The term 'Optical constants' is used for the so-called dielectric function ε = ε1+ i ε2 or its square root, the complex refractive index n + i k. The dielectric function represents a material in Maxwell's equations and determines the solutions for electromagnetic waves.

Light propagation through any system depends on the optical constants of all involved materials and geometry (shapes, sizes, distances). Hence optical constants must be the basis of any physical model. SPRAY is equipped with a large database of optical constants. There are fixed data sets taken from literature sources, and flexible models that can be adapted to individual cases.

If you are not familiar with optical constants, the next section about typical materials could be useful for you.

The optical constants of the demo pigments used in this text are given in separate sections below.