Patent ID: 7227098

Claim:
A method for operating a laser characterized by a PRF parameter that specifies a PRF at which pulses produced by the laser have desirable pulse properties for irradiating a target that is one of a set of structures on or within a workpiece, the laser emitting a laser pulse that propagates along a laser beam propagation path terminating at a laser beam spot on the workpiece, the method being effective to operate the laser at an effective PRF lower than the PRF parameter without substantially degrading the desirable pulse properties, the method comprising: receiving data indicating the location on the workpiece of the target to be selectively irradiated with the laser pulse; determining a firing position of the laser beam spot relative to the workpiece at which the laser should emit a pulse directed at the target; calculating, based on a desired charging time, a charging start position of the laser beam spot relative to the workpiece at which the laser should begin charging so as to charge for the desired charging time before the laser beam spot reaches the firing position, wherein the charging start position is not a location of a structure on the workpiece; moving the workpiece and the laser beam spot relative to one another such that the laser beam spot moves over the charging start position and then to the firing position; sensing a position of the laser beam spot relative to the workpiece as the workpiece moves relative to the laser beam spot; commencing charging of the laser when the laser beam spot is at the charging start position, whereby the laser charges for approximately the desired charging time; and firing the laser when the laser beam spot reaches the firing position, whereby the laser emits a pulse having desired pulse properties.