Our ambition is to create the foundations of spectral metrology by: - A robust and accurate measure of the distance between two reflectance or radiance spectra, - The characterisation of the spatial variations of reflectance spectra acquired from a coloured surface perceived as homogeneous but which is spectrally not uniform. The necessity to control the stability and the accuracy of such optical measures is always required in civil industry, e.g. in military, Aerospatiale, medical applications, or in the valorisation of the cultural heritage. There is no metrology solution corresponding to this need while the use of spectral sensor increases. This lack is related to the problem complexity: measure processing is related to Digital Sciences, but the validation and interpretation comes from Physics. DigiPi proposes to break this boundary by combining two laboratories, one expert in digital processing of colour and the other one expert in the characterisation of complex heterogeneous materials and modelling their optical properties. As part of this bi-disciplinary approach, we will produce new expressions of similarity/distance measure between spectra embedding constraints of robustness, genericity and uncertainty reduction. Our contribution will integrate the mathematical specificity of the spectrum, which is not a vector or a probability density function, but closer to a series or a function. Another contribution of DigiPi will decompose the distance measure in subparts allowing straightforward interpretations well reflecting the spectral variability. There is no metrology without standards or references. We will create surface ranges ordered by the change in different manufacturing settings. The characterisation by various methods (profilometry, microscopy, spectrophotometry ...), and physical modelling of the optical properties of the paint layers will allow us to better understand the spectral variability of a pigment according to the physical and chemical characteristics. In particular, we will adapt existing models to embed parameters never previously integrated. All this knowledge will allow us to measure the rank correlation between the spectral distance measurements and the data characterisation or parameter models to obtain a complete validation. These surfaces and reference data will allow the development of this metrology beyond DigiPi. The second objective is to produce digital attributes characterising non-uniformity colour from hyperspectral images. This objective is related to the analysis of the micro-textured surface appearance. Our scientific contribution will be to define digital attributes that must be metrologically valid in the physical sense (spectral aspect) and that can be correlated with models of human vision (colour and subjective aspect). The digital attributes will be compared using rank correlations to morphological and chemical parameters extracted from the physical models describing the paint layers of reference surfaces. In parallel, fractal image models coming from the work of the CIE TC8-14 will be used to assess the uncertainty stability whatever is the spatio-chromatic content. Distance/similarity measures between spectra and attributes characterising the non-uniform appearance correspond to industrial, economic, medical, environmental ... requirements. The last part of DigiPi will establish the performance gain in two use cases: one related to industrial quality control in production of colour products and the other in cultural heritage context to characterise colour shading-off in a wide collection of royal vellums.

Fiber Lasers are nowadays changing the idea people have regarding laser systems by allowing reaching high powers, higher compactness and easy use (compared to classical laser systems). In particular, fiber lasers are expected to occupy 30 to 40% of the laser market. The main interests of the optical fiber devices remain in their unique geometry which provides their adaptability to be used in various environments and allows minimizing the thermal effects induced by the laser emission. Even though the advantages of the fibers are obvious, important issues remain to be solved and it appears clearly that the silica based materials are definitely not, for several applications, the best candidates to meet the challenge. Tellurite glasses and glass-ceramics will offer new opportunities to extend the operational wavelength range in the near infrared (above 1µm up to 5-6 µm) and will allow accessing high second order and third order optical nonlinearities. Glass-ceramics have been considered in the past as very attractive materials for photonics but their use has led so far only to limited applications, mainly due to technological difficulties in relation with the complex nature of the materials in fiber form. However, the benefit of achieving glass-ceramics fibers would be considerable and real, justifying completely this project. Several issues, specific to glass-ceramics, will have to be addressed. In particular, the size of nanocrystals disseminated within the glassy matrix will have to be carefully controlled to avoid their excessive growth. As well, a small refractive index difference between the crystallites and the glassy matrix will constitute a key focus to maintain optical scattering losses at a low level. In addition, the low phonon energy intrinsic to the tellurite glass matrix, combined to that of selected crystals, will be essential parameters to reach important laser efficiency for the targeted applications above 1µm and up to 5-6 µm. Finally, glass-ceramics should present higher laser damage thresholds, in comparison to the “equivalent” glass compositions, due to their improved mechanical properties. Thus, in order to guaranty the success of the HOLIGRALE project, the strategy will be to select the most adapted materials for the fabrication of fibers for Gain and fibers for Non-Linear Optics, to develop the drawing technique, to test and adopt innovative geometries for fibers and to establish some correlation between fiber architectures, materials chemistry and optical properties. This unique project will rely on the excellence of the French expertise in the aforementioned fields of research, and on the quality of the consortium created by the gathering of the laboratories implied.

This project is aligned with the theme 1 "Sécurité et sûreté des systèmes numériques". Considering that reverse engineering of code and the recovery of sensitive data are nowadays one of the greatest threats in secure devices, COGITO proposes an innovating solution that puts into perspective the use of runtime code generation in order to increase the level of security in embedded information systems. Security in embedded devices and runtime code generation are, a priori, two technological fields that hardly combine together. On one hand, secure elements must target small production costs, silicon and energy consumption, and as such, offer very limited computing and memory resources. On the other hand, compilation is a computation-intensive process, and dynamic compilation techniques require a fair amount of computing power and of memory resources at runtime. However, the objective of the COGITO project is to demonstrate the applicability and the effectiveness of code generation techniques applied at runtime and on board for security purposes in embedded devices. In this project we will define and validate a unique protection mechanism that implements a wide range of ad hoc countermeasures and provide a means for effective code obfuscation. The objective of the “factorization” of a large set of countermeasures is to obtain a better trade-off between security and performance than the state-of-the art solutions. To reach this objective, the partners of the project COGITO plan to adapt a technology for runtime code generation developed, by the CEA. This technology, called deGoal, is fundamentally different from the traditional approaches (interpretation and dynamic compilation): ad hoc code generators compiled statically and are embedded in the target application, each code generator being dedicated for each computing kernel whose binary code will be updated at runtime. Thus, these code generators are lightweight and very fast, allowing to target small architectures that are usually out of reach of the standard techniques for dynamic code generation such as the small microcontrollers used in secure devices. Furthermore, we are confident about the ability of our solution to combine well with other software and hardware state-of-the-art countermeasures for cryptography. The three main tasks to achieve the objective are : 1. Provide an in-depth analysis of the opportunities and threats of runtime code generation to increase the level of security in secure devices. 2. Demonstrate the applicability of runtime code generation to the field of secure devices. To achieve this objective, we will adapt the tool deGoal. 3. Experiment, measure and validate the effectiveness of runtime code generation in illustrative use cases. In parallel to these technical tasks, the dissemination of the project results will be carried out via a dedicated website, via publications in outstanding journals in the fields of interest, via the participation in conferences, workshops and the events organised by the ANR, and via the organization of a special workshop at mid term focusing industrials in particular.