1. Reminders

For physicists, chemists and engineers, the notion of color involves the characterization of a spectral quantity. Reflection, transmission or emission spectra are therefore essential and relevant to the specialist's interpretation. In many professions, the information provided by these spectra is neither sufficient nor even the most relevant. The main reason for this lies in the angular variations of optical phenomena, which are superimposed on spectral variations. Today, industry in general, and product design simulation in particular, require control and formulation instrumentation that can link directional spectral information between source and detector. It is therefore necessary to develop models for the optical behavior of materials as a function of their nature, their solid, liquid, gas or plasma state, and their surface state when solid. Of these three concepts, the first is expressed...