Dr. Ralf D. Geckeler Profile

Dr. Ralf D. Geckeler

at Physikalisch-Technische Bundesanstalt

SPIE Involvement:

Conference Program Committee | Author

Publications (24)

PROCEEDINGS ARTICLE | September 7, 2017

A new ultra-high-accuracy angle generator: current status and future direction

Proc. SPIE. 10385, Advances in Metrology for X-Ray and EUV Optics VII

KEYWORDS: Mirrors, Metrology, Calibration, Autocollimators, Optical encoders, Position sensors, Prototyping, Positioning equipment, Precision calibration

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PROCEEDINGS ARTICLE | September 5, 2014

Pushing the limits: latest developments in angle metrology for the inspection of ultra-precise synchrotron optics

Proc. SPIE. 9206, Advances in Metrology for X-Ray and EUV Optics V

KEYWORDS: Mirrors, Metrology, Calibration, Inspection, Computer programming, Optical testing, Head, Autocollimators, Synchrotrons, Optics manufacturing

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PROCEEDINGS ARTICLE | May 13, 2013

Modelling PTB's spatial angle autocollimator calibrator

Proc. SPIE. 8789, Modeling Aspects in Optical Metrology IV

KEYWORDS: Mathematical modeling, Modeling, Reflectors, Metrology, Reflection, Calibration, Manufacturing, Optical testing, Autocollimators, Profilometers

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SPIE Journal Paper | July 1, 2011

Optimal alignment of mirror-based pentaprisms for scanning deflectometric devices

Barber, Samuel , Yashchuk, Valeriy , Geckeler, Ralf , Gubarev, Mikhail , Buchheim, Jana , Siewert, Frank , Zeschke, Thomas

OE Vol. 50 Issue 07

KEYWORDS: Mirrors, Autocollimators, Optical alignment, Alignment procedures, Error analysis, Ray tracing, Optical engineering, Light sources, Reliability, Computer simulations

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SPIE Journal Paper | May 1, 2011

Developmental long-trace profiler using optimally aligned mirror-based pentaprism

Barber, Samuel , Morrison, Gregory , Yashchuk, Valeriy , Gubarev, Mikhail , Geckeler, Ralf , Buchheim, Jana , Siewert, Frank , Zeschke, Thomas

OE Vol. 50 Issue 05

KEYWORDS: Mirrors, Autocollimators, Alignment procedures, Optical alignment, Kinematics, Optical engineering, Spherical lenses, Error analysis, Light sources, Calibration

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PROCEEDINGS ARTICLE | September 2, 2010

Developmental long trace profiler using optimally aligned mirror-based pentaprism

Proc. SPIE. 7801, Advances in Metrology for X-Ray and EUV Optics III

KEYWORDS: Mirrors, X-ray optics, Calibration, Error analysis, Kinematics, Ray tracing, Autocollimators, Optical alignment, Spherical lenses, Alignment procedures

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PROCEEDINGS ARTICLE | January 12, 2009

Interferometry at the PTB Nanometer Comparator: design, status and development

Proc. SPIE. 7133, Fifth International Symposium on Instrumentation Science and Technology

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PROCEEDINGS ARTICLE | October 17, 2008

Development of a 1.5D reference comparator for position and straightness metrology on photomasks

Proc. SPIE. 7122, Photomask Technology 2008

KEYWORDS: Microscopes, Mirrors, Beam splitters, Metrology, Interferometers, Sensors, Calibration, Computer programming, Image registration, Photomasks

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PROCEEDINGS ARTICLE | September 3, 2008

Distance-dependent influences on angle metrology with autocollimators in deflectometry

Proc. SPIE. 7077, Advances in X-Ray/EUV Optics and Components III

KEYWORDS: Optical components, Mirrors, Reticles, Metrology, Sensors, Calibration, Autocollimators, Objectives, Charge-coupled devices, Spherical lenses

