Key concept: what do the zoneplates of Benton holograms look like, as opposed to those conventional (off axis) holograms? A Benton white light hologram is comp

Key concept: what do the zoneplates of Benton holograms look like, as opposed to those conventional (off axis) holograms? A Benton white light hologram is composed of narrow horizontal slices of zoneplates, one for each reconstructed point. Something like this: http://amasci.com/graphics/swatch.gif http://amasci.com/graphics/swatch.gif My insight was this: if the above zoneplate-slice is squared off and increased in spatial frequency, it still reconstructs the same 3D image point. If we drew the nested fringes of that above zoneplate by scratching with a needle, it still produces the same glowing pixel floating in space. In other words, white-light holograms are frequency-independent, just as always claimed. Yes, if we change the frequency of the above zoneplate pattern, the rainbow coloration will shift, and may even appear white. Yet the reconstructed 3D image remains unaltered. The 3D image data is not contained in the spacing of the interference fringes. That's another way to say that the hologram still functions even if the spacing between fringes is randomized. It even keeps working if all fringes but one are removed. Here's the relationship between the zoneplates of Benton holograms, versus the 'zoneplates' of scratch holograms: http://amasci.com/graphics/holo/onestp2.gif http://amasci.com/graphics/holo/onestp2.gif Benton white-light holograms only use interference to record their zoneplates. They don't use interference to reconstruct the 3D image. (That's why they still function under white-light illumination.) Or, here's another approach. Benton holograms and scratch holograms are based on Poisson's Spot. They don't act like a fresnel lens, instead they act like a conical lens, causing an incoming beam to both converge and scatter into a long locus with no focal point. The "facets" of Benton holograms and scratch holograms need no be diffraction patterns or prisms, they can be random striations, parallel fibers, narrow cylinder lenses, reflective wires, etc. It's perfectly OK to insist that scratch holograms aren't genuine holograms. But to remain honest and consistent, we're also then forced to declare that Benton holograms aren't true holograms. Or, as I said in the linked articles, the bench setup for making Benton white-light holograms is actually an optical device for producing entire scratch holograms all at once, with no individual scratching needed. Heh, "metal rods are the interference fringes!" needs quotation marks, since I guess it wasn't obvious that I was being silly.