If I Had A Lab

[belovelife]

i have been pondering this since i was at a university

 

a holographic monitor

 

my first idea was to create a ball of fibreoptics, put it inside a parabolic mirror situation to give a 3d hologram,

 

 

 

 

 

 

 

i

 

 

 

then i was working for a company called nu-salt lasers, and i got to see the full color laser situation,

 

using a 3 color laser and having 3 beams intersect in a 3d spatial matrix would make a reflectable hologram, if the

 

top of the hologram chamber were a filter that only allowed light a 3 laser intersect intensity to flow through

 

then we could have a decent holographic monitor

 

anyway, i was thinking some sort of dididium lense for the top, and some really good reflective mirrors on the inside

 

ideas?

[CraigD]

i have been pondering this since i was at a university … a holographic monitor ... my first idea was to create a ball of fibreoptics, put it inside a parabolic mirror situation to give a 3d hologram ...

If you mean what I think you do, I think something like “a ball of fiberoptics” is a pretty good idea for a volumetric display.

 

If you’re going discuss something technical, it’s important to be technically correct, and call this kind of device volumetric, not holographic. A holographic display is one that displays a hologram, which is the reproduction of the wavefront of light from some object by recording an interference pattern of light from 2 paths from that object, then illuminating it with the same wavelength(s) of light. A volumetric display is essentially a 3-D model made of light – it doesn’t reproduce the light from a recorded object, but rather recreates an object that emits similar light.

 

“Static volumetric displays” are trivial – any model, such as a realistic sculpture, is one. 3D laser engraved glass cubes are another – less easy to make, and less realistic, but pretty.

 

Very low resolution dynamic (moving) volumetric displays are easy to make: just hang many little lights in a big volume of space, and switch them on and off as needed to generate a moving 3D object. Animated neon signs (here are a few good, amusing ones – I got a chuckle out of the one of R2D2 projecting the Leia “hologram”) are a 2D example of this. Many folk (including I) follow this approach to throw up “abstract” static and moving volumetric displays by hanging steady or blinking Christmas tree lights in leafless trees. :)

 

If this approach could be greatly miniaturized, enough to exceed human eye resolution, the switching speed of the lights kept above 0.015 or so, the lights be RGB triples, and the lights and their supporting and signal/power supplying parts not block one another, one could follow it to make a nearly perfect volumetric display. Most of the best and most useful present day volumetric displays use mechanical “sweeping” display surfaces. While useful, they’re far from perfect - beyond looking merely unrealistic, they’re hard to look at for long.

 

While it might be possible to do this with optical fibers (perhaps with diffusers on their ends), I wonder if might be possible to do it with ultra-miniature LEDs – essentially a volume created by stacking 2D true discrete LED panels, though not necessarily fabricated that way.

 

Real image-producing parabolic mirror gadgets like this are fun – the image looks so real, it’s amazing when you try to touch it, and you fingers pass through the space it appears to occupy. This effect isn’t just cool - the ability to, for example, place a physical pointer inside the image of an object can be very useful.

 

However, you must have either a physical object or a nearly perfect volumetric display of an object to place in it for the effect to appear. Once you’ve got that, parabolic mirror trickery is easy.

 

... using a 3 color laser and having 3 beams intersect in a 3d spatial matrix would make a reflectable hologram, if the top of the hologram chamber were a filter that only allowed light a 3 laser intersect intensity to flow through then we could have a decent holographic monitor

Again, this wouldn’t be a hologram in the strict sense, but a volumetric display.

 

The basic physical problem with using intersecting beams of light (not necessarily from lasers, though they’re pretty good for this sort of thing) to make a volumetric display is that beams of light don’t interact with one another at all. So what you have to do is have them intersect within some medium – air, a transparent solid, etc. – that’s excited (typically heated) too little by a single beam, but enough by the intersection of 2 beams, to emit noticeable light. Getting the color right with such an approach is difficult, as the light being produced isn’t a reflection of the beams’ light, but a “glow” of the medium it excites. To the best of my knowledge, nobody’s yet got such an approach to produce realistic colors, or more than low-resolution images, such as this one:

(from the wikipedia article)

 

A truly realistic moving holographic or volumetric display would be a major tech breakthrough, and a lot of applied scientists and technologists are working on them. It’s proving a harder accomplishment then I expected.

