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Roger Hersch

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Related publications (70)

Beating Shapes Relying on Moire Level Lines

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

A New Anti-Counterfeiting Feature Relying on Invisible Luminescent Full Color Images Printed with Lanthanide-Based Inks

Roger Hersch, Jacques-Edouard Moser, Anne-Sophie Chauvin, Julien Alexandre Andres

Europium and terbium trisdipicolinate complexes are inkjet printed onto paper with commercially available desktop inkjet printers. Together with a commercial blue luminescent ink, the red-emitting luminescent ink containing europium and the green-emitting ...

Wiley-Blackwell2014

Synthesis of authenticable color multi-halftone images

Roger Hersch, Romain Rossier

The present invention enables creating authenticable continuous tone color multi-ink multi-halftone images offering means of verifying their authenticity. The invention relies on color halftones, color separation into different ink surface coverages for di ...

2013

High-resolution 1D moirés as counterfeit security features

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

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

Spectral Prediction of Juxtaposed Halftones Relying on the Two-by-two Dot Centering Model

Roger Hersch, Vahid Babaei

In a color reproduction workflow, spectral prediction models are useful for establishing the correspondence between colorant sur- face coverages and resulting printed halftone color. Spectral predic- tion models enable calculation of the color gamut and es ...

2013

Synthesis of authenticable halftone images with non-luminescent halftones illuminated by a luminescent emissive layer

Roger Hersch, Julien Alexandre Andres

A method and computing system are proposed for producing an authenticable security device with two sides. The verso side is covered with a luminescent emissive variable intensity layer formed for example by invisible luminescent ink halftones and the recto ...

2012

Synthesis of authenticable luminescent color halftone images

Roger Hersch, Romain Rossier

The present invention enables creating authenticable multi-ink luminescent continuous tone color halftone images offering means of verifying their authenticity. The invented luminescent color halftone image synthesizing techniques enable increasing the att ...

2012

Enhancing the Specular Effect of Metallic Color Prints by Reducing the Use of Yellow Ink

Roger Hersch, Thomas Bugnon, Andrea Maesani

The MetallicArt technique is used as a visual security feature to hide patterns in CMY images using an additional silver ink. The patterns are hidden under nonspecular viewing conditions and visible under specular viewing conditions. By varying the amount ...

2011

Constrained Acquisition of Ink Spreading Curves From Printed Color Images

Roger Hersch, Thomas Bugnon

Today's spectral reflection prediction models are able to predict the reflection spectra of printed color images with an accuracy as high as the reproduction variability allows. However, to calibrate such models, special uniform calibration patches need to ...

2011

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

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

Analyzing halftone dot blurring by extended spectral prediction models

Roger Hersch, Mathieu Hébert

Spectral prediction models for halftone prints generally assume homogeneously thick and sharply edged ink dots, i.e., bilevel halftones. In real prints, the ink thickness often decreases at the boundaries of the ink dots, thereby forming continuous-level h ...

2010

Mathematical moiré models and their limitations

Isaac Amidror, Roger Hersch

In a previous recent paper we discussed the limitations of the Fourier-based model in the prediction of visible moiré effects. Here, we extend the discussion to other mathematical models that are also being used in the moiré theory: the classical indicial ...

2010

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

Isaac Amidror, Roger Hersch

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

Yule-Nielsen approach for predicting the spectral transmittance of halftone prints

Roger Hersch, Mathieu Hébert

The transmittance spectrum of halftone prints on paper is predicted thanks to a model inspired by the Yule-Nielsen modified spectral Neugebauer model used for reflectance predictions. This model is well adapted for semi-opaque printing supports and applica ...

IS&T2009

Deducing Ink Thickness Variations by a Spectral Prediction Model

Roger Hersch, Safer Mourad, Thomas Bugnon, Peter Amrhyn, Mathieu Brichon, Frédérique Crété

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

Reflectance and transmittance model for recto-verso halftone prints: spectral predictions with multi-ink halftones

Roger Hersch, Mathieu Hébert

We extend a previously proposed spectral reflectance and transmittance prediction model for recto-verso prints to the case of multi-ink halftones. The model takes into account the multiple reflections and the lateral propagation of light within the paper s ...

2009

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

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

Isaac Amidror, Roger Hersch

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 Spreading Curves from Reflection Spectra Acquired Within Printed Color Images

Roger Hersch, Thomas Bugnon, Mathieu Hébert, Mathieu Brichon

The Yule–Nielsen modified spectral Neugebauer model (YNSN) enhanced for accounting for ink spreading in the different ink superposition conditions provides accurate spectral predictions, but requires one to measure the reflectances of special halftone cali ...

2009

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