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PROCEEDINGS ARTICLE | September 20, 2007

Optimized use and calibration of autocollimators in deflectometry

Proc. SPIE. 6704, Advances in Metrology for X-Ray and EUV Optics II

KEYWORDS: Optical components, Mirrors, Metrology, Calibration, Deflectometry, Head, Autocollimators, Objectives, Charge-coupled devices, Standards development

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PROCEEDINGS ARTICLE | September 20, 2007

Proposal for a universal test mirror for characterization of slope measuring instruments

Proc. SPIE. 6704, Advances in Metrology for X-Ray and EUV Optics II

KEYWORDS: Optical components, Mirrors, Light sources, X-ray optics, Metrology, Nano opto mechanical systems, Calibration, Autocollimators, Free electron lasers, Precision calibration

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PROCEEDINGS ARTICLE | June 18, 2007

Stability analysis for the TMS method: Influence of high spatial frequencies

Proc. SPIE. 6616, Optical Measurement Systems for Industrial Inspection V

KEYWORDS: Spatial frequencies, Interferometers, Sensors, Interferometry, Wavefronts, Distortion, Computer simulations, Autocollimators, Distance measurement, Optical scanning systems

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The Traceable Multi Sensor (TMS) system is a scanning system for the measurement of the topography of large optical surfaces. The system uses a compact interferometer with an aperture of some millimetres to realize multiple distance sensors and an autocollimator for the angle measurement. In contrast to common stitching techniques, the systematic sensor errors are calculated in addition to the entire topography by the TMS algorithm. Additionally, piston and tilt at each position of the interferometer are determined by the algorithm. An essential requirement for the algorithm is the exact lateral positioning of the sensor at given locations. The goal of this paper is to investigate the influence of a class of error sources on the resulting topography estimation using computer simulations. The errors of this class result in inexact measurement positions of the distance sensors. Especially the lateral positioning errors of the scanning stage lead to increasing errors for short wavelengths. For topography wavelengths below 3mm with an amplitude of 100nm the resulting topography error increases to 3nm and more. For longer wavelengths the positioning errors are no longer the dominant error source and the root mean square error of the resulting topography is approximately 1 nm for positioning errors with a standard deviation of 5 &mgr;m. The pixel distance error and distortion of the interferometer strongly influence the topography measurement of specimens with large deviations from a plane. The simulations show that for a topography with a peak to valley of 50 &mgr;m the root mean square error of the reconstructed topography is below 10 nm. Furthermore, a possibility to compensate the lateral positioning error of the scanning stage is presented which makes the TMS method nearly independent of positioning errors of the scanning stage. As a consequence, it is possible to use systems of non equidistant distance sensors whose lateral distances are independent of the positioning interval.

PROCEEDINGS ARTICLE | September 11, 2006

ESAD shearing deflectometry: potentials for synchrotron beamline metrology

Proc. SPIE. 6317, Advances in X-Ray/EUV Optics, Components, and Applications

KEYWORDS: Prisms, Metrology, Nano opto mechanical systems, Calibration, Interferometry, Deflectometry, Autocollimators, Measurement devices, Synchrotrons, Zerodur

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PROCEEDINGS ARTICLE | August 14, 2006

Error minimization in high-accuracy scanning deflectometry

Proc. SPIE. 6293, Interferometry XIII: Applications

KEYWORDS: Mirrors, Prisms, Interferometers, Calibration, Mercury, Interferometry, Deflectometry, Autocollimators, Solids, Measurement devices

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PROCEEDINGS ARTICLE | September 15, 2005

Scanning form measurement for curved surfaces

Proc. SPIE. 5921, Advances in Metrology for X-Ray and EUV Optics

KEYWORDS: Mirrors, Interferometers, Sensors, Calibration, Image resolution, Autocollimators, Distance measurement, Charge-coupled devices, CCD image sensors, Spherical lenses

