NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Rolf Rascher, Christian J. Trum, Sebastian Sitzberger
Improved performance of CMP processes through targeted adjustment of polishing slurry and polish pad
Proceedings of SPIE Optical Engineering + Applications (19-23 August, 2018; Optical Manufacturing and Testing XII; San Diego, CA, USA), San Diego, United States, vol. 10742
2018
ISBN: 978-1-5106-2055-1
DOI: 10.1117/12.2321031
Abstract anzeigen
Chemical-mechanical polishing (CMP) of optical glasses is widespread and forms the basis for many high-precision polishing processes. The pads, slurries and glass materials used in polishing have many different properties. The effects of these properties on the process results are often unknown. The right choice and combination is therefore often a challenge.
By means of a plan processing of N-BK7 and SF56 samples by a plan-polishing process, the influence on the process results, material removal rate (MRR), micro roughness and cleanliness caused by slurry and polishing pad is shown. It turns out that the type of polish pad has the biggest impact on the results. The easy-to-process material N-BK7 shows only little influence by the type of slurry used. The more challenging SF56, however, shows significant effects, especially in the area of the resulting micro roughness and the appearance of surface damages like orange peel. Especially the use of Auerpol® PZ500 shows clear advantages here.
For a selection of three out of nine polishing pads, the effect of density variation of the slurry was also investigated. Lower particle concentrations lead to lower material removal rates. This applies to both materials. The more sensitive SF56 shows a reduction in micro roughness by the use of a less dense slurry.
The correct selection of the polishing pad has a positive effect on the material removal rate and/or the micro roughness in all tested materials. An adaptation of the type and concentration of the slurry is especially important for more sensitive materials and in combination with the right polishing pad.
In view of the development towards special materials and small lot sizes, the targeted and correct selection of polishing slurries and pads becomes more and more important. The information required for this purpose on the behavior of the pads and slurries available on the market must therefore first be determined in a targeted manner and clearly presented.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Gerald Fütterer, W. Krais, A. Engelbrecht, A. Sperl, S. Killinger, M. Werni
Abschattungsfreies Multi-Schiefspiegel-Teleskop als studentisches Entwicklungsprojekt
DGaO Proceedings zur 119. Jahrestagung in Aalen (22.-26.05.2018) 2018
2018
Abstract anzeigen
An der Fakultät für Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen der Technische Hochschule Deggendorf wird ein breites Wissensspektrum vermittelt. Um dieses praxisnah zu gestalten, wurde ein Teleskopbau-Projekt ins Leben gerufen. Mit dem Technologie-Campus Teisnach existiert die Basis für die Fertigung und Messung hoch präziser Teleskop-Optiken. Ausgangsparameter sind 400 mm Durchmesser des Primärspiegels und der Ansatz, am Markt bestehende Systeme in der optischen Abbildungsleistung einzuholen. Das optische Design beruht auf einer Untermenge des Parameterraums, der 1989 von M. Brunn veröffentlicht wurde. Das Konzept wurde später von D. Stevick als F12 System (mit Bezug auf die Arbeit von M. Paul, 1935) gebaut. Das THD-Projekt startete mit einem Vergleich von F7 Systemen, die in Zemax implementiert wurden. Die Abbildungsleistung wurde über ein Feld von 0,7 ° deg verglichen. Das mechanische Design schließt FEM Simulation thermischer Effekte an leichtgewichteten Spiegeln ein. Unterschiedliche Tuben wurden miteinander verglichen, einschließlich CFK Monocoquetubus. Ein weiterer Punkt ist die Auslegung der Nachführung. Es wird der Stand der Entwicklung dargelegt.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Gerald Fütterer, W. Krais, A. Engelbrecht, A. Sperl, S. Killinger, M. Werni
Developing a four-tilted-mirror telescope as a student project
Optics Education and Outreach V, vol. volume 10741
2018
ISBN: 9781510620537
DOI: 10.1117/12.2320542
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The Faculty of Applied Natural Sciences and Industrial engineering, which is a part of the Deggendorf Institute of Technology (DIT), transfers a broad spectrum of knowledge to the students. Edifying the interrelations, which are present between seemingly isolated fields of knowledge, is a permanent process. In order to make this practical, a telescope construction project was launched. The Technology Campus Teisnach bundles capacities for process development, production and measurement of highprecision optics. This also includes telescope optics. This qualifies the Campus for being the base of the in-house project. Fixed boundary conditions are e.g. 400 mm diameter of the primary mirror M1 and the objective to realize an image performance, which is equivalent to commercial telescopes. Furthermore, an unobscured tilted-mirror-system should be realized. The optical design, which was chosen as a result of an analysis of the state of the art, is based on a subset of the parameter space, which was published in 1989 by M. Brunn 1, 2. The concept was later built by D. Stevick as f/12-system (with reference to the work of M. Paul, 1935) 3. The DIT project started with a comparison of f/7-systems. They had been implemented in the optical design software Zemax. The imaging performance was compared within a field of view of 0.7 ° deg. The mechanical design includes FEM simulation of thermal effects on slightly weighted mirrors. Different tubes had been compared, including carbonfiber- reinforced-polymer (CFRP) Monocoquetubus. Another task is the realization of fast and precise tracking. The state of the development is set out.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Gerald Fütterer
CSLM illumination for 1D and 2D encoded holographic 3D displays
Illumination Optics V; SPIE Illumination Optics Conference; SPIE Optical Systems Design (OSD) [May 14-16, 2018; Frankfurt, Germany], vol. 10693
