I’m trying to find a good explanation for how and why holograms work. (the high quality three dimensional kind)
Also, can a holographic image be created on a piece of paper?
Could you be more specific? There are a number of ways to create a hologram. All involve the use of coherent light and a surface… Beyond that, well, what type are you asking about?
Regular dead-tree paper, no. Paper that has been coated or treated, sure!
The kind that is usually produced on glass (?) plates and hung on the wall in galleries. The kind that looks like you have a 3D image behind a window. The only other kind I know of is the cheap kind that they mass produce.
A hologram can be embossed into plastic or metal foil and then applied to paper. That’s how the “cheap mass produced” holograms are created.
Here is an explanation of how holograms work (and Google’s cached copy).
The good 3D holograms that you need to have a laser to see?
If you have a widnow that’s passing light from something illuminated by a laser beam (spread-out, not a dot), and you’re on the other side of that window, then the magnitude and phase of the light at each point on the window surface is all there is, right? If you can recreate the magnitude and phase at each point on the window surface, whether or not anything is behind it, then it will look like there’s something back there.
That’s not true, you can view extremely high quality holograms using a point-white-light source. The only disadvantage to this is that the “deeper” you look in the hologram, the more blurred the image is going to look, but of course, if the image is of something fairly close, this isn’t a problem.
The explanation that makes the most sense to me is to look at a mirror.
Obviously, if you look at one spot on the mirror without moving, you see the same item reflected back to you. But if you move your viewpoint and look at the same spot on the mirror, you see something else reflected. That means that everything visible from the mirror is reflected from every spot on the mirror.
That makes it easier for me to understand that the mirror is not reflecting individual items, but the whole interference pattern rattling around in the room.
A Hologram is a way of storing the wavefront from light that impinged upon the photographic plate. It can be reconstructed with another laser, or (depending on circumstances) an ordinary light source. The storing is done by recording the interference pattern between the wavefront from the object and a reference beam. playing a new reference beam through the plate not only lets the reference beam pass through, but re-creates the original wavefront as well. Since you have captured the whole wavefront, the plate acts very much like a window, and as you move around you can see the scene from different viewpoints (as long as you’re looking through the “window”). Because you have captured what the view going to each eye will be, the image is three-dimensional. Unlike lenticular 3-D shots and anaglyphic 3-D, the shots are still three-D even if you turn them sideways or upside-down.
There are a number of tricks you can use to make the holograms appear to move, or to be “projected” in front of the “window”, or to be usable in reflection (with ordinary daylight), but that takes us outside the “simple explanation” part.
If you want to make holograms, get the book by Unterseher et al. entitled something like “Making Holograms”. You’ll need a good laser with a long coherence length and photographic plates with really fine emulsion. If you getr really serious, get Collier, Burkhardt, and Lin’s book.