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Prof. Dr. rer. nat. Gerald Fütterer, Dipl.-Phys.

Methods engineering / Metrology / Simulation optical systems & optical components Scientific Management

Faculty of Applied Natural Sciences and Industrial Engineering

Professors

Professor

Scientific management Institute for precision manufacturing and high-frequency technology - IPH

L 204

0991/3615-533

consulting time

Office hours by appointment by e-mail

Sortierung:
Patent
  • Gerald Fütterer

Autokollimationsfernrohr und Verfahren zur Abbildung einer Messmarke hierfür.

  • (2005)
Contribution
  • Gerald Fütterer

Enhancement of high-resolution electronic autocollimators by application of phase grating technology.

In: Proceedings of SPIE Volume 5856 (Optical Measurement Systems for Industrial Inspection IV) [Event: Optical Metrology; June 13th, 2005; Munich, Germany].

  • Eds.:
  • SPIE - The International Society for Optical Engineering

  • (2005)

DOI: 10.1117/12.612745

Patent
  • Gerald Fütterer

Verfahren zur interferometrischen Bestimmung einer optischen Weglänge zwischen der Oberfläche eines Objekts und einer Referenzfläche und Interferometeranordnung.

  • (2006)
Contribution
  • Gerald Fütterer

Simulation of the detectors response of an autocollimator.

In: Modeling Aspects in Optical Metrology. Proceedings of SPIE, Volume 6617 vol. Art. No. 661703 pg. 1-8

  • Eds.:
  • B. Bodermann
  • R. Silver
  • H. Bosse

  • (2007)
Contribution
  • R. Probst
  • Gerald Fütterer
  • J. Illemann
  • J. Mokroš
  • P. Lui
  • E. Bachish

An angular reversal technique for error separation between a dual axis electronic autocollimator and a PZT tilting platform.

In: Proceedings of the Seventh Euspen International Conference 2007 (European Society for Precision Engineering and Nanotechnology).

  • Eds.:
  • E. Thornett

  • (2007)
Lecture
  • Gerald Fütterer

Compact Holographic Display Product Solutions. Invited Talk.

In: International Workshop on Holographic Memories and Display (IWHM&D)

Tokyo, Japan

  • 15.-16.11.2010 (2010)
Patent
  • Gerald Fütterer
  • R. Häußler
  • B. Kroll
  • N. Leister
  • S. Reichelt

Combined light modulation device for tracking users.

  • (2011)
Patent
  • Gerald Fütterer

Beam divergence and various collimators for holographic or stereoscopic displays.

  • (2011)
Lecture
  • Gerald Fütterer
  • N. Leister
  • R. Haussler
  • S. Reichelt
  • C. Erler

Small Form Factor for Holographic 3D Display Product.

In: 2011 Collaborative Conference on 3D & Materials Research (3DMR)

Jeju City, South Korea

  • 27.06.-01.07.2011 (2011)
Patent
  • Gerald Fütterer

Optisches System zur Messung der Polarisation und der Phase (Inhalt: Verfahren und Anordnungen zur flächigen optischen Darstellung von Ladungsträgern, ihrer Verteilungen und ihrer Beweglichkeit).

  • (2014)
Patent
  • Gerald Fütterer
  • B. Kroll
  • N. Leister
  • H. Stolle

Projektionsvorrichtung und Verfahren zum Darstellen einer zweidimensionalen und/oder dreidimensionalen Szene oder von Inhalt.

  • (2015)
Patent
  • Gerald Fütterer

Anzeigevorrichtung für eine holografische Rekonstruktion.

  • (2015)
Patent
  • Gerald Fütterer

Display Device for Holographic Reconstruction.

  • (2015)
Patent
  • Gerald Fütterer
  • B. Kroll
  • N. Leister
  • H. Stolle

Projection display and method for displaying at least one of two-dimensional and three-dimensional scene or of content.

  • 30.06.2015 (2015)
Journal article
  • Gerald Fütterer

Enabling Holographic 3D Displays with Bragg Diffraction Based Volume Gratings and First Approaches to the Reduction of Diffractive Cross Talk.

In: Bavarian Journal of Applied Sciences pg. 130-145

  • (2016)

DOI: 10.25929/276j-2q41

show abstract

Photonics products often require enhanced optical functionality, which cannot be provided by state of the art optics. This is the case when high-end optical systems as for example holographic 3D displays are developed. Implementation of Bragg diffraction based volume gratings enables small form factor and high definition (HD) natural viewing experience of 3D objects. This is important for modeling 3D data, prototyping, CAD-CAM, computer-integrated manufacturing (CIM), global 3D teleconferencing and mobile infotainment. For example, holographic 3D displays, which are based on space bandwidth limited wave segment reconstruction, profit from the specific characteristics of thick hologram gratings, which can be referred to as Bragg diffraction based volume gratings. It is explained how to adapt angular, spectral and polarization selectivity in order to provide specific optical functionality, which is mandatory in order to realize HD holographic 3D displays. A short introduction to backlight units (BLU), complex valued spatial light modulators (C-SLM) and combined field lenses (cFL) of holographic 3D displays is given. The description of Bragg diffraction based volume gratings is based on the coupled wave theory (CWT). The usage of the 2nd on-Bragg maximum modulation is described. The advantage of the 2nd Bragg diffraction order is explained. Polarization beam splitter (PBS) geometries are described. Specific layouts of holographic 3D displays are explained. BLU and cFL are evaluated. It is shown how the suppression of diffractive crosstalk can be obtained. Oftmals benötigen neue Produkte der Photonik eine erweiterte optische Funktionalität, die nicht von optischen Standard-Komponenten bereitgestellt werden kann. Dies ist auch für die Entwicklung von holographischen 3D-Displays der Fall. Hierbei ermöglicht die Implementierung von Volumengittern, die auf der Bragg-Beugung basieren, eine kompakte Bauweise und eine natürliche Wahrnehmung von 3D-Objekten in HD-Auflösung. Dies ist für die Modellierung von 3D-Daten, die Erstellung von Prototypen, CAD-CAM, Computer integrierte Fertigung (CIM), weltweit arbeitende Telekonferenz-Systeme und mobiles Infotainment von Bedeutung. Holographische 3D-Displays, die auf einer, in der Bandbreite limitierten Rekonstruktion von Wellenfrontsegmenten beruhen, profitieren von der spezifischen Charakteristik dicker holographischer Gitter, welche als Bragg-Beugung basierte Volumengitter bezeichnet werden können. Es wird beschrieben, wie die Winkel-, Wellenlängen- und Polarisationsselektivität ausgelegt werden kann, um spezifische optische Funktionalitäten bereitzustellen. Diese sind unter anderem notwendig, um HD-fähige holographische 3D-Displays zu realisieren. Es wird eine kurze Einführung zu Hintergrundbeleuchtungseinheiten, komplexwertigen räumlichen Modulatoren und kombinierten Feldlinsen von holographischen 3D-Displays gegeben. Die Beschreibung Bragg-Beugung basierter Volumengitter erfolgt unter Nutzung der CWT (coupled wave theory). Es wird dargelegt, wie das 2-te Maximum der on-Bragg Modulation genutzt werden kann. Der Vorzug der 2-ten Bragg-Beugungsordnung wird erklärt. Polarisations-Strahlteiler-Geometrien werden beschrieben. Spezifische Anordnungen von holographischen 3D-Displays werden erklärt. Beleuchtungseinheiten und kombinierte Feldlinsen werden untersucht. Es wird beschrieben, wie die Unterdrückung diffraktiven Übersprechens erreicht werden kann.
Contribution
  • Gerald Fütterer

