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Roger Hersch

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Related publications (69)

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Extending the Clapper-Yule model to rough printing supports

Roger Hersch, Mathieu Hébert

The Clapper-Yule model is the only classical spectral reflection model for halftone prints that takes explicitly into account both the multiple internal reflections between the print-air interface and the paper substrate and the lateral propagation of ligh ...

Optical Society of America, Washington, DC 20036-1023, United States2005

A simulator for adaptive parallel applications

Roger Hersch, Basile Schäli, Sebastian Gerlach

Dynamically allocating computing nodes to parallel applications is a promising technique for improving the utilization of cluster resources. Detailed simulations can help identify allocation strategies and problem decomposition parameters that increase the ...

2007

Angular Color Prediction Model for Anisotropic Halftone Prints on a Metallic Substrate

Roger Hersch, Lin Yang, Petar Pjanic

Under specular reflection, non-isotropic halftones such as line halftones printed on an ink-receiving plastic layer superposed with a metallic layer change their colors upon in-plane rotation of the print. This color change is due to the orientation-depend ...

I S & T-SOC IMAGING SCIENCE TECHNOLOGY2019

Ink thickness variations for the control of color printers

Roger Hersch

The present invention proposes a method and a computing system for deducing ink thickness variations from spectral reflectance measurements performed on a printing press or on a printer. The computed ink thickness variations enable controlling the ink depo ...

2007

Beating Shapes Relying on Moire Level Lines

Roger Hersch, Sylvain Chosson

We consider the problem of obtaining a recognizable shape as superposition moire of two line gratings. The method we propose generates moire lines located between the shape foreground and background centers and the shape boundaries. Upon relative displacem ...

Association for Computing Machinery2014

The role of Fourier theory and of modulation in the prediction of visible moiré effects

Roger Hersch, Isaac Amidror

Modern moiré theory is largely based on the Fourier approach. And yet, it seems that the Fourier theory by itself cannot answer all questions related to moiré effects. We present some visible phenomena in the superposition of periodic structures (such as l ...

2009

Deducing Ink Thickness Variations by a Spectral Prediction Model

Roger Hersch, Thomas Bugnon, Safer Mourad

Most existing techniques for regulating the ink flow in offset presses rely oil density measurements carried out oil specially printed patches. In the present contribution. we develop a methodology to deduce ink thickness variations from spectral measureme ...

Wiley-Blackwell2009

Synthesis of superposition images for watches, valuable articles and publicity

Roger Hersch, Sylvain Chosson

The present invention aims at synthesizing superposition images formed either by band moire shapes or by shape level lines for making the information forwarded by valuable articles or by time pieces such as watches and clocks more dynamic, as well as for i ...

2007

Hiding patterns with daylight fluorescent inks

Roger Hersch, Romain Rossier

We propose a method for hiding patterns within printed images by making use of classical and of two daylight fluorescent magenta and yellow inks. Under the D65 illuminant we establish in the CIELAB space the gamut of a classical cmyk printer and the gamut ...

2011

Prediction model for color separation, calibration and control of printers

Roger Hersch, Patrick Emmel

The present invention facilitates the calibration of printers and the color separation of input images into a set of inks by disclosing methods and systems for populating device-calibration lookup tables. The disclosed methods and systems rely on a compreh ...

2005

Authentication of documents and articles by moire patterns

Roger Hersch, Sylvain Chosson

The present invention relies on the moiré patterns generated when superposing a base layer made of base band patterns and a revealing line grating (revealing layer). The produced moiré patterns comprise an enlargement and a transformation of the individual ...

2010

Compositional reflectance and transmittance model for multilayer specimens

Roger Hersch, Mathieu Hébert

We propose a compositional model for predicting the reflectance and the transmittance of multilayer specimens composed of layers having possibly distinct refractive indices. The model relies on the laws of geometrical optics and on a description of the mul ...

2007

Calibrating the ink spreading curves enhanced Yule-Nielsen modified spectral Neugebauer model with the two-by-two dot centering printer model

Roger Hersch, Romain Rossier

The Yule-Nielsen modified spectral Neugebauer model enhanced for accounting for ink spreading in the different ink superposition conditions (EYNSN) requires measuring the reflectances of halftone calibration patches in order to compute the ink spreading cu ...

2009

Synthetic electronic video containing a hidden image

Sabine Süsstrunk, Roger Hersch, Mahmut Sami Arpa

We present a method for hiding images in synthetic videos and reveal them by temporal averaging. We developed a visual masking method that hides the input image both spatially and temporally. Our masking approach consists of temporal and spatial pixel by p ...

2019

High-resolution 1D moirés as counterfeit security features

Jürgen Brugger, Roger Hersch, Katrin Sidler Arnet, Victor Javier Cadarso Busto, Sylvain Chosson

A moire is an interference pattern that appears when two different periodic structures are overlaid. The image created is extremely sensitive to small variations in the original layers and is thus very interesting for anti-counterfeit protection. We presen ...

Nature Publishing Group2013

An Ink Spreading Model for Dot-On-Dot Spectral Prediction

Roger Hersch

Due to increasing printing accuracies and the possibility of printing several droplets at the same pixel location, there is a renewed interest in dot-on-dot printing models. In the present contribution, we improve a dot-on-dot spectral prediction model rel ...

2006

Printing color images visible under uv light on security documents and valuable articles

Roger Hersch, Sylvain Chosson

In the present invention, we propose a method of creating fluorescent color images visible under UV light. It relies on the new colorants that can be achieved by superposing ink dots, possibly at a reduced size, in order to avoid quenching effects. It also ...

2008

Method and Apparatus for Generating Digital Halftone Images by Using Multi Color Dithering

Roger Hersch

The invention provides a method and apparatus for the reproduction of color images by multi-color dithering. Multi-color dithering is an extension of bi-level dithering for halftoning an input image using as primary colors an arbitrary number of inks. The ...

2006

Authentication with built-in encryption by using moire parallax effects between fixed correlated s-random layers

Roger Hersch, Isaac Amidror

This invention discloses new methods and security devices for authenticating documents and valuable products which may be applied to any support, including transparent synthetic materials and traditional opaque materials such as paper. The invention relate ...

2009

Authentication of secure items by shape level lines

Roger Hersch, Sylvain Chosson

The disclosed method and system may be used for creating advanced protection means for various categories of documents (e.g. bank notes, identity documents, certificates, checks, diploma, travel documents, tickets) and valuable products (e.g. optical disks ...

2006