Laser processing power output stabilization apparatus and method employing processing position feedback

Abstract

A Q-switched solid state laser system (,) operates in a pulse processing control system (,) that employs an autopulse mode and a pulse-on-position mode to stabilize the pulse-to-pulse laser energy delivered to a workpiece (,) that is moved by an X-Y positioner (,). In the autopulse mode, laser pulses are emitted at a near maximum PRF, but the pulses are blocked from reaching the workpiece by an external modulator (,), such as an acousto-optic modulator (“AOM”) or electro-optic modulator (also referred to as a Pockels cell). In the pulse-on-position mode, the laser emits a pulse in response to the positioner moving to a location on the workpiece that coincides with a commanded coordinate location. The processing control system delivers a stream of coordinate locations, some requiring processing, at a rate that moves the positioner and triggers the laser at about the near maximum PRF. The pulse processing control system sets the AOM to a transmissive state whenever a coordinate location requiring processing is commanded and otherwise sets the AOM to a blocking state. This pulse timing technique provides a nearly constant interpulse period for the laser, thereby improving its pulse-to-pulse energy stability at the near maximum PRF.