| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical system having a simple constitution in which two focal points are formed on the optical axis, capable of suppressing generation of spatter by reducing evaporation reaction force in a workpiece, and to provide a laser beam machining apparatus.SOLUTION: An optical system 7 includes a convex lens 8 for condensing a laser beam, and a concave lens 9 arranged on the same optical axis as the laser beam passing through the convex lens 8, and the concave lens 9 has a first region having a through hole 11 positioned on the optical axis and not having a lens characteristic, and a second region surrounding the first region, and diverging the laser beam. |
