Abstract: A method for determining one or more dimensions of one or more structures is disclosed. The method comprises focusing illumination light on a focal plane of a lens system so that the lens system forms a collimated illumination light beam that is incident on the sample surface. The method also comprises, using said lens system or, respectively, a further lens system, collecting reflected or, respectively, transmitted illumination light reflected from or transmitted through the sample surface. Further, the method comprises capturing an image of said focal plane or, respectively, further focal plane, said image representing a distribution in said focal plane or further focal plane of radiant power of the reflected or transmitted illumination light. A further step of the method comprises, based on the captured image, determining the one or more dimensions of the structures on the sample surface.