NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenIPH Teisnach
R. Schachtschneider, I. Fortmeier, M. Stavridis, J. Asfour, G. Berger, R. Bergmann, A. Beutler, T. Blümel, H. Klawitter, K. Kubo, Johannes Liebl, F. Löffler, R. Meeß, C. Pruss, D. Ramm, M. Sandner, G. Schneider, M. Wendel, I. Widdershoven, M. Schulz, C. Elster
Interlaboratory comparison measurements of aspheres
Measurement Science and Technology, vol. 29, no. 5
The need for high-quality aspheres is rapidly growing, necessitating increased accuracy in their measurement. A reliable uncertainty assessment of asphere form measurement techniques is difficult due to their complexity. In order to explore the accuracy of current asphere form measurement techniques, an interlaboratory comparison was carried out in which four aspheres were measured by eight laboratories using tactile measurements, optical point measurements, and optical areal measurements. Altogether, 12 different devices were employed. The measurement results were analysed after subtracting the design topography and subsequently a best-fit sphere from the measurements. The surface reduced in this way was compared to a reference topography that was obtained by taking the pointwise median across the ensemble of reduced topographies on a $1000 \times 1000$ Cartesian grid. The deviations of the reduced topographies from the reference topography were analysed in terms of several characteristics including peak-to-valley and root-mean-square deviations. Root-mean-square deviations of the reduced topographies from the reference topographies were found to be on the order of some tens of nanometres up to 89 nm, with most of the deviations being smaller than 20 nm. Our results give an indication of the accuracy that can currently be expected in form measurements of aspheres.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenMaschinenbau und Mechatronik
Beitrag (Sammelband oder Tagungsband)
Florian Schneider, Roland Maurer, Christine Wünsche, R. Stamp, G. Smith
Analysis of three different measurement strategies carried out with the TII-3D coordinate measurement system
SPIE Optics + Photonics 2013, Optical Engineering + Applications
Together with the group of interferometry based systems, coordinate measurement machines are an essential part of the metrology in the modern optical industry. Coordinate measurement machines commonly consist of a multi axes framework. They are designed to operate in a defined three dimensional work zone, where every possible point can be reached by the measurement tool tip. This basic design principle leads to some interdependent challenges. A detailed measurement result needs a large amount of measurement points to detect even minor irregularities and short-wave errors. However, a rising of the amount of measurement points increases the corresponding measurement time analogous. On the other hand, the extended operation time increases the access of undesired thermal and dynamic influences, which cause multiple errors to the measurement result. Furthermore, modern production processes need rapid metrology systems to aid the machining time. This paper discusses results obtained by operating with three different measurements in order to find an agreement between speed and certainty of the coordinate measurement machine. The topographic coordinate measurement system TII- 3D had been re-developed at the University of Applied Sciences Deggendorf in the laboratory of optical Engineering and it is equipped with three different measurement strategies. The first mode, the Track-Mode operates in concentric circles on top of the surface of the object to be measured. The Spiral-Mode measures along a dynamic moveable spiral line and the Section-Mode produces multiple cross-sections. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenHochschulleitung und -einrichtungenMaschinenbau und Mechatronik
Christian Vogt, R. Stamp, G. Smith, Rolf Rascher, Peter Sperber, Florian Schneider, Roland Maurer, Markus Schinhärl
Strategies for grinding optical free-forms using ball-shaped grinding wheels
SPIE Optifab, Rochester, NY, USA
The demand for non-spherical surfaces and free-forms is steadily growing. Aspherical lenses can reduce the number of necessary lenses in optical systems e.g. used for lithographic devices for production of microprocessors. Parabolic mirrors can be used to focus light beams highly efficiently because of low absorption rates without colour distortion. Combined optical devices with included mechanical functions for assembly reduce necessary production steps. The most common pre-machining method for small numbers of high-precision lenses and mirrors is grinding. Depending on the required shape there are different options for generating surfaces e. g. spheres, parabolic mirrors or combined forms. The most flexible ones are grinding with (i) workpiece and ball-shaped tool rotating and (ii) fixed workpiece with ball-shaped tool rotating. In this manuscript grinding strategies dealing with meander and spiral tool paths are investigated in order to define which strategy works best for machining off-axis parabolic mirrors.