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SECURITY DEVICE

  • US 20100230615A1
  • Filed: 03/11/2009
  • Published: 09/16/2010
  • Est. Priority Date: 02/27/2009
  • Status: Active Grant
First Claim
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1. A device comprising:

  • luminescent means, which when stimulated, produces luminescent radiation of first and second wavelengths, the second wavelength being different to said first wavelength, said luminescent means including a luminescent material; and

    an optically variable structure for controlling emission of the luminescent radiation of at least one of said first and second wavelengths from said device, the device being arranged to permit, from within an area of said optically variable structure, emission of luminescent radiation of said first wavelength from said device at a first angle of emission, and to permit, from said area, emission of luminescent radiation of said second wavelength from said device at one or both of (1) said first angle of emission and (2) a second angle of emission, different to said first angle of emission, and said optically variable structure is arranged to cause, from said area, the emissivity of said device for luminescent radiation of said first or second wavelengths to change relative to the emissivity of the device for luminescent radiation of the other of the first or second wavelengths with a change in emission angle of luminescent radiation from said device from said first emission angle to said second emission angle.

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