# Johannes Liebl, Dipl.-Ing. (FH)

Laboringenieur

Laboringenieur Mess- und Fertigungstechnik Optik

T 119

### Bürozeiten

Montag - Donnerstag / Technologiecampus Teisnach T119 / 07:00 - 16:00 Freitag / Technologiecampus Teisnach T119 / 07:00 - 11:30

### Publikationen

Beitrag (Sammelband oder Tagungsband)
• Simon Killinger
• Johannes Liebl
• Rolf Rascher
Interferometric measurement with robot kinematics, pg. 114870I.
• 2020

#### Abstract anzeigen

Polishing precision optics is highly depending on the operator. Hence, a good result relies on a skilled optician who controls the process chain. This process chain consists of different manual steps such as loading, cleaning and calibrating different machines. To get more control over the process and to speed up the production we currently build an operator independent polishing cell using a single robot. Therefore, we positioned the robot in the middle of the production cell, which enables the robot to reach and manipulate different tools located around the kinematic. One major issues is the lower positioning accuracy and stiffness of an industrial robot in comparison to standard optic machines. Probably the most challenging step concerning accuracy in precision optics manufacturing is the interferometric measurement. In this paper, we present a method using an ESDI Intellium H2000 interferometer, designed for use in unsteady conditions. The robot positions the surface under test without the use of any additional mechanics to enhance the accuracy. The measurement position was manually teached in and approached several times for a statistically significant evaluation. The results show that the robot is sufficiently accurate and stable to perform interferometric measurements. This is a key element towards a completely operator-independent manufacturing cell for precision optics.
• TC Teisnach Optik
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• DIGITAL
• NACHHALTIG
Beitrag (Sammelband oder Tagungsband)
• Simon Killinger
• Johannes Liebl
• Rolf Rascher
First steps towards an automated polishing process chain using one robot, pg. 114780I.
• 2020

#### Abstract anzeigen

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.
• TC Teisnach Optik
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• NACHHALTIG
Beitrag (Sammelband oder Tagungsband)
• Sebastian Sitzberger
• Johannes Liebl
• Christian J. Trum
• Rolf Rascher
Concept of a two-part clamping system for lenses in optical metrology, pg. 114780G.
• 2020

#### Abstract anzeigen

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.
• TC Teisnach Optik
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• NACHHALTIG
Beitrag (Sammelband oder Tagungsband)
• Sebastian Sitzberger
• Johannes Liebl
• J. Reitberger
• Rolf Rascher
Zero-point clamping systems in optical production, pg. 111710J1-111710J10.
• 2019

#### Abstract anzeigen

Zero point clamping systems are an integral part of the manufacturing industry. They have only yet to find their way into the optical industry. This article compares the hydraulic expansion holder, a clamping system currently used in the optical industry with a zero-point clamping system. The achievable accuracies of both systems are compared over several measurement series. In addition, the process capability evaluation is used for the comparison. Finally, the results are summarized to provide every researcher and practitioner with a foundation for assessing whether zero point clamping systems meet the requirements for the use in optical manufacturing.
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• TC Teisnach Optik
• NACHHALTIG
Vortrag
• F. Weidner
• J.-M. Asfour
• Johannes Liebl
CGH-Based Interferometer Measurements of Round Robin Asphere

In: 10th High Level Expert Meeting (HLEM) Asphere Metrology on Joint Investigations

• 2019
• TC Teisnach Optik
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• NACHHALTIG
Beitrag (Sammelband oder Tagungsband)
• Simon Killinger
• Johannes Liebl
• Rolf Rascher
Mid-spatial frequency errors in feed direction occurring in ADAPT polishing, pg. 111710G1-111710G8.
• 2019

#### Abstract anzeigen

Previous work shows the effectiveness of computer controlled polishing (CCP) with the ADAPT tool by Satisloh for correcting form errors in optics manufacturing. This method however has a risk of producing residual errors in the range of mid spatial frequency errors (MSFE). In order to prevent these errors the residual in feed direction is investigated as well as the behavior at different parameters.
• TC Teisnach Optik
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• NACHHALTIG
Beitrag (Sammelband oder Tagungsband)
• Alexander Haberl
• Johannes Liebl
• Rolf Rascher
ABC-polishing, pg. 1082906.
• 2018

#### 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.
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• TC Teisnach Optik
• NACHHALTIG
Beitrag (Sammelband oder Tagungsband)
• Johannes Liebl
• Christian Schopf
• Rolf Rascher
DefGO, pg. 108290I.
• 2018

