The image processing experts at Bi-Ber recently conducted a study on 3D monitoring of plastic chocolate forms with a 3D laser profile sensor. It proves that a 3D camera is suitable for reliably recognising defective nicks on the underside of the forms. For example, abrasion on the forms can be monitored automatically. Because broken pieces of plastic can make their way into the chocolate paste, this monitoring also serves to maintain the strict quality requirements placed on the food industry. The plastic forms examined measured 620 x 355 x 30 mm and were in different colours – this factor is not critical in recording data and does not lead to differences in lighting. A 3D camera, type DS1100 from Cognex, was used for monitoring and employed the triangulation method: a laser beam shines vertically onto the object while the camera monitors it at a 25° angle. In order to create a 3D image, then the object must be moved relative to the camera. The camera is attached to a PC. It can be connected directly via a speed sensor in order to synchronise the images with the movement. Nicks in the forms are usually larger than one square centimetre. The narrowest ridge width on a form is 3 mm.  With a resolution of up to 0.17 mm in the direction of motion, this corresponds to more than 15 pixels, which is completely sufficient for reliable evaluation. The DS1100 camera model used captures a width of around 120 mm, so several devices placed side by side are currently required to cover the entire form width. However, an additional sensor from the same series that will measure at least 300 mm will be available within the next few months.

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