Rainbow holograms are a very popular type of holograms which can be viewed in white light. The rainbow holograms are very practical holograms displaying three-dimensional images because the images are reconstructed by white light. It is also known as Benton hologram, named after its inventor, Dr. Stephen A. Benton of MIT. The Benton hologram or the rainbow hologram is a transfer transmission holograms. It is essentially a hologram of a hologram. Here the first-generation hologram , that is the "master" hologram is masked with a narrow slit. The rainbow hologram distributes wavelengths of white light in different directions. This leads the viewer to see the image by light of only one wavelength and the actual wavelength is determined by the viewpoint. Depending on the viewing angle, the color of the hologram changes and hence the term "rainbow". A popular example of the use of rainbow hologram is in visa cards.