Abstract: Disclosed is an apparatus for scanning a surface with electromagnetic radiation. The apparatus comprises a base plate for supporting a medium said medium having a scanning surface to be scanned, an optical head unit adapted to scan the scanning surface with electromagnetic radiation propagating along an optical axis, a fluid film generation unit connected to the optical head unit and adapted to generate a fluid film between the scanning surface and a gliding surface of the fluid film generation unit for maintaining a predetermined distance between the gliding surface and the scanning surface during scanning operation of the optical head unit across the scanning surface, and control means for controlling the position of the fluid film relative to the optical axis.