Dr. Robert Leitel Profile

Dr. Robert Leitel

Senior Scientist, Group Manager at Fraunhofer Institute for Applied Optics IOF

SPIE Involvement:

Author

Area of Expertise:

interference coatings , plasma etching , microoptical systems , grayscale lithography , molding , nano-imprint

Websites:

Company Website

Publications (20)

Proceedings Article | 2 October 2023 Presentation + Paper

Multi-aperture pattern projection using arbitrary shaped microlenslets

R. Kundu, D. Michaelis, P. Schreiber, P. Schleicher, A. Schöneberg, R. Leitel, A. Tünnermann, U. Breyer

Proceedings Volume 12666, 1266608 (2023) https://doi.org/10.1117/12.2675559

KEYWORDS: Stray light, Lens arrays, Projection systems, Light emitting diodes, Light sources and illumination, Design and modelling, Collimation, Crosstalk, Micro optics

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Proceedings Article | 12 July 2023 Open Access

Black aperture coating with an anti-reflective clear aperture: developed and qualified for space-based applications

S. Schwinde, P. Munzert, S. Shestaeva, R. Leitel, S. Kleinle, S. Schröder

Proceedings Volume 12777, 127775I (2023) https://doi.org/10.1117/12.2691027

KEYWORDS: Coating, Prisms, Antireflective coatings, Stray light, Astronomical imaging, Transmittance, Reflectivity, Optical surfaces, Optical components, Visual inspection

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Proceedings Article | 18 October 2021 Presentation + Paper

Modeling of grayscale lithography and calibration with experimental data for blazed gratings

Pankaj Bhardwaj, Andreas Erdmann, Robert Leitel

Proceedings Volume 11875, 118750K (2021) https://doi.org/10.1117/12.2597203

KEYWORDS: Calibration, Photoresist materials, Grayscale lithography, Photomasks, Diffraction gratings, Lithography, Data modeling, Transmittance, Photoresist developing

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Proceedings Article | 6 April 2020 Presentation

Etendue conserving light shaping using irregular fly's eye condensers (Conference Presentation)

Peter Schreiber, Christoph Wächter, Dirk Michaelis, Marko Stumpf, Stephanie Fischer, Peter Dannberg, Robert Leitel

Proceedings Volume 11351, 113512C (2020) https://doi.org/10.1117/12.2567106

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Proceedings Article | 15 June 2018 Paper

Evaluation of lenslet fabrication technologies for micro-optical array projectors

Robert Leitel, Stephanie Fischer, Peter Dannberg, Sylke Kleinle, Peter Schreiber, Christoph Wächter

Proceedings Volume 10692, 1069206 (2018) https://doi.org/10.1117/12.2313971

KEYWORDS: Projection systems, Grayscale lithography, Microlens array, Stars, Microlens, Photoresist materials, Collimation, Lenses, Photomasks, Calibration

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Proceedings Article | 15 March 2016 Paper

High dynamic grayscale lithography with an LED-based micro-image stepper

Hans-Christoph Eckstein, Uwe Zeitner, Robert Leitel, Marko Stumpf, Philipp Schleicher, Andreas Bräuer, Andreas Tünnermann

Proceedings Volume 9780, 97800T (2016) https://doi.org/10.1117/12.2219099

KEYWORDS: Grayscale lithography, Light emitting diodes, Freeform optics, Optical lithography, Direct write lithography, New and emerging technologies, Liquid crystal on silicon, Ultraviolet radiation, Calibration, Spatial resolution, Lithography, Ions, Photoresist materials, Optical components

