We have been testing a so-called "seeing cash register" in the cafeteria Studierendenhaus, cafeteria Berliner Tor and cafeteria Harburg. You place your plate under the camera, the cash register scans and recognises your food (including drink) and shows you the price on the display. You pay by EC or credit card. This is quite quick.
You can use this self-checkout counter for all dishes except those from the salad, vegetable or pasta bar.
And you can be sure: The use of the "Seeing cash register" is data protection compliant. No data is stored.