3D images without a screen

[BowlOfRed]

I saw this article with a demo of a light display that creates points of light at particular points in space. http://www.thisiscolossal.com/2014/...-capable-of-projecting-3d-objects-in-mid-air/

This is just the same youtube that is in the article:


Anyone know how this works? If it's projected from one point, I don't understand how they achieve distance control. The poster in the background at one point in the video seems to imply that it's single-point projection.

 

[Denver]

Some googling seems to say this was first revealed a couple years ago.
I'm kind of suspicious...

 

[Buckaroo]

I've seen a display like this in person, at SIGGRAPH in 2006. The way I inferred it works is by focusing an IR laser to a point in space, such that the air parcel heats and ionizes. When the ionized electrons drop back down into an unenergized state, they release a photon. By scanning the beam back and forth and varying the focus position, you get a 3D image. It's pretty loud, like hundreds of miniaturized thunderclaps per second. I also worry about stray IR getting in to eyes.

 

[GodMark2]

Distance control is easy: use a diffuse source and focus it strongly on the point of interest. All other points along the way don't have enough energy to light up.

Harder is the ionizing radiation containment.
You can't just focus non-ionizing radiation and suddenly make it ionized. You need to start with ionizing photons (this 'problem' is what led to the modern understanding of light's wave-particle dual existence), which means that ionizing photons will likely be emitted. In order to cause air (whether they stimulate O2 or N2, I don't know) to ionize, you'd need a huge amount of energy to begin with, and I'd imagine you'd easily have at least as much wasted as a tanning bed. Even tanning beds require you to sign a safely waiver with their comparatively low levels of radiation. They might get 'around' this by only projecting straight up, as most waste would simply keep going that direction. Using it indoors might be a problem.

Still, for the design goal (portable communications for emergency response workers for displaying information to the general populace), it looks quite plausible.

 

[Buckaroo]

Still, for the design goal (portable communications for emergency response workers for displaying information to the general populace), it looks quite plausible.

It's more than plausible -- it's a fait accompli. I've seen it in person.

ETA: nevermind, I see the point you're making. Dunno about the portability -- the unit I saw was big, and required a substantial power source.

Using it indoors might be a problem.

I saw it indoors, but had the same safety concerns that you talk about. Only the operators were wearing eye protection.

In order to cause air (whether they stimulate O2 or N2, I don't know) to ionize, you'd need a huge amount of energy to begin with,

Maybe not as much as you'd think -- the display was made up of very small dots, so you'd only need to heat small volumes, not the full volume of the image.

 

[fuelair]

I've seen a display like this in person, at SIGGRAPH in 2006. The way I inferred it works is by focusing an IR laser to a point in space, such that the air parcel heats and ionizes. When the ionized electrons drop back down into an unenergized state, they release a photon. By scanning the beam back and forth and varying the focus position, you get a 3D image. It's pretty loud, like hundreds of miniaturized thunderclaps per second. I also worry about stray IR getting in to eyes.

Yaaaaaaaaaaay, SIGGRAPH!!! Have not, unfortunately, done it since San Antonio - but, as I said to many students when I taught media production, a week on the main floor at Siggraph was worth a semester at a decent production school.

 

[Aepervius]

Distance control is easy: use a diffuse source and focus it strongly on the point of interest. All other points along the way don't have enough energy to light up.

Harder is the ionizing radiation containment.
You can't just focus non-ionizing radiation and suddenly make it ionized. You need to start with ionizing photons (this 'problem' is what led to the modern understanding of light's wave-particle dual existence), which means that ionizing photons will likely be emitted. In order to cause air (whether they stimulate O2 or N2, I don't know) to ionize, you'd need a huge amount of energy to begin with, and I'd imagine you'd easily have at least as much wasted as a tanning bed. Even tanning beds require you to sign a safely waiver with their comparatively low levels of radiation. They might get 'around' this by only projecting straight up, as most waste would simply keep going that direction. Using it indoors might be a problem.

Still, for the design goal (portable communications for emergency response workers for displaying information to the general populace), it looks quite plausible.

