Rapid excimer laser cleaning of plane objects

Weak or sensitive surfaces like pigment lacquer, finishing varnish, art paintings or plastics are much more precarious to clean due to the danger of a partial or complete damage of the layer which may have a protective function or artistic merit. So it is essential only to remove the contamination itself or, if necessary, the contamination together with some very thin coating without affecting or destroying the underlying structure. For such kind of gentle laser applications we set up a prototype machine based on a KrF-excimer laser. An easy and rapid adaptation of the pulse energy is achieved by passing the radiation through a computer controlled variable attenuator followed by a beam forming system to ensure homogeneous irradiation at the target with intensity variations smaller 5%. The device is preferentially designed to operate with plane objects like electrical circuits, wavers or paintings. In combination with an improved handling system, however, also three-dimensional surfaces can be treated. Actually the laser cleaning unit is set up as a mobile system, allowing wide applications for cleaning of sensitive surfaces in industrial fabrication, for the restoration of antiques or the sterilization of biological and medical instruments.