Method of minimizing diffraction groove formation on laser etched surfaces

A method of forming an etching of predetermined configuration on a target surface with a laser beam directed through an opening of an aperture, said opening being of predetermined outline, said aperture being positioned between a source of said laser beam and said target surface such that said laser beam is directed to impinge upon said target surface to form said etching, and wherein a portion of said laser beam passing immediately adjacent the perimeter of said opening experiences a diffractive effect which causes an initial formation of a plurality of diffractive grooves having alternating peaks and troughs about the perimeter of said etching on said target surface, the method comprising:

• during formation of said etching, changing the positional relationship between said laser beam and said target surface in a first direction substantially transverse to said alternating peaks and troughs, said change in positional relationship being such as to satisfy the condition:
• A.sub.target .gtoreq.D
• wherein A.sub.target is the range over which said diffraction pattern is shifted, and D is the distance between the first peak, and the first trough on the groove pattern produced by a single pulse,
• whereby said formation of diffractive grooves is minimized.