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Japan Technology

Femto Fairy Lights - Touchable Holograms (i-programmer.info) 57

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."
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Femto Fairy Lights - Touchable Holograms

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  • by Anonymous Coward

    Not yet practical, but maybe this is the technology that one day will give us real working light sabres.
    Why project boring fairies, when you can configure it in a straight line and use it for cutting.... butter? Small amounts of butter.

    • No military would make a light saber -- and you'd