Apparatus and method for edge detection when machining workpieces

Abstract

An apparatus and method for detecting edges or for seam tracking when machining workpieces by means of a laser beam, e.g. joining or cutting. The present invention provides an apparatus for seam tracking of the process in the laser material processing, comprising at least two separate illumination elements, each emitting differently polarized light and a polarization camera.

1 - 15 . (canceled) 
     
     
         16 . An apparatus for tracking a seam during laser material processing with a laser beam, the apparatus comprising:
 a plurality of illumination elements being configured to emit polarized light to illuminate an area of interest, one or more first of the illumination elements being configured to emit first of the polarized light to illuminate the area of interest, one or more second of the illumination elements being configured to emit second of the polarized light to illuminate the area of interest, the second polarized light being differently polarized than the first polarized light;   a polarization camera being configured to capture at least one image of the area of interest illuminated with both of the first and second differently polarized light; and   an evaluation unit in operable communication with the polarization camera and being configured to evaluate the at least one image to track the seam.   
     
     
         17 . The apparatus of  claim 16 , wherein the evaluation unit comprises a device for data processing. 
     
     
         18 . The apparatus of  claim 16 , wherein to evaluate the at least one image, the evaluation unit is configured to determine contrast in the at least one image based on polarization properties of reflected light on differently inclined surfaces in the area of interest. 
     
     
         19 . The apparatus of  claim 16 , wherein the plurality of illumination elements comprises polarized light sources, or light sources having polarizing filters. 
     
     
         20 . The apparatus of  claim 16 , wherein the illumination elements are arranged in a longitudinal direction; and wherein the illumination elements are configured to emit the polarized light in a polarization direction along the longitudinal direction. 
     
     
         21 . The apparatus of  claim 16 , wherein the illumination elements are arranged in a longitudinal direction; and wherein the illumination elements are configured to emit the polarized light in a polarization direction perpendicular to the longitudinal direction. 
     
     
         22 . The apparatus of  claim 16 , wherein the one or more first of the illumination elements comprise a first pair of the illumination elements facing one another and having a same first polarization direction; and wherein the one or more second of the illumination elements comprise a second pair of the illumination elements facing one another and having a same second polarization direction different from the first polarization direction. 
     
     
         23 . The apparatus of  claim 22 , wherein the illumination elements of the first pair are arranged opposite to each other, and wherein the illumination elements of the second pair are arranged opposite to each other. 
     
     
         24 . The apparatus of  claim 16 , wherein the one or more first of the illumination elements are configured to emit the first polarized light having polarization rotated by 90° relative to the second polarized light emitted by the one or more second of the illumination elements. 
     
     
         25 . The apparatus of  claim 16 , wherein the plurality of illumination elements comprise an even multiple number of the illumination elements for the first polarized light; and an even multiple number of the illumination elements for the second polarized light. 
     
     
         26 . The apparatus of  claim 16 , wherein the polarization camera is arranged coaxially to the laser beam of the laser material processing. 
     
     
         27 . A laser material processing head comprising an apparatus according to  claim 16 . 
     
     
         28 . An apparatus for tracking a seam in laser material processing, the apparatus comprising:
 first illumination elements being configured to emit first identically polarized light and being configured to illuminate an area of interest with the first identically polarized light,   second illumination elements being configured to emit second identically polarized light and being configured to illuminate the area of interest with the second identically polarized light, the second identically polarized light being different than the first identically polarized light;   a polarization camera being configured to capture at least one image of the illuminated area of interest; and   an evaluation unit in operable communication with the polarization camera and being configured to evaluate the at least one image for the seam.   
     
     
         29 . The apparatus of  claim 28 , wherein the first illumination elements with the first identically polarized light are arranged in a first pair opposite each other; and wherein the second illumination elements with the second identically polarized light are arranged in a second pair opposite each other. 
     
     
         30 . The apparatus of  claim 28 , wherein to evaluate the at least one image, the evaluation unit is configured to determine contrast in the at least one image based on polarization properties of reflected light on differently inclined surfaces in the area of interest. 
     
     
         31 . The apparatus of  claim 28 , wherein the first and second illumination elements comprise polarized light sources, or light sources having polarizing filters. 
     
     
         32 . The apparatus of  claim 28 , wherein: the first and second illumination elements are arranged in a longitudinal direction, and the first and second illumination elements are configured to emit the first and second identically polarized light in a polarization direction along the longitudinal direction; or wherein: the first and second illumination elements are arranged in a longitudinal direction, and the first and second illumination elements are configured to emit the first and second identically polarized light in a polarization direction perpendicular to the longitudinal direction. 
     
     
         33 . The apparatus of  claim 28 , wherein the first illumination elements are configured to emit the first identically polarized light having polarization rotated by 90° relative to the second identically polarized light emitted by the second illumination elements. 
     
     
         34 . The apparatus of  claim 28 , wherein the polarization camera is arranged coaxially to the laser beam of the laser material processing. 
     
     
         35 . A laser material processing head comprising an apparatus according to  claim 28 .