 

I think there’s some concern that a successful moving volumetric or holographic display wouldn’t automatically be a revolutionary commercial success, in much the same way that past and present day stereo-optical 3D TVs and video games have failed to succeed in more than a niche/novelty area. Folk who frequented video arcades in the early 1990s might remember this rather amazing cabinet game

which, with no more than a hidden 20” TV, a curved mirror, a light shading hood, a laser video disc player and some clever programming, looked very much like a Star Wars-style “projected hologram”. Though its gameplay was lousy, I recall thinking that the basic display technology (which I never could figure out looking at it in an arcade, only years later, seeing one taken apart on a website) would spark a revolution, but instead this cabinet and its approach disappeared from arcades within about a year, never to return.

[belovelife]

i rememebr that type of game, it was with a cowboy of some sort, i was just a kid, and i couldn't figure out how to play

 

difficult controls, and you had to bend your hear to see the display

 

 

 

the idea i am talking about would make a hologram, in the sam fashon as the toy, ( i've pondered this for years without experimentation )

when 2 lasers intersect, the intersect point is much brighter than the rest of the laser line, therfeore as the intensity of the bump-pixles increases

the intensity needed to make it through the filter is achieved

 

you could use the same scanning a monitor uses, accept in 3d, for display uses

 

although, i am not sure if the lack of a physical object would prevent the hologram from being produced, ( like i said, if i had a lab )

 

a crystal medium would be nice, but using lasers and mediums, creates alot of heat

 

i even pondered if the parabolic inner mirrors were 2 way mirrors, and the intensity of the laser going through the 2-way mirror

intersect would be enough

 

lots of loss of energy due to heat, and the convex nature of the mirror would change the direction of the laser

 

i think these issues could be gotton around,

 

first thing i would do if i had a lab, would be intersect 3 lasers inside one of those toys, and see if it projects a hologram

 

if it does, the rest is relatively easy to get past

[belovelife]

another point, i bought a caramic coffee cup that changed colors when it got warm

 

and i remember reading about a type of gass that when excited with electricity, produced different colors

 

could a chamber filled with this clear gas, in turn be excited by a laser to produce light, tuned by the lasers that intersect?

or is there a crystam emultion that has this effect?

 

interesting concept

 

i have always like thinking about this, its such a fun topic

[Racoon_v2.0]

If I had a lab, I would start with some bunsen burners

 

[belovelife]

i have a glass torch, does that count?

[CraigD]

when 2 lasers intersect, the intersect point is much brighter than the rest of the laser line, ...

No, it is not. What you describe just doesn’t happen in this universe, BL.

 

This is a very important physics principle: Laser beams are streams of photons; photons don’t interact with one another; so while the flux of light – what a light meter would read if you stuck it at that point – at the point where 2 laser beams intersect is the sum of the flux two beams, no light is scattered from that intersecting point in a way that can be measured at any other point.

 

What’s happening with displays like the “pyramid of dots” image in my previous post is that a single laser beam has been focused with a lens so that it is very narrow at a single point. This causes the air at that point to be heated into a glowing plasma, which we see. By switching this laser on and off while changing its direction and focus very quickly, many glowing dots are made in the air.

 

In principle, this could be done using intersecting laser beams, where a single beam is not powerful enough to make the air glow, but two are. I don’t think this has ever been done with balls of plasma in air, only in glass containing (doped with) special substances.

 

If you think for a moment, you can see that it’s a good thing photons don’t interact. Imagine how a cloudless night sky would look if they did, the faint stream of photons from distant stars scattered by the strong streams from the nearby sun and from the many stars it passed by. The universe would be effectively opaque, not transparent, and astronomy difficult to impossible. :( Fortunately, we don't live in that universe!