Field lens multiplexing in holographic 3D displays by using Bragg diffraction based volume gratings.

In: Proceedings of SPIE 10151 (Optics and Measurement International Conference 2016 [11.-14.10.2016, Liberec, Tschechische Republik]).

  • (2016)
Contribution
  • Gerald Fütterer

From Holographic displays to Volume Gratings and Off-Axis Parabolic Mirrors.

In: Proceedings of SPIE 10009 (Third European Seminar on Precision Optics Manufacturing, 100090Y [April 12th 2016, Teisnach]). pg. 1000912

  • Eds.:
  • Christian Schopf
  • O. Fähnle
  • Rolf Rascher
  • Christine Wünsche

  • (2016)

DOI: 10.1117/12.2245183

show abstract

An important chain link in modeling of three dimensional data (3D data), 3D prototyping, CAD-CAM, computerintegrated manufacturing (CIM), PC gaming, global 3D teleconferencing, future e-commerce, product advertisement and mobile infotainment is the visualization of 3D data and 3D objects. On the one hand, there is an increasing demand for 3D displays providing natural three dimensional viewing experience, but on the other hand there is a lack of available 3D displays capable of generating all depth cues. Available state of the art 3D displays can provide only a few depth cues and a very limited 3D experience. This is due to the inherent physical limits of the different approaches used. Holographic displays, for instance based on space bandwidth limited wave segment reconstruction, can provide all depth cues and a large viewing volume. They can provide satisfying 3D visualization. But still they are not available. Thick hologram gratings 1, which also can be referred to as Bragg diffraction based volume gratings, are key components, which enable small form factor holographic 3D displays. Manufacturing large, display size Bragg diffraction based volume gratings is challenging. Collimators are key components within interference lithographic exposure setups. Using off-axis parabolic mirrors (OAPM) as collimating optical elements enables the generation of exact plane waves by using a single reflective surface. Thus, off-axis parabolic mirrors are preferred in order to realize the collimation of large wave fronts. The surface roughness has to be very low. The relationship between holographic 3D displays and specific requirements, which have to be taken into account when manufacturing off-axis parabolic mirrors, will be presented. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Patent
  • Gerald Fütterer

Light Modulation Device.

  • 20.01.2016 (2016)

show abstract

The invention relates to a light modulation device (60) for a display device (10), in particular a holographic display device, for the representation of two-dimensional and/or three-dimensional reconstructed scenes. The light modulation device (60) has at least one spatial light modulator (70), having modulation elements, for the modulation of incident light and an optical element (80) with known optical characteristics. The light falling on the at least one spatial light modulator (70) is thereby sufficiently coherent. The at least one spatial light modulator (70) and the optical element (80) are combined with one another in such a way that the optical element (80) scatters the unmodulated light emitted from the spatial light modulator (70) into an angle range.
Patent
  • Gerald Fütterer
  • R. Haussler
  • B. Kroll
  • N. Leister
  • S. Reichelt

Combined Light Modulation Device for Tracking Users.

  • 21.03.2016 (2016)
Patent
  • Gerald Fütterer

Beam Divergence and Various Collimators for Holgraphic or Stereoscopic Displays.

  • 24.06.2016 (2016)
Patent
  • Gerald Fütterer

Display Device, in Particular a Head-Mounted Display, Based on Temporal and Spatial Multiplexing of Hologram Tiles.

  • 30.06.2016 (2016)
Contribution
  • Gerald Fütterer

Advantages of on-axis PBS based Fizeau interferometers.

In: DGaO Proceedings zur 118. Jahrestagung in Dresden (06.-10.06.2017).

  • (2017)
Patent
  • Gerald Fütterer

Illumination device.

  • (2017)
Contribution
  • Gerald Fütterer

Fast Fizeau interferometer with polarization selective reference and reduced measurement uncertainty for production integrated measurement.

In: Forschungsbericht 2016/2017 der Technischen Hochschule Deggendorf. pg. 97-101

  • (2017)
Contribution
  • Gerald Fütterer

Polarization-Fizeau interferometer enabling phase measurement with reduced uncertainty.

In: Proceedings of SPIE 10326 (Fourth European Seminar on Precision Optics Manufacturing, 1032601 [April 4th-5th 2017, Teisnach]). pg. 103260B

  • Eds.:
  • Christian Schopf
  • O. Fähnle
  • Rolf Rascher
  • Christine Wünsche

  • (2017)

DOI: 10.1117/12.2272001

Contribution
  • Gerald Fütterer

Tailored complex degree of mutual coherence for plane-of-interest interferometry with reduced measurement uncertainty.