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PROCEEDINGS ARTICLE | August 31, 2005

Traceable multiple sensor system for absolute form measurement

Proc. SPIE. 5878, Advanced Characterization Techniques for Optics, Semiconductors, and Nanotechnologies II

KEYWORDS: Imaging systems, Interferometers, Sensors, Calibration, Autocollimators, Distance measurement, Charge-coupled devices, Spatial resolution, CCD image sensors, Sensor calibration

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PROCEEDINGS ARTICLE | June 13, 2005

High-accuracy profile form measurement by a scanning system consisting of an angle sensor and coupled distance sensors

Proc. SPIE. 5856, Optical Measurement Systems for Industrial Inspection IV

KEYWORDS: Mathematical modeling, Interferometers, Sensors, Calibration, Error analysis, Optical testing, Autocollimators, Distance measurement, Optical scanning systems, CCD image sensors

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PROCEEDINGS ARTICLE | September 10, 2004

A new method and a novel facility for ultra precise 2D topography measurement of large optical surfaces

Proc. SPIE. 5457, Optical Metrology in Production Engineering

KEYWORDS: Monochromatic aberrations, Reticles, Sensors, Calibration, Optical testing, Deflectometry, Autocollimators, Charge-coupled devices, Reconstruction algorithms, Algorithm development

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PROCEEDINGS ARTICLE | November 20, 2003

High-accuracy form measurement of large optical surfaces

Proc. SPIE. 5190, Recent Developments in Traceable Dimensional Measurements II

KEYWORDS: Prisms, Interferometers, Sensors, Calibration, Optical testing, Deflectometry, Time metrology, Autocollimators, Spherical lenses, Zerodur

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PROCEEDINGS ARTICLE | December 24, 2002

Topography measurement of nanometer synchrotron optics

Proc. SPIE. 4782, X-Ray Mirrors, Crystals, and Multilayers II

KEYWORDS: Optical components, Mirrors, Prisms, Calibration, Optical testing, Head, Autocollimators, Synchrotrons, Synchrotron radiation, Zerodur

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PROCEEDINGS ARTICLE | November 11, 2002

Novel concept for the ultraprecise and fast measurement of the nanotopography of large wafers

Proc. SPIE. 4779, Advanced Characterization Techniques for Optical, Semiconductor, and Data Storage Components

KEYWORDS: Wafer-level optics, Spatial frequencies, Interferometers, Sensors, Deflectometry, Distance measurement, Measurement devices, Reconstruction algorithms, Algorithm development, Semiconducting wafers

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The measurement of the topography or the nanotopography of large wafers up to 450 mm in diameter with satisfactory lateral resolution and nanometer uncertainty is still an unsolved problem. The topography of wafers covers a relatively large measurement range as wafers have surfaces with a so-called "slightly unflat" topography which mostly exceeds the measurement capabilities of interferometers. For the ultraprecise and traceable measurement of the slope and topography of slightly unflat optical surfaces, a novel scanning deflectometry principle has been developed. An uncertainty of the topography in the nanometer range will be achieved, as this principle minimizes error influences and allows a highly precise calibration of the angle measuring device. The main goal is to use this principle for the ultraprecise measurement of the nanotopography of large wafers. The measurement principle is based on the analysis of differences of reflection angles obtained at surface points which are separated by large lateral shears. It does not rely on external reference surfaces of matched topography and in first and second order is independent of any stage errors and the whole-body motion of the specimen. The measurands are directly traced back to the base units of angle and length. The specific idea of wafer measurement is to combine rotational and linear scanning with the measurement of slope difference vectors and to arrive at an unambiguous solution for the topography and nanotopography. The equations with the slope difference vectors are solved to reconstruct the slope vectors, as newly developed mathematical algorithms allow the surface slope to be reconstructed from slope differences for two different shears. This is reached by applying natural extensions and shearing transfer functions by a mathematically exact method over the whole surface area. Further the differential equations for the slope vectors are solved to unambiguously reconstruct the topography. With this method it is possible to achieve nanometer uncertainty and at the same time a high lateral resolution, short measurement times and the possibility of mastering the large measurement range necessary for slightly unflat wafer surfaces.

