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Roger Hersch

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Related publications (69)

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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

Level-line moirés by superposition of cylindrical microlens gratings

Jürgen Brugger, Roger Hersch, Valentin Flauraud, Thomas Walger, Théophane Besson

Two superposed layers of transparent cylindrical lenslet gratings create classical moiré fringes when illuminated from behind. We rely on this observation to conceive special devices made of superposed lenslet gratings that produce compelling beating shape ...

2020

Sculpture paintings

Sabine Süsstrunk, Roger Hersch, Mahmut Sami Arpa

ACM2018

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

Mathematical moiré models and their limitations

Roger Hersch, Isaac Amidror

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

Color Reproduction of Authenticable Luminescent Backlit Transmissive Color Images

Roger Hersch, Julien Alexandre Andres

We propose a method for creating authenticable color images under UV excitation backlight by printing an invisible luminescent white emissive ink layer on the verso side of a transmissive substrate and a classical cmy image on the recto side of the substra ...

Wiley-Blackwell2014

Spectral reflection and dot surface prediction models for color halftone prints

Roger Hersch, Patrick Emmel

The proposed new spectral reflection model enhances the classical Clapper-Yule model by taking into account the fact that proportionally more incident light through a given colorant surface is reflected back onto the same colorant surface than onto other c ...

2005

Deducing Ink-Transmittance Spectra from Reflectance and Transmittance Measurements of Prints

Roger Hersch, Mathieu Hébert

The color of prints is mainly determined by the light absorption of the inks deposited on top of paper. In order to predict the reflectance spectrum of prints, we use a spectral prediction model in which each ink is characterized by its spectral transmitta ...

2007

Distance preserving flattening of surface sections

Roger Hersch, Laurent Saroul

Curved cross-sections extracted from medical volume images are useful for analyzing nonplanar anatomic structures such as the aorta arch or the pelvis. For visualization and for performing distance measurements, extracted surface sections need to be adequa ...

2006

A simulator for parallel applications with dynamically varying compute node allocation

Roger Hersch, Basile Schäli, Sebastian Gerlach

Dynamically allocating computing nodes to parallel applications is a promising technique for improving the utilization of cluster resources. We introduce the concept of dynamic efficiency which expresses the resource utilization efficiency as a function of ...

2006

High Relief from 3D Scenes

Sabine Süsstrunk, Roger Hersch, Mahmut Sami Arpa

We present a method for synthesizing high reliefs, a sculpting technique that attaches 3D objects onto a 2D surface within a limited depth range. The main challenges are the preservation of distinct scene parts by preserving depth discontinuities, the fine ...

Wiley-Blackwell2015

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

Interaction between Light, Paper and Color Halftones: Challenges and Modelization Approaches

Roger Hersch, Mathieu Hébert

We review the phenomena having an impact on the interaction between light, paper and color halftones. They comprise surface reflections and refractions at the air-paper interface, propagation of light within the paper, internal reflections at the paper-air ...

IS&T2006

Calibrating the Yule-Nielsen modified spectral Neugebauer model with ink spreading curves derived from digitized RGB calibration patch images

Roger Hersch

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

2008

Deducing Ink Spreading Curves from Reflection Spectra Acquired Within Printed Color Images

Roger Hersch, Mathieu Hébert, Thomas Bugnon

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

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

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

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

Reflectance and transmittance model for recto-verso halftone prints

Roger Hersch, Mathieu Hébert

We propose a spectral prediction model for predicting the reflectance and transmittance of recto-verso halftone prints. A recto-verso halftone print is modeled as a diffusing substrate surrounded by two inked interfaces in contact with air (or with another ...

2006

Model-based synthesis of band moire images for authenticating security documents and valuable products

Roger Hersch, Sylvain Chosson

The present invention relies on a band moiré image layout model capable of predicting the band moiré image layer layout produced when superposing a base band grating layer of a given layout and revealing line grating layer of a given layout. Both the base ...

2006