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Holograms for security markings

  • US 5,623,347 A
  • Filed: 06/02/1994
  • Issued: 04/22/1997
  • Est. Priority Date: 06/21/1991
  • Status: Expired due to Fees
First Claim
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1. An apparatus for reading light reflected from a hologram and a hologram for security markings comprising a laser transmission hologram known per se formed as a surface relief pattern embossed into an embossable material, said laser transmission hologram being formed by sequential layers of a carrier layer, an embossable thermo-plastic lacquer into which the hologram is formed, and a layer for adhesively bonding the hologram to a substrate, a thin metallic layer coated onto said thermo-plastic lacquer whereby the laser transmission characteristics of the hologram are transformed into laser reflection characteristics capable of reflecting light from a laser, said apparatus comprising a laser light source for projecting a laser light beam onto the hologram to be read, and means located on the same side as the laser light source for recognising a real image of the hologram, said hologram having an information image and a triggering image, said information image being a series of light reflective portions and light non-reflective portions, together forming a binary code, said triggering image being formed to indicate the presence of an information image area and so as to reflect the laser light beam at a different angle to that reflected by said information image, and a light detector provided for receiving said information image and a further light detector provided for receiving said triggering image, whereby said light detector is activated only when triggered by a signal from said further light detector indicating the presence of a light reflective portion.

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