For this purpose, the envelope is uniformly illuminated by means of an LED light band and then images at a suitable angle with a wide-angle camera. The software can evaluate shadow areas that inevitably occur due to an incorrectly closed envelope flap.

Since the relevance of a non-sealed area depends on the type of application (pay slips must be completely closed right up to the edge, info letters on the other hand, may have tolerances), one or more sectors (ROI = Region Of Interests) on the envelope can be modelled in the software and evaluated with a sensitivity that can also be set.

Depending on the analysis result, when a threshold value is reached, the decision is made whether or not to divert out the envelope. The sealing control for envelopes can be used with the Kern 3500 (SL) and Kern 3600 inserting systems, other systems on request.