more info here

oOOOOooo i have never encountered this stuff. Taa for sub

nerd

Grr, it's not a hologram.

Holograms are a recording of light from other objects such that when you view the hologram from different angles, the object appears to be viewed from that same angle.

These are hand scratched 3D illusions NOT friggen holograms.

These are not holograms. Those bullshit things CNN did during the election were not holograms. Those prismatic wrapping papers or stickers or any number of other prismatic things are NOT holograms.

I just wish people would stop throwing labels around that don't belong on things. THESE are not holograms. Grumble, bitch, moan.

Hey spoco, did you see them holograms in the video?

I swear it like watching CNN all over again!

What else can they be but holograms? Perhaps holograms of hand scratched 3D illusions.

Holograms!

It's not a hologram like a portrait isn't a person. Yes it may not be a real hologram, but in some ways it's more impressive.

The other day someone mailed me a letter, but there was nothing in the envelope.

I hate hollow grams.

Whatever you call them, they're really impressive!

^ Oh indeed... it's very clever, and time consuming to put the correct points in the right places etc. No doubt there.

Spoco, I'm not sure you are right. Holograms store interference fringes from a diffraction grating in holographic media. You can then take the burned media and shine light (same wavelength as the original incident light) on it from the reverse angle (originating from where the scattered light would have landed behind the media) and you will get an image of the original diffraction grating projected on a screen (or eye). you can store entirely different fringe patterns at different angles in the same spot (within the limits set by the physical lattice of the media and the wavelength of light being used), but in typical holograms you store the fringe pattern of the SAME grating at a different angle.

It looks like these things accomplish these end result: a recording of fringes for a given diffraction grating on a media. Sure, the images aren't actually produced by light, but I don't think that is a requirement. The point is that his scratching pattern contains the information required to reconstruct the point sources that would have created such an image for multiple incident angles.

This is what makes holographic data storage so exciting, storing a whole X by X grid worth of information on some Y by Y by Y chunk of media, and storing ANOTHER X by X grid of info ON THE SAME SPOT at a different angle.

PS I'm drunk. and this guy is my hero.

No, he is actually correct. A hologram is a very specific thing. You could say maybe that these are holographic, as in they have elements of a hologram, but they are not holograms.

It would be like saying the print out of a jpg from facebook is a photograph.

> Grr, it's not a hologram.

spoco2, go to the website and read FAQ entry 9 (links below)

These are Benton Rainbow Holograms where the spacing between fringes is wider than normal.

Rainbow holograms are based only on fringe angle and not fringe spacing. They are size-independent; that's why they reconstruct with incoherent white-light illumination. With Benton Holograms, the distance between fringes is irrelevant. With Benton Holograms, the fringes can be drawn by hand. Apparently nobody realized this until I saw the phenomenon occurring naturally when someone polished a car hood with a gritty cloth.

FAQ #9: http://amasci.com/amateur/holo3.html
Full FAQ: http://amasci.com/amateur/holohint.html


> Holograms are a recording of light from other objects such that

So you're saying that Computer Generated holograms aren't holograms, since their zoneplates are drawn by computer? Really? If CG holograms are holograms, then so are mine.

> These are not holograms.

If you knew how those Rainbow Holograms on credit cards actually worked, perhaps you'd be angry when people called them by the name "hologram." If my Hand Drawn holograms aren't real holograms, then Rainbow holograms aren't real holograms either.

> No, he is actually correct. A hologram is a very specific thing.

No, an "Off-axis" hologram is a very specific thing. Those 1960s-type off-axis holograms require lasers both for recording and for reconstruction (playback.) Those are the very definition of "hologram."

But credit card holograms, rainbow holograms, are different. The spacing of the zoneplate fringes in Rainbow holograms doesn't play a part in creating the 3D image. It only creates the rainbow-colored artifact. Rainbow holograms can be viewed with incoherent white light. So, should we even be calling them by the name "hologram?" Well, they're certainly not photographs. They don't use interference for playback. Yet they still employ light-scattering by fringes in order to create a 3D scene.

The stunning fact is that Rainbow holograms are size-independent. Increase or decrease their fringe spacing, and they still function as holograms. Use randomized fringe spacing, and they still keep working. Or rather than hundreds of close-spaced fringes, use just one fringe per image-pixel. They still keep working! You can generate the fringes with a laser. Or you can scribe them with a needle. Or you can make giant "fringes" using curved, highly polished steel pipes.

I guess it can be painful to suddenly have to think outside the box; to realize that "holograms" are not exactly what everyone thought they were. I've found that many people are angered when someone suddenly goes and moves the limits encompassing a well known concept. But a rare few are delighted.

>> ^billb:
> No, he is actually correct. A hologram is a very specific thing.
No, an "Off-axis" hologram is a very specific thing. Those 1960s-type off-axis holograms require lasers both for recording and for reconstruction (playback.) Those are the very definition of "hologram."


That was exactly my point.

It was not to indicate how I myself use the word hologram, I would without any hesitation refer to your work as holograms had socco2 not made his point. I just saw it as 'neat' that he caught that.