#### Abstract anzeigen

The manufacturing of optical lenses has various steps. Generally, the manufacturing can be split up into the following steps: the workpiece is pre-ground with a coarse tool; it is then fine-ground with a finer tool. As the final polishing is a demanding and time-consuming process that cannot manage large removal rations not can it equalise rough shape errors, the starting quality and surface quality needs to be as high as possible. According to the current state of technology, ground lenses must be measured with tactile measuring techniques in order to detect shape errors. This is timeconsuming and expensive, and only two dimensional profiles can be measured. DefGO’s project objective is to introduce deflectometry as a new, three dimensional lens measuring standard. A problem with the application of deflectometry is that the object to be measured has to reflect enough light, which is not the case for ground glass with rough surfaces. DefGO’s solution is to wet the lens with a fluid to create a closed reflecting surface.
• TC Teisnach Optik
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• NACHHALTIG
Beitrag (Sammelband oder Tagungsband)
• 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, pg. 108290L.
• 2018

#### Abstract anzeigen

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).
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• TC Teisnach Optik
• NACHHALTIG
Zeitschriftenartikel
• 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, vol. 29, pg. 055010.

In: Measurement Science and Technology

• 2018

#### Abstract anzeigen

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 Wirtschaftsingenieurwesen
• TC Teisnach Optik
• NACHHALTIG
Beitrag (Sammelband oder Tagungsband)
• 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, pg. 107490T.
• 2018
• TC Teisnach Optik
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• NACHHALTIG
Vortrag
• 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

• 2018
• TC Teisnach Optik
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• DIGITAL
• NACHHALTIG
Vortrag
• 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

• 2017
• TC Teisnach Optik
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• NACHHALTIG
Beitrag (Sammelband oder Tagungsband)
• Christian Schopf
• Rolf Rascher
• Johannes Liebl
Cheap and fast measuring roughness on big surfaces with an imprint method, pg. 1044822.
• 2017
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• NACHHALTIG
Beitrag (Sammelband oder Tagungsband)
• Engelbert Hofbauer
• Rolf Rascher
• Manon Schilke
• Johannes Liebl
• J.-P. Richters
Deflectometric acquisition of large optical surfaces (DaOS) using a new physical measurement principle: vignetting field stop procedure
• 2016

• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• NACHHALTIG
Beitrag (Sammelband oder Tagungsband)
• Johannes Liebl
• Horst Linthe
• Sebastian Sitzberger
• Rolf Rascher
Interferometric measurement of highly accurate flat surfaces
• 2016

#### Abstract anzeigen

The most important part in manufacturing precision optics is a reliable measurement procedure which provides results a few times more accurate than the quality to be produced. In general two specific values are important, the repeatability of several measurements which are done in a row and the absolute accuracy which is mostly defined by the systematical error of the measurement device. The repeatability can be improved relatively simple, by increasing the number of measurements and a following averaging step. To increase the absolute accuracy of a measurement device in the field of precision optics is far more challenging. In this paper several interferometer absolute testing methods to measure flat surfaces are compared. The main objective was to name a value for the achievable accuracy. Therefor four different methods were analyzed: 1. The three flat test, a method which is already used several decades to determine the quality of a flat surface. As a result, two absolute measured profiles, horizontal and vertical, can be calculated. 2. The multi rotation test, an extension of the classical three flat test. The big advantage of this method is a fully three dimensional map of the systematical error. 3. The systematical error calculated by the SSI-A. Hereby several subapertures are measured over the whole surface. The redundant information’s of the overlapping regions can be used to calculate the systematical error of the system. 4. The rotation of the transmission flat relatively to the interferometer. Thereby the rotation unsymmetrical errors can be calculated and subtracted. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• NACHHALTIG
Zeitschriftenartikel
• Engelbert Hofbauer
• Rolf Rascher
• Manon Schilke
• Johannes Liebl
• J.-P. Richters
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), pg. 146-161.

