1. A method for detecting foam on a liquid surface in a vessel, the method comprising: providing a vessel having an upper opening surrounded by a border and containing an amount of a liquid; taking at least one image from a region suspected to contain foam in the vessel by using an image sensing device that provides corresponding image data, wherein the at least one image is taken from the top of the vessel through the open upper opening onto the liquid surface and wherein the border of the vessel is included in the image; performing an automatic evaluation of the image on the basis of the image data by a data processing system using an image evaluation program, wherein the image evaluation program identifies foam areas and non-foam areas in the at least one image and provides information about the presence or absence of foam areas in the at least one image as a result of the image evaluation; and detecting the border of the vessel and the center of the opening by application of image evaluation algorithms.