Label quality inspection (content, front–back label match)

Need

The opaque plastic bottle is glossy and curved; direct light reflects on the label. Front and back labels are applied by separate machines, so a code mismatch cannot be caught from one face. The bottle may rotate a few degrees on the belt and the label edge is close to the body colour.

Solution approach

Two opposed area-scan cameras capture the front and back labels on the same trigger; 45° bar lights steer reflections away from the cameras and sharpen the label edge. Label position is measured relative to the bottle shoulder, skew is the angle of the edge line to the body axis; the product code on each face is read and front–back compared.

Process steps

1. 01

   Infeed

   Bottles arrive at constant speed with their label faces towards the cameras.

2. 02

   Trigger

   The photo-sensor sees the bottle and triggers both cameras and the bar lights.

3. 03

   Acquire

   Front and back labels are captured together under 45° bar lighting.

4. 04

   Match

   Label position and skew are measured and the product codes on both faces are compared.

5. 05

   Decide

   Position and skew tolerance and the front–back match are evaluated together.