The invention relates to a non-contact laser engraving apparatus and process. A laser beam is directed onto a work piece by a mask arrangement. The mask can be transparent or reflective. Optical means are used to transfer the laser beam and thus the image produced by the mask onto the work piece. In...http://www.google.com/patents/US4156124?utm_source=gb-gplus-sharePatent US4156124 - Image transfer laser engraving