 

first thing i would do if i had a lab, would be intersect 3 lasers inside one of those toys, and see if it projects a hologram

You should be able to put together an experiment to show that intersecting lasers beams don’t project holograms or do anything else without much effort or cost – just get a few laser pointers, figure out a way to clamp down their “on” buttons (I use bits of wood and rubber bands) hold them securely (I use modeling clay), then aim them to intersect (smoke or mist helps with this by allowing you to see the beams) and see what happens.

 

PS: I searched around a bit, and found, not too surprisingly, that low-resolution version of what I imagined here

While it might be possible to do this with optical fibers (perhaps with diffusers on their ends), I wonder if might be possible to do it with ultra-miniature LEDs – essentially a volume created by stacking 2D true discrete LED panels, though not necessarily fabricated that way.

Have been around, even for sale, for a while: This one, which has only 1000 “3D-pixels” (which a stickler for technical detail would insist be called voxels), was for sale for US$3,000 in 2005 (see this archive). The video of someone playing 3D pong on one (about halfway down on the first link) is super-cool! :) James Clar is super-cool.

 

These low-resolution machine also shows a major problem with such displays: the light from the on LEDs makes the off LEDs and their supporting structure visible. I’m not sure my idea that, if miniaturized enough, this problem would disappear, the way it does at night from a distance with the view of my annual Christmas-lights-in-a-leafless-tree display, would prove true, but if I “had a lab” (which, for me, mostly means enough free time, and either some remedial electronic engineering education or a capable helper), this is something I’d love to tinker with. :)

[belovelife]

this just seems like a fun project,

 

good point on the intersecting lights though

 

interesting, from any angle, a person obsrving the intersect point sees an increase in intesity

not because they interact, but at the focal point of the intersection, there are more photons

 

i think this is the nature of light scattering in the medium of air

 

where in space there is no medium to direct a photon to a different point

 

but as the photons traveling through the air, interact with the air atoms/molecules

 

they are slightly reflected to different directions,

 

besides that, there are ceramic glazes that change color when heated

 

this could be used for at least a single color display

 

with a constantly cooled object in the center of the "toy"

 

use a co2 laser to heat pixles in a matrix fashon

[CraigD]

this just seems like a fun project,

It’s more than fun – I’d call it a “holy grail” for technologists since at least the 1970s

 

These 2005 lecture notes (alas, its diagrams didn’t archive properly, but aren’t needed for a casual read), linked to from the wikipedia article, if full of good info, such as

Research groups had addressed the possibility of such an endeavor as early as the early 1970's, but lacked the required exitation sources or display materials to make it feasible. The solution came from fiber optic industry in the form of high quality rare-earth ion doped glasses. These glasses are transparent to visible light, except for when two infrared beams (invisible to the naked eye) of appropriate wavelength intersect in the medium. Then a two photon absorption process occurs in which …

Summarizing, this says you don’t need to heat some medium ‘til it glows, but, using the right materials, rare earth ion dopants, can make a transparent glass medium that emits visible light from any point when that point is illuminated with 2 infrared laser beams. As the laser power can be low, heat isn’t a problem. Getting the right dopants to produce good colors is.

 

in space there is no medium to direct a photon to a different point but as the photons traveling through the air, interact with the air atoms/molecules they are slightly reflected to different directions

Visible light doesn’t interact much with dry air (which is mostly nitrogen). These infrequent interactions can produce subtle effects when acting on gigantic volumes of air, such as the blue sky and red sunsets, but are essentially invisible to the naked eye in small volumes. Again, it’s a good thing this is so, or our air would be an nearly opaque glowing fog, or almost completely dark, like the bottom of the ocean.

 

To scatter light, you need big, reflective particles, like water droplets, fog, dust, or smoke. This is why folk who work with lasers use little fog machines, or in a pinch, smoke, to make the beams visible when setting up equipment.

[belovelife]

how about compressed air, like a gas bonded with an element like the one you said, then have it compressed for more potential pixel action?

i'm not a chemist, but it should be possible right?

[Chewbalka]

Anyone see this before? How it works is a single strip of led's vertically aligned which rotates quick enough to fool the eye while changing color when required to display the image. I first saw this on ted talks.

 

link for some mobile devices

Edited November 9, 2012 by CraigD
Added browser-compatible link

[belovelife]

that is definatly cool