Abstract: A method for establishing and reading secret information using holographic interference pattern techniques. A holographic plate is placed in a holder and exposed with a laser light reflected from an object and a reference laser light to create a hologram. The exposed hologram is removed and a second holographic plate is inserted into the holder. The object, which may be a matrix, is selectively deformed to provide letters or numbers in accordance with the secret information to be established. The second holographic plate is then exposed with a light reflected from the deformed object and with the reference laser light to create a second hologram. The information contained on each hologram, when viewed individually, appears to be substantially identical. However, when the two holograms are later combined and illuminated, the secret information in the form of a holographic interference pattern will be observed in the hologram.

Abstract: A document such as an ID-card is provided with check markings comprising a material based upon rare earth metals and having the property that when excited by IR radiation it emits visible light. When checking the document, the document is irradiated with pulsed IR radiation, the occurrence of corresponding visible light pulses originating from said material being detected. The visible light pulses have well defined rise and decay times dictated by the check material used, which fact is used to check that output pulses from the detector are the correct ones for indicating the genuiness of the document.

Abstract: A method of and an apparatus for reading a manually fed data carrier are disclosed. The data carrier has at least one line of coded positions and is fed manually past reader means including at least one pair of reader means which viewed in the direction of motion of the data carrier are spaced apart by a distance less than the extension of a coded position in said direction. Said pair of reader means detects the direction of motion of the data carrier each time a transition between two successive positions passes said reader means. If the detected direction is opposite to the given read-out direction, the count of a counter is increased with one unit. If the detected direction corresponds with the given direction, the count of the counter is reduced with one unit provided that the count exceeds zero. If the direction corresponds with the given direction and the count is zero, read-out result is fed out.

Abstract: An identity card contains a radioactive substance and information on the intensity of the radiation of said substance. When the card is used, for example in a banking transaction, the current intensity is measured and compared with the information on the intensity given on the card. If the current intensity and the given intensity agree, the card is to be considered genuine.