Abstract: The invention relates to a forge-proof document comprising a security feature in the form of a perforation pattern which displays gray tones when viewed against a bright background, wherein the document is manufactured from a material which transmits light to a limited extent, at least some of the perforations forming part of the perforation pattern extend over only a part of the thickness of the document at the position of the perforation, and the thickness of the remaining part of the document at the position of the perforation is modulated in accordance with the image to be displayed. The invention also relates to such a document comprising a security feature in the form of a perforation pattern which displays gray tones when viewed against a bright background, wherein at least some of the perforations forming part of the perforation pattern extend at an angle differing from 90° relative to the main plane of the document.

Abstract: A document to be protected against forgery. The document includes a security feature in the form of a perforation pattern, wherein the perforation pattern extends over a surface of the document and represents an image comprising brightness tones. The perforation pattern is herein formed such that, for instance when the thus treated document is held up to the light or placed on a light box, an image becomes visible at the location of the perforation pattern. It will be apparent that arrangement of such an image representing brightness tones requires extremely advanced technologies. Such technologies are not easily accessible to potential forgers. Hence, documents provided with such a perforation pattern are very difficult to forge. The perforation pattern is preferably applied by a laser.

Abstract: The invention relates to a document to be protected against forgery comprising a security feature in the form of a perforation pattern, wherein the perforation pattern extends over a surface of the document and represents an image comprising brightness tones. The perforation pattern is herein formed such that, for instance when the thus treated document is held up to the light or placed on a light box, an image becomes visible at the location of the perforation pattern. It will be apparent that arrangement of such an image representing brightness tones requires extremely advanced technologies. Such technologies are not easily accessible to potential forgers, so that documents thus provided with such a perforation pattern are very difficult to forge. The perforation pattern is preferably applied by means of laser light.

Abstract: The invention relates to a fraud-proof document comprising a carrier and at least one marking arranged on the carrier, wherein at least a part of the surface of the marking or along at least a part of the periphery of the marking a weakening pattern is arranged in the carrier which, when detached, results in a permanent an easily visible distortion of the pattern. When removing the glued-on passport photo or foil a forger will irrevocably distort the weakening pattern, this such that the regularity is permanently and visibly disturbed so that it is easy to ascertain that the document in question has been subjected to an attempted fraud.

Abstract: For transport on rough terrain as well as on the floor of a hospital, a mobile X-ray diagnostic apparatus has exchangeable wheels which are adapted to the relevant surface. When the apparatus is transported on an uneven and soft surface, wide wheels having a large diameter can be used, while in hospital conditions narrow wheels having a small diameter can be used. In order to render the X-ray diagnostic apparatus suitable for transport on different surfaces in a simple operation, the wheels can be readily exchanged without using tools; a towbar is also provided.