Publikationen


Suche nach „[Rolf] [Rascher]“ hat 181 Publikationen gefunden
Suchergebnis als PDF
    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH Teisnach

    Beitrag (Sammelband oder Tagungsband)

    M. Pohl, R. Boerret, Rolf Rascher, Olga Kukso

    On the metrology of the MSF errors

    Proceedings of SPIE 10829 (Fifth European Seminar on Precision Optics Manufacturing [April 10-11, 2018; Teisnach])

    2018

    ISBN: 978-1-5106-2270-8

    DOI: 10.1117/12.2318675

    Abstract anzeigen

    The aim of our research is to study middle spatial frequency errors (MSFE) on optical surfaces. We investigate the surfaces after all manufacturing processes to find out the main affecting factors and to choose the proper processing parameters to minimize the size of the errors. In this paper we describe some middle spatial frequency errors, which occur during grinding. As there are limited possibilities to measure ground surfaces, their analysis from the point of measurement is most difficult. Therefore, it is of utmost importance to optimally organize the measurement guaranteeing sufficient data for the reconstruction of the toolpath and avoidance of aliasing effects. In the paper discuss possible classifications and some difficulties during measuring of grinded surfaces.

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH Teisnach

    Beitrag (Sammelband oder Tagungsband)

    Rolf Rascher, M. Zaeh, Christian J. Trum, Sebastian Sitzberger

    Workpiece self-weight in precision optics manufacturing: compensation of workpiece deformations by a fluid bearing

    Proceedings of SPIE 10829 (Fifth European Seminar on Precision Optics Manufacturing [April 10-11, 2018; Teisnach])

    2018

    ISBN: 978-1-5106-2270-8

    DOI: 10.1117/12.2318577

    Abstract anzeigen

    The effects, the extent and the importance of workpiece deformations, particularly lenses, caused by the weight of the workpiece itself, were examined in a previous paper1 . The considered deformations are in the single-digit to two-digit nanometer range. The investigation was carried out by FEM calculations. The conclusion of the previous aper was that a full-surface support of a workpiece in the processing of one surface presumably produces the best results. Furthermore, it was found that if the second functional surface is not to be touched in the process, a full contact lens mounting on its circumference is advisable. An alternative method for fixing precision lenses is therefore desirable. This can be accomplished in two steps. As a first step, the lens must be gripped at its periphery so that none of the optically functional surfaces of the lens is compromised. However, the complete circumference has to be fixated gaplessly because a punctual fixation has the disadvantage of deforming the lens surface asymmetrically. As a second step, the freely hanging lens surface should be supported to minimize deformation. An approach had to be found that supports the surface like a solid bearing but at the same time does not touch it. Therefore, the usage of an incompressible fluid as a hydrostatic bearing for full-surface support is pursued. For this purpose, the bottom side of the lens has to be stored on water. The results of the FEM simulation showed that with a fluid bearing the resulting deformations can be drastically reduced in comparison to a freely hanging surface. Furthermore, under the right conditions, a resulting deformation comparable to a full surface solid support can be achieved. The content of this paper is a test series under laboratory conditions for a first validation of the theoretical results. Therefore, a prototype model to test a lens fixation with a fluid bearing was developed and manufactured. The resulting deformations were measured with an interferometer and the effects are discussed.

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH Teisnach

    Beitrag (Sammelband oder Tagungsband)

    Rolf Rascher, Alexander Haberl, Johannes Liebl

    ABC-polishing

    Proceedings of SPIE 10829 (Fifth European Seminar on Precision Optics Manufacturing [April 10-11, 2018; Teisnach])

    2018

    ISBN: 978-1-5106-2270-8

    DOI: 10.1117/12.2318549

    Abstract anzeigen

    In the past, steadily increasing demands on the imaging properties of optics have led more and more precise spherical apertures. For a long time, these optical components have been produced in a satisfying quality using classic polishing methods such as pitch polishing. The advance of computer-controlled subaperture (SA) polishing techniques improved the accuracy of spheres. However, this new machine technology also made it possible to produce new lens geometries, such as aspheres. In contrast to classic polishing methods, the high determinism of SA polishing allows a very specific correction of the surface defect. The methods of magneto-rheological finishing (MRF) [1], [2] and ion beam figuring (IBF) [3], [4] stand out in particular because of the achievable shape accuracy. However, this leads to the fact that a principle of manufacturing "As exact as possible, as precise as necessary" [5] is often ignored. The optical surfaces often produced with unnecessary precision, result at least in increased processing times. The increasing interconnection of the production machines and the linking with databases already enables a consistent database to be established. It is possible to store measurements, process characteristics or tolerances for the individual production steps in a structured way. The difficulty, however, lies in the reasonable evaluation of the measurement data. This is where this publication comes in. The smart evaluation of the measurement data with the widespread Zernike polynomials should result in a classification, depending on the required manufacturing tolerance. In combination with the so-called ABC analysis, all surface defects can be categorized. In this way, an analytic breakdown of a - initially confusing - overall problem is made. With the aid of cost functions [6] an evaluation and consequently a deduction of actions is made possible. Thus, for example, the isolated processing of rotationally symmetrical errors in spiral mode, setup times and machining times can be reduced while avoiding mid spatial frequency errors (MSFE) at the same time.

