US Patent 7459655 Laser beam processing machine

A laser beam processing machine comprising a chuck table for holding a workpiece and a laser beam application means comprising a laser beam oscillation means and a condenser having an objective lens for converging a laser beam oscillated by the laser beam oscillation means to apply it to the workpiece held on the chuck table, wherein a first lens for transmitting a laser beam oscillated by the laser beam oscillation means, a second lens for transmitting a laser beam that has passed through the first lens, and an optical path length changing means for changing the length of the optical path between the first lens and the second lens are interposed between the laser beam oscillation means and the objective lens.