Partial laser modification of surfaces - useful for shallow or deep engraving or inscription

摘要

Partial surface modification of metallic or non-metallic bodies is carried out using a Q-switched continuous wave Nd:YAG laser having opt. a beam expander in the beam path, a beam deflector with a computer-controlled rotary deflection mirror, and a plane field objective for focussing the laser beam, the laser being moved over the surface along one or more reference lines present by the computer. The novelty is that the laser beam is moved within an outline (U1, U2) delimiting the surface portion (A) to be modified, along reference lines forming the grid lines (R1, R2, R3) of a grid field (N) and then the entire grid field (N) is shifted at least once by a certain amount, while maintaining the relative position of the outline (U1, U2) and the entire surface portion (A) is re-scanned by the laser beam along the grid lines (R1, R2, R3). During each scan, the operating time and the energy content level of the laser pulses are limited so that material evapn. is effected with minimal plasma formation. USE/ADVANTAGE - The process is useful in laser engraving or insorption processes carried out e.g. on metallic or plastic surfaces. It achieves the prescribed shallow penetration depth for prodn. of inscriptions, but can also produce deeper penetration depths to achieve relief-like material surface removal.