Machine readable data carrier esp. entrance pass - with invisible markings which are difficult to counterfeit and needing infra red light to interpret

摘要

A machine-readable data carrier, such as an entrance pass used to gain access to restricted-entry buildings, has at least two sets of markings, at least one of which is not detectable by the human senses. The two sets of markings may be in the same or different areas of the carrier. Pref. at least one set of markings can be detected by means of infra red radiation. The fact that one set of markings cannot be seen or felt means that it would be very difficult to produce a counterfeit pass without keeping the authentic pass for a long period to time, during which its absence would be noticed by the owner.