Numerical recognition for quality control of surgical sachets

In this paper we describe an application of OCR techniques to quality control in industrial production. The purpose of the system is to verify the correct printing of numerical information in sachets with surgical material. Numerals are printed on an aluminium surface covered by a transparent plastic film, which can produce shadows or reflections in the image. The main difficulties for character recognition arise from low acquisition resolution, noise, heavy or light printing, and different printing patterns. The system must perform with an error rate lower than 0.1% and with the minimal computation time. Thus, we have decided to use well-known and simple algorithms, adding to them some refinements which take advantage of specific domain knowledge, making them more robust and reliable. The system is currently working with real production complying with the required specifications.