In modern engineering, the term laser scanning is used with two related, but separate meanings. The first, more general, meaning is the controlled deflection of laser beams, visible or invisible. Scanned laser beams are used in some 3-D printers, in rapid prototyping, in machines for material processing, in laser engraving machines, in ophtalmological laser systems for the treatment of presbyopia, in confocal microscopy, in laser printers, in laser shows, in Laser TV, in ceramic laser treatments] and in barcode scanners.