Laser marking

Abstract

A method for marking a polymeric surface includes directing a first laser beam on the surface to form a lightened area on the surface and directing a second laser beam upon the lightened area to form a mark darker than the lightened area.

1 - 24 . (canceled)  
   
   
       25 . An article marking system comprising: 
 a laser; and    a controller configured to generate control signals, wherein the laser is configured to form a lightened area upon a surface of an article and is also configured to form a darker mark over the lightened area in response to the control signals.    
   
   
       26 . The system of  claim 25 , wherein the laser is configured to direct a first laser beam on the surface to form the lightened area and a second laser beam upon the lightened area to form the darker mark.  
   
   
       27 . The system of  claim 26 , wherein the first laser beam has a first energy density and wherein the second laser beam has a second greater energy density.  
   
   
       28 . The system of  claim 26  including an actuator configured to move the first laser beam across the surface at a first speed and the second laser beam across the lighted area at a second slower speed in response to control signals from the controller.  
   
   
       29 . The system of  claim 26  including an actuator configured to move the surface relative to the first laser beam at a first speed and a lightened area relative to the second laser beam at a second slower speed in response to control signals from the controller.  
   
   
       30 . The system of  claim 26 , wherein the laser is configured to generate the first laser beam having a first duty cycle and the second laser beam having a second greater duty cycle in response to the control signals.  
   
   
       31 . The system of  claim 26 , wherein the laser is configured to form a second darker mark over the lighted area that is spaced from the first mark.  
   
   
       32 . The system of  claim 31 , wherein the controller is configured to generate the control signals such that the first mark and the second mark are readable by an optical scanning device.  
   
   
       33 . The system of  claim 31 , wherein the controller is configured to generate the control signals such that the first mark and the second mark are part of an identification matrix.  
   
   
       34 . The system of  claim 25 , wherein the laser is configured to vaporize at least one additive along the surface of the article in response to the control signals.  
   
   
       35 . The system of  claim 25 , wherein the laser is an Nd:YAG laser configured to produce a laser beam having a 1,064 nanometer wavelength.  
   
   
       36 . The system of  claim 25 , wherein the laser is configured to generate a laser beam having a wavelength of between about 1,000 nanometers and about 1,500 nanometers in response to the control signals.  
   
   
       37 . The system of  claim 25 , wherein the laser comprises a carbon dioxide laser and is configured to produce a laser beam having a wavelength of between about 9.2 micrometers and about 10.6 micrometers in response to the control signals.  
   
   
       38 - 47 . (canceled)