Patent ID: 8049133

Claim:
A laser beam machining apparatus comprising: a chuck table for holding a work; laser beam irradiation means for irradiating said work held by said chuck table with a laser beam; and machining feeding means for relative machining feeding of said chuck table and said laser beam irradiation means, wherein said laser beam irradiation means includes laser beam oscillation means for oscillating a laser beam, a beam splitter by which said laser beam oscillated by said laser beam oscillation means is split into a first laser beam having a first plane of polarization and a second laser beam having a second plane of polarization orthogonal to said first plane of polarization, a rotary half-wave plate disposed between said laser beam oscillation means and said beam splitter, a condenser lens disposed in a first optical path for guiding said first laser beam split by said beam splitter, first reflecting mirror which is disposed in a second optical path for guiding said second laser beam split by said beam splitter and by which said second laser beam is returned to said beam splitter, first quarter-wave plate disposed between said beam splitter and said first reflecting mirror, a second reflecting mirror which is disposed in a third optical path for splitting thereinto said second laser beam returned to said beam splitter through said second optical path and by which said second laser beam split into said third optical path is returned to said beam splitter, a second quarter-wave plate disposed between said beam splitter and said second reflecting mirror, and a cylindrical lens disposed between said beam splitter and said second quarter-wave plate, and wherein said second laser beam returned to said beam splitter through said third optical path is guided to said condenser lens through said first optical path.