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Spectral differential coded card

  • US 3,919,447 A
  • Filed: 03/20/1974
  • Issued: 11/11/1975
  • Est. Priority Date: 12/28/1971
  • Status: Expired due to Term
First Claim
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1. A CARD OR THE LIKE SUITABLE FOR USE IN PERSONAL AND ITEM IDENTIFICATION COMPRISING:

  • A FIRST FILM HAVING AN OPTICAL BANDPASS TRANSMISSION FREE FROM SHARP BAND ABSORPTION CHARACTERISTICS IN A PREDETERMINED NON-VISIBLE LIGHT WAVE REGION;

    AND A SELECTIVELY APERTURED SECOND FILM LAMINATED UPON THE FIRST FILM AND HAVING A SUBSTANTIALLY SIMILAR SPECTRAL RESPONSE AS THAT OF THE FIRST FILM WITHIN THE PREDETERMINED NON-VISIBLE LIGHT WAVE REGION OF THE FIRST FILM BANDPASS BUT FOR A SHARP BAND ABSORPTION CHARACTERISTIC AT A NEAR SINGLE FREQUENCY, THE LAMINATE INCLUDING THE APERTURED PORTIONS THEREOF FURTHER EXHIBITING A SUBSTANTIALLY UNIFORM TRANSMISSIVITY AND SURFACE REFLECTANCE IN THE VISIBLE LIGHT WAVE REGION.

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