Innoview Sarl

Ecole Polytechnique Federale De Lausanne

Hersch, Roger D.

Romain Rossier

Roger David Hersch

Roger D Hersch

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 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

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

Vionnaz, Switzerland

Romain Rossier