Prof. Ralf B. Bergmann Profile

Prof. Ralf B. Bergmann

at BIAS - Bremer Institut für angewandte Strahltechnik GmbH

SPIE Involvement:

Author

Area of Expertise:

optical metrology , opto-electronic systems , diffractive optics , optical sensors , 3D displays , nano optics

Websites:

Company Website

Publications (48)

Proceedings Article | 20 November 2024 Paper

Calibrating multispot illumination for asphere metrology using shear-interferometry

André Müller, Beñat Gutiérrez-Cañas Pazos, Nikodem Mitura, Gerd Ehret, Claas Falldorf, Ralf Bergmann

Proceedings Volume 13241, 132410N (2024) https://doi.org/10.1117/12.3037594

KEYWORDS: Calibration, Light sources and illumination, Light sources, Spectral calibration, Aspheric metrology, Reflection, Optical surfaces, Freeform optics, Wavefronts

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SPIE Journal Paper | 12 July 2024

High resolution lensless microscopy based on Fresnel propagation

André Müller, Ralf Bergmann, Claas Falldorf

OE, Vol. 63, Issue 11, 111805, (July 2024) https://doi.org/10.1117/12.10.1117/1.OE.63.11.111805

KEYWORDS: Microscopy, Holograms, Digital holography, Cameras, Holography, Image restoration, Sensors, Diffraction limit, Wave propagation, Light sources and illumination

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Proceedings Article | 18 June 2024 Paper

Phase measuring deflectometry with monoscopic active display registration

Yann Sperling, Ralf Bergmann

Proceedings Volume 12997, 1299713 (2024) https://doi.org/10.1117/12.3015111

KEYWORDS: Cameras, Image registration, Phase measurement, 3D modeling, Calibration, Data modeling, 3D metrology

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Proceedings Article | 15 August 2023 Presentation + Paper

Improved 3D form profiler based on extending illumination aperture

Mostafa Agour, Claas Falldorf, Ralf Bergmann

Proceedings Volume 12618, 126180T (2023) https://doi.org/10.1117/12.2673783

KEYWORDS: Light sources and illumination, Light emitting diodes, Light sources, 3D metrology, Cameras, Speckle, Partial coherence, Objectives, LED lighting, Imaging systems

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Proceedings Article | 10 August 2023 Presentation + Paper

The coherence function for optical metrology: a new paradigm and the role of information theory and compressed sensing

Ralf Bergmann, Claas Falldorf, Alberto Garcia Ortiz, André Müller, Mostafa Agour, Carsten Bockelmann

Proceedings Volume 12619, 1261902 (2023) https://doi.org/10.1117/12.2675922

KEYWORDS: Compressed sensing, Optical metrology, Optical coherence, Information theory, Interferograms, Cameras, Terahertz radiation, Fourier transform interferometers, Phase reconstruction, Image restoration

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SPIE Journal Paper | 10 November 2022

Characterization of terahertz wavefront aberrations using computational shear-interferometry

Mostafa Agour, Claas Falldorf, Fatima Taleb, Enrique Castro-Camus, Martin Koch, Ralf Bergmann

OE, Vol. 61, Issue 11, 114102, (November 2022) https://doi.org/10.1117/12.10.1117/1.OE.61.11.114102

KEYWORDS: Terahertz radiation, Wavefronts, Spherical lenses, Diffraction gratings, Cameras, Diffraction, Wavefront aberrations, Sensors, Interferometers, Monochromatic aberrations

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Proceedings Article | 31 May 2022 Presentation + Paper

Shear interferometry for terahertz wavefront sensing

Mostafa Agour, Claas Falldorf, Fatima Taleb, Enrique Castro-Camus, Martin Koch, Ralf Bergmann

Proceedings Volume 12134, 121340B (2022) https://doi.org/10.1117/12.2621696

KEYWORDS: Terahertz radiation, Cameras, Wavefronts, Spherical lenses, Diffraction gratings, Diffraction, Wavefront sensors, Sensors, Interferometers, Wave propagation

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Proceedings Article | 20 May 2022 Presentation + Paper

Approaching optical metrology with multiple light sources and compressive sensing