In: Proceedings of SPIE 10448 (SPIE Optifab [October 16-19, 2017; Rochester, NY, USA]). pg. 104481I

  • Eds.:
  • S. Stoebenau
  • J. Bentley

  • (2017)

DOI: 10.1117/12.2279834

show abstract

A problem of interferometers is the elimination of parasitic reflections. Parasitic reflections and modulated intensity signals, which are not related to the reference surface (REF) or the surface under test (SUT) in a direct way, can increase the measurement uncertainty significantly. In some situations standard methods might be used in order to eliminate reflections from the backside of the optical element under test. For instance, match the test object to an absorber, while taking the complex refractive index into account, can cancel out back reflections completely. This causes additional setup time and chemical contamination. In some situations an angular offset might be combined with an aperture stop. This reduces spatial resolution and it does not work if the disturbing wave field propagates in the same direction as the wave field, which propagates from the SUT. However, a stack of surfaces is a problem. An increased spectral bandwidth might be used in order to obtain a separation of the plane-of-interest from other planes. Depending on the interferometer used, this might require an optical path difference of zero or it might cause a reduction of the visibility to V < 0.5. Contrary to these methods, a tailored complex degree of mutual coherence can be used. High visibility is obtained for a single plane-of-interest. Wave fields of interest are shifted against each other. The reduction of the measurement uncertainty, as well as the embodiment of a modified interferometer, will be discussed.
Patent
  • Gerald Fütterer

A Display for Two-Dimensional and/or Three-Dimensional Images.

  • (2017)
Patent
  • Gerald Fütterer
  • R. Häußler
  • B. Kroll
  • N. Leister
  • S. Reichelt

Combined light modulation device for tracking users.

  • (2017)
Lecture
  • Gerald Fütterer

Polarization-Fizeau interferometer enabling phase measurement with reduced uncertainty.

In: SPIE Precision Optics Manufacturing, Session - Measurement in Production

Teisnach

  • 04.04.2017 (2017)
Lecture
  • Gerald Fütterer

Advantages of on-axis PBS based Fizeau interferometers.

In: 118. Jahrestagung der Deutschen Gesellschaft für angewandte Optik (DGaO)

Dresden

  • 10.06.2017 (2017)
Patent
  • Gerald Fütterer
  • R. Häußler
  • N. Leister

Method for producing holograms.

  • 28.08.2017 (2017)
Lecture
  • Gerald Fütterer

Optical surface measurement technologies. Invited Talk.

In: 3rd International Summer School: Trends in energy and particle beam ultra-precision optical surface engineering

Leibniz Institute of Surface Engineering Leipzig

  • 01.09.2017 (2017)
Lecture
  • Gerald Fütterer
  • Johannes Liebl
  • Alexander Haberl

Contribution of the phase transfer function of extended measurement cavities to mid spatial frequencies and the overall error budget.

In: Fifth European Seminar on Precision Optics Manufacturing

Teisnach

  • 10.-11.2017 (2017)
Lecture
  • Gerald Fütterer

Tailored complex degree of mutual coherence for plane-of-interest interferometry with reduced measurement uncertainty.

In: SPIE Optifab

Rochester, NY, USA

  • 16.10.2017 (2017)
Patent
  • Gerald Fütterer

Display Device, holographic head-mounted display.

  • (2018)
Contribution
  • Gerald Fütterer
  • A. Sperl
  • A. Engelbrecht
  • Simon Killinger
  • M. Werni
  • W. Krais

Abschattungsfreies Multi-Schiefspiegel-Teleskop als studentisches Entwicklungsprojekt.

In: DGaO Proceedings zur 119. Jahrestagung in Aalen (22.-26.05.2018) 2018.

  • (2018)

show abstract

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.
Contribution
  • Alexander Haberl
  • H. Harsch
  • Gerald Fütterer
  • Johannes Liebl
  • C. Pruß
  • Rolf Rascher
  • W. Osten

Model based error separation of power spectral density artefacts in wavefront measurement.

In: Proceedings of SPIE 10749 (SPIE Optical Engineering + Applications Conference on Interferometry XIX [August 19-23, 2018; San Diego, CA, USA]). pg. 107490T

  • (2018)

DOI: 10.1117/12.2321106

Contribution
  • Gerald Fütterer

CSLM illumination for 1D and 2D encoded holographic 3D displays.

In: Illumination Optics V; SPIE Illumination Optics Conference; SPIE Optical Systems Design (OSD) [May 14-16, 2018; Frankfurt, Germany]. (Proceedings of SPIE) pg. 4

  • Eds.:
  • T. Kidger
  • S. David

  • (2018)

DOI: 10.1117/12.2312745

show abstract

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.
Contribution
  • Gerald Fütterer
  • Johannes Liebl
  • Alexander Haberl

Contribution of the phase transfer function of extended measurement cavities to mid spatial frequencies and the overall error budget.

In: Proceedings of SPIE 10829 (Fifth European Seminar on Precision Optics Manufacturing [April 10-11, 2018; Teisnach]). pg. 108290L

  • Eds.:
  • Christian Schopf
  • Rolf Rascher

  • (2018)

