Ecole Polytechnique Federale De Lausanne

Innoview Sarl

Other

Innoview Arl

Ecole Polytechnique Féderale De Lausanne (epfl)

Roger David Hersch

Romain Rossier

Sylvain Chosson

Isaac Amidror

Thomas Walger

Patrick Emmel

Petar Pjanic

Juergen Brugger

Bernard Wittwer

Fabien Collaud

Valentin Flauraud

Matthias Riepenhoff

Victor Ostromoukhov

Sabine Süsstrunk

Théophane Besson

Sami Arpa

Vahid Babaei

Artin Saberpour Abadian

Justin Bur

Claude Betrisey

Jürgen Brugger

Bernard Krummenacher

Rhaleb Zayer

Hans-Peter Seidel

Dominique Bongard

Daniel Gorostidi

Daniel Biemann

Edouard Forler

Peter Amrhyn

Pascal Fehr

Ran Seri

Philipp Donzé

Julien Andres

Philip Donze

Moiré is an appealing visual effect observable when two or more repetitive patterns are superposed. We introduce a method for designing and fabricating level-line moirés on curved surfaces. These moiré shapes are obtained by superposing a partly absorbing or partly light deviating curved base layer and a curved revealing layer formed by a grating of transparent lines or cylindrical lenses. The distances between base layer and revealing layer are adapted to the locally varying distances between successive transparent lines or cylindrical lenses of the curved revealing layer grating. We demonstrate the quality of our method by rendered simulations and by fabrication. The resulting level-line moiré display devices can be manufactured using different fabrication techniques, from multi-material 3D printing to molding.

Fabrication of moiré on curved surfaces

Methods are disclosed for hiding a two-dimensional code such as a QR code within a visible layer of randomly scattered line segments. The scattering parameters comprise the length of successive line segments as well as their relative offsets. These parameters are stored in a key. The hidden 2d code is recovered with a computing device such as a smartphone carrying out the acquisition, perspective correction, and rectification of the visible layer of scattered line segments. This computing device synthesizes in its memory according to that same key a hidden layer of scattered line segments. The superposition of the acquired, perspectively corrected and rectified visible layer and of the hidden layer yields an image from which the hidden 2D code is revealed. The presented methods enable the secret transmission of information from the real world of documents and objects to databases located on computer networks.

Two-dimensional codes hidden as scattered line segments

We disclose a method for printing by rotogravure, flexography, offset, inkjet or electrophotography invisible images that are viewable under UV light. The method generates juxtaposed dispersed dot halftones by first creating juxtaposed clustered dot halftones and by applying to them dispersed dot halftoning according to a blackness reduction factor. Dispersed dot halftoning is embodied by random threshold error diffusion. The resulting dispersed dot halftones comprise pixel segments located within the areas defined by the clustered dots. These pixel segments specify the areas of the cells to be engraved onto the rotogravure cylinder. For offset, they can be imaged onto an offset plate or for electrophotography, onto a photoconductor. The disclosed juxtaposed dispersed dot halftoning method can be embedded into a framework for the reproduction of fluorescent full color images with three or more invisible fluorescent inks. These invisible fluorescent color images offer a strong protection against counterfeits.

Juxtaposed clustered dispersed dot halftoning

The present invention proposes a method for producing an authenticable moir&#xe9; shape that simultaneously moves and shows a beating effect. The method relies on a combination of the 1D or the 2D moir&#xe9; and the level line moir&#xe9;. When tilting a compound showing such a moir&#xe9;, the moir&#xe9; shape moves, its intensity levels change significantly but its shape remains the same and is recognizable. Embodiments comprise a base layer made of patterned metallic tiny shapes and a revealing layer made of a 1D array of cylindrical lenslets or of a 2D array of spherical or aspherical lenslets.

Synthesis of moving and beating moir&#xe9; shapes

The present disclosure describes a method and computerized means for creating dynamically evolving moir&#xe9; shapes on curved surfaces. The method applies geometrical transformations in order to obtain curvilinear moir&#xe9;s and creates the moir&#xe9;s on curved surfaces by applying mappings from planar space to 3D space. The method relies on the superposition of a base layer with base bands and of a revealing layer with sampling elements. The dimensions of the revealing layer sampling elements such as cylindrical or spherical lenses as well as the distances between the base and revealing layer surfaces are adapted to the space between neighbouring isoparametric lines that define the curved surface. The resulting moir&#xe9; shapes evolve smoothly on the specified curved surface and show recognizable shapes such as words, letters, numbers, flags, logos, graphic motifs, drawings, clip art, and faces.

Synthesis of curved surface moir&#xe9;

The present invention describes methods and apparatuses for creating superposition shape images by superposed base and revealing layers of lenslet gratings. The superposition shape images form a message recognizable by a human observer or by an image acquisition and computing device such as a smartphone. The superposition shape images may be created by different superposition techniques ranging from 1D moir&#xe9;, 2D moir&#xe9; and level-line moir&#xe9; superposition techniques to lenticular image and phase shift superposition techniques. Moir&#xe9; superposition techniques enable creating superposition shape images at different apparent depth levels. Applications comprise the protection of documents and valuable articles against counterfeits, the creation of eye-catching advertisements as well as the decoration of buildings and exhibitions.

