From apples to oranges, from avocado to zucchini — the fruit and vegetable departments of large supermarkets offer an overwhelming choice of fresh products. Consumers benefit from this broad selection, as most fruits are now available year round. Another advantage of self-service supermarkets is that consumers can check and choose the fruit and vegetables themselves. Difficulties start, however, when you reach the self-service scale — how to find the right button among dozens of different types of produce. The vast choice can quickly turn into an ordeal when it takes ages to locate the papaya or peppers button. But there might finally be a solution. A compact, integrated USB camera helps self-service scales automatically recognize individual products.
The analysis process starts automatically as soon as a weight is placed on the scale. The scale’s operating panel displays: “Recognition in progress.” First, the scale checks whether the image captured by the camera changes; for example, because the user’s hand was in the field of view. As soon as the image remains still, the system starts analyzing. This takes about a second. Then four possible matches are presented for selection in large, colored fields.
The consumer can now choose the desired type, and the scale prints the label. Due to various disturbance factors, a fully automatic system cannot be implemented, as highly fluctuating light conditions or covered areas in the image affect the analysis. If conditions are good, however, the camera system achieves a high accuracy even if the weighed products are in plastic bags.
When selecting the camera, the size, the USB 2.0 connection and the color quality were at the top of the requirements list. Walter Grom, the engineer in charge of the project, explains: “An important factor in our decision was of course an excellent image quality, which the uEye provides.” The engineers from METTLER TOLEDO opted for the UI-1226LE-C, a model from the USB uEye LE camera series from IDS. The lightsensitive CMOS color sensor of the board-level camera captures up to 87 frames per second at the full 752 x 480 pixel resolution. Another major aspect is that the uEye’s automatic white balance works reliably even against the blue background of the scale.
The second essential factor was the camera’s software integration. Depending on the customer’s specifications, METTLER TOLEDO installs either a Linux-based or a Windows-based operating system on the scale’s integrated PC. “Another reason for choosing IDS was that they also offer a Linux driver that comes right with the camera,” adds Grom. The fact that the machine vision specialist IDS is located not far away from METTLER TOLEDO was a further advantage: During the development stage, the engineer visited IDS a couple of times to inspect the quality of production on-site and discuss various customizations of the camera hardware.
In Germany, the successful combination of precision scale and industrial camera is already in use in over 300 stores of a major food retailing chain. Other retailers in Germany and Europe have also started using the system and are planning to expand usage companywide, as well.
This article was written by Daniel Seiler, Technical Communication Specialist, IDS Imaging Development Systems GmbH (Obersulm, Germany). For more information, contact Mr. Seiler at