DOI: 10.1117/12.2318711

show abstract

A challenge of coaxial - measurement cavity based - interferometer is to realize an interference contrast in the vicinity of one and to realize a complete elimination of the parasitic reflections. Another challenge, which also exists in non-coaxial setups, is the phase transfer function of extended measurement cavities. Ideally, the surface under test (SUT) and the reference surface (REF) are both exactly imaged onto the detector plane. In practice, SUT and REF have to be placed within the depth of field (DOF), which refers to the object space. The term depth of focus refers to the image space. To avoid confusion, the depth of field might be referred to as DOOF (depth of object field) and the depth of focus might be referred to as DOIF (depth of image field). However, in many measurement situations, the REF is not placed within the DOOF, which is the small z-range, which is imaged onto the detector plane. Furthermore, the phase transfer function (PTF) of the REF and the image distortion of the REF are both dependent on the focal plane used to image the SUT onto the detector plane. Effects as phase deformation, image distortion and image blurring have to be taken into account when using extended measurement cavities. This can be done by using a look up table (LUT), which contains simulated and/or calibrated data. Thus, the related system error can be subtracted. A remaining challenge is an unknown object under test (OUT), which is measured by using a double path arrangement. The measured wave front depends on the two surfaces of the OUT and the position of the return mirror. For simplicity, a homogeneous substrate and a perfect return mirror might be presumed. The simulation of waves propagating within extended measurement cavities, as well as measurement results, will be discussed. In addition, the influence on the power spectral density (PSD) will be described. This is important for high end correction techniques as e.g. magneto rheological figuring (MRF) and ion beam figuring (IBF).
Contribution
  • Gerald Fütterer
  • A. Sperl
  • Simon Killinger
  • A. Engelbrecht
  • M. Werni
  • W. Krais

Developing a four-tilted-mirror telescope as a student project.

In: Optics Education and Outreach V. 22 August 2018, San Diego, California, United States (Proceedings of SPIE) pg. 23

  • Eds.:
  • G. Gregory

  • (2018)

DOI: 10.1117/12.2320542

show abstract

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.
Contribution
  • Gerald Fütterer

Optimization of the complex coherence function for diffraction-based wavefront transformations.

In: Unconventional Optical Imaging. Proceedings of SPIE Volume 10677, Unconventional Optical Imaging; 106773H; SPIE Photonics Europe, Strasbourg, France (May 2018) pg. 129

  • Eds.:
  • M. Georges
  • G. Popescu
  • C. Fournier

  • (2018)

DOI: 10.1117/12.2307245

show abstract

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.
Lecture
  • Gerald Fütterer

Optimization of the complex coherence function for diffraction-based wavefront transformations.

In: SPIE Photonics Europe 2018

Strasbourg, Frankreich

  • 2018 (2018)
Lecture
  • Gerald Fütterer

Etalon effect suppression in optical measurements by using complex coherence optimization. Posterpräsentation.

In: 5. Tag der Forschung der THD 2018

Technische Hochschule Deggendorf Deggendorf

  • 08.03.2018 (2018)
Lecture
  • Gerald Fütterer

CSLM illumination for 1D and 2D encoded holographic 3D displays.

In: Illumination Optics V, Symposium: EOD18 SPIE Optical Systems Design

Frankfurt am Main

  • 14.05.2018 (2018)
Lecture
  • Gerald Fütterer
  • A. Sperl
  • A. Engelbrecht
  • Simon Killinger
  • M. Werni
  • W. Krais

Abschattungsfreies Multi-Schiefspiegel-Teleskop als studentisches Entwicklungsprojekt.

In: 119. Jahrestagung der Deutschen Gesellschaft für angewandte Optik (DGaO)

Aalen

  • 22.-26.05.2018 (2018)
Lecture
  • Gerald Fütterer
  • A. Sperl
  • Simon Killinger
  • A. Engelbrecht
  • M. Werni
  • W. Krais

Developing a four-tilted-mirror telescope as a student project.

In: SPIE Optics Education and Outreach V

San Diego, CA, USA

  • 19.-23.08.2018 (2018)
Lecture
  • Alexander Haberl
  • H. Harsch
  • Gerald Fütterer
  • Johannes Liebl
  • C. Pruß
  • Rolf Rascher
  • W. Osten

Model based error separation of power spectral density artefacts in wavefront measurement.

In: SPIE Optical Engineering + Applications Conference on Interferometry XIX

San Diego, CA, USA

  • 19.-23.08.2018 (2018)
Contribution
  • Gerald Fütterer

Wave front sensing for metrology by using optical filter.

In: Proceedings of SPIE 11171 (Sixth European Seminar on Precision Optics Manufacturing, 1117101 [9-10 April 2019, Teisnach]). pg. 111710K1-111710K11

  • Eds.:
  • Christian Schopf
  • Rolf Rascher

Bellingham, WA, USA

  • (2019)

DOI: 10.1117/12.2530013

show abstract

An interferometric problem is the limited fringe density, which is due to the limited allowed slope difference of superimposed wave fronts. Thus, the angular dynamic range of measurable surfaces and objects under test is limited. In other words, all shapes that deviate from a plane surface or a sphere represent a measuring problem in interferometers, or require an individually adapted null optics, which might cost e.g. 10 k∈ or more. In addition, ground surfaces cannot be measured in standard interferometers, except by using Speckle interferometry, which is limited in resolution. Freeform optics are very problematic. Even when polished, only tactile or confocal coordinate measurement might work. Several interferometers address the problem of the angular deviation to a sphere. For instance, lateral stitching on a curved surface, which is equivalent to the best-fit sphere, or longitudinal stitching is used. To use a tilted wave interferometer for asphere metrology is another option, which provides versatile measurement configurations. The approach discussed here is to use optical filters. The development of this technique is part of a project most recently started at the Technology Campus in Teisnach. The surface under test (SUT) is imaged onto an optical filter, which has a calibrated angular selectivity. Thus, the angles of the local wave front normal vectors are transferred into an intensity distribution. A set of angular measurements enables reduced uncertainty of the wave front measurement. Aspects as e.g. the working principle, boundary conditions and the identification of practical filters are discussed in the paper.
Contribution
  • Gerald Fütterer
  • Michael Wagner
  • Lucas Bauer
  • Simon Wittl

Alignment and thermal drift aspects of a four-tilted-mirror student project telescope.