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We developed a novel LED projection based direct write grayscale lithography system for the generation of optical surface profiles such as micro-lenses, diffractive elements, diffusors, and micro freeforms. The image formation is realized by a LCoS micro-display which is illuminated by a 405 nm UV High Power LED. The image on the display can be demagnified from factors 5x to 100x with an exchangeable lens. By controlling exposure time and LED power, the presented technique enables a highly dynamic dosage control for the exposure of h-line sensitive photo resist. In addition, the LCoS micro-display allows for an intensity control within the micro-image which is particularly advantageous to eliminate surface profile errors from stitching and limited homogeneity from LED illumination. Together with an accurate calibration of the resist response this leads to a superior low surface error of realized profiles below <0.2% RMS. The micro-display is mounted on a 3-axis (XYθ) stage for precise alignment. The substrate is brought into position with an air bearing stage which addresses an area of 500 × 500 mm² with a positioning accuracy of <100 nm. As the exposure setup performs controlled motion in the z-direction the system to maintain the focal distance and lithographic patterning on non-planar surfaces to some extent. The exposure concept allows a high structure depth of more than 100 μm and a spatial resolution below 1 μm as well as the possibility of very steep sidewalls with angles larger than >80°. Another benefit of the approach is a patterning speed up to 100 cm²/h, which allows fabricating large-scale optics and microstructures in an acceptable time. We present the setup and show examples of micro-structures to demonstrate the performance of the system, namely a refractive freeform array, where the RMS surface deviation does not exceed 0.2% of the total structure depth of 75 μm. Furthermore, we show that this exposure tool is suitable to generate diffractive optical elements as well as freeform optics and arrays with a high aspect ratio and structure depth showing a superior optical performance. Lastly we demonstrate a multi-level diffraction grating on a curved substrate.

Proceedings Article | 16 March 2015 Paper

Sub-aperture EUV collector with dual-wavelength spectral purity filter

Torsten Feigl, Marco Perske, Hagen Pauer, Tobias Fiedler, Uwe Zeitner, Robert Leitel, Hans-Christoph Eckstein, Philipp Schleicher, Sven Schröder, Marcus Trost, Stefan Risse, Ralf Steinkopf, Frank Scholze, Christian Laubis

Proceedings Volume 9422, 94220E (2015) https://doi.org/10.1117/12.2175666

KEYWORDS: Extreme ultraviolet, Reflectivity, Mirrors, Optical filters, Binary data, Carbon dioxide lasers, Diffraction, Infrared radiation, Multilayers, Spherical lenses

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Proceedings Article | 25 September 2014 Paper

Multi-aperture microoptical system for close-up imaging

René Berlich, Andreas Brückner, Robert Leitel, Alexander Oberdörster, Frank Wippermann, Andreas Bräuer

Proceedings Volume 9192, 91920E (2014) https://doi.org/10.1117/12.2061562

KEYWORDS: Imaging systems, Prototyping, Optical design, Modulation transfer functions, Microlens array, Semiconducting wafers, Microlens, Image sensors, Spherical lenses, Manufacturing

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Proceedings Article | 2 May 2014 Paper

Curved artificial compound-eyes for autonomous navigation

Robert Leitel, Andreas Brückner, Wolfgang Buß, Stéphane Viollet, Ramon Pericet-Camara, Hanspeter Mallot, Andreas Bräuer

Proceedings Volume 9130, 91300H (2014) https://doi.org/10.1117/12.2052710

KEYWORDS: Sensors, Microlens array, Visualization, Micro optics, Channel projecting optics, Eye, Navigation systems, Photodetectors, Glasses, Prototyping

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SPIE Journal Paper | 1 October 2011

Multi-aperture optics for wafer-level cameras

Andreas Brückner, Robert Leitel, Alexander Oberdörster, Peter Dannberg, Frank Wippermann, Andreas Bräuer

JM3, Vol. 10, Issue 04, 043010, (October 2011) https://doi.org/10.1117/12.10.1117/1.3659144

KEYWORDS: Wafer-level optics, Cameras, Modulation transfer functions, Channel projecting optics, Image sensors, Microlens array, Microlens, Semiconducting wafers, Image resolution, Prototyping

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Proceedings Article | 21 September 2011 Paper

Recent developments in wafer-level fabrication of micro-optical multi-aperture imaging systems

R. Leitel, P. Dannberg, A. Brückner, A. Bräuer

Proceedings Volume 8167, 81670P (2011) https://doi.org/10.1117/12.896939

KEYWORDS: Imaging systems, Eye, Glasses, Polymers, Microlens, Microlens array, Chromium, Cameras, Reactive ion etching, Metals

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Proceedings Article | 15 February 2011 Paper

First results on electrostatic polymer actuators based on UV replication

N. Lange, F. Wippermann, R. Leitel, C. Bruchmann, E. Beckert, R. Eberhardt, A. Tünnermann

Proceedings Volume 7926, 792609 (2011) https://doi.org/10.1117/12.873555

KEYWORDS: Actuators, Polymers, Electrodes, Polymeric actuators, Semiconducting wafers, Silicon, Etching, Finite element methods, Optical simulations, Ultraviolet radiation

