The term “hologram” is incorrectly used to refer to so-called surface embossing which uses light diffraction to show an image and angle-dependent colors. In addition to the visual properties of the image, the metallized aluminum structures serve as anti-copy protection features. They belong to the group of “optically variable devices” (OVDs). This hinders reproduction by means of scanners or color copiers. See also Hologram threads and Hologram stripes.