Patent ID: 7732729

Claim:
A laser processing device comprising: a chuck table for holding a workpiece; a laser beam irradiating unit for irradiating the workpiece held on said chuck table with a pulsed laser beam, said laser beam irradiating unit including a laser oscillator, and including an irradiation unit for irradiating the workpiece with the pulsed laser beam oscillated by said laser oscillator; a controller for controlling said laser beam irradiating unit; a processing feed unit for moving said chuck table in an X-axis direction, and for outputting X-axis coordinate values of said chuck table; and an indexing feed unit for relatively moving said chuck table and said laser beam irradiating unit in a Y-axis direction, and for outputting Y-axis coordinate values based on a location of said chuck table and said laser beam irradiating unit, wherein said controller includes a pulse number setting section for setting a pulse number, a pulse signal output section for outputting a pulse signal to said laser oscillator according to the pulse number set in said pulse number setting section, a pulse signal detector for detecting the pulse signal output from said pulse signal output section, and for detecting a timing of the pulse signal, a pulsed laser beam detector for detecting the pulsed laser beam by branching a part of the pulsed laser beam such that the part of the pulsed laser beam is received by a photodetector, and for detecting a timing of the pulsed laser beam, a first judgment section for judging when the timing of the pulse signal detected by said pulse signal detector and the timing of the pulsed laser beam detected by said pulsed laser beam detector match each other after comparing the timings, and for outputting an abnormal signal in the case of not matching, and a second judgment section for judging when a timing based on a value of the pulse number set by said pulse number setting section and the timing of the pulse signal detected by said pulse signal detector match each other after comparing the timings, and for outputting an abnormal signal in the case of not matching.