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Proceedings Article | 14 February 2011 Paper

A multi-aperture approach to wafer-level camera lenses

Andreas Brückner, Robert Leitel, Peter Dannberg, Frank Wippermann, Andreas Bräuer

Proceedings Volume 7930, 79300B (2011) https://doi.org/10.1117/12.873158

KEYWORDS: Cameras, Channel projecting optics, Modulation transfer functions, Microlens array, Image sensors, Wafer-level optics, Microlens, Semiconducting wafers, Image resolution, Image fusion

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Proceedings Article | 14 February 2011 Paper

Ultra-compact imaging system based on multi-aperture architecture

Julia Meyer, Andreas Brückner, Robert Leitel, Peter Dannberg, Andreas Bräuer, Andreas Tünnermann

Proceedings Volume 7930, 79300C (2011) https://doi.org/10.1117/12.873520

KEYWORDS: Image sensors, Eye, Imaging systems, Cameras, Microlens array, Modulation transfer functions, Lenses, Wafer-level optics, Microlens, Optical design

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Proceedings Article | 20 August 2010 Paper

Ultra-compact close-up microoptical imaging system

Andreas Brückner, Jacques Duparré, Frank Wippermann, Robert Leitel, Peter Dannberg, Andreas Bräuer

Proceedings Volume 7786, 77860A (2010) https://doi.org/10.1117/12.860025

KEYWORDS: Imaging systems, Image sensors, Microlens array, Microlens, Modulation transfer functions, Glasses, Channel projecting optics, Image resolution, Biomedical optics, Prototyping

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Proceedings Article | 13 May 2010 Paper

A wafer-level camera approach based on the Gabor superlens

R. Leitel, K. Stollberg, A. Brückner, J. Duparré, P. Dannberg, A. Bräuer

Proceedings Volume 7716, 77160L (2010) https://doi.org/10.1117/12.853797

KEYWORDS: Microlens, Superposition, Image sensors, Cameras, Microlens array, Imaging systems, Ray tracing, Eye, Micro optics, Wafer-level optics

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Proceedings Article | 13 May 2010 Paper

Driving micro-optical imaging systems towards miniature camera applications

Andreas Brückner, Jacques Duparré, Peter Dannberg, Robert Leitel, Andreas Bräuer

Proceedings Volume 7716, 77160J (2010) https://doi.org/10.1117/12.853976

KEYWORDS: Image sensors, Modulation transfer functions, Eye, Image resolution, Image processing, Distortion, Semiconducting wafers, Microlens, Channel projecting optics, Imaging systems

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Proceedings Article | 25 September 2008 Paper

New plasma processes for antireflective structures on plastics

U. Schulz, P. Munzert, R. Leitel, N. Bollwahn, I. Wendling, N. Kaiser, A. Tünnermann

Proceedings Volume 7101, 710107 (2008) https://doi.org/10.1117/12.796705

KEYWORDS: Etching, Antireflective coatings, Plasma, Polymers, Plasma etching, Polymethylmethacrylate, Silica, Reflection, Positron emission tomography, Titanium dioxide

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Proceedings Article | 20 October 2005 Paper

Optical properties of stochastic subwavelength surface structures

Robert Leitel, Jörg Petschulat, Antje Kaless, Ulrike Schulz, Olaf Stenzel, Norbert Kaiser

Proceedings Volume 5965, 59651O (2005) https://doi.org/10.1117/12.624363

KEYWORDS: Reflection, Refractive index, Metals, Polymethylmethacrylate, Coating, Plasma treatment, Etching, Absorption, Plasma, Stochastic processes

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Proceedings Article | 5 October 2005 Paper

Design of hybrid coatings composed of homogeneous layers and refractive index gradients

Vesna Janicki, Robert Leitel, Steffen Wilbrandt, Olaf Stenzel, Dieter Gäbler, Norbert Kaiser

Proceedings Volume 5963, 59631D (2005) https://doi.org/10.1117/12.624348

KEYWORDS: Refractive index, Reflectivity, Optical coatings, Antireflective coatings, Gradient-index optics, Computer aided design, Thin film coatings, Software development, Niobium, Optical properties

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Showing 5 of 20 publications

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