2018
ISBN: 9781510619234
DOI: 10.1117/12.2312745
Abstract anzeigen
To leave the path of classic holography and limit the space-bandwidth-product of the holographic reconstruction is one way to enable interactive real time holographic 3D displays. Thus, a couple of major problems - among several others - can be reduced to a practical level. This holds e.g. for the computation power, the data transfer rate and the pixel count of the spatial light modulator (SLM) used. Although this idea is almost twenty years old, the maximum time span of IP protection, displays based on space-bandwidth-limited CGH reconstruction, which also can be referred to as spacebandwidth- limited reconstruction of wave front segments, are still not on the market. There are several technological reasons for that. However, the technological barriers can be tackled gradually. One problem to be solved is the illumination of the entrance plane of the preferable complex valued spatial light modulator (CSLM). Here, CSLM means to modulate the phase and the amplitude of each pixel. The display diagonals of desktop and TV type CSLM might be e.g. 32 and 65 inch respectively. In other words, reasonable large collimated illumination wave fields are mandatory. In addition a small form factor is a must have in order to obtain commercial success. The solution is an optical system design, which is based on Bragg diffraction based volume gratings. Classic refractive optics fails here. In other words, Bragg diffraction based volume gratings are key components of illumination units of holographic 3D displays. They can be used within a parameter space, which cannot be addressed by surface relief type diffraction optics. But their layout depends on the parameters of the illumination wave field, which has to be tailored in regards to the optical system of the discrete, e.g. 1D or 2D encoded holographic 3D display. This will be described in more detail. The example used for the description is a double wedge type backlight unit. Furthermore, it will be explained why the use of complex valued secondary light sources is a must have in holographic 3D displays. For this, a short explanation of coherent retinal inter object point cross talk will be given too. Finally, the description of the wave field shaping (WFS), which is required in order to form the optimized complex valued light source planes, is provided. In other words, a description of a tailored coherence preparation is given, which is up to now not state of the art. The cause and effect relationship of the light propagating from the primary light sources, which are lasers, to the final receptor, which is the retina, will be pointed out. Although this tailored partial coherent illumination totally differs from the state of the art of information displays, it might help to understand a technology, which will come in the next decades.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
Gerald Fütterer
Optimization of the complex coherence function for diffraction-based wavefront transformations
Unconventional Optical Imaging
2018
ISBN: 9781510618800
DOI: 10.1117/12.2307245
Abstract anzeigen
Partial coherence is used in a plurality of applications, magnifying microscopic imaging, interferometric measurement, lithographic imaging, CGH based wave front shaping, interference lithography and space-bandwidth-limited wave front reconstruction, just to name a few. In some applications the primary light source is characterized by a limited coherence length and an extended angular spectrum of plane waves, which has to be narrowed, e.g. if an Excimer laser is used. Sometimes the angular spectrum of plane waves of the primary light source has to be increased in order to be practical. There are several possibilities in general, the primary light source can be used directly, the system has to be adapted or the coherence function Γ has to be tailored in order to provide the specific requirements. Almost all embodiments come with little changes of the light sources coherence properties only. For example, to use a spectral bandpass filter or to limit the size of the light source seem to be the standard solution for almost everything. However, more advanced tailoring of the complex valued coherence function Γ leads to an increased image quality, e.g. in interferometers, but is not limited to this, reduces background noise, decouples Fizeau cavities or it enables complete new illumination and imaging system designs, which provide unique features. This aspect will be discussed herein. Furthermore, the propagation of the complex coherence will be taken into account. This is done in order to provide defined conditions in defined planes of imaging devices. In other words, the usage of the Wiener-Khintchin theorem and the van Cittert-Zernike theorem is just a part of the system analysis and system optimization, which has to be done. Although generic approaches are used, discrete light source layouts are strongly related to the discrete optical devices, which make use of them. The specific tailoring of the complex coherence function, which is related to the space-bandwidth-limited reconstruction of wave front segments, which also can be referred to as space-bandwidth-limited CGH reconstruction, will be described in more detail. For this type of real time dynamic imaging two major problems - among several others - have to be solved. One problem is the huge computation power and the other one is the coherent retinal cross talk of adjacent image points, which are reconstructed in the image volume. The disclosed layouts of tailored secondary light sources are based on the Wiener-Khintchin theorem and the van Cittert-Zernike theorem. Both problems, which are mentioned above, can be solved. Tailored complex valued light sources reduce the required computation power by enabling reduced coherent overlay of sub-CGH areas. Furthermore, they reduce the coherent retinal cross talk of dynamic real time spacebandwidth- limited CGH reconstruction, which is used in advanced imaging applications, too. This results in an increased image quality of partial coherent wave field reconstruction based imaging.
