Rainbow hologram

The rainbow or Benton hologram is a type of hologram invented in 1968 by Dr. Stephen A. Benton at Polaroid Corporation (later MIT). Rainbow holograms are designed to be viewed under white light illumination, rather than laser light which was required before this. The rainbow holography recording process uses a horizontal slit to eliminate vertical parallax in the output image, greatly reducing spectral blur while preserving three-dimensionality for most observers. A viewer moving up or down in front of a rainbow hologram sees changing spectral colors rather than different vertical perspectives. Stereopsis and horizontal motion parallax, two relatively powerful cues to depth, are preserved.