Patent ID: 8227724

Claim:
A laser processing apparatus for forming a modified region which functions as a starting point for cutting within an object to be cut, comprising: a stage adapted for mounting the object; a laser source for emitting a laser light transparent to the object; a laser light source controller for controlling the laser source; an image-pick up device for imaging the laser light reflected from a surface of the object; a converging lens for converging the laser light emitted from the laser light source within the object mounted on the stage to form the modified region at a converging point of the laser light; and a controller for controlling the movement of at least one of the converging lens and the stage to focus the laser light on the surface of the object thereafter to move the converging point of the laser light at a position within the object and spaced from the surface of the object by a predetermined distance from a reference position in a thickness direction of the object, and thereafter to move the converging point of the laser within the object along a line along which the object is intended to be cut to form the modified region in the object, the reference position being a position of the converging lens with respect to the object at which the laser light is focused on the surface of the object through the converging lens, wherein the laser source controller controls the laser light source so that the output of the laser light in the focus on the surface of the object is smaller than that of formation of the modified region.