NachhaltigElektrotechnik und MedientechnikTC FreyungBeitrag (Sammelband oder Tagungsband)
Luis Ramirez Camargo, Wolfgang Dorner, K. Gruber, F. Nitsch
Assessing regional reanalysis data sets for planning small-scale renewable energy system
20th EGU General Assembly, EGU2018, Proceedings from the conference held 4-13 April, 2018 in Vienna, Austria, p.4996
2018
Abstract anzeigen
An accurate resource availability estimation is vital for proper location, sizing and economic viability of renewable energy plants. Large photovoltaic (PV) and wind installations undergo a long and exhaustive planning process that would imply unacceptably high costs for developers of small-scale installations. In a context of abolition of feed-in tariffs, electricity feed-in restricted by grid capacity constraints and storage systems being commercialized at lower costs, the acquisition of high quality solar radiation and wind speed data becomes important also for planners of small scale installations. These data allow the characterization of short-term and inter-annual variability of the resources availability. Global reanalysis data sets provide long time series of these variables with temporal resolutions that can be as high as one hour and at no cost for the final user. However, due to the coarse spatial resolution and relatively low accuracy these products only provide an inferior alternative for data retrieval compared to e.g. satellite derived radiation data sets or advanced interpolation methods for wind speed data. The COSMO-REA6 and COSMOS-REA2 regional reanalysis overcome this limitation by increasing the resolution of the reanalysis to six and two kilometres respectively. The accuracy of these data sets for variables with high relevancy for meteorology, such as rainfall, has been assessed with satisfactory results but an independent evaluation for variables relevant for renewable energy generation has not been performed yet. This work presents an assessment of the variables of these data sets that have been made available to the public until November 2017. This assessment is performed for the area of the federal state of Bavaria in Germany and whole Czech Republic using data of the Bavarian agro-meteorological network and the Czech Hydrometeorological Institute. Accuracy indicators are calculated for horizontal global radiation or cloud coverage (depending on data availability from the weather stations) and wind speeds at 10 meters height. While there are important differences between weather stations and cloud coverage data, the results for wind speeds and global solar irradiance are satisfactory for most of the locations. For certain locations widely used indicators such as the Pearson's correlation coefficient reach values above 0.8 for wind speeds and above 0.9 for global solar irradiance and the mean biased error is consistently lower than 10 W/m2 and can be as low as 0.3 W/m2 for the irradiance data and is, with a few exceptions, lower than 2 m/s in Germany and lower than 1 m/s in the Czech Republic for wind speed data. A total of eight indicators for the hourly data in the period between 1995 and 2015 are calculated, presented, discussed and compared against international literature dealing with data accuracy for solar irradiance and wind speed data sets.
