Methods and systems for decreasing the effective pulse repetition of a laser

A system for operating a machine having a laser characterized by a PRF parameter that specifies a PRF at which pulses produced by the laser have desirable pulse properties for irradiating structures on or within a workpiece for a given purpose, the structures being arranged in on the workpiece a linear pattern having an approximately equal pitch between adjacent structures, the laser emitting a laser pulse that propagates along a laser beam propagation path terminating at a laser beam spot on the workpiece, the machine being capable of moving the workpiece and the laser beam spot relative to one another at a maximum speed that is less than the product of the PRF parameter and the pitch, the machine being effective to move the laser beam spot across the structures along the linear pattern to selectively irradiate selected ones of the structures with the laser without substantially degrading the desirable pulse properties, the system comprising:

• a means for receiving data indicating the locations on the workpiece of the structures;
• a means for moving the workpiece and the laser beam spot relative to one another such that the laser beam spot moves along the linear pattern across the structures at a motion speed less than the product of the PRF parameter and the pitch;
• a means for commencing charging of the laser approximately a desired charging time before the laser beam spot is expected to reach each structure location, wherein the desired charging time is less than the quotient of the pitch divided by the motion speed;
• a means for firing the laser when the laser beam spot reaches each structure location, whereby the laser emits a pulse having desired pulse properties;
• and
• a means for selectively blocking the laser beam propagation path depending upon whether the structure to which the laser beam is directed has been selected for irradiation.

A system for irradiating selected targets in a series of structures on or within a workpiece, the series of structures being arranged on the workpiece in a linear pattern having an approximately equal pitch between adjacent structures, the system comprising:

• a laser characterized by a PRF parameter that specifies a PRF at which pulses produced by the laser have desirable pulse properties;
• a laser beam propagation path from the laser to the workpiece, the path having an axis that intersects the workpiece at a laser beam spot;
• one or more motion stages that move the workpiece and the laser beam spot relative to one another, said one or more motion stages being able to achieve a maximum acceptable speed of the laser beam spot relative to the workpiece during irradiation, the maximum acceptable speed being less than the product of the PRF and the pitch;
• an optical shutter disposed in the laser beam propagation path, the optical shutter capable of selectively blocking the laser pulse from reaching the workpiece or passing the laser pulse to the workpiece;
• and
• a controller configured to receive data indicating locations on the workpiece of the structures;
• to cause charging of the laser to commence approximately a desired charging time before the laser beam spot is expected to reach each structure location, to cause the laser to fire when the laser beam spot reaches each structure location, whereby the laser emits a pulse having desired pulse properties;
• and to selectively cause the optical shutter to block or to pass the laser beam propagation path depending upon whether the structure to which the laser beam is directed has been selected for irradiation, whereby the system can move the laser beam spot across the structures along the linear pattern at a speed up to the maximum acceptable speed of said one or more motion stages without substantially degrading the desirable pulse properties.