In: Proceedings of SPIE 11171 (Sixth European Seminar on Precision Optics Manufacturing, 1117101 [9-10 April 2019, Teisnach]). pg. 111710L1-111710L9

  • Eds.:
  • Christian Schopf
  • Rolf Rascher

Bellingham, WA, USA

  • (2019)

DOI: 10.1117/12.2530076

show abstract

The Deggendorf Institute of Technology (DIT) and its Faculty of Applied Natural Sciences and Industrial engineering transfer a broad spectrum of knowledge to the students. The clarification of the interrelations that exist between seemingly isolated fields of knowledge is a permanent process. In order to put this into practice, a telescope construction project was started. The base of the in-house student project is the Technology Campus in Teisnach, which bundles capacities for process development, production and measurement of high-precision optics, including telescope optics. A first optical design, which is based on a subset of the parameter space published in 1989 by M. Brunn1, 2 (later built by D. Stevick as f/12-system3 ), made use of a primary mirror M1 with a diameter of 400 mm. An f/8-system provide a Strehl ratio SR ≥ 0.8 over an entire field of view of 0.7° deg. Even if this seems to be sufficient, manufacturing tolerances, adjustment tolerances, thermal drift and positional changes considerably reduce the Strehl ratio. In order to obtain reliable values of acceptable tolerances, statistical Monte Carlo analyses had been carried out. As consequences, the tube design was changed and the design of new mirror mounts started. This was done to achieve the required stiffness. The new tube designs, one based on carbon-fiber-reinforced polymer (CFRP) and one based on FeNi36, had been tested by using FEM analysis. In addition, the practicability of deep learning based aberration detection was tested. Zernike polynomials obtained by analyzing the star images with a Convolutional Neuronal Network (CNN). The current state of the development is described.
Contribution
  • Gerald Fütterer
  • Michael Wagner
  • Lucas Bauer
  • Simon Wittl

Four-Tilted-Mirror Telescope: Alignment and Stability Aspects.

In: Forschungsbericht 2018/2019 der Technischen Hochschule Deggendorf. pg. 153-158

  • Eds.:
  • Technische Hochschule Deggendorf

Deggendorf

  • (2019)
Contribution
  • Gerald Fütterer
  • Michael Wagner
  • Lucas Bauer
  • Simon Wittl

4-Schiefspiegel-Teleskop: Justage und Stabilitätsaspekte.

In: Untertitel. Das Magazin der Technischen Hochschule Deggendorf pg. 118-119

  • Eds.:
  • Technische Hochschule Deggendorf

Deggendorf

  • (2019)
Patent
  • Gerald Fütterer

Beam divergence and various collimators for holographic or stereoscopic displays.

  • 20.05.2019 (2019)
Patent
  • Gerald Fütterer
  • N. Leister
  • R. Haussler
  • G. Lazarev

Spatial light modulator device for the modulation of a wave field with compex information.

  • 18.03.2019 (2019)
Lecture
  • Gerald Fütterer

4x-Schiefspiegel-Teleskop-Projekt. Posterpräsentation.

In: 6. Tag der Forschung der THD 2019

Technische Hochschule Deggendorf Deggendorf

  • 10.04.2019 (2019)
Lecture
  • Gerald Fütterer

Wave front sensing for metrology by using optical filter.

In: Sixth European Seminar on Precision Optics Manufacturing (POM19)

Technische Hochschule Deggendorf Teisnach

  • 10.04.2019 (2019)
Lecture
  • Gerald Fütterer

Patente: Praxiserfahrungen.

In: Patentworkshop der Technischen Hochschule Deggendorf

Deggendorf

  • 18.06.2019 (2019)
Contribution
  • Armin Reif
  • Sebastian Sitzberger
  • Rolf Rascher

Cutting high-performance materials with ultrasonically modulated cutting speed.

In: Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]).

  • Eds.:
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer
  • Rolf Rascher

Bellingham, WA, USA

  • (2020)

DOI: 10.1117/12.2565757

show abstract

The continuing trend towards lightweight construction and the associated machining rates of up to 95 % lead to an increased use of high-performance materials. The ever growing demands on the strength and quality of components and the associated use of materials which are hard to machine require the further development of new, economical machining techniques. In ultrasonic-assisted machining, an additional high-frequency vibration is superimposed on the conventional machining process. The vibration of the tool is usually excited axially or longitudinally to the workpiece, i.e. vertical to the cutting direction. An additional vibration overlay around the rotation axis (torsional) of the tool is also possible. This generates a vibration overlay in the cutting direction. The vibration initiation causes vibration amplitudes in the range of a few micrometers at the tool cutting edge. This leads in turn to a high-frequency change in the cutting speed or feed rate. Overall, an additional torsional vibration overlap can further reduce cutting forces, increase tool life and improve workpiece quality. In order for a grinding tool to generate a torsional vibration, a special tool was required that had to be designed by simulation. The formation of a torsional vibration was achieved by helical slots in the sonotrode. Depending on the angle of rotation and the length of the slots, a part of the axial vibration is converted into a torsional vibration by an axial excitation of the sonotrode. The aim in designing the slots was to achieve the highest possible vibration amplitude. Following the simulation, the slots were inserted into the tool in the corresponding optimum geometric position. Afterwards, the specially designed grinding tool was validated by machining the brittle-hard glass-ceramic material Zerodur. The first test results with the torsionally vibrating tool are presented in the following.
Contribution
  • Olga Kukso
  • Rolf Rascher
  • M. Pohl
  • R. Börret

On the metrology and analysis of MSF error.

In: Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]). pg. 1147809

  • Eds.:
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer
  • Rolf Rascher

Bellingham, WA, USA

  • (2020)

DOI: 10.1117/12.2566251

show abstract

The aim of our research was to study middle spatial frequency errors (MSFE) on optical surfaces. We investigate the surfaces after manufacturing processes to find out the main affecting factors and to choose the proper processing parameters to minimize the size of the errors. To find an appropriate parameter window we have to be able not only to define the factors, which lead to MSFE, but also to analyze the change of the error after next following production steps.
Contribution
  • Jessica Stelzl
  • Christine Wünsche
  • S. Höfer

Influencing factors for a continuous wave UV-laser component.

