Laser processing systems and methods for beam dithering and skiving

Abstract

A laser processing system includes a first positioning system for imparting first relative movement of a beam path along a beam trajectory with respect to a workpiece, a processor for determining a second relative movement of the beam path along a plurality of dither rows, a second positioning system for imparting the second relative movement, and a laser source for emitting laser beam pulses. The system may compensate for changes in processing velocity to maintain dither rows at a predetermined angle. For example, the dither rows may remain perpendicular to the beam trajectory regardless of processing velocity. The processing velocity may be adjusted to process for an integral number of dither rows to complete a trench. A number of dither points in each row may be selected based on a width of the trench. Fluence may be normalized by adjusting for changes to processing velocity and trench width.

1 - 8 . (canceled) 
     
     
         9 . A laser processing system comprising:
 a first positioning system for imparting first relative movement of a laser beam path along a beam trajectory with respect to a surface of the workpiece;   one or more processors for determining a second relative movement of the laser beam path along a plurality of dither rows, the second relative movement superimposed on the first relative movement at a predetermined angle with respect to the beam trajectory, the determination of the second relative movement including compensation for changes in a processing velocity along the beam trajectory so as to maintain the predetermined angle for each of the plurality of dither rows;   a second positioning system for imparting the second relative movement of the laser beam path; and   a laser source for emitting a plurality of laser beam pulses to the workpiece at a plurality of spot locations along the plurality of dither rows to widen a trench in a direction defined by the predetermined angle.   
     
     
         10 . The system of  claim 9 , wherein the predetermined angle is substantially perpendicular to the beam trajectory. 
     
     
         11 . The system of  claim 9 , wherein the one or more processors selectively adjust the processing velocity so as to process an integral number of dither rows to complete the trench. 
     
     
         12 . The system of  claim 9 , wherein the first positioning system comprises one or more beam positioners selected from a group comprising a galvanometer-driven mirror and a fast steering mirror. 
     
     
         13 . The system of  claim 9 , wherein the second positioning system comprises one or more beam positioners selected from the group comprising an acousto-optic deflector and an electro-optic deflector. 
     
     
         14 . The system of  claim 9 , wherein the one or more processors are further configured to select a number of dither points to include in each of the plurality of dither rows, wherein the selection reduces an amount of time used to process each dither row, and wherein the number of dither points in each dither row is based on the width of the trench corresponding to the respective dither row. 
     
     
         15 . The system of  claim 9 , wherein the one or more processors are further configured to adjust a power of the laser source to maintain a constant fluence at a center of the trench, wherein adjusting the power accounts for changes to the processing velocity, and wherein adjusting the power further accounts for changes to the width of the trench. 
     
     
         16 . The system of  claim 15 , wherein the one or more processors are further configured to adjust the power as a function of dither point position with respect to an inside radius and an outside radius of an arc segment. 
     
     
         17 . A method for dithering a laser beam to create a trench in a workpiece, the method comprising:
 imparting, using a first positioning system, first relative movement of a laser beam path along a beam trajectory defining a length of the trench with respect to a surface of the workpiece;   imparting, using a second positioning system, a second relative movement of the laser beam path along a plurality of dither rows, the second relative movement superimposed on the first relative movement to widen the trench, wherein a width of the trench is variable;   selecting a number of dither points to include in each of the plurality of dither rows, wherein the selection reduces an amount of time used to process each dither row, and wherein the number of dither points in each dither row is based on the width of the trench corresponding to the respective dither row; and   emitting a plurality of laser beam pulses to the workpiece at a plurality of spot locations corresponding to the dither points in each of the plurality of dither rows.   
     
     
         18 . The method of  claim 17 , wherein selecting the number of dither points comprises:
 determining an effective spot size comprising a width of an undithered trench at a desired depth for a target material of the workpiece;   selecting a bite size ratio comprising a maximum deflection per laser spot; and   for one or more dither rows corresponding to a selected width of the trench, calculating the number of dither points as a function of the selected width, the effective spot size, and the bite size ratio.   
     
