Flatness monitor

Abstract

A system method of monitoring flatness of a material. A beam of coherent light is projected on to a surface of the material to provide a line on the surface. An image of the line on the surface is obtained, and the image is used to determine a deviation of the line from a predetermined configuration. The deviation corresponds to an irregular pattern or unevenness of the material.

1 . A method of measuring the conformity of a surface of a material to a known topography comprising the steps of projecting a beam of coherent radiation on to said surface of said material to provide a line on said surface, obtaining an image of said line, and determining a deviation of said line from a predetermined configuration to compute a degree of conformity.  
   
   
       2 . A method according to  claim 1  wherein said method measures the flatness of said surface, and said degree of conformity is a degree of flatness.  
   
   
       3 . A method according to  claim 1  wherein said line is scanned along said surface and a plurality of images are obtained at predetermined positions of said line.  
   
   
       4 . A method according to  claim 3  wherein said beam is directed towards a mirror and reflected by said mirror onto said surface, and wherein rotation of said mirror scans said line along said surface.  
   
   
       5 . A method according to  claim 2  wherein said material is steel and said degree of flatness is measured in I Units.  
   
   
       6 . A method according to  claim 1  wherein prior to projecting said beam, a background image of said material is obtained, said-background image being subtracted from said image to remove ambient light noise from said image.  
   
   
       7 . A method according to  claim 1  further comprising the step of applying a subpixel interpolation on said image prior to determining said deviation to determine the lateral extent of said line.  
   
   
       8 . A method according to  claim 7  wherein said subpixel interpolation comprises subdividing pixels of said image based on the intensities of neighbouring pixels and determining an average intensity of said pixels based on said neighbouring pixels.  
   
   
       9 . A method according to  claim 1  wherein deviation of said image is evaluated on the basis of the number of pixels traversed by said line.  
   
   
       10 . A method according to  claim 9  wherein the number of pixels traversed by said line is measured from a centroid of said line.  
   
   
       11 . A method according to  claim 10  wherein said centroid is measured by first locating a region of interest of said image containing said centroid.  
   
   
       12 . A method according to  claim 9  wherein the number of pixels traversed by said line is converted to a unit of distance in one of millimetres and inches, based on a scaling factor determined by a calibration procedure executed prior to projecting said beam.  
   
   
       13 . A method according to  claim 12  wherein said unit of distance is used to determine said degree of conformity.  
   
   
       14 . A method according to  claim 13  wherein prior to determining said degree of conformity, said method further comprises a step of processing said image.  
   
   
       15 . A method according to  claim 14  wherein said processing includes one or more of applying a median filter and smoothing.  
   
   
       16 . A method according to  claim 3  further comprising the step of calculating the standard deviation of the line on each said image in said scan, wherein each said standard deviation is compared to a threshold, and if said threshold is exceeded, said image is not used in determining said degree of conformity.  
   
   
       17 . A method according to  claim 16  further comprising the step of calculating a median degree of flatness from a collection of values of the degree of flatness obtained from each image in said scan.  
   
   
       18 . A method according to  claim 1  further comprising a calibration procedure prior to projecting said beam.  
   
   
       19 . A method according to  claim 18  wherein said calibration procedure comprises the steps of inserting a block of known dimensions at an intended location of said material; projecting said beam on to said block and an underlying surface along one of said dimensions; obtaining an image of said line; determining a deviation of said image from a predetermined configuration, said deviation altered according to the extend of said one of said dimensions and being evaluated on the basis of the number of pixels traversed by said line; and calculating a scale correlating pixels of said image to a standard unit of distance using said deviation and said one of said dimensions.  
   
   
       20 . A method according to  claim 19  wherein said calibration procedure is repeated a plurality of times for a plurality of locations of said line as said line is scanned along said block.  
   
   
       21 . A method according to  claim 19  wherein the number of pixels traversed by said line is measured from a centroid of said line.  
   
   
       22 . A method according to  claim 21  wherein said centroid is measured by first locating a region of interest of said image containing said centroid.  
   
   
       23 . A method according to  claim 20  wherein said one dimension is the height of said block.  
   
   
       24 . A method according to  claim 23  wherein said scale at each location is mapped to a 2 nd  order curve, said curve indicating said scale at each location.  
   
   
       25 . A method according to  claim 20  wherein said one dimension is the width of said block.  
   
   
       26 . A method according to  claim 25  wherein said scale at each location is mapped to a 1 st  order curve.  
   
   
       27 . A system for measuring the conformity of a surface of a material to a known topography, said system comprising: 
 a coherent radiation source arranged to direct a beam of coherent radiation on to a surface of said material to provide a line on said surface;    an imaging device for obtaining an image of said line; and    a computing device having a processor to receive an input from said imaging device and process said image in order to determine a deviation of said line from a predetermined configuration.    
   
   
       28 . A system according to  claim 27  wherein said system measures the flatness of said surface.  
   
   
       29 . A system according to  claim 27  further comprising a table for supporting said material.  
   
   
       30 . A system according to  claim 27  wherein said material is steel and said computing device uses said deviation to compute a degree of flatness measured in I Units.  
   
   
       31 . A system according to  claim 27  wherein said imaging device is a camera.  
   
   
       32 . A system according to  claim 31  wherein said camera is a smart camera and said computing device and said processor are operated by said smart camera.  
   
   
       33 . A system according to  claim 27  wherein said beam is redirected towards a plurality of locations on said surface enabling said line to scan said material and said imaging device to obtain a plurality of images at predetermined positions of said line.  
   
   
       34 . A system according to  claim 33  wherein said processor receives a plurality of images from said imaging device, each of said plurality of images being processed to determine said deviation of said line in each image, said deviations used to determine a representative deviation for said material.  
   
   
       35 . A system according to  claim 33  further comprising a mirror for reflecting said beam onto said surface, said mirror being rotatable about an axis wherein rotation of said mirror scans said line along said surface.  
   
   
       36 . A system according to  claim 35  further comprising a motor for rotating said mirror, said motor controlled by said computing device.  
   
   
       37 . A system according to  claim 27  further comprising an interface connected to said computing device enabling an operator to view and interact with said image.  
   
   
       38 . A system according to  claim 27  wherein said computing device is connected to an auxiliary interface enabling interaction between said system and an auxiliary entity.  
   
   
       39 . A system according to  claim 38  wherein said auxiliary entity is a process control system.  
   
   
       40 . A system according to  claim 39  wherein said process control system further comprises an interface enabling a user to view and interact with said image and said computing device.