Small faults in the manufacture of Pharmaceutical cartons can have dangerous consequences. A Braille dot which is too small or not of sufficient height can cause confusing or incorrect medicine and dosage information.
To eliminate faults packaging manufacturers must implement thorough quality control procedures. As the recommended Braille font dot height of 0.2mm is indiscernable to untrained fingers mechanical inspection systems are used to assess the tactile quality of the dots. This is done by measuring the dot height with a fine micrometer. However this method is time consuming and mechanical contact with the micrometer can damage the Braille dots, leading to inaccurate measurements. There are alternative solutions involving Braille reading quality control personnel or manual inspection using test films. But these methods cannot be adequately documented and often prove to be too slow in a production environment.
in-situ GmbH, a Munich based specialist for vision and sensor systems, has developed the DotScanoptical inspection system to reliably recognise Braille dots and evaluate their tactile quality. Testing is non-contact using an industrial camera based vision system. The camera captures 2D images and the height information is then calculated using a shape-from-shading algorithm. To obtain accurate results the Braille dots are illuminated from four directions to ensure the 3D shape of a raised dot can be accurately scanned. As there is no contact with the board surface the physical integrity of the dots is not affected during testing.
The production workflow is simple: After the Pharmaceutical carton is embossed with Braille and die-cut, the box is assembled and glued. Braille inspection is performed by sampling. Each sample is folded flat and positioned on a drawer in the unit. The camera scans at a resolution of 1.3 megapixels and the system captures 25 frames per second at full resolution, which allows for very fast inspection.
The system checks not only if the raised dots have the correct shape and Marburg Medium Braille font proportions, but also if the information given in the Braille meets the specifications. So the system gives visually impaired patients the peace of mind that they can safely identify their medication and confidence that the correct dosage is taken.
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