theoretical holography question

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xaviergisz

theoretical holography question

Post by xaviergisz »

I have a purely theoretical question; I have no intention of trying to make this, I just want to know if it's theoretically possible.

Basically it's a static version of 'augmented reality'. Say you have a fixed scenery (mountains, rivers etc) from a particular vantage point and you want to indicate to a viewer what each of the landmarks are. Is it possible to construct a 'window' that you look through so you can see a text holograph hovering above each landmark (ie so the holograph and landmark are at the same focal length for the viewer)?

I'm thinking for the simple case: replacing the sun with a powerful laser at a fixed location, this would be possible. I was wondering if this would be possible in the the 'real-world' with the scenery undergoing a variety of lighting conditions due to movement of the sun, overcast conditions etc.
manalokos

theoretical holography question

Post by manalokos »

Hello Xavier,

I'm new here and still don't know much about this,
but I think it is possible, the only thing you need to do is place
the object at infinity, and this might be done at least with
computer generated holograms like those made by RabbitHoles,
using holopixels, I've tried to do it using moiré holograms,
but those are not real holograms and are very very opaque and uninteresting.

There might be a way to simulate an object at infinity
using a convering cone of laser light as reference beam...?
The convergence would be matched to the distance of the object
to the plate...

But maybe I am saying very silly things! :D

Best regards
Filipe Alves
Colin Kaminski

theoretical holography question

Post by Colin Kaminski »

I would start with computer generated holographic stereograms. It would not be to hard for a lab used to printing from the TI DLP chips. You would have to play with the raw images to get the feel you want.

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Ed Wesly

theoretical holography question

Post by Ed Wesly »

You can get an object to appear at infinity if it is placed one focal length from a lens. This would be your object beam. You could also use the lens to image your text at any position you would like following the simple lens formula, 1/object distance + 1/image distance = 1/focal length.
MfA

theoretical holography question

Post by MfA »

You could probably simply combine the real view with the text through a combiner, like they do in HUDs ... those are generally holographic in nature (search for "Holographic Combiner").
DigiFlash

theoretical holography question

Post by DigiFlash »

xaviergisz wrote:I'm thinking for the simple case: replacing the sun with a powerful laser at a fixed location, this would be possible. I was wondering if this would be possible in the the 'real-world' with the scenery undergoing a variety of lighting conditions due to movement of the sun, overcast conditions etc.
Obviously, whatever the source of light you use, it will produce at least as big of an image as the light is at infinity, i.e. if you use sun - it would be your brush for image at infinity... So, only laser can reconstruct the image you are talking about.. but that's not really a problem nowadays, i.e. it should be H1, i.e. laser transmission hologram.

Movement of sun, overcast etc would be important if you would make white light viewable hologram, but you do not want to do it, for the reason of movement, because image will follow as reflection of the lighting source, so it will not follow the landmarks. + the reasons mentioned before.

So, if you record the laser transmission hologram with landmark name transmission mask through some optical system, you should be close to your goal.
Then you need some laser pointer to replay it, and voila... well, it will take some time to get it perfect :)
That "optical system" needs some consideration.. :)

I can be wrong, and often I am.. so, comments are welcome! I might learn something.
Tom B.

theoretical holography question

Post by Tom B. »

Further to the previous mention of HUDs (Head Up Displays), here's a brief description of some systems:
http://www.mikesflightdeck.com/head_up_displays.htm

Wikipaedia article: http://en.wikipedia.org/wiki/Head-up_display

One limitation is that the useful viewing zone is typically rather small, being limited by the size of the collimating lens/mirrror and combiner - too small for multiple viewers, so it would not be possible to point out objects to someone else. If it didn't have to fly in an aircraft. though, the optics could be made as big as your budget would allow :)
Jeffrey

theoretical holography question

Post by Jeffrey »

Paula Dawson created a similar hologram situation, installed on the north coast of Australia. As you view the scenery through the hologram, you see, superimposed, the shore as it appeared millions of years ago. No labels, that I recall, but there was alignment.

Labels would just be a HUD trick.

Someone in the 80's made a gunsight by holographing a piece of string that stretched way out there - looking through the holo you saw the line touch your target (not like a laser beam which actually DOES touch your target)
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