## 3D holograpy a different perspective.

These are all of the old posts from the first two years of the forum. They are locked.
Updated: 2005-03-28 by HoloM (the god)
Nick

### 3D holograpy a different perspective.

Just a general idea: Everyone is trying to create holographic projections in one set way using screens and lenses. Maybe we need to look at this with a different approach.

We've all been to discos and partied at onetime in our lifes, the idea was sparked when I notice the disco beams converging and moving, I did notice that at the point of convergence was rather brighter area of light, which seemed more apparent than the very beams themselves. This brighter area being the mixture of rgb colours from varying light sources led my to think that if this could be controlled one could create some kind of projection in 3dimensional space. Just an idea! Thats all! I guess from experts its just a dream, but if anyone has also had ideas on this?

Is there a way to manipulate the very essence of light itself by crossing the three primary beams , red, green and blue at certain points say on a 3d dimensional grid XYZ? WOuld you not get a very small point of light? If so, how would you achieve this and could the beams be manipulated into creating a single point in 3 dimensional space? If one could achieve a small single point of light , even if it was very tiny, this could be half the battle into generating and creating a 3dimensional hologram.

Is this possible to create solid light from light itself without using the holo plates or any kind of solid medium or gas?

Nick

JohnFP

### 3D holograpy a different perspective.

Now, I am in no way an expert on this matter but I think every holographer, especially myself has thought about this idea. The problem being, one, how to stop light in mid air (vacuum) and second, how to see light in mid air without it having to bounce off of a solid particle. Because you were at a disco, there was problable smoke or some other material in the air so that the light could be seen as a beam (bouncing off each of these particles) instead of a spot light (just where it hit). Producing this controlled environment (smoke or water vapor etc.) is the basis of some of the 3-D display. But keep thinking, we only need one breakthrough and HELLO princess Lea.
Andy Dean

### 3D holograpy a different perspective.

I agree with john, you were most probably seeing the reflection coming from dust of smock particles. This is an idea I have also thought about and your next thought might be to fill a room full of controlled smoke or create a smoke filled box or liquid box? The main problem I came across was with the viewing position around the object you are trying to represent. With out going into to much detail, every viewing angle would have to have a considered projection point and an ability to change or be concealed by any other construction point on the object. I have read somewhere about light sensitive liquids that react and move when hit by light, but my understanding of such liquids is very limited. The use of such a liquid would to be to have a “clever” projection surface which could distinguish between wave length and intensity of light and react accordingly. Once again this is riddled with major problems which I have as yet been unable to solve. Andy
Dinesh

### 3D holograpy a different perspective.

Not sure I completely understand about the viewing direction thing. However, wavelength sensitive scattering is not too difficult. Remember that Rayleigh scattering predominates when the scattering object is small and Mie scattering dominates when the object gets larger. For Mie scattering, the scattered color is pretty much the color of the scattering center - an object about 700nm across will scatter red light. You can sort of see this by getting a glass of water and dropping a single drop of milk into it. If you shake up the mixture, shine a bright light through one side and observe from the front you see a blue haze.
So-o-o here's a possible thought experiment. Get a hollow box, about 5x4x2 in. Insert a fan at the bottom, a light to reconstruct at the top and a hologram at the back end made so as to create a real image about 1 in. in front ( an H1 might do it if the recon light is a LED). Fill the box with a liquid with some sort that forms a suspension in the liquid, say "oil" in water. When the light (LED) reconstructs the hologram and the fan churns up the "oil", every particle of "oil" will scatter the particular object point in every direction. Normally such a hologram is only seen along the hologram axis - "at it" as it were. Now, the hologram should be visible at pretty much any angle since the mulitudinous object points that create the image are all scattering off tiny droplets of "oil". By varying the size of the "oil", ie choosing a suitable suspension, you can take advantage of Mie and Rayleigh scattering and create colors.
If I see such a device, expect a beer in return!
JP

### 3D holograpy a different perspective.

A slightly different take on what you may have been seeing...

"...notice that at the point of convergence was rather brighter area of light, which seemed more apparent than the very beams themselves. This brighter area being the mixture of rgb colours from varying light sources led my to think that if this could be controlled one could create some kind of projection in 3dimensional space."

For those of you who attended my talk on "depth perception" at PCGG1 (that's my plug to attend all future PCCG's lest you miss something good!) you will remember what I said about "depth cues". Brightness and color both create sensory perceptions which our brains use to create the illusion of depth. It would not surprise me to know that the convergence of lesser beams, especially in the contrast of a darkened room, would create a spot which seemed to float in space forward of the beams which created it. This is a common optical illusion. But I'm sorry to say, it is not a holographic one. There are, however people working in other fields of 3D who could incorporate this effect. Personally, I think ALL 3D stuff is fun.
Tom B.

### 3D holograpy a different perspective.

Nice idea! From descriptions that I've read of the optical appearance of aerogels, these might make a good "solid-state" display medium.

Also, I wonder how a focused image projection would look - brightly lit object 2f from big lens, 3D focused 1:1 image appears (upside down) at 2f on the other side of the lens.