Image: Visa Dove Hologram Rainbow
Description: A white light "Rainbow" transmission hologram. There is no 3D illusion when the hologram is rotated through 90°, but there is the advantage that the image can be viewed without the need for a coherent light source such as a laser. The "backlighting" is provided by printing / micro embossing the hologram on a reflective film. Photographed using extension tubes. The full range of rainbow colours seen in a single view was obtained by placing the small illuminating light source (a halogen desk lamp) very close (a few centimeters) to the hologram, so that the angle of incidence of light varied significantly over the surface of the dove. The interference pattern needed for the dove hologram must be recorded at a resolution of approximately 1,400 fringes per mm / 35,000 fringes per inch, making holograms difficult to forge.
As an additional security measure (one of very many), more than one (subtly different) version of the hologram is in use. Which one is used where? Ahhh. Now that's a secret...
Author: Dominic Alves
Usage Terms: Creative Commons Attribution-Share Alike 3.0
License: CC-BY-SA-3.0
License Link: http://creativecommons.org/licenses/by-sa/3.0/
Attribution Required?: Yes
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