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Optically readable card carrying digital data, and an access control system using said card

  • US 4,605,846 A
  • Filed: 03/07/1984
  • Issued: 08/12/1986
  • Est. Priority Date: 03/11/1983
  • Status: Expired due to Fees
First Claim
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1. An optically readable card for carrying a digital data message, comprising:

  • at least one succession of marks and spaces having respective different optical properties, the marks and spaces being detectable by an opto-electronic pick-up means, the pick-up means including a source of light radiation and a detector therefor;

    wherein the succession of marks includes genuine data-significant marks having a first optical spectral response to light emitted by the source of light radiation, the genuine data-significant marks being interspersed with dummy or decoy marks having the same appearance visually and photographically as the genuine data-significant marks, the dummy or decoy marks responding to light emitted by the source of light radiation with a second optical spectral response, the second response being analogous to the response of the spaces to the light radiation.

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