Any comparison with porous media air bearings must include a recognition of the constantly changing, multiple forces which act on the raceway integral to the function of the competitive rolling element bearing. The changing directions of the balls within this raceway result in velocity ripples which, in turn, compromise stability and impact performance.
These velocity ripples manifest themselves in a jittery motion which cannot be completely corrected by controllers, and which compromise nanometer stability at velocity. Obviously, this will impact scanning performance.
Without contact or competing forces, porous media air bearings provide smooth, virtually silent motion, without vibration, for significantly better scanning performance.