André Müller, Claas Falldorf, Ralf Bergmann

Proceedings Volume 12137, 121370L (2022) https://doi.org/10.1117/12.2621647

KEYWORDS: Mars, Light sources, Compressed sensing, Spatial light modulators, Freeform optics, Signal to noise ratio, Fourier transforms, Aspheric optics, Wavefronts, Spatial frequencies, Coherence (optics)

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Proceedings Article | 20 June 2021 Poster + Presentation + Paper

Qualification of holistic and generic camera-system calibration by fringe projection

Jonas Bartsch, Yann Sperling, Ralf Bergmann

Proceedings Volume 11787, 117870G (2021) https://doi.org/10.1117/12.2592295

KEYWORDS: Calibration, Cameras, Stereoscopic cameras, LCDs, Imaging systems, Visual process modeling, 3D metrology, Refraction, Ray tracing, Projection systems

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Proceedings Article | 20 June 2021 Poster + Presentation + Paper

Vision threads: a novel approach to generic camera calibration

Shishir Gauchan, Jonas Bartsch, Ralf Bergmann

Proceedings Volume 11787, 117870H (2021) https://doi.org/10.1117/12.2592296

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Proceedings Article | 3 September 2019 Paper

Phase measurement deviations in deflectometry due to properties of technical surfaces

Shekhar Kumar Patra, Jonas Bartsch, Michael Kalms, Ralf Bergmann

Proceedings Volume 11102, 111020Q (2019) https://doi.org/10.1117/12.2527894

KEYWORDS: Phase measurement, Cameras, Manufacturing, Deflectometry, Diamond turning, Reflection, Surface finishing, Surface properties, Scattering, Imaging systems

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Proceedings Article | 1 April 2019 Paper

In-line quality control using dimensional metrology of 3D metal parts printed by laser beam melting

Michael Kalms, Ralf Bergmann

Proceedings Volume 10971, 109710N (2019) https://doi.org/10.1117/12.2514240

KEYWORDS: Metals, Dimensional metrology, 3D metrology, Cameras, Structured light, Additive manufacturing, Visualization, Data acquisition, Optical metrology, Clouds

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SPIE Journal Paper | 14 February 2019

Polymer-based holograms with individually adjustable structure angle

Thorsten Klein, Fabian Thiemicke, Claas Falldorf, Ralf Bergmann

OE, Vol. 58, Issue 02, 025105, (February 2019) https://doi.org/10.1117/12.10.1117/1.OE.58.2.025105

KEYWORDS: Holograms, Polymers, Phase measurement, Absorption, Optical engineering, Lithography, Computer generated holography, Diffractive optical elements, Polymerization, Wave propagation

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Proceedings Article | 27 September 2018 Presentation + Paper

Spatio-temporal sampling of the coherence function for step height measurements

Claas Falldorf, Andreas Hyra, Aleksander Simic, Ralf Bergmann

Proceedings Volume 10749, 107490Y (2018) https://doi.org/10.1117/12.2321145

KEYWORDS: Mirrors, Interferometers, Spatial light modulators, Imaging systems, Coherence (optics), Optical interferometry, Interferometry, Cameras, Reflectivity, Light emitting diodes

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Proceedings Article | 14 September 2018 Presentation + Paper

2.5-dimensional polymer-based holograms with individually adjustable structure angle

Thorsten Klein, Fabian Thiemicke, Claas Falldorf, Ralf Bergmann

Proceedings Volume 10744, 107440A (2018) https://doi.org/10.1117/12.2320991

KEYWORDS: Holograms, Polymers, Phase measurement, Computer generated holography, Multiphoton lithography, Diffractive optical elements, Diamond turning, Wave propagation, Modulation, Gold

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Proceedings Article | 4 September 2018 Presentation + Paper

Metric for comparison of generic camera calibration

Martin H. U. Prinzler, Jonas Bartsch, Michael Kalms, Ralf Bergmann

Proceedings Volume 10750, 107500I (2018) https://doi.org/10.1117/12.2319366

KEYWORDS: Calibration, Cameras, Visual process modeling, Imaging systems, Optical calibration, Metrology, Optical metrology, CCD cameras, Precision calibration

