A device for determining the properties of surfaces having at least one first radiation means having a least one radiation source which emits radiation, at least one radiation detector means which captures at least a portion of the radiation emmitting from the at least one radiation source and then diffused and/or reflected off a measurement surface and emits at least one measurement signal which is characteristic of the reflected and/or diffused radiation, an optical divider means having a specified thickness positioned in the optical path between the radiation means and the radiation detector means. The optical divider means includes at least one aperture extending at least in sections at a specified angle different from 0 degrees to the thickness of said optical divider means.