Method and a device for cleaning a surface with a laser

A process for removing pollutants from a surface of an object by employing a laser for producing a laser beam which is focused onto the surface to be cleaned, comprising the steps of:

• using a solid amplifier medium laser of the neodymium-doped YAG crystal or glass type operating in Q-switch mode;
• choosing the diameter of the laser beam applied to the surface to be cleaned to obtain a peak power density between 0.1 megawatts per cm.sup.2 and 100 megawatts per cm.sup.2 on the surface to be cleaned;
• pulsing the laser in pulse durations between 10 and 30 nanoseconds, and in which the maximum energy per pulse is close to 500 millijoules, and the diameter of the beam issuing from said laser having a diameter smaller than about ten millimeters on the surface to be cleaned;
• contacting the pulsating laser beam with an area on the surface to be cleaned;
• cleaning the surface in the absence of an observable thermal effect to the object;
• and
• removing the laser from the area on the surface after the area is clean.

Device for cleaning pollutants from a surface, comprising:

• a mechanical assembly 1 containing a laser 2 for producing a laser beam 5 and an electrical supply 3 for said laser;
• a hand-piece 7 sized for manipulation by an operator cleaning the surface of pollutants coupled with said laser beam 5;
• a box 4 between said hand-piece and placed in the path of the laser beam 5 emitted from said mechanical assembly and including an optical system for separating the laser beam into a plurality of individual laser beams 5a, 5b, 5c, 5d, 5e, 5f, 5g with energies approximately equal to one another;
• means including an optical fiber assembly 6 for guiding said laser beams 5a, 5b, 5c, 5d, 5e, 5f, 5g towards said hand-piece 7, said last-mentioned means including optical means 8 for recombining said laser beams into a single recombined laser beam 9;
• and
• optical means 10 for adjusting the diameter 11 of said recombined laser beam 9, said optical means 10 comprising an afocal optical assembly 12, said a focal optical assembly includes a divergent lens and a convergent lens.