Machine vision validates disposable beverage packaging
PC-based camera system supports German vending-machine deposit system with high-speed image processing.
By Ulli Lansche
Ulli Lansche is technical editor, Matrix Vision, Oppenweiler, Germany;
www.matrix-vision.de.
In 1991, with an order to recycle packaging waste by then environment minister Klaus Töpfer, the foundation of today's bottle and can deposit system in Germany was laid. Since May 1, 2006, cans and other disposable beverage packaging can be received throughout Germany in one deposit system. After some dispute in the courts and interim isolated applications, the Deutsche Pfandsystem (German deposit system, DPG) was founded, which was tasked to create a consistent Germanywide deposit system.
Until now, only a barcode has been used to identify disposable beverage packaging. With reverse vending machines and industrial image processing, it became possible to classify packaging without manpower. The new packaging order, however, binds store owners with a sales area as small as 200 m² to accept all beverage cans and bottles, even if they weren't purchased in their store. Therefore, a new deposit logo was introduced by the DPG so that store owners can differentiate between German and foreign packaging. This logo ensures that businesses are secure from deposit fraud.
New security procedure
First, an ultraviolet procedure was tested to make the deposit logo forgery-proof. But after this procedure was outwitted in November 2005, the DPG elected to use an infrared (IR) procedure. With the support of Matrix Vision (Oppenweiller, Germany) and some other image-processing companies, the IR procedure was defined, and a tight timetable was worked out to redevelop a reader for the deposit system. However, the manufacturer of the reverse vending machines could not develop a reader for its machines in the time frame.
So, Matrix Vision developed a modular system, which is based on its mvBlueLYNX technology. The Security Mark Reader (mvSMR) smart camera unit features two essential advantages: the camera can process the acquired images directly, and it can control the different exposures of the lights to recognize the deposit logo. A retrofitting with the mvSMR and a firmware update was sufficient to update the reverse vending machines. Since the reverse vending machine only receives the positive or negative result from the camera unit, no reverse vending machine had to be redeveloped.
The camera unit features a 400-MHz processor and a sensor with 1280 x 1024-pixel resolution. This sensor is necessary to support the both-way inlaid direction of the bottles and cans, because the camera unit has to cover a larger field of vision. The mvSMR supports diameters up to 120 mm and a maximum rotation speed of 25 m/min. The algorithm can identify the deposit logo even on slightly deformed cans or bottles.
Manufacturers can adjust and refit the mvSMR to the requirements of their counting centers and reverse vending machines. Future development of the deposit system with additional security checks can be done with online updates of the firmware. For this reason the mvSMR is prepared for all possible new DPG guidelines.