Synthesis of superpostion shape images by light interacting with superposed layers of lenslet gratings

The present disclosure describes an authentication and tracking system relying on spatial codes hidden into a grayscale, variable intensity or color multigrating reproduced on a substrate. The authentication software running in a smartphone takes pictures of the multigrating and applies perspective correction and fine grain rectification. The hidden spatial code is made apparent by the phase-controlled superposition of the fine grain rectified multigrating and a corresponding digital revealing layer grating. Subsequent image processing operations enable extracting the hidden spatial code, decode it and authenticate the corresponding document or good, by sending the decoded message to an authentication and tracking computing server. Applications include the authentication and tracking of documents and goods as well as the localization of persons.

Authentication and tracking by hidden codes

We disclose a method for synthesizing by computer an artwork where 2D and 3D contents are integrated within a same composition. Such an artwork creates plausible effects for the viewers by showing a different relationship between 2D and 3D at each viewing angle. Methods are proposed for ensuring the continuity between the 2D and the 3D parts in terms of mesh geometry and reflected colors. The user selects from a given scene a region of interest (ROI) to be reproduced in 3D. A flat rendering grid is created that matches the topology and tesselation of the ROI. The ROI is attached to the rendering grid. To enhance the continuity between the 2D and the 3D parts of a scene object, the 2D part of the object can be represented as bas-relief. Designers can create 2D-3D sculpture paintings for decoration, exhibitions, and homes.

2D-3D sculpture paintings

Synthesis of superposition shape images by light interacting with layers of lenslets

We propose new methods for creating color varying prints with classical cyan, magenta, yellow inks on a metallic specularly reflecting or on a white diffusely reflecting substrate. We use a special cross-line halftone with optimized surface coverages of the inks to create cross-halftone prints whose colors change when rotating the print in-plane under specular reflection. These prints enable viewing at the same location a first image with a first set of colors and upon in-plane rotation of the print or displacement of the observer, a similar or a different image whose parts are colored with a different set of colors. Applications comprise counterfeit prevention, art, advertisement, decoration, exhibitions and surprising displays in amusement parks.

Color changing effects with cross-halftone prints

We propose new methods for creating color varying prints with classical cyan, magenta, yellow inks on a metallic substrate. We use a special crossline halftone with optimized surface coverages of the inks to create color prints on a metallic surface whose colors change when rotating the print in-plane under specular reflection. These prints enable viewing on the same metallic print a first image with a first set of colors and upon in-plane rotation, the same image with parts colored with a different set of colors. They also enable viewing a first color image and upon rotation a second independent color image. Applications comprise counterfeit prevention, art, advertisement exhibitions and amusement parks.

Color changing effects with cross-halftone prints on metal

We propose new methods for creating color or achromatic images that are printed with classical cyan, magenta, yellow and a white diffusing ink on a metallic substrate. We optimize the surface coverages of the cyan, magenta, yellow and white inks in order to create color prints on a metallic surface that look bright and colorful under specular reflection and also look good under non-specular observation conditions. We also provide new means for the prevention of counterfeits. A first effect enables viewing on the same metallic print one achromatic image in specular viewing mode and a second independent achromatic image in non-specular viewing mode. The second effect enables hiding a pattern such as text, graphics or a grayscale image within the printed color image in one viewing mode, specular or non-specular and showing that pattern in the second viewing mode, non-specular or specular, respectively.

Color reproduction, pattern hiding and image alternations with halftone prints on metal

A method and computing system are proposed for producing an authenticable security device with two sides. The verso side is covered with an adjustable luminescent emissive layer formed by invisible luminescent ink halftones and possibly a UV absorbing printed layer. The recto side is covered with transmissive non-luminescent ink halftones. The backlit colors resulting from the emissions of the luminescent layer or resulting from illumination by normal white light through the transmissive non-luminescent ink halftones are predicted by a backlighting model. This model enables computing the surface coverages of the luminescent and/or non-luminescent ink halftones in order to obtain a desired color either under excitation light (UV light) or under normal white light. This enable creating authenticable backlit images substantially similar to pre-stored reference images, either under normal white light, under excitation light, or under both the normal white light and the excitation light.

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

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 different halftoning methods, mapping of an input gamut into a gamut defined by a set of inks, calculating the optimal boundary between region halftones created with different halftoning methods, and color multi-halftone image generation. The basic authentication is performed by examining the color multi-halftone image under a reference illumination and verifying that the message incorporated within the color multi-halftone is hidden and revealed under a different illumination. Authentication can further be performed by observing the color multi-halftone image both in reflection and transmission modes and verifying that in one of these modes the message is hidden and that in the other mode the message is revealed.

Synthesis of authenticable color multi-halftone images

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 attractiveness and aesthetics of color images. The invention relies on daylight luminescent inks, color prediction models for daylight luminescent halftones, color gamuts of luminescent and non-luminescent inks, color separation into luminescent and non-luminescent ink layers, mapping of input gamuts into a luminescent target gamuts by gamut reduction and/or expansion strategies, and luminescent color halftone image generation. The basic authentication is performed by examining the excitation trace image of the synthesized luminescent color halftone image under an illuminant active within its excitation wavelength range. Further authentication means include hiding messages under one or several different illuminants as well as hiding message with different sets of luminescent inks. Hidden messages are recovered under illuminants different from their reference illuminant.

Growing community of inventors

Epalinges, Switzerland

Roger David Hersch