PROCEEDINGS ARTICLE | November 11, 2002

Sub-nm topography measurement by deflectometry: flatness standard and wafer nanotopography

Proc. SPIE. 4779, Advanced Characterization Techniques for Optical, Semiconductor, and Data Storage Components

KEYWORDS: Prisms, Calibration, Error analysis, Deflectometry, Autocollimators, Measurement devices, Reconstruction algorithms, Algorithm development, Semiconducting wafers, Zerodur

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PROCEEDINGS ARTICLE | October 22, 2001

Tracing back radius of curvature and topography to the base unit of length with ultraprecision

Proc. SPIE. 4401, Recent Developments in Traceable Dimensional Measurements

KEYWORDS: Mirrors, Optical spheres, Interferometers, Sensors, Calibration, Manufacturing, Wavefronts, Aspheric lenses, Spherical lenses, Sensor calibration

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PROCEEDINGS ARTICLE | October 22, 2001

Use and treaceable calibration of autocollimators for ultra-precise measurement of slope and topography

Proc. SPIE. 4401, Recent Developments in Traceable Dimensional Measurements

KEYWORDS: Mirrors, Reflection, Calibration, Error analysis, Head, Autocollimators, Charge-coupled devices, Reconstruction algorithms, Algorithm development, Temperature metrology

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Recently, a novel scanning principle (ESAD - Extended Shear Angle Difference) has been presented for the ultra-precise determination of slope and topography of near-plane surfaces which is based on the measurement of differences of reflection angles with an autocollimator. It uses large lateral displacements (shears) of the order of mm to cm, and a newly developed algorithm allows the exact reconstruction of the slope from the angle differences with two different shears. The topography is then derived from the slope by an accurate integration procedure. Reproducibility of the reconstructed topography of the order of below 1 nm for scans over a near-flat surface has already been achieved. In contrast to interferometric techniques, this scanning method does not rely on an external reference surface of matched topography. The measurands are directly traced back to the base units of angle and length. Therefore, this technique is well suited for creating a very precise standard for straightness and flatness. A central element considerably influencing the overall uncertainty is the autocollimator itself, making a high-accuracy traceable calibration of the device necessary. Autocollimators are calibrated at the PTB by the use of a primary standard angle comparator which is traced back to the natural standard of the full angle of 2Pi rad. The traceable calibration is realized by an incremental circular scale, incorporated into a highly precise rotary table as a measuring system, consisting of a radial optical phase grating and several photoelectric reading heads, thus reaching an angular resolution of approximately 0.001 arcsec. With this comparator, calibration of an electronic autocollimator with 0.001 arcsec resolution and a measurement range of (150 arcsec with an uncertainty of 0.007 arcsec has currently been achieved. The autocollimator type to be used in the ESAD scanning facility was calibrated and investigated with respect to its resolution, reproducibility and accuracy in the range of 0.01 arcsec over a variety of measurement ranges. These experiences will be described. Methods to avoid or control error influences are discussed.

Showing 5 of 24 publications

Conference Committee Involvement (8)

Advances in Metrology for X-Ray and EUV Optics VII

6 August 2017 | San Diego, California, United States

Advances in Metrology for X-Ray and EUV Optics VI

29 August 2016 | San Diego, California, United States

Advances in Metrology for X-Ray and EUV Optics V

18 August 2014 | San Diego, California, United States

Advances in Metrology for X-Ray and EUV Optics IV

12 August 2012 | San Diego, California, United States

Advances in Metrology for X-Ray and EUV Optics III

1 August 2010 | San Diego, California, United States

Showing 5 of 8 published special sections

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