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Proceedings Article | 24 May 2018 Presentation + Paper

Effects of non-ideal display properties in phase measuring deflectometry: A model-based investigation

Jonas Bartsch, Johann R. Nüß, Martin H. Prinzler, Michael Kalms, Ralf Bergmann

Proceedings Volume 10678, 106780Y (2018) https://doi.org/10.1117/12.2306463

KEYWORDS: Cameras, Device simulation, Calibration, Deflectometry, Phase measurement, Model-based design, Visual process modeling, Reflection, Refraction, Displays

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Proceedings Article | 27 March 2018 Paper

Characterization of technical surfaces by structure function analysis

Michael Kalms, Thomas Kreis, Ralf Bergmann

Proceedings Volume 10599, 1059924 (2018) https://doi.org/10.1117/12.2296309

KEYWORDS: Digital signal processing, Analytical research, Clouds, Tin, Modulation, Physics, Electrical engineering, Materials processing, Americium, All optical signal processing

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SPIE Journal Paper | 7 December 2017

Spatial multiplexing digital holography for speckle noise reduction in single-shot holographic two-wavelength contouring

Mostafa Agour, Reiner Klattenhoff, Claas Falldorf, Ralf Bergmann

OE, Vol. 56, Issue 12, 124101, (December 2017) https://doi.org/10.1117/12.10.1117/1.OE.56.12.124101

KEYWORDS: Holograms, Digital holography, Speckle, Multiplexing, Cameras, Denoising, Holography, Objectives, Semiconductor lasers, Optical engineering

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Proceedings Article | 26 June 2017 Paper

Error influences of the shear element in interferometry for form characterization of optics

Jan-Hendrik Hagemann, Claas Falldorf, Gerd Ehret, Ralf Bergmann

Proceedings Volume 10329, 103291T (2017) https://doi.org/10.1117/12.2269932

KEYWORDS: Wavefronts, Shearing interferometers, Light emitting diodes, Aspheric optics, Freeform optics, Wavefront sensors, Spatial light modulators, Interferometry, Optics manufacturing, Metrology, Sensors, Aspheric lenses, Optical testing

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Proceedings Article | 15 May 2017 Paper

Holographic 3D imaging through diffuse media by compressive sampling of the mutual intensity

Claas Falldorf, Thorsten Klein, Mostafa Agour, Ralf Bergmann

Proceedings Volume 10233, 102330Q (2017) https://doi.org/10.1117/12.2265007

KEYWORDS: Holography, Stereoscopy, Interferometry, Digital holography, Phase contrast, Scattering, Light scattering, Medicine, Sensors, Spatial coherence, Temporal coherence, Remote sensing, Phase shifts, Holograms

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Proceedings Article | 15 May 2017 Paper

Speckle noise reduction in single-shot holographic two-wavelength contouring

Mostafa Agour, Reiner Klattenhoff, Claas Falldorf, Ralf Bergmann

Proceedings Volume 10233, 102330R (2017) https://doi.org/10.1117/12.2264971

KEYWORDS: Speckle, Holography, Digital holography, Multiplexing, Microscopy, Holograms, Optical metrology, Cameras, Denoising

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Proceedings Article | 15 May 2017 Presentation + Paper

In-line quality control of micro parts using digital holography

Aleksandar Simic, Hendrik Freiheit, Mostafa Agour, Claas Falldorf, Ralf Bergmann

Proceedings Volume 10233, 1023311 (2017) https://doi.org/10.1117/12.2265780

KEYWORDS: Mirrors, Charge-coupled devices, Beam splitters, Microscopy, Light sources, Digital holography, Inspection, Holography, Metrology, Optical inspection, Confocal microscopy, Optical interferometry, Phase shifting, Cameras, Optical testing

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Proceedings Article | 9 March 2016 Presentation + Paper

Shape measurements of microscopic objects using computational shear interferometry

Mostafa Agour, Claas Falldorf, Ralf Bergmann

Proceedings Volume 9718, 97182M (2016) https://doi.org/10.1117/12.2212910

KEYWORDS: Interferometry, Spatial light modulators, Phase contrast, Diffraction gratings, Inspection, Microscopy, Wave sensors, 3D metrology, Reflectivity, Interferometers, Cameras, Charge-coupled devices, Sensors, Inverse problems, Optical filters