In: Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]). pg. 114780C

  • Eds.:
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer
  • Rolf Rascher

Bellingham, WA, USA

  • (2020)

DOI: 10.1117/12.2564916

show abstract

During the development of an optical system, one comes to the point where you have to build the optically active element into a mechanical device that becomes part of the system. At this point you come across the well-known question that it is not only necessary to consider and ensure the quality of the individual element. It is also important to look at the entire component in order to identify potential influencing factors on the performance of the optical system. At the beginning of a two-year project at Technologiecampus Teisnach the polishing process of a nonlinear crystal as the crucial component of the optical system was being explored. This system is designed to create continuous wave laser beams in the deep UV range. The crystal has to be embedded between two prisms. Roughness and shape of the crystal is ensured via the polishing process which alone has many influencing factors and was examined at the beginning of the project. The quality of the crystal can be as good as it can be, but if the contacting prisms do not fit, the whole prism-coupled device will become unusable in the overall optical laser system. The performance of the laser can only be achieved by harmonizing all elements of the PCD and the PCD itself into the laser set-up. In the current phase of the project this question will be dealt with. The prism-coupled device is split up into its individual parts, which are the nonlinear crystal, the prisms as optical auxiliary components, micro screws and mechanical support. Going through the requirements to the properties of the crystal and their limitations, the influence of the PCD on the optical performance of the crystal is presented. Here, the main focus is placed on the mode of fixing the crystal between the prisms and on putting the stack of crystal and prisms in the laser beam. The influencing factors between the crystal, the prisms and the method of fixing the PCD are described.
Contribution
  • M. Pohl
  • R. Börret
  • Olga Kukso
  • Rolf Rascher

Mid spatial frequency error prevention strategies for the grinding process.

In: Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]). pg. 114780E

  • Eds.:
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer
  • Rolf Rascher

Bellingham, WA, USA

  • (2020)

DOI: 10.1117/12.2565261

show abstract

This research is focused on the link between manufacturing parameters and the resulting mid-spatial frequency error in the manufacturing process of precision optics. The goal is to understand the generation mechanisms of mid-spatial frequency errors and avoid their appearance in the manufacturing process. Also, a simulation which is able to predict the resulting mid spatial frequency error from a manufacturing process is desired.
Contribution
  • M. Jung
  • Christian J. Trum
  • Beate Schmidbauer
  • E. Willenborg
  • Rolf Rascher

Non-ablative removal of sub surface damages in ground optical glass substrates by controlled melting of thin surface layers using CO2-laser radiation.

In: Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]). pg. 1147804

  • Eds.:
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer
  • Rolf Rascher

Bellingham, WA, USA

  • (2020)

DOI: 10.1117/12.2564801

show abstract

The form generation of optical surfaces by grinding and mechanical polishing results in small sub surface damages in the form of micro cracks that conventionally have to be removed by further removal of the damaged surface layers. In order to reduce process time and material cost non-ablative methods for removal of micro cracks are desired. Utilising the low optical penetration depths of less than 10 μm for CO2-laser radiation in glass, the laser energy can be used to heat up and melt thin surface layers. Using a 1.5 kW CO2-laser, a quasi-line focus formed by a scanner unit and a constant feed speed, it is possible to close all micro cracks present in the rough grinded test surfaces (max. SSD-depth ~ 63 μm), while achieving a process time of less than 2 seconds for a Ø 30 mm N-BK7 lens, respectively 7.5 seconds for fused silica. With a Sa as low as 50 nm and low distortion from the original shape the surfaces can directly be conventionally polished, further reducing the process chain complexity.
Contribution
  • Simon Killinger
  • Johannes Liebl
  • Rolf Rascher

First steps towards an automated polishing process chain using one robot.

In: Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]). pg. 114780I

  • Eds.:
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer
  • Rolf Rascher

Bellingham, WA, USA

  • (2020)

DOI: 10.1117/12.2564840

show abstract

Manufacturing precision optics is a complex process chain, which requires many operations on different machines. This is combined with operator-dependent steps such as manual cleaning, loading and measuring. In order to realize this process chain on a smaller shop area and to achieve a higher level of automation we build an operator-independent polishing cell. In this cell, an ABB robot serves as the actuator handling the workpiece. We positioned the robot in the center of the polishing cell to operate several workstations, so the whole process chain works with one single actuator. This arrangement allows a smaller and cheaper system, since no additional handling is required.
Contribution
  • Michael Wagner
  • Gerald Fütterer

Computer-aided beam path generation and assessment for Stevick-Paul telescopes.

In: Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]). pg. 114780B

  • Eds.:
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer
  • Rolf Rascher

Bellingham, WA, USA

  • (2020)

DOI: 10.1117/12.2564852

show abstract

At Deggendorf Institute of Technology a student project is currently under way to build a Stevick-Paul telescope for astrophotography. An important step in the overall development procedure of each telescope is the design of a beam-path and ensuring its suitability under optical and engineering aspects. The students performed this process in a sequential manner by using several different computer programs (e.g. MATLAB, Zemax, Creo Parametric). To accelerate the beam path design process, a Python program to automate the major part of the design process with minimum human supervision was created. The input data of the python program consists of ranges of the desired characteristics of the Stevick-Paul telescope, such as focal lengths, primary mirror diameters and tilts etc., mirror thickness and mount geometries, as well as the specific type of camera. After setting the input, the program creates 2D cross-sections of beam paths according to the formulas of D. Stevick and may introduce a flat fold mirror to reduce the overall system size as well as improve the accessibility of the focus plane. The subsequent assessment routine checks against the susceptibility for stray light and performs a complex analysis of the available installation space to ensure sufficient mechanical tolerances. In this way, collisions between mirrors, mounts and cameras are avoided and obstructions of the beam path are prevented. At any stage, the program can produce graphical representations of the beam paths. In this paper the computer-aided design of a telescope beam path with a focal length of 2400 mm is demonstrated. During development of the software, a subset of folded Stevick-Paul telescopes, in which certain components are parallel, was found. This subset may be useful to simplify the alignment procedure. In conclusion, further refinement of the software is necessary, although the program is already a useful aid for certain aspects when creating a beam path design.
Contribution
  • Sebastian Sitzberger
  • Johannes Liebl
  • Christian J. Trum
  • Rolf Rascher

Concept of a two-part clamping system for lenses in optical metrology.

