated reflection is suggested as the most appropriate method. A simple method for top CD evaluation is proposed by the measurement of reflection and using the polynomial approximation of reflection versus TSV filling coefficient which is determined as ratio of CD to pitch. The 3D RCWA simulations confirm this dependence.
In this work, we present for the first time a partially slotted silicon ring resonator (PSRR) covered with an electro-optical polymer (Poly[(methyl methacrylate)-co-(Disperse Red 1 acrylate)]). The PSRR takes advantage of both a highly efficient vertical slot waveguide based phase shifter and a low loss strip waveguide in a single ring. The device is realized on 200 mm silicon-on-insulator wafers using 248 nm DUV lithography and covered with the electro-optic polymer in a post process. This silicon-organic hybrid ring resonator has a small footprint, high optical quality factor, and high DC device tunability. A quality factor of up to 105 and a DC device tunability of about 700 pm/V is experimentally demonstrated in the wavelength range of 1540 nm to 1590 nm. Further, we compare our results with state-of-the-art silicon-organic hybrid devices by determining the poling efficiency. It is demonstrated that the active PSRR is a promising candidate for efficient optical switches and tunable filters.
Das autonome Fahren ist eines der großen Themen im Automobilbereich der Gegenwart. Umsatzstarke Software-Unternehmen gehen Kooperationen mit Unternehmen der Automobilbranche ein, um das automatisierte Fahren schnellstmöglich voranzutreiben (Fuest 2015). Gleichzeitig forschen diverse Universitäten an dem Thema und zeigen bereits weitgehende Fortschritte. Exemplarisch ist die Universität Ulm zu nennen, die bereits Testfahrten im urbanen Gebiet erfolgreich absolviert hat (Dietmayer 2014). Auch die Politik fördert den Forschungsschwerpunkt zunehmend. Als Beispiel ist das Förderprogramm »Elektroniksysteme für das vollautomatisierte Fahren (ELEVATE)« zu nennen, welches vom Bundesministerium für Bildung und Forschung angeboten wird (Bundesministerium für Bildung und Forschung 2015). Diese intensive Forschung, die gleichzeitig von der Wirtschaft, der Wissenschaft und der Politik vorangetrieben wird, zeigt wie viel Potential das Thema besitzt. Auch dadurch stellen sich neue Herausforderungen an die Sensorik innerhalb der Fahrzeuge. Aktuell wird der Großteil der Sensordaten einmalig für den jeweiligen Zweck genutzt und anschließend verworfen.
An diesen Punkt setzen das Vorhaben und der damit verbundene Einsatz von Data-Mining-Methoden an. Ziel ist die systematische Auswertung von Daten im Fahrzeug und von außerhalb (Car2X) in Echtzeit, um aktuelle Fahrsituationen mit einem digitalen Gedächtnis abzugleichen und somit einen kurzen Blick in die Zukunft abzuleiten. Hierbei werden Situationen durch Muster erkannt und Fahrzeug bzw. Fahrer konditioniert, um die Situation positiv zu beeinflussen.
Das Vorhaben ist nicht ausschließlich auf das autonome Fahren ausgerichtet, sondern auch als Hilfe für fahrergelenkte Fahrzeuge konzipiert.