     
         19 . The method of  claim 18 , wherein calculating the number of dither points comprises calculating:
   Nd>=1+ceil((Width−Deff)/(Deff*BiteSizeRatio)),
   wherein Nd is the number of dither points, ceil is a ceiling function that rounds to a next higher integer, Width is the selected width of the trench, Deff is the determined effective spot size, and BiteSizeRatio is the selected bite size ratio.   
     
     
         20 . The method of  claim 17 , further comprising:
 adjusting a power of the laser beam to maintain a constant fluence at a center of the trench,   wherein adjusting the power accounts for changes to a velocity of the laser beam along the beam trajectory, and   wherein adjusting the power further accounts for changes to the width of the trench.   
     
     
         21 . The method of  claim 17 , wherein the fluence at the center of the trench is a function of a dosage applied to the workpiece within a grid defined by the plurality of dither rows, wherein the dosage equals the power divided by the velocity, wherein an effective width of each dither row equals the number of points in the dither row multiplied by a distance between the number of points in the dither row, and wherein the fluence of each dither row equals the dosage divided by the effective width of the respective dither row. 
     
     
         22 . The method of  claim 21 , wherein the trench includes an arc segment wherein the velocity of the laser beam with respect to an inside radius of the arc segment is less than the velocity of the laser beam with respect to an outside radius of the arc segment, the method further comprising:
 further adjusting the power of the laser beam as a function of dither point position with respect to the inside radius and the outside radius of the arc segment.   
     
     
         23 . The method of  claim 22 , wherein further adjusting the power comprises:
 reducing the power along the inside radius of the arc segment to account for reduced velocity; and   increasing the power along the outside radius of the arc segment to account for increased velocity.   
     
     
         24 . A method for laser processing a two-dimensional skive area on a workpiece using a laser direct ablation system, the method comprising:
 generating a grid of laser spot locations within the skive area, wherein spacing between the laser spot locations within the grid is based at least in part on a laser spot size and a desired overlap of adjacent laser spots;   dividing the grid into a plurality of strips corresponding to respective passes of a laser beam path along a beam trajectory, wherein each strip comprises a plurality of dither rows along a dither direction with respect to the beam trajectory;   imparting, using a first positioning system, first relative movement of the laser beam path successively through the plurality of strips along the beam trajectory;   imparting, using a second positioning system, second relative movement of the laser beam path along the dither direction for each dither row, wherein the second relative movement is superimposed on the first relative movement; and   emitting a plurality of laser beam pulses to the workpiece along the laser beam path to the laser spot locations within the skive area.   
     
     
         25 . The method of  claim 24 , further comprising:
 filtering data for each of the dither rows to slope laser spot intensity profiles along the sides of adjacent strips of the grid to shape overlap between the passes of the laser beam such that depth variation is controlled within the skive area, wherein the laser spot intensity for each of the plurality of laser beam pulses is selected based on the filtered data.   
     
     
         26 . The method of  claim 25 , wherein the data includes a set of amplitude points per dither row. 
     
     
         27 . The method of  claim 25 , further comprising:
 further filtering the data to slope the laser spot intensity profiles at one or more ends of the respective strips.   
     
     
         28 . The method of  claim 27 , wherein the first positioning system comprises one or more beam positioners selected from a group comprising a galvanometer-driven mirror and a fast steering mirror. 
     
     
         29 . The method of  claim 27 , wherein the second positioning system comprises one or more beam positioners selected from the group comprising an acousto-optic deflector and an electro-optic deflector. 
     
     
         30 . The method of  claim 29 , further comprising:
 controlling the acousto-optic deflector to adjust an amplitude of each of the laser beam pulses according to laser spot intensity profiles.   
     
     
         31 . The method of  claim 24 , further comprising:
 adjusting a velocity of the beam trajectory such that each strip in the grid includes an integral number of dither rows.   
     
     
         32 . The method of  claim 24 , wherein on-axis spacing between laser spot locations in a direction of the beam trajectory is based at least in part on processing velocity and dithering parameters. 
     
     
         33 . The method of  claim 24 , further comprising:
 reversing the dither direction as the laser beam path moves from a first strip of the grid to a second strip of the grid.   
     
     
         34 . The method of  claim 24 , further comprising:
 changing a direction of the beam trajectory between processing successive strips of the grid; and   selecting the dither direction based on the direction of the beam trajectory.