×

Document with an optical diffraction safety element

  • US 4,984,824 A
  • Filed: 02/15/1989
  • Issued: 01/15/1991
  • Est. Priority Date: 03/03/1988
  • Status: Expired due to Term
First Claim
Patent Images

1. A document comprisingan embossed microscopic structure which operates through optical diffraction to serve as a security element for preventing unauthorized copying, said embossed structure including numerous surface portions,each of said surface portions having a predetermined relief structure with a spatial frequency larger than 10 lines/mm, each relief structure of each surface portion being different from that of adjoining surface portions, anda group of said surface portions having a predetermined geometric shape which carries security information and a largest dimension of less than 0.3 mm.

View all claims
  • 3 Assignments
Timeline View
Assignment View
    ×
    ×