METHOD AND APPARATUS FOR FORMING AND IMAGING LASER BEAMS

摘要

In one respect the invention relates to an optical method, ensuring maximum depth of field, of forming and imaging laser beams onto a scanning surface, comprising the steps of generating laser beams with diverging or converging axes and imaging each of the laser beams by means of an optical system onto a scanning surface in such a way that each of the laser beams provides a predetermined spot size on the scanning surface and the axes of adjacent laser beams intersect the scanning surface with a distance from each other, which corresponds to a predetermined raster spacing on the scanning surface. According to the invention a first crossing place of the axes of the laser beams and waists of the laser beams are formed at an input focal plane or in the vicinity of an input focal plane, of an equivalent lens corresponding to that subsystem of the optical system which forms the image of said crossing place, and the scanning surface is placed at an output focal plane, or in the vicinity of an output focal plane, of said equivalent lens. The invention on the other hand relates to an apparatus for forming and imaging laser beams, where laser beams of diverging or converging axes are provided and imaged onto a scanning surface by an optical system, which comprises an imaging element (14, 27, 34, 44, 53, 63, 71, 82, 93, 102) having its input focal plane at a crossing place of the laser beams or in the vicinity of said crossing place, said imaging element forming real waists of the laser beams onto the scanning surface (4) with a predetermined waists size and with a distance between the axes of the adjacent waists, said distance corresponding to a predetermined raster spacing on the scanning surface (4).