The invention relates to an optical system for the collimation or concentration of light radiation. The invention specifically relates to an optical system that enables a high level of collimation from a light source or enables the concentration of the radiation with different degrees of collimation over a determined surface. The system comprises two zones: zone 1 including a surface (1) that has the geometry of a cartesian elipsoid, captures the light from the light source (4) of the system, and collimates said light by means of a single refraction; and zone 2 including two parts: a parabola (2) reflecting the light collimated in zone 1, and a conical surface (3) with a straight cross-section where the light reflected on the parabola (2) is subjected to a refraction and exits parallel to the optical axis (5) of the system. When the collimation system works the other way round, it acts like a radiation concentrator. With this basic configuration, the parameters defining the system can be optimised by means of mathematic models.