Laser processing apparatus

A laser processing apparatus comprising:

• a chuck table that holds a workpiece;
• laser beam irradiating means that irradiates the workpiece held by the chuck table with a pulse laser beam;
• X-axis direction moving means that moves the chuck table and the laser beam irradiating means relatively in an X-axis direction that is a processing feed direction;
• Y-axis direction moving means that moves the chuck table and the laser beam irradiating means relatively in a Y-axis direction that is an indexing feed direction orthogonal to the X-axis direction;
• and
• control means that controls the laser beam irradiating means, the X-axis direction moving means, and the Y-axis direction moving means,
• wherein the laser beam irradiating means includes
• pulse laser beam oscillating means that oscillates the pulse laser beam,
• a condenser that condenses the pulse laser beam oscillated from the pulse laser beam oscillating means and emits the pulse laser beam to the workpiece held by the chuck table,
• a dichroic mirror that is disposed between the pulse laser beam oscillating means and the condenser and reflects the pulse laser beam oscillated from the pulse laser beam oscillating means to lead the pulse laser beam to the condenser, the dichroic mirror allowing transmission of light having a wavelength other than a wavelength of the pulse laser beam through the dichroic mirror,
• strobe light irradiating means that emits light to a path on which the dichroic mirror and the condenser are disposed,
• a beam splitter that is disposed between the strobe light irradiating means and the dichroic mirror and splits light from the workpiece held by the chuck table, and
• imaging means disposed on a path of light split by the beam splitter, and
• the control means actuates the strobe light irradiating means and the imaging means according to timing of the pulse laser beam that is oscillated by the pulse laser beam oscillating means and is emitted to the workpiece held by the chuck table, and detects width of a laser-processed groove immediately after emission of the pulse laser beam on the basis of an image signal from the imaging means.