| 摘要 |
PCT No. PCT/DK88/00201 Sec. 371 Date May 7, 1990 Sec. 102(e) Date May 7, 1990 PCT Filed Dec. 2, 1988 PCT Pub. No. WO89/05208 PCT Pub. Date Jun. 15, 1989.An optical system for laser marking, such as for engraving marks such as numbers and dates on surfaces, and exhibiting improved efficiency and improved quality of the resulting mark. The optical system includes a focusing system, such as a lens, and a concave mirror situated between the laser and the mask with its vertex at the focal point of the focusing system and its reflecting surface facing the mask. An inlet opening in the concave mirror is formed about the vertex, and the transverse measurement of the inlet opening is slightly larger than the transverse measurement of the focal point. The mask is formed as a mirror, preferably a plane mirror, with the reflecting surface facing the concave mirror, and the radius of curvature of the concave mirror is longer than twice the distance between the mask and the concave mirror. In operation, the portion of the laser beam radiated through the mask is increased because the portion thereof not passing directly through the mask openings is reflected by the mirror face of the mask back to the concave mirror, which in turn reflects the light back to the mask, such that additional portions of the laser beam pass through the mask openings. The size of the reflecting surface of the concave mirror and consequently the amount of the light reflected by the concave mirror are optimized by the laser beam being focused by the focusing system in the small opening in the vertex of the mirror. |