In: Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]). pg. 114780G

  • Eds.:
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer
  • Rolf Rascher

Bellingham, WA, USA

  • (2020)

DOI: 10.1117/12.2566547

show abstract

The developed concept represents a universally applicable clamping system designed to fit in any measuring machine with any measuring principle. The design ensures that, as long as the lens remains clamped, the measurement results are reproducible. Form errors due to tension remain constant across all measuring and processing steps. The version presented in this paper was developed especially for small lenses in the diameter range up to 40 mm. On the one hand, the design allows for fast measurement of loose lenses. On the other hand, the device can also be used for measurement comparisons, since lenses can also be mounted permanently. In the following, the concept and first results of measurement tests are presented.
Contribution
  • Michael Benisch
  • O. Fähnle
  • Rolf Rascher
  • Werner Bogner

Force and pressure analysis during overarm polishing.

In: Proceedings of SPIE 11478 (Seventh European Seminar on Precision Optics Manufacturing [8 July 2020; Teisnach]). pg. 114780H

  • Eds.:
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer
  • Rolf Rascher

Bellingham, WA, USA

  • (2020)

DOI: 10.1117/12.2564903

show abstract

The Preston-equation implies, that, besides the relative speed υrel and a specific constant KP, the pressure p plays a significant role for the removal rate when polishing an optical component. This paper demonstrates a possibility for a qualitative evaluation of the pressure distribution before the polishing process. A pressure-sensitive foil is used as a gauge for pressure measurement. The effectiveness of this measuring method is explained. Specific weaknesses and limitations in the use of these foils are discussed. A method for an integrated evaluation of the pressure on different spots of the polishing pad is proposed at the end of the paper.
ConferenceProceedings

Proceedings of SPIE 11853 (Eighth European Seminar on Precision Optics Manufacturing, 100090Y [April 13th-14th, 2021, Teisnach]).

vol. Volume 11853

  • Eds.:
  • Rolf Rascher
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer

SPIE, Society of Photo-Optical Instrumentation Engineers Teisnach, Germany

  • (2021)

DOI: 10.1117/12.2602818

Contribution
  • Stefan Anthuber
  • Michael Benisch
  • Rolf Rascher

Industry 4.0 in the fabrication of optical components: development, presence, and requirements.

In: Proceedings of SPIE 11853 (Eighth European Seminar on Precision Optics Manufacturing, 100090Y [April 13th-14th, 2021, Teisnach]). pg. 118530D

  • Eds.:
  • Rolf Rascher
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer

SPIE, Society of Photo-Optical Instrumentation Engineers

  • (2021)

DOI: 10.1117/12.2595037

show abstract

Optics and photonics are considered as an enabling technology for innovations in other technological fields (e. g. astronomy, medicine, military, …). Their first applications date back to jewellery processing in ancient times. In the medieval age Vikings on Gotland (1050) buried the Visby lenses. They have a quality of workmanship and imaging comparable to a high quality lens made in the mid-20th century. The specific use of spectacles to correct long-sightedness or presbyopia is known from the 13th century. Around the transition from the 16th to the 17th century, the microscope and the telescope were invented, combining several lenses for the first time. This shows that the exploitation of the optical properties of materials can be dated back very early in human history. In particularly, today`s optics industry is still based on personal knowledge which results in a relatively workmanship production environment. The challenges of globalisation and the current pandemic situation demonstrate that increasing the degree of automation is a possible way to keep a leading position in the market. This is not only important due to the high quality of optical components but also by enabling competitive prices for production through reducing the labour costs. The third industrial revolution established the digitalisation of production and the usage of CNC-machinery. In most industries including optics industries this is the status quo of production. The target of industry 4.0 and internet of things is to lead into a new industrial revolution. The German government developed the buzzword “Industrie 4.0” (eng. Industry 4.01 ). This concept includes the contradiction of mass production and production according to individual customer requests. This should be carried out by connecting all production units with the goal of an intelligent factory. Among other things this includes seamless monitoring of the manufacturing processes along all steps and remote access to involved machines. A further target is manufacturing under the constraint of a small batch size down to one piece. This publication aims to present the current situation in the manufacturing of optical components and compare this with manufacturing of metallic components. It will outline, which measures are necessary to ensure a comprehensive transformation of the optical industry in accordance with the Industry 4.0 idea and which benefits can be expected.
Contribution
  • Olga Kukso
  • Michael Benisch
  • Rolf Rascher
  • S. Sundar
  • M. Hacker
  • M. Duschl
  • M. Nussbaum

Acoustic measurements for optics.

In: Proceedings of SPIE 11853 (Eighth European Seminar on Precision Optics Manufacturing, 100090Y [April 13th-14th, 2021, Teisnach]). pg. 118530K

  • Eds.:
  • Rolf Rascher
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer

SPIE, Society of Photo-Optical Instrumentation Engineers

  • (2021)

show abstract

The aim of the research was the development of a measurement and analysis method that enables the detection of errors and malfunctions within a machine tools and in the manufacturing process using acoustic sensors (microphones).
Contribution
  • David Moszko
  • O. Fähnle
  • Christian Vogt
  • D.W. Kim

In-process surface roughness measuring device for information-based real-time polishing process adjustment and optimization.

In: Proceedings of SPIE 11853 (Eighth European Seminar on Precision Optics Manufacturing, 100090Y [April 13th-14th, 2021, Teisnach]). pg. 118530E

  • Eds.:
  • Rolf Rascher
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer

SPIE, Society of Photo-Optical Instrumentation Engineers

  • (2021)

DOI: 10.1117/12.2596034

show abstract

In this paper we present a feasible variant of a device for in-process roughness measurement during an optical polishing process. The system, already presented as Tirm respectively I-Tirm, has been technically varied and can now be integrated into almost any lever polishing process with little effort. This enables new possibilities regarding real-time optical manufacturing process monitoring and optimization.
Contribution
  • Christian Vogt
  • Helge Thiess
  • J. Blasl
  • N. Hanenkamp
  • Klaus Lichtinger

Superposition of cryogenic and ultrasonic assisted machining of Zerodur.

