How holography works (entire explanation)

[vanesch]

So, I assume there is no picture of how 1 mm2 of a complex hologram looks like enlarged tens of thousands of times.

But of course you can enlarge that. Hey, the opposite is even regularly done. In computer holography, one let's a computer calculate a certain interference pattern, PRINT IT OUT ON A BIG SHEET OF PAPER, and then make the hologram by photographically sizing down that very printout onto photographic film (which will become a hologram).

 

[SAZAR]

Ah, there it is.
Computer generated holograms.
Zone plates, that's it.

Why no one posted pictures of it in the first place?

 

[Gza]

If you looked at a hologram under a microscope you would see the grain of the film used, is this surprising?

The pattern on the film is the interference pattern created by the reflected beam and the reference beam. If you create a hologram of nothing, that is just the image beam and the reference beam you get a series of lines, this is the Fourier Transform of 2 point sources (your 2 beams). What you get on the film is the Fourier Transform of your image, only when the image is very simple can we know what this will be.

A lens is a form of analog computer, it transforms a interference pattern in the focal plane to an image. When you create a hologram you capture a interference pattern.

I'm actually in the process of writing a paper for my upper division lab class for a holography lab, and was interested in how the image on the screen is related to a Fourier transform. Are you saying that the laser point sources are delta functions, and that you Fourier transform them which yields the periodic light and darkness patterns (interference patterns) indicitive of a sin/cos function? Do you have any good sources behind the theory for this? (I tried Folwes, and wasn't very impressed, and I sadly haven't gotten a chance to take a class in optics)

 

[Integral]

I'm actually in the process of writing a paper for my upper division lab class for a holography lab, and was interested in how the image on the screen is related to a Fourier transform. Are you saying that the laser point sources are delta functions, and that you Fourier transform them which yields the periodic light and darkness patterns (interference patterns) indicitive of a sin/cos function? Do you have any good sources behind the theory for this? (I tried Folwes, and wasn't very impressed, and I sadly haven't gotten a chance to take a class in optics)

It has been ~30 years since I went through the theory of this, we used Optics by Rossi. I am pretty sure any good Optics text ought to cover it. I have to be very careful about what I post, It has been so long since I have seen the formal development that all I have left are the very broad strokes.

 

[ZapperZ]

Try Introduction to Fourier Optics by Goodman. It was what I used.

Zz.

 

[Electronica]

Helping Sazar

Well maybe Sazar and I do not understand the details.
Sazar it is important that it can be cut up and shows all of it.

That makes it totally different than a paper printout.
The bits on the sheet in question have 'knowledge' about the entire picture. That is what draws me into this.

Lets try an analogy.
Each hologram sings a chord (yes ahhhhhh or doooooooo) and the chorus is set into triplets similar to the rgb pockets of your screen.
If the entire screen is blue then cutting it up still reveals blue but with less intensity.
If the chorus is cut up each sings the same chord but at a lower intensity.
Depending on your angle you hear a variance of the chord.
How to relate the vibrations on the spot to make this analogy work the rest of the way such as in an animation is for the next post to describe? :)
We are looking for a mechanical animated understanind of photons interacting with the smallest elements of the hologram.
I would like to know how the different views are stored in one area and the whole view is stored on each spot.
It is similar to DNA in that way. The source code for your entire body is in about every part of your body.
Seems very inefficient and redundant yet a hologram stores that way but allows a different DNA to be stored in every cell AND a different DNA for each angle that the cell is viewed from?

Explaining how it works as mechanically as possible with as much Newtonian concepts as possible works best for those who have expertise elsewhere. It is a grand compliment and gesture to explain this to the average guy in average terms.

 

[Electronica]

or simply stated Sazar we need to get into the Wave club to understand and avoid being 'Newtonian Nuisances'