NachhaltigElektrotechnik und MedientechnikTC FreyungZeitschriftenartikel
Q. Chaudhry, J. Lewis, A. Dudkiewicz, Boxall, A. B. A., G. Allmaier, Peter Hofmann, K. Tiede, A. Lehner, K. Molhave
Development of a sample preparation approach to measure the size of nanoparticle aggregates by electron microscopy
[Available online 29 November 2018]
Particuology
2018
DOI: 10.1016/j.partic.2018.05.007
Abstract anzeigen
Electron microscopy (EM) is widely used for nanoparticle (NP) sizing. Following an initial assessment of two sample preparation protocols described in the current literature as “unperturbed”, we found that neither could accurately measure the size of NPs featuring a broad size distribution, e.g., aggregates. Because many real-world NP samples consist of aggregates, this finding was of considerable concern. The data showed that the protocols introduced errors into the measurement by either inducing agglomeration artefacts or providing a skewed size distribution towards small particles (skewing artefact). The focus of this work was to develop and apply a mathematical refinement to correct the skewing artefact. This refinement provided a much improved agreement between EM and a reference methodology, when applied to the measurement of synthetic amorphous silica NPs. Further investigation, highlighted the influence of NP chemistry on the refinement. This study emphasised the urgent need for greater and more detailed consideration regarding the sample preparation of NP aggregates to routinely achieve accurate measurements by EM. This study also provided a novel refinement solution applicable to the size characterisation of silica and citrate-coated gold NPs featuring broad size distributions. With further research, this approach could be extended to other NP types
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
O. Fähnle, M. Doetz, Christian Vogt, O. Dambon, F. Klocke, Rolf Rascher
Ductile mode single point diamond turning (SPDT) of binderless tungsten carbide molds
Proceedings of SPIE Optical Engineering + Applications (19-23 August, 2018; Optical Manufacturing and Testing XII; San Diego, CA, USA), San Diego, United States, vol. 10742
2018
ISBN: 978-1-5106-2055-1
DOI: 10.1117/12.2323244
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
O. Fähnle, Christian Vogt, Rolf Rascher, Olaf Dambon, Fritz Klocke, Marius Doetz
From turning to grinding: ductile machining with gPVA
Proceedings of SPIE Optical Engineering + Applications (19-23 August, 2018; Optical Manufacturing and Testing XII; San Diego, CA, USA), San Diego, United States, vol. 10742
2018
ISBN: 978-1-5106-2055-1
DOI: 10.1117/12.2323246
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH TeisnachBeitrag (Sammelband oder Tagungsband)
O. Fähnle, M. Doetz, Christian Vogt, O. Dambon, F. Klocke, Rolf Rascher
Ductile grinding of tungsten carbide molds applying standard CNC machines
Proceedings of SPIE Optical Engineering + Applications (19-23 August, 2018; Optical Manufacturing and Testing XII; San Diego, CA, USA), San Diego, United States, vol. 10742
2018
ISBN: 978-1-5106-2055-1
DOI: 10.1117/12.2323245
NachhaltigIPH TeisnachVortrag
Christian Vogt
Standardized evaluation of grinding tools for brittle and ductile mode grinding
European Optical Society Biennial Meeting (EOSAM) 2018, Delft, Niederlande
2018
Abstract anzeigen
Grinding processes offer a variety of parameters that influence the quality and quantity of the optical elements to be produced. Systematic optimization can also uncover unused potential in "stable and efficient" processes.
gPVA (grinding Process Validation Approach) is a system for describing grinding processes. It was first presented in 2017 as a tool for process optimization.
gPVA is a method to evaluate different grinding tools in terms of maximum material removal. Therefore, a standardized testing procedure was developed, that can be carried out on standard CNC grinding machines (Fig 1). The data is used to identify parameter sets with valid points of operation with a linear proportion of feed speed and force. In order to evaluate the data independently of cutting speed and tool geometry, a so-called removal rate is calculated. This can essentially be understood as material removal rate.
NachhaltigIPH TeisnachVortrag
O. Fähnle, Christian Vogt, Rolf Rascher, Eckart Langenbach
In situ laser monitoring of laser polishing
119. Jahrestagung der Deutschen Gesellschaft für angewandte Optik (DGaO), Technische Hochschule Aalen
2018
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A novel fabrication parameter controlling method for laser polishing is presented, measuring within the footprint the smoothening process in real time.
Recently, a new method for in situ measuring level of surface roughness has been developed [1] where a HeNe laser beam is being reflected from within the sample at the surface under test and the intensity of its reflected beam is being monitored.In this paper we report on an experimental study where this method has been applied to laser polishing. The internal local surface area under test is chosen to be located at the very spot where the laser polishing footprint is located from the outside of the sample melting its surface locally. Because fused silica is not transparent at the operating CO2 laser wavelength, the intensity of the reflected beam can be monitored enabling an in situ control of the laser polishing process. Consequently, the optimum dwell time can be determined, a footprint needs to stay at a certain point before moving further enabling a more stable and cost optimized polishing. [1] O.Fähnle,“In process monitoring of optics fabrication”, SPIEconference “PrecisionOptics Manufacturing”2017
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