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH Teisnach

    Beitrag (Sammelband oder Tagungsband)

    M. Pohl, R. Boerret, Rolf Rascher, Olga Kukso

    Simulation of MSF errors using Fourier transform

    Proceedings of SPIE 10829 (Fifth European Seminar on Precision Optics Manufacturing [April 10-11, 2018; Teisnach])

    2018

    ISBN: 978-1-5106-2270-8

    DOI: 10.1117/12.2317484

    Abstract anzeigen

    This research is focused on the link between manufacturing parameters and the resulting mid spatial frequency error in the manufacturing process of precision optics. This first publication focuses on the parameters of the grinding step. The Goal is to understand and avoid the appearance of the mid spatial frequency error and develop a simulation which is able to predict the resulting mid spatial frequency error for/of a manufacturing process.

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    O. Fähnle, Christian Vogt, Rolf Rascher, D.W. Kim

    Closed-loop laser polishing using in-process surface finish metrology

    Applied Optics, vol. 57, no. 4, pp. 834-838

    2018

    DOI: 10.1364/AO.57.000834

    Abstract anzeigen

    This paper lays out the trail onto a closed-loop polishing process of optical elements enabling the application of the optimum polishing time needed. To that aim, an in-process testing method for monitoring an inclusive micro surface quality (e.g., comprising surface roughness and scratch-and-dig) within the polishing spot is analyzed and its applicability to closed-loop polishing for classical loose-abrasive full-aperture polishing as well as for computer controlled laser polishing is experimentally tested and verified. This enables the determination of the optimum local dwell time resulting in a stable and cost optimized polishing.

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    Christian Vogt, Bin Dong, Rolf Rascher

    Wear detection of brass bond diamond grinding wheel by spectral coherence of grinding forces

    Proceedings of the 17th International Conference of the European Society for Precision Engineering and Nanotechnology [euspen] (May 29 - June 2, 2017; Hanover, Germany)

    2017

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    Christian Vogt, Rolf Rascher, C. Faehnle

    Grinding Process Validation Approach (gPVA)

    Journal of Physical Science and Application, vol. 7, no. 5

    2017

    DOI: 10.17265/2159-5348/2017.05.004

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    Rolf Rascher, Christian Schopf, Johannes Liebl

    Cheap and fast measuring roughness on big surfaces with an imprint method

    Proceedings of SPIE 10448 (SPIE Optifab [October 16-19, 2017; Rochester, NY, USA])

    2017

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    O. Fähnle, Christian Vogt, Rolf Rascher

    Setting-up high-end cnc grinding processes: a Preston-based approach

    Proceedings of EOS Optical Technologies Conferences at the World of Photonics Congress (WPC 2017) [Munich, Germany; June 26-29, 2017]

    2017

    Abstract anzeigen

    The design of grinding processes is commonly based on the principle of trial and error. In most cases this will end up with a usable setup that delivers acceptable results. On the other hand this method is unlikely to reveal the process’s total potential. Allthough the principles of grinding and polishing are entirly different, the preston approach can be used to design grinding processes more intelligent and highly efficient. Carrying out a testing procedure for grinding tools reveals the tool’s removal properties on different materials. This allows to choose ideal sequences of pre and fine-grinding. Furthermore it is possible to choose the optimum machining parameters to optain a maximum output.

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    O. Fähnle, Christian Vogt, Rolf Rascher

    Three wagons Approach Applied to Optimization of Industrial Grinding Processes

    Optical Fabrication and Testing part of Optical Design and Fabrication: 9-13 July 2017, Denver, Colorado, United States, Washington, D.C., USA

    2017

    ISBN: 978-1-943580-31-6

    DOI: 10.1364/OFT.2017.OTu2B.2

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    Christian Vogt, Rolf Rascher, C. Faehnle

    In situ laser polishing optimization method: Control of LASer Surface Optimisation (C-Lasso)

    Proceedings of EOS Optical Technologies Conferences at the World of Photonics Congress (WPC 2017) [Munich, Germany; June 26-29, 2017]

    2017

    Abstract anzeigen

    Laser polishing is achieved by local absorption of laser power within the polishing spot causing the surface and its sub-surface region to melt and flow reducing surface roughness and removing sub-surface damage. In this paper we present a novel fabrication controlling method for laser polishing processes called C-Lasso (Control of LASer Surface Optimization, Patent Pending), monitoring in situ the surface smoothening process. It is possible to determine and control the minimum dwell time a footprint needs to stay at a certain point before moving further. C-Lasso enables to avoid unnecessarily long local dwell times. Besides the functioning principle, a proof of concept will be presented as well as experimental data demonstrating the in situ monitoring.

