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					Machine Vision Applications

       Cae Study No. 5

      Bottles and Labels
                   The Product
•   Square, clear, glass bottles
•   Transported on a continuously moving conveyor
•   Bottles are filled with a clear yellow fluid.
•   Orientated so that the labels face the camera.
•   Small multi-coloured labels
    – Block colours
    – Blending of colours
•       Labels have three highly saturated colours:
    yellow, mauve and orange.
  Lighting, Viewing and Camera
• Silhouette and fill level
   – Back-lighting (Methods 17 & 18)
   – Dark-field lighting (Methods 20 & 21)
• Labels (diffuse front lighting, Method 11)
   – Turbo-charged LED arrays
      • Benefits
      • Avoiding danger
• Camera
   – Line-scan camera
      • Must measure conveyor belt speed accurately
   – Array camera with fast shutter
• Sensing bottle is in place
   – Proximity sensor can spoil the image
 Radius of Curvature
(Shoulder of a bottle)
       Fitting a Circle to 3 Points

D = 2*(Ay*Cx + By*Ax -By*Cx - Ay*Bx - Cy*Ax + Cy*Bx);

Px = (By*Ax^2 - Cy*Ax^2 - Ay*By^2 + Ay*Cy^2 ...
    + Cy*Bx^2 + By*Ay^2 + Ay*Cx^2 - By*Cy^2 ...
    - By*Cx^2 - Ay*Bx^2 + Cy*By^2 - Cy*Ay^2 )/ D;

Py = (Cx*Ax^2 + Cx*Ay^2 + Ax*Bx^2 - Cx*Bx^2 ...
    + Ax*By^2 - Cx*By^2 - Bx*Ax^2 - Bx*Ay^2 ...
    - Ax*Cx^2 + Bx*Cx^2 - Ax*Cy^2 + Bx*Cy^2 ) / D;

R = sqrt((Ax - Px)^2 + (Ay - Py)^2);
Fitting a Polynomial Curve
(to the shoulder of a bottle)
     Bottle Shape Measurements

• Symmettry
• Parallel & vertical sides
• Radius of curvature of
  shoulder
• Neck prfile and diameter
• Height
• Mouth diameter
• Rim thickness
            Viewing Stress

  Use two crossed
polarisers (Method 52)


                         QuickTime™ and a TIF F (Uncompressed) decompressor are needed to see t hi s pi cture.
        Embossing and Cracks
• Back Illumination
  (Method 18)
• Also works well for
  “birdswings”
                        QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.

				
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posted:12/16/2011
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