In: Tenth European Seminar on Precision Optics Manufacturing. pg. 15

  • Eds.:
  • Christine Wünsche
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer

SPIE, Society of Photo-Optical Instrumentation Engineers

  • (2023)

DOI: 10.1117/12.2678074

show abstract

Cryogenic machining is a cooling strategy that has recently been frequently found in research in machining processes for materials such as inconel or titanium. In particular it is reported that these processes are more efficient in terms of tool life and material removal rate compared to those with water-based cooling lubrication. An increase in efficiency and productivity has significant potential from a cost perspective, especially when grinding Ceramic Matrix Composite materials and similar. These processes are used, for example, in the lightweighting of telescope mirrors made of e.g. fiber-reinforced silicon carbide, or Zerodur. An increase in productivity would be clearly noticeable in the manufacturing costs due to normally long machining times. In the "KryoSonic" project, we investigated whether and to what extent the use of cryogenic machining affects the rough machining of Zerodur with and without ultrasonic support.
Contribution
  • Michael Wagner

Simulation of System Transmission Values for different Angles of Incidence.

In: Tenth European Seminar on Precision Optics Manufacturing. pg. 1275509

  • Eds.:
  • Christine Wünsche
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer

SPIE, Society of Photo-Optical Instrumentation Engineers

  • (2023)

DOI: 10.1117/12.2676121

show abstract

For the design of a new asphere measuring system, it is necessary to know transmission values for a system consisting of a source, an optional auxiliary filter and an optical filter, on which angle-tuning is performed. To generate these transmission values for different angles of incidence and polarizations a simulation program was created. Input data of the simulation were based on data provided by the manufacturers. Simulation results are presented for a sample of four systems. Simulation was deemed successful and accelerates the design process of the metrology system, since a large range of source and filter combinations can be evaluated swiftly. Limitations of the simulation are discussed as well.
Lecture
  • Helge Thiess
  • Gerald Fütterer
  • Alexander Haberl

Optikfertigung am Technologiecampus Optik in Teisnach TH Deggendorf.

In: 41. gemeinsames Treffen Arbeitsgemeinschaft „Optik-Design und Simulation“ von Photonics BW und Arbeitsgruppe „Optik-Design“ von bayern photonics

Wendelstein

  • 14.11.2023 (2023)
Contribution
  • M. Krödel
  • Alexander Haberl
  • Gerald Fütterer
  • Benedikt Winter
  • Raimund Förg
  • S. Utsunomiya
  • T. Ozaki

CFRP mirror with optical quality manufactured by replica technology.

In: Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave. pg. 130923Z

  • Eds.:
  • L. Coyle
  • M. Perrin
  • S. Matsuura

SPIE

  • (2024)

DOI: 10.1117/12.3018411

show abstract

In the frame of an international R&D project, a team from Japan and Germany developed a replica process to manufacture a CFRP honeycomb mirror for visible application. The main target was to generate the optical surface with minimized effort to achieve a microroughness of better (1 – 2) nm RMS. This technology would enable the team to manufacture cost-effective mirrors for larger amounts, like for constellations. In this paper, we will present the recent results of this development and the finally achieved performance of a 300 mm light CFRP mirror. We will also present lessons learned for next steps of development to achieve such mirrors with an optical performance not only for microroughness but also for surface accuracy.
Contribution
  • Gerald Fütterer

Reticles in autocollimators: change in image quality due to changed coherence properties.

In: Eleventh European Seminar on Precision Optics Manufacturing 2024. pg. 1322103

  • Eds.:
  • Helge Thiess
  • Christine Wünsche
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer

SPIE

DOI: 10.1117/12.3035187

show abstract

Autocollimators (AC) are used for different metrological measurement tasks. These instruments are compact and versatile and easy to use. Angle deviations of polygons, local slopes, fiducials, e.g., are measured with autocollimators. If calibrated electronic autocollimators are used, then the measurements can be performed with uncertainties down to 0.01 arc sec. The uncertainty might be increased further by one order of magnitude or more if surfaces with small apertures, aberrant surfaces or surfaces placed at long working distances are measured. To define the measuring window, respectively the limiting parameters, a model of the optical system was implemented. Aberrations, diffraction, temporal and spatial coherence are used. To increase the measurement range, a phase-shifting reticle can be used. Simulations made for small apertures show, that a significant reduction of the uncertainty can only be realized for a limited parameter range of the components used. For example, incoherent and coherent illumination are rather exceptions than standards. Partial coherence is used in a plurality of applications, e.g. for interferometry and space-bandwidth-limited wave front reconstruction, just to name a few. The system and the coherence function Γ must be tailored to provide specific operation. Almost all embodiments come with little changes of the light source's coherence properties only. For example, to use a spectral bandpass filter or to limit the size of the light source seems to be the standard solution for almost everything. Some error sources related to reticle imaging within an AC are identified. And the acceptable parameter range will be described.
Contribution
  • Christian Vogt
  • Ghanshyam Babariya
  • Olga Kukso

An experimental approach to temperature measurement in the contact zone when grinding brittle-hard materials.

In: Eleventh European Seminar on Precision Optics Manufacturing 2024. pg. 132210E

  • Eds.:
  • Helge Thiess
  • Christine Wünsche
  • Alexander Haberl
  • O. Fähnle
  • Gerald Fütterer

SPIE

  • (2024)

DOI: 10.1117/12.3030935

show abstract

Temperature is an important process factor in grinding. Cryogenic cooling has proven to be very successful in metal machining, for example, as oxidation is prevented by lowering the temperature level. This enables significantly higher cutting speeds and longer tool life. In our research, we aim to determine whether similar effects occur when grinding brittle-hard materials, which is why the temperature in the contact zone is explicitly examined here. This article presents a very simple and extremely cost-effective approach using a germanium window and an infrared temperature sensor. It explains how the system is constructed, what results can be achieved with it and how the system compares to other commercially available approaches.

labs

Teaching-Lab Optics Faculty NUW (L104)