Machine Vision Applications
Cae Study No. 5
Bottles and Labels
• 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
• Avoiding danger
– 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
• Parallel & vertical sides
• Radius of curvature of
• Neck prfile and diameter
• Mouth diameter
• Rim thickness
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
• Also works well for
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.