Femto Fairy Lights - Touchable Holograms (i-programmer.info)

mikejuk writes with this story about a Japanese team working on creating touchable holograms. I Programmer reports: "One method of creating a volumetric, i.e. true 3D, display, is to use a high power laser and focus it on a small spot in space. The air in that spot will be heated to the point where it ionizes and glows with a bright blue light. Scan the laser really fast and you can make a full 3D arrangement of glowing points of light — not exactly a hologram but as good as. Of course, the big problem is that you have a lot of energy being focused on small areas and human interaction could be a problem. You might well get burned by the laser if you attempted to touch or interact with the display. The solution is to use a really fast laser, a femtosecond laser, that heats a small spot to a high temperature but only for a very short time. This is much safer because the total energy involved is smaller. This is the reason you can touch sparks without getting burned."

Comments

The smell.

[Anonymous Coward]

I love waking up to the smell of ozone. I'm sure others share my sentiments.

I saw tech like this ionizing the atmosphere to create holograms years ago. Have they improved on it? Sure, but I can't see it being anything but a diversion from looking for a better path. Even those pools of liquid that use wave forms to create shapes would be better than this. The only thing I can see a use for this tech, of rapid tracking lasers that ionize things, would be in things like a laser defense system, and it could lower the energy cost for such a thing.

Re:The smell.

[jeffb (2.718)]

Well, see, that's exactly what I want. A small (patio-scale) laser defense system, to protect my family from disease-bearing mosquitoes and aggressive stinging insects. If you've got the tech to track targets at that scale of size and velocity, distinguishing desirable from undesirable insects is probably not too tough. I've already seen some demos.

Would I spend a million bucks on such a system? Of course not. A thousand? I wouldn't, but many would. A hundred? Sure. Come on, exponential advancement!

Would interference work?

[140Mandak262Jamuna]

When sound waves of nearly equal frequencies interfere we hear a beat frequency which is the difference between the two frequencies. We could create two sound waves in beyond audible range but produce beat frequencies in audible range. We could send these two sound beams and people on their individual paths would not hear anything. But where these two beams intersect, the beat frequency sound would be heard by those in that area.

Can we think of doing something in light waves, two lasers in beyond visible range, but they interfere with beat frequency in visible range. So the intersection point would have a visible spot. We would only see it if there is dust or something that would scatter the visible light produced there due to interference. And if it is possible to move the interference location by scanning we might be able to project a visible 3D image.

I obviously don't have either the math, or the physics or the electronic skills to do it. In fact I am not even sure it is a viable idea. Wondering if people have tried to use interference between sound waves for such interesting applications?

Indeed

[rmdingler]

Let's agree that the acceptable level of burnt humans is zero,

since the technology is likely to be initially exploited for gamers and pron users.

One question

[DarkOx]

Will it be possible to mount these things on a shark?

Burnt or blinded?

[burtosis]

It's not easy to burn humans, skin is usually covered by a film of moisture and skin is composed of mainly water which has a high specific heat.
Eyes on the other hand are easily blinded by lasers orders of magnitude less energetic that those causing burns. Even reflections from objects can cause temporary or permenant blindness. A technology for hologram displays that blinds it's users is of limited value.

Re:Burnt or blinded?

[SuricouRaven]

I ran into this problem while trying to build a laser lawnmower. You have to boil the water out of the grass before the laser will cut it, so the lawnmower needs to move at a very slow speed to cut effectively.

Laser beam carries on

[Roger W Moore]

Not yet practical, but maybe this is the technology that one day will give us real working light sabres.

Unlikely. The problem with using lasers for this is that they focus the beam to get the intensity needed to ionize the air and so much of the beam will carry on only slightly attenuated by the plasma. Assuming you had the power requirements to run this intensity continuously (or at least at a far higher repetition rate than todays femto-second lasers) then you could certainly imagine using this to create a tube of plasma like a light sabre but in reality what you have created is a massively powerful laser beam which you have focussed to ionize the nearby air.

This would undoubtedly cut through things but the cutting power would not be limited to the length of the blade and, if you did not bother to focus it, it would extend a great deal further and be harder to detect...but at the cost of looking nowhere near as cool. However I expect that, unlike Hollywood, when it comes to real world weapons effectiveness will outrank the "looking cool" factor by quite a lot. If you really want a lightsabre I think it is far more likely to come from other ways of generating and containing plasma (such as this) rather than using laser-created plasma because in the latter case you might as well just use the laser beam without the plasma.

Re:Laser beam carries on

[artfulshrapnel]

Doesn't seem too crazy that it would be used for novelty purposes a couple dozen years from now though. You could project rings of glowing dots up a space about 3 feet from the hilt, creating a cylinder of glowing light in the air very similar to the appearance of a lightsaber, but harmless. A great toy for rich adults.

If you did want to use the lasers as a cutting tool (hooked up to a power source) it could actually be a pretty nifty UI. Project a line of dots through the air to show where the "blade" is, and whenever they detect contact as shown in the tech demo focus an intense laser pulse onto that point to cut through whatever is there. No need to inefficiently blast lasers everywhere when you can detect the precise point where the "beam" is disrupted. Since it's using optics technology you could probably set it not to cut things like flesh and cloth while you're at it.