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Reliable detection of medicine packages

Reliable detection of medicine packages

Applications such as the fully automated warehousing modules for pharmacy picking systems from Gollmann show that light section sensors offer a number of advantages over camera-based image processing systems are not only in the price.

Whenever the position or volume of moving or static objects needs to be determined, light section sensors offer ideal application solutions. Light section sensors operate according to the so-called light-section method, a commonly used method for optical shape recognition. With this method, a line projector projects a wide light beam onto the measurement object at a known angle. The thereby produced light plane cuts the object along the profile line, which is why such sensors are often referred to as profile section sensors.

From the perspective of a position-sensitive detector (camera), the path of this profile is bent to a greater or lesser extent as a function of the object height. With knowledge of the geometry of light beam and camera, exact 3D coordinates of the test sample can be determined according to the triangulation principle. Due to its accuracy and robustness, this process has proven itself in many areas of application. A big advantage of this type of object detection over camera-based image processing systems is the exceptionally economical price/performance ratio as well as the overall very compact and easy-to-integrate sensor solution.

The compact design of the sensors is, however, just one of the advantages, which is why Maximilian Pfau, software developer at Gollmann Kommissioniersysteme, chose the LPS 36 from Leuze Electronic. The company from Halle (Saale) is among the leading manufacturers of picking machines for pharmacies. With this patented, automated, roll-fronted system, the ‘wandering gap’ storage principle,  proven over decades, achieves a very high storage density and, compared to conventional storage methods with classic drawer systems, reduces space by up to two thirds.

Depending on the design, the compact and flexible picking systems in a pharmacy hold several thousand packages in every meter of housing length. In such a system, each package lies ready in its own storage space for direct and fast access. Even in the basic version, these systems allow for the storage and immediate availability of 100 packages in less than eight minutes as well as the retrieval of 350 packages per hour.

The stored packages can be dispensed directly at the machine or at any location in the room by means of an optional conveyor system. The benefits of this system include an increase in retail space and in time savings in inventory management. The acceptance of goods, returns, inventory, goods issue and assortment maintenance can be handled much more effectively, allowing resources to be used for other value-creating activities in the pharmacy and making more time available to consult with customers.

The light section sensors from Leuze Electronic are used in fully automated warehousing modules, which can optionally be adapted to the picking machines. With these modules, the picking machines are loaded fully automati-cally within seconds. Goods deliveries are simply emptied unsorted into a container and separated on a conveying belt. An LPS 36 light section sensor then detects the contour, position and volume of the individual medicine packages as they pass through.

“We originally wanted to use image recognition systems here,” explains Pfau. “Due to the widely varying patterns and colours of the medicine cartons, however, this did not function reliably.” In spite of the considerable effort taken to create stable lighting conditions through the use of additional lights, not all packages were fully detected depending on pattern and colour differences.

“With the height information provided by the light section sensors, reliable detection of all packages was ensured right from the start,” confirms Pfau, who, in this regard, greatly values the fact that no additional lighting is needed for the LPS 36. The sensors function exclusively with their own laser light.

Using the 3D coordinates ascertained for the medicine cartons, the handling system in the warehousing module can correctly and gently receive the packages and deposit them in the transfer bin of the picking machines. “At the same time, the volume information is used for space-saving storage in the picking machines,” adds Pfau.

For data transfer, he uses the Ethernet interface of the LPS 36, eliminating the need for a serial connection or laying of a USB cable. “Even aside from this, the Leuze Electronic sensors ideally complement our application,” confirms Pfau: “With a line length of 600mm and a measurement range of up to 800mm, we detect the entire range of package sizes, from the smallest eye ointment to the largest dressing package.”

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