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Proceedings Article | 9 March 2016 Presentation + Paper

Quantitative phase contrast imaging using a Nomarski microscope with variable shear distance

Claas Falldorf, Mostafa Agour, Jonas Kötter, Ralf Bergmann

Proceedings Volume 9718, 97182I (2016) https://doi.org/10.1117/12.2212757

KEYWORDS: Phase contrast, Spatial light modulators, Interferometry, Microscopes, Coherence (optics), Microscopy, Wave sensors, Phase measurement, Vibration isolation, Modulation, Phase shift keying, Reflectivity, Sensors, Microelectromechanical systems, Digital image correlation, Image processing

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Proceedings Article | 17 July 2015 Paper

Precision optical metrology without lasers

Ralf Bergmann, Jan Burke, Claas Falldorf

Proceedings Volume 9524, 952403 (2015) https://doi.org/10.1117/12.2183451

KEYWORDS: Interferometry, Deflectometry, Optical metrology, Light sources, Cameras, Spatial frequencies, Laser metrology, Laser optics, Calibration, Light emitting diodes

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SPIE Journal Paper | 20 May 2015

Single shot lateral shear interferometer with variable shear

Claas Falldorf, Reiner Klattenhoff, Ralf Bergmann

OE, Vol. 54, Issue 05, 054105, (May 2015) https://doi.org/10.1117/12.10.1117/1.OE.54.5.054105

KEYWORDS: Sensors, Interferometers, Modulation, Glasses, Interferometry, Prisms, Optical engineering, Cameras, Wave plates, Wavefront sensors

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SPIE Journal Paper | 25 February 2015

Digital holography and quantitative phase contrast imaging using computational shear interferometry

Claas Falldorf, Mostafa Agour, Ralf Bergmann

OE, Vol. 54, Issue 02, 024110, (February 2015) https://doi.org/10.1117/12.10.1117/1.OE.54.2.024110

KEYWORDS: Interferometry, Phase contrast, Digital holography, Interferometers, Light emitting diodes, Microscopes, Spatial light modulators, Digital image correlation, Sensors, Fiber couplers

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Proceedings Article | 18 August 2014 Paper

Advanced wave field sensing using computational shear interferometry

Claas Falldorf, Mostafa Agour, Ralf Bergmann

Proceedings Volume 9204, 92040C (2014) https://doi.org/10.1117/12.2062814

KEYWORDS: Interferometry, Phase contrast, Interferometers, Digital holography, Digital image correlation, Microscopes, Light emitting diodes, Wave sensors, Fiber couplers, Light sources

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Proceedings Article | 18 August 2014 Paper

A comparative study between deflectometry and shearography for detection of subsurface defects

Philipp Huke, Jan Burke, Ralf Bergmann

Proceedings Volume 9203, 92030C (2014) https://doi.org/10.1117/12.2063650

KEYWORDS: Deflectometry, Shearography, Mirrors, Cameras, Defect detection, Foam, Nondestructive evaluation, Imaging systems, Lightweight mirrors, Temperature metrology

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Proceedings Article | 18 August 2014 Paper

Measuring deformations with deflectometry

Wansong Li, Philipp Huke, Jan Burke, Christoph von Kopylow, Ralf Bergmann

Proceedings Volume 9203, 92030F (2014) https://doi.org/10.1117/12.2063446

KEYWORDS: Mirrors, Deflectometry, Cameras, Calibration, Phase measurement, Fringe analysis, Monochromatic aberrations, Reflectivity, Actuators, Error analysis

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Proceedings Article | 18 August 2014 Paper

Complete shape measurement of micro parts by digital holography

S. Huferath-von Luepke, R. Klattenhoff, C. Dankwart, C. Falldorf, R. Bergmann

Proceedings Volume 9203, 920302 (2014) https://doi.org/10.1117/12.2063389

KEYWORDS: Digital holography, Holography, Microscopes, Reconstruction algorithms, Clouds, Inspection, Holograms, Manufacturing, Objectives, Beam splitters

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Proceedings Article | 2 May 2014 Paper

Three dimensional fabrication of optical waveguiding elements for on-chip integration

V. V. Parsi Sreenivas, M. Bülters, M. Schröder, R. Bergmann

Proceedings Volume 9130, 91300M (2014) https://doi.org/10.1117/12.2052452

KEYWORDS: Waveguides, Polymers, Absorption, Computer aided design, Photons, Optical components, Electroluminescent displays, Polymer multimode waveguides, Lithography, Two photon polymerization

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SPIE Journal Paper | 25 April 2014

Beam shaping using liquid crystal-on-silicon spatial light modulators for laser ultrasound generation

Michael Kalms, Sandra Hellmers, Philipp Huke, Ralf Bergmann

OE, Vol. 53, Issue 04, 044110, (April 2014) https://doi.org/10.1117/12.10.1117/1.OE.53.4.044110

KEYWORDS: Ultrasonography, Pulsed laser operation, Fiber lasers, Nondestructive evaluation, Composites, Beam shaping, Carbon, Laser crystals, Liquids, Crystals

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Proceedings Article | 9 March 2014 Paper

Assessment of bond defects in adhesive joints before and after the treatment with laser generated shock waves

Michael Kalms, Sandra Hellmers, Philipp Huke, Ralf Bergmann

Proceedings Volume 9063, 906327 (2014) https://doi.org/10.1117/12.2044792

KEYWORDS: Adhesives, Laser bonding, Nondestructive evaluation, Defect detection, Inspection, Metals

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Proceedings Article | 16 April 2013 Paper

Nondestructive testing in an automated process chain for mass manufacturing of fiber-reinforced thermoplastic components

Michael Kalms, Sandra Hellmers, Christoph v. Kopylow, Ralf Bergmann

Proceedings Volume 8694, 869429 (2013) https://doi.org/10.1117/12.2008805

KEYWORDS: Ultrasonography, Signal detection, Nondestructive evaluation, Interferometers, Manufacturing, Image processing, Inspection, Sensors, Mirrors, Laser systems engineering

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Proceedings Article | 11 September 2012 Paper

Measuring the complex amplitude of speckle fields by means of a shear interferometer

Claas Falldorf, Christoph von Kopylow, Ralf Bergmann

Proceedings Volume 8413, 84130Q (2012) https://doi.org/10.1117/12.977829

KEYWORDS: Interferometry, Speckle, Cameras, Interferometers, Spatial light modulators, Diffusers, Light scattering, Mendelevium, Optimization (mathematics), Wave sensors

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Proceedings Article | 11 September 2012 Paper

A fast and robust approach to phase shift registration from randomly phase shifted interferograms

Alexander Hildebrand, Claas Falldorf, Christoph von Kopylow, Ralf Bergmann

Proceedings Volume 8413, 84130R (2012) https://doi.org/10.1117/12.978027

KEYWORDS: Phase shifts, Modulation, Phase shifting, Reconstruction algorithms, Phase shift keying, Speckle, Interferometry, Matrices, Computer simulations, Sensors

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Proceedings Article | 11 September 2012 Paper

Non-destructive testing of carbon reinforced plastics by means of phase retrieval

Mostafa Agour, Claas Falldorf, Christoph von Kopylow, Ralf Bergmann

Proceedings Volume 8413, 841318 (2012) https://doi.org/10.1117/12.978175

KEYWORDS: Spatial light modulators, Carbon, Phase retrieval, Inspection, Nondestructive evaluation, Phase measurement, Light wave propagation, Cameras, Speckle, Time metrology

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Proceedings Article | 5 April 2012 Paper

Laser-generated ultrasound with liquid crystal on silicon (LCoS) technology in the thermoelastic regime

Michael Kalms, Sandra Hellmers, Ralf Bergmann

Proceedings Volume 8347, 83470N (2012) https://doi.org/10.1117/12.914770

KEYWORDS: Ultrasonography, Liquid crystal on silicon, Pulsed laser operation, Holograms, Modulators, 3D image reconstruction, Nondestructive evaluation, Laser applications, Composites, Computer generated holography

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Proceedings Article | 29 November 2011 Paper

Robust digital speckle photography based on radon and Fourier-Mellin transforms

E. Kamau, C. Falldorf, C. von Kopylow, R. Bergmann

Proceedings Volume 8202, 82020A (2011) https://doi.org/10.1117/12.904375

KEYWORDS: Digital signal processing, Speckle pattern, Digital photography, Transform theory, Speckle, Photography, Radon, Heat treatments, Image processing, Radon transform

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Proceedings Article | 27 May 2011 Paper

Reference wave adaptation in digital lensless Fourier holography by means of a spatial light modulator

Thomas Meeser, Claas Falldorf, Christoph von Kopylow, Ralf Bergmann

Proceedings Volume 8082, 808206 (2011) https://doi.org/10.1117/12.889472

KEYWORDS: Digital holography, Spatial light modulators, Holography, Transmittance, Holograms, Fourier transforms, Spherical lenses, Wave propagation, Modulation, Sensors

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Proceedings Article | 27 May 2011 Paper

The effect of misalignment in phase retrieval based on a spatial light modulator

Mostafa Agour, Claas Falldorf, Christoph von Kopylow, Ralf Bergmann

Proceedings Volume 8082, 80820M (2011) https://doi.org/10.1117/12.889200

KEYWORDS: Spatial light modulators, Phase retrieval, Wave propagation, Charge-coupled devices, Modulation, Fourier transforms, Sensors, Diffraction, Optical filters, Phase only filters

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Proceedings Article | 2 August 2010 Paper

Optical metrology and optical non-destructive testing from the perspective of object characteristics

Ralf Bergmann, T. Bothe, C. Falldorf, P. Huke, M. Kalms, C. von Kopylow

Proceedings Volume 7791, 779102 (2010) https://doi.org/10.1117/12.862266

KEYWORDS: Nondestructive evaluation, Ultrasonography, Shearography, Optical metrology, Reflectometry, Reflection, Pulsed laser operation, Interferometry, Mirrors, Phase measurement

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Proceedings Article | 26 October 2004 Paper

Computer tomography for nondestructive testing in the automotive industry

Walter Bauer, Florian Bessler, Erich Zabler, Ralf Bergmann

Proceedings Volume 5535, (2004) https://doi.org/10.1117/12.555578

KEYWORDS: Computed tomography, Clouds, Tomography, Precision measurement, X-rays, Data modeling, Nondestructive evaluation, Computer aided design, Algorithm development, Computing systems

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Proceedings Article | 1 August 2003 Paper

Spectral staining of tumor tissue by fiber optic FTIR spectroscopy

Reiner Salzer, Gerald Steiner, Angelique Kano, Tom Richter, Ralf Bergmann, Heike Rodig, Bernd Johannsen, Jens Kobelke

Proceedings Volume 5047, (2003) https://doi.org/10.1117/12.484153

KEYWORDS: Tumors, Silver, Tissues, Chalcogenides, FT-IR spectroscopy, Spectroscopy, Infrared radiation, Bromine, Optical fibers, Fiber optics

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Proceedings Article | 26 March 2002 Paper

Probing brain cancer by fiber optic FTIR spectroscopy

Gerald Steiner, Angelique Kano, Tom Richter, Ralf Bergmann, Heike Rodig, Jens Kobelke, Bernd Johannsen, Reiner Salzer

Proceedings Volume 4616, (2002) https://doi.org/10.1117/12.463822

KEYWORDS: Silver, Chalcogenides, Tumors, Tissues, FT-IR spectroscopy, Spectroscopy, Principal component analysis, Optical fibers, Infrared radiation, Fiber optics

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Proceedings Article | 14 March 2000 Paper

Identification of cancer cells by a combination of FTIR spectroscopy and PET

Gerald Steiner, Tom Richter, Reiner Salzer, Ralf Bergmann, Heike Rodig, Bernd Johannsen

Proceedings Volume 3920, (2000) https://doi.org/10.1117/12.379587

KEYWORDS: Tissues, Positron emission tomography, Tumors, FT-IR spectroscopy, Cancer, Tissue optics, Spectroscopy, Principal component analysis, Connective tissue, Sensors

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