Dr. Claas Falldorf Profile

Dr. Claas Falldorf

at BIAS - Bremer Institut für angewandte Strahltechnik GmbH

SPIE Involvement:

Conference Program Committee | Author

Publications (41)

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 | 5 November 2024 Open Access

Special Section Guest Editorial: Lensless Imaging in Optical Metrology

Claas Falldorf, Pascal Picart, Cosme Furlong, Percival Almoro

OE, Vol. 63, Issue 11, 111801, (November 2024) https://doi.org/10.1117/12.10.1117/1.OE.63.11.111801

KEYWORDS: Digital holography, Holography, Optical metrology, Microscopy, Optical imaging, Physics, Optical engineering, Holograms, Wave propagation, Light sources and illumination

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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 | 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 May 2022 Presentation + Paper

Exploring the coherence function for optical metrology and beyond

Claas Falldorf

Proceedings Volume 12137, 1213709 (2022) https://doi.org/10.1117/12.2624481

KEYWORDS: Interferometry, Interferometers, Coherence (optics), Wavefronts, Spatial light modulators, Optical metrology, Fourier transforms, Terahertz radiation, Mars, Wavefront analysis

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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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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 | 29 August 2016 Paper

Day-time local phasing of neighbouring segments of the E-ELT primary mirror, based simultaneous multi-λ shearing interferometry

S. Leveque, C. Falldorf, R. Klattenhoff, A. Cheffot

Proceedings Volume 9912, 99124G (2016) https://doi.org/10.1117/12.2235241

KEYWORDS: Interferometry, Mirrors, Sensors, Image segmentation, Wavefronts, Interferometers, Shearing interferometers, Cameras, Calibration, Light sources

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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 | 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 | 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

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 | 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 | 15 May 2012 Paper

3D shape measurement using deterministic phase retrieval and a partially developed speckle field

Percival Almoro, Laura Waller, Mostafa Agour, Claas Falldorf, Giancarlo Pedrini, Wolfgang Osten, Steen Hanson

Proceedings Volume 8384, 83840Q (2012) https://doi.org/10.1117/12.919223

KEYWORDS: Speckle, Phase retrieval, Wavefronts, Diffusers, Spatial light modulators, Speckle pattern, 3D metrology, Diffraction, Wave propagation, Cameras

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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

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 | 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 | 14 September 2010 Paper

Optical metrology: from the laboratory to the real world

W. Osten, E. Garbusi, D. Fleischle, W. Lyda, C. Pruss, R. Reichle, C. Falldorf

Proceedings Volume 7387, 73871G (2010) https://doi.org/10.1117/12.873356

KEYWORDS: Inspection, Optical metrology, Sensors, Aspheric lenses, Image processing, Interferometers, Shearography, Digital micromirror devices, Mirrors, Chemical elements

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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 | 17 June 2009 Paper

Towards deconvolution in holography

Nan Wang, Claas Falldorf, Christoph von Kopylow

Proceedings Volume 7390, 73900Y (2009) https://doi.org/10.1117/12.827507

KEYWORDS: Holograms, Holography, Deconvolution, Convolution, Image processing, Digital holography, 3D image processing, Scattering, Particles, Electronic filtering

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Proceedings Article | 10 September 2004 Paper

Digital holography and grating interferometry: a complementary approach

Claas Falldorf, Christoph von Kopylow, Wolfgang Osten, Werner Juptner

Proceedings Volume 5457, (2004) https://doi.org/10.1117/12.545645

KEYWORDS: Interferometry, Diffraction gratings, Holograms, Digital holography, Polymers, Cameras, Diffraction, Metals, Sensors, 3D image reconstruction

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Proceedings Article | 27 May 2003 Paper

Fringe compensation in multiband speckle shearography using a wedge prism

Claas Falldorf, Steen Hanson, Wolfgang Osten, Werner Juptner

Proceedings Volume 4933, (2003) https://doi.org/10.1117/12.516581

KEYWORDS: Prisms, Speckle, Diffraction, Shearography, Modulation, Shearing interferometers, Lamps, Light sources, Refractive index, Mercury

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Proceedings Article | 29 July 2002 Paper

Features of multiband speckle shearography

Claas Falldorf, Wolfgang Osten, Ervin Kolenovic, Werner Jueptner

Proceedings Volume 4900, (2002) https://doi.org/10.1117/12.484535

KEYWORDS: Speckle, Shearography, Lamps, Light sources, Mercury, Spatial coherence, Modulation, Temporal coherence, Michelson interferometers, Interferometry

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Proceedings Article | 29 July 2002 Paper

Progress with the implementation of a shearography system for the testing of technical components

Wolfgang Osten, Torsten Baumbach, Claas Falldorf, Michael Kalms, Werner Jueptner

Proceedings Volume 4900, (2002) https://doi.org/10.1117/12.484540

KEYWORDS: Shearography, Inspection, Speckle, Light sources, Sensors, Nondestructive evaluation, Charge-coupled devices, Image sensors, Decision support systems, Infrared radiation

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Proceedings Article | 19 June 2002 Paper

Remote interferometry by digital holography for shape control

Torsten Baumbach, Wolfgang Osten, Claas Falldorf, Werner Jueptner

Proceedings Volume 4778, (2002) https://doi.org/10.1117/12.473553

KEYWORDS: Digital holography, Holograms, LCDs, Holography, Wavefronts, Modulators, Interferometry, CCD cameras, 3D image reconstruction, Inspection

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Modern production requires more and more effective methods for the inspection and quality control at the production place. Outsourcing and globalization result in possible large distances between co-operating partners. This may cause serious problems with respect to the just-in-time exchange of information and the response to possible violations of quality standards. Consequently new challenges arise for optical measurement techniques especially in the field of industrial shape control. A possible solution for these problems can be delivered by a technique that stores optically the full 3D information of the objects to be compared and where the data can be transported over large distances. In this paper we describe the progress in implementing a new technique for the direct comparison of the shape and deformation of two objects with different microstructure where it is not necessary that both samples are located at the same place. This is done by creating a coherent mask for the illumination of the sample object. The coherent mask is created by Digital Holography to enable the instant access to the complete optical information of the master object at any wanted place. The transmission of the digital master holograms to this place can be done via digital telecommunication networks. The comparison can be done in a digital or analogue way. Both methods result in a disappearance of the object shape and the appearance of the shape or deformation difference between the two objects only. The analogue reconstruction of the holograms with a liquid crystal spatial light modulator can be done by using the light modulator as an intensity modulator or as an phase modulator. The reconstruction technique and the space bandwidth of the light modulator will influence the quality of the result. Therefore the paper describes the progress in applying modern spatial light modulators and digital cameras for the effective storage and optical reconstruction of coherent masks.

Proceedings Article | 23 October 2001 Paper

Features of the subjective speckle field and their use for noise-immune unwrapping

Claas Falldorf, Wolfgang Osten, Frank Elandaloussi, Ervin Kolenovic, Werner Jueptner

Proceedings Volume 4398, (2001) https://doi.org/10.1117/12.445558

KEYWORDS: Speckle, Numerical simulations, Computer simulations, Interferometry, Phase measurement, Virtual reality, Objectives, Line scan image sensors, Holographic interferometry, Coherence imaging

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