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^ Cy*Bx^2 + By*Ay^2 + Ay*Cx^2 - By*Cy^ 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^ Ax*By^2 - Cx*By^2 - Bx*Ax^2 - Bx*Ay^ 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)

Embossing and Cracks Back Illumination (Method 18) Also works well for “birdswings”