In: Bavarian Journal of Applied Sciences

• 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.
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• NACHHALTIG
Beitrag (Sammelband oder Tagungsband)
• Manon Schilke
• Johannes Liebl
• Christine Wünsche
Surface reconstruction by using Zernike polynomials
• 2016

#### Abstract anzeigen

The development of high precision methods for the measurement of plano surfaces became of increasing importance over the last years. Recently accuracies in sub-nanometer range have been achieved on samples up to one meter in diameter. The used measurement method was based on direct deflectometry. The main part of the system was an electronic autocollimator measuring local angular displacements on defined traces along the surface of the plano lens. To stabilize the optical path a pentaprism was used. The measurement accuracy of a similar system was evaluated at the Technologie Campus Teisnach. The used system delivered twenty measurement spots along the profile on one diameter. Four diameters were measured at every 45 degrees. An evaluation algorithm was developed to model the complete threedimensional surface out of a small amount of measurement points. Within this modelling Zernike polynomials were used to reconstruct the surface topography. Two different approaches in using the hierarchy of the polynomials were compared. At first a reference surface was created by rotating a symmetrical averaged curve of all measured profiles. On the residuals of the original measurements to the symmetrical averaged curve a serial development of the error surface was applied with the help of Zernike polynomials. Different order of Zernike terms were tested because we saw a big influence on the result. This surface was added to the reference surface. The results of the two different approaches were compared. To enable us to compare the results of this measurement method to interferometric and optical 3Dprofilometric measurements the data was converted to xyz-format. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• NACHHALTIG
Beitrag (Sammelband oder Tagungsband)
• Engelbert Hofbauer
• Rolf Rascher
• Felix Friedke
• Thomas Stubenrauch
• Johannes Liebl
• J.-P. Richters
The vignetting field stop procedure: A new physical measurement principle for the Deflectometric acquisition of big Optical Surfaces - DaOS
• 2015
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
• NACHHALTIG
Vortrag
• Johannes Liebl
HLEM Round Robin Asphere Test 2015 at the Deggendorf Institute of Technology

In: 7th High Level Expert Meeting 2015 - Asphere Metrology On Joint Investigations

• 2015
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Zeitschriftenartikel
• Johannes Liebl
• Heiko Biskup
• S. Draxinger
• Rolf Rascher
• Christine Wünsche
Process developement fort the reproducible roughness measurement of optical surfaces using white light interferometry, vol. 5, pg. 29-35.

In: International Journal of Metrology and Quality Engineering (EDP Sciences)

• 2014

• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Vortrag
• Johannes Liebl
Shape and roughness in white light interferometric measurement

In: 1st European Seminar on Precision Optics Manufacturing

• 2014
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Vortrag
• Rolf Rascher
• Johannes Liebl
• Paul Schötz
• P. Frieder
Automatische Kratzererkennung an hochpräzisen Drehteilen. „Projekt KonoScan“

In: SENSOR + TEST

• 2014
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Beitrag (Sammelband oder Tagungsband)
• O. Fähnle
• E. Langenbach
• F. Frost
• A. Schindler
• Heiko Biskup
• Johannes Liebl
• Christine Wünsche
• Rolf Rascher
Generation and field testing of roughness reference samples for industrial testing of surface roughness levels below 0.5nm Sq, pg. 216-218.
• 2014
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Beitrag (Sammelband oder Tagungsband)
• Engelbert Hofbauer
• Rolf Rascher
• Thomas Stubenrauch
• Johannes Liebl
• Roland Maurer
• et al.
Approach to the measurement of astronomical mirrors with new procedures
• 2013
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Vortrag
• Johannes Liebl
Messportal TC Teisnach

In: 6. Optikseminar - Agenda zur modernen Optikfertigung

• 2013
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Vortrag
• Johannes Liebl
• Rolf Rascher
• Katharina Dieser
GF-Projekt Optasens - Combination and evaluation of different optical and tactile sensor and measuring methods for analysis and global form-measurement on optical surfaces. Posterpräsentation

In: F.O.M.-Marktplatz der Forschungsprojekte

• 2012
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Zeitschriftenartikel
• Johannes Liebl
Dreistrahllaserinterferometrie zur Topographievermessung ebener Flächen, vol. 4, pg. 38-40.

In: Photonik - Fachzeitschrift für die optischen Technologien

• 2012
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Vortrag
• Rolf Rascher
• Johannes Liebl
• et al.
Hochgenaue Optische Abstandssensoren in Messtechnik und Qualitätssicherung

In: 1. Optence Messtechnik Symposium

• 2012
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
Vortrag
• Paul Schötz
• Johannes Liebl
• Rolf Rascher
• Christine Wünsche
• Engelbert Hofbauer
• Karlheinz Penzkofer
Metrology at Technologie Campus Teisnach

In: 8th Workshop Asphere Metrology

• 2012
• Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen