Dr. Nicolas Rudaz Profile

Dr. Nicolas Rudaz

Senior Scientist

SPIE Involvement:

Author

Area of Expertise:

security , printing , counterfeit , deterrence , microstructure , signal

Websites:

Company Website

Former stained glass artist turned computer scientist. Worked as a research assistant at the Peripheral Systems Laboratory, Ecole Polytechnique Fédérale de Lausanne, Switzerland. Received a PhD in 2003 in the field of microstructure imaging. Now working with AlpVision SA , a swiss company active in the fields of product authentication, anti-counterfeiting and fraud protection.

SPIE Journal Paper | 1 April 2004

Protecting identity documents by microstructure color differences

Nicolas Rudaz, Roger-David Hersch

JEI, Vol. 13, Issue 02, (April 2004) https://doi.org/10.1117/12.10.1117/1.1687731

KEYWORDS: Color difference, Photography, Information security, Colorimetry, Image processing, RGB color model, Resistance, Transform theory, Digital watermarking, Printing

Read Abstract +

Proceedings Article | 19 April 2002 Paper

Protecting identity documents with a just-noticeable microstructure

Nicolas Rudaz, Roger Hersch

Proceedings Volume 4677, (2002) https://doi.org/10.1117/12.462739

KEYWORDS: Color difference, Photography, Information security, Colorimetry, Raster graphics, Image processing, RGB color model, Resistance, Digital watermarking, Transform theory

Read Abstract +

Proceedings Article | 7 February 1997 Paper

Multilevel color halftoning algorithms

Victor Ostromoukhov, Patrick Emmel, Nicolas Rudaz, Isaac Amidror, Roger Hersch

Proceedings Volume 2949, (1997) https://doi.org/10.1117/12.266337

KEYWORDS: Printing, Inkjet technology, Visualization, Diffusion, Halftones, Solids, RGB color model, Manufacturing, Visibility, Phase shifts

Read Abstract +

Proceedings Article | 20 December 1996 Paper

Anticounterfeiting features of artistic screening

Victor Ostromoukhov, Nicolas Rudaz, Isaac Amidror, Patrick Emmel, Roger Hersch

Proceedings Volume 2951, (1996) https://doi.org/10.1117/12.262419

KEYWORDS: Printing, Halftones, Image processing, Moire patterns, Scanners, Modulation, Raster graphics, Analog electronics, Nonimpact printing, Transform theory

Read Abstract +

In a recent publication (Ostromoukhov95), a new image reproduction technique, artistic screening, was presented. It incorporates freely created artistic screen elements for generating halftones. Fixed predefined dot contours associated with given intensity levels determine the screen dot shape's growing behavior. Screen dot contours associated with each intensity level are obtained by interpolation between the fixed predefined dot contours. A user-defined mapping transforms screen elements from screen element definition space to screen element rendition space. This mapping can be tuned to produce various effects such as dilatations, contractions and non-linear deformations of the screen element grid. Although artistic screening has been designed mainly for performing the creation of graphic designs of high artistic quality, it also incorporates several important anti-counterfeiting features. For example, bank notes or other valuable printed matters produced with artistic screening may incorporate both full size and microscopic letters of varying shape into the image halftoning process. Furthermore, artistic screening can be used for generating screen dots at varying frequencies and orientations, which are well known for inducing strong moire effects when scanned by a digital color copier or a desktop scanner. However, it is less known that frequency-modulated screen dots have at each screen element size a different reproduction behavior (dot gain). When trying to reproduce an original by analog means, such as a photocopier, the variations in dot gain induce strong intensity variations at the same original intensity levels. In this paper, we present a method for compensating such variations for the target printer, on which the original security document is to be printed. Potential counterfeiters who would like to reproduce the original with a photocopying device may only be able to adjust the dot gain for the whole image and will therefore be unable to eliminate the undesired intensity variations produced by variable frequency screen elements.

Keywords/Phrases

Search In:

Publication Years