The invention relates to a system for the combined shadow-free illumination of a pre-definable area and for referencing three-dimensional spatial co-ordinates, and to an active or passive referencing system, each in particular for referencing surgical or medical instruments. The system is characterized in that at least two cameras and the light source (operation lamp) are held together such that the optical signals detected by the cameras, for referencing three-dimensional spatial co-ordinates in the area illuminated by the light source, can be evaluated. Since the field of view of the light source, in its conventional use, is not obscured or only negligibly obscured, this field of view can simultaneously be used for optical navigation by the cameras held together with the light source. In accordance with the invention, the cameras are automatically aligned optimally for optical navigation.The cameras can be rigidly or flexibly connected to the light source. The position and/or orientation of the cameras can be adjustable.