PERFORATION OF SHEET MATERIAL BY LASER

摘要

In providing perforation uniformity both in the spacing between multiple rows of perforations in sheet material 10 eg: cigarette filter paper and in the spacings among perforations within each row, a common laser beam 36 is shared among the rows, being directed to the sheet material through a common focusing element 40 for each adjacent pair of rows. In conducting the laser beam to each such common focusing element, a pair of modified beams 64, 66 is derived from the laser beam, each modified beam having light ray content divergent about an axis of symmetry thereof 64a, 66a which is parallel to the optical axis 40a of the focusing element.