If it really work that way, it is true that this is probably in the high energy ultra violet zone (the first ionisation of N2 is IIRC I think the order of magnitude of 10 eV --- can't recall if it is about 15eV ?). O2 is probably similar. So it is in the ionizing zone. Not good.

The real question is about the intensity (assuming fix photon energy around 10-15 eV that means for a fix energy pumped per square Cm^3 , a fix number of photon would be emited, and thus you can calculate exposure at a distance assuming perfect spherical repartition) whether it would damage your skin & eyes, Especially taking into acount the 1/r^2 diminushing intensity, if it has a significant chance of rising the probability of ionizing radiation hurting your cell or if it is too small to be significant, how much is absorbed by the surrounding air etc...

Without reading the spec it would be hard to say, but my gut feeling is that I doubt they are pumping so much energy that it would generate that much ionizing radiation that it would significantely negatively impact they persons watching.

 

[Buckaroo]

Yaaaaaaaaaaay, SIGGRAPH!!! Have not, unfortunately, done it since San Antonio - but, as I said to many students when I taught media production, a week on the main floor at Siggraph was worth a semester at a decent production school.

I know, right?! Emerging Tech is my favorite bit, where this display was demo'ed. Was just at the Vancouver SIGGRAPH a few months ago -- GREAT venue. Next time it's there, try to go!

 

[BowlOfRed]

focusing an IR laser to a point in space

That was the part I didn't understand. I would assume that an IR laser has a rather small aperture. That made me think that if you were trying to focus it more than a meter away (from the look of the video), you'd have a large slop in the distance focus. 0.95m and 1.05m would be almost equally in focus. But the video shows very sharp points of light, even in distance dimension.

How big would the aperture be on one of these things? It says it was just feeding high intensity IR through a 3D scanner. I can't imagine they use extra-large lasers on such equipment.

 

[Horatius]

Here's some links to two US patents that look like they describe the same device:

https://www.google.com/patents/US77...a=X&ei=5PdlVJWuCdWzyAS7u4KgAg&ved=0CB0Q6AEwAA

https://www.google.com/patents/US75...a=X&ei=5PdlVJWuCdWzyAS7u4KgAg&ved=0CCsQ6AEwAg

Key quote:

If the energy density of the pulse beam is 10 millijoules (mJ) per pulse, when this pulse beam is narrowed to a spot beam with the diameter of 0.1 mm, a peak output of about 1010 W/cm2 is gained.

Here, an Nd:YAG laser is used for the laser source 2, its oscillating wave length is 1.06 μm, the energy density per pulse is 10 mJ, repetition frequency is 20 Hz, and it is oscillated intermittently.

By this narrowing of the infrared laser beam, breakdown is caused in a gas in the air, which locally brings the gas into a high-density plasma state, whereby a flash light is generated locally. Also, together with the flash light, an impact noise is generated.

That is, when an infrared laser beam is collected by the condenser lens 11 at a visible-image formation scheduled point (drawing scheduled point) 13 in the air, a gas existing at the visible-image formation scheduled point 13 is locally brought into the plasma state, a flash light is generated at the visible-image formation scheduled point 13 in the air, and this visible-image formation scheduled point 13 is recognized as a light emitting point when visibly checked from a remote location.

Thus, as shown in FIG. 2, at a time t1, the scanning means 3 is controlled in the X direction so that an infrared laser beam is led to a visible-image formation scheduled point 13 a in the air, and the laser source 2 is oscillated immediately after that so as to have the gas at the visible-image formation scheduled point 13 a emit plasma light, and then, at a time t2, the scanning means 3 is controlled in the X direction so that the infrared laser beam is led to a visible-image formation scheduled point 13 b in the air and the laser source 2 is oscillated immediately after that so as to have the gas at the visible-image formation scheduled point 13 b emit plasma light and next, at a time t3, the scanning means 3 is controlled in the X direction so that the infrared laser beam is led to a visible-image formation scheduled point 13 c in the air and the laser source 2 is oscillated immediately after that so as to have the gas at the visible-image formation scheduled point 13 c emit plasma light.