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    Rolf Rascher, Alexander Haberl, Robert Schneider

    Parametrization of a Subaperture Polishing Tool - Analysis of the Path Tests

    Optical Fabrication and Testing part of Optical Design and Fabrication: 9-13 July 2017, Denver, Colorado, United States, Washington, D.C., USA

    2017

    ISBN: 978-1-943580-31-6

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    Rolf Rascher, Christian J. Trum, Sebastian Sitzberger

    Analysis of the influence of the workpiece self-weight in precision optics manufacturing using FEM simulation

    Proceedings of SPIE 10326 (Fourth European Seminar on Precision Optics Manufacturing, 1032601 [April 4th-5th 2017, Teisnach])

    2017

    DOI: 10.1117/12.2273023

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    O. Fähnle, Christian Vogt, Rolf Rascher

    Force-controlled analysis tool for optimization of precision CNC grinding processes

    Proceedings of SPIE 10326 (Fourth European Seminar on Precision Optics Manufacturing, 1032601 [April 4th-5th 2017, Teisnach])

    2017

    DOI: 10.1117/12.2272713

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    Rolf Rascher, Christian J. Trum, Sebastian Sitzberger

    Advanced method for the characterization of polishing suspensions

    Proceedings of SPIE 10326 (Fourth European Seminar on Precision Optics Manufacturing, 1032601 [April 4th-5th 2017, Teisnach])

    2017

    DOI: 10.1117/12.2272431

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    Rolf Rascher, Alexander Haberl

    Yet one more dwell time algorithm

    Proceedings of SPIE 10326 (Fourth European Seminar on Precision Optics Manufacturing, 1032601 [April 4th-5th 2017, Teisnach])

    2017

    DOI: 10.1117/12.2270540

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    Felix Friedke, Rolf Rascher, R. Kometer, Engelbert Hofbauer

    Resolution, measurement errors and uncertainties on deflectometric acquisition of large optical surfaces "DaOS"

    Proceedings of SPIE 10326 (Fourth European Seminar on Precision Optics Manufacturing, 1032601 [April 4th-5th 2017, Teisnach])

    2017

    DOI: 10.1117/12.2267513

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Beitrag (Sammelband oder Tagungsband)

    Rolf Rascher, Alexander Haberl, Robert Schneider

    Polishing tool and the resulting TIF for three variable machine parameters as input for the removal simulation

    Proceedings of SPIE 10326 (Fourth European Seminar on Precision Optics Manufacturing, 1032601 [April 4th-5th 2017, Teisnach])

    2017

    DOI: 10.1117/12.2267415

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    Rolf Rascher, Engelbert Hofbauer

    Deflectometric Acquisition of Large Optical Surfaces DaOS

    Using a new physical measurement principle: vignetting field stop procedure

    Optik&Photonik, vol. 11, no. 5, pp. 40-44

    2016

    DOI: 10.1002/opph.201600036

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    J.-P. Richters, Rolf Rascher, Johannes Liebl, Engelbert Hofbauer, Manon Schilke

    Deflectometric Acquisition of Large Optical Surfaces “DaOS” Using a New Physical Measurement Principle: Vignetting Field Stop

    (Reprinted from Proceedings of SPIE Volume 10009: Third European Seminar on Precision Optics Manufacturing, 100090Y [Teisnach, April 12th 2016] doi:10.1117/12.2236134)

    Bavarian Journal of Applied Sciences, no. 2, pp. 146-161

    2016

    Abstract anzeigen

    The vignetting field stop procedure uses a deflectometric approach to acquire big Optical Surfaces – DaOS – and it offers the possibility to measure nearly any shape or form using a scanning routine. The basic physical measurement principle in DaOS is the vignettation of a quasi-parallel light beam emitted by an expanded light source in auto collimation arrangement with a reflecting element. Thereby nearly any curvature of the specimen, is measurable. Due to the fact, that even sign changes in the curvature can be detected, also aspheres and freeform surfaces of any size can be evaluated. In this publication the vignetting field stop procedure is discussed. Additionally the deflectometric setup is described. Because of some typical influences of beam deflection to the accuracy of angle measurement by using the vignetting principle, suitable methods of calibration for the sensor are examined and the results of these methods are presented. Furthermore, the technical principle of deflectometric measurements using an angle detecting device is explained inclusive of all random and systematic errors generated by the setup. The last part of this publication shows the actual result of test measurements with calculated absolute deviation of errors with a large lateral dimension as well as the determination of the maximal achievable lateral resolution by detecting mid frequent structures on flat and spherical test parts with a diameter of 300 mm. These measurements are compared critically to reference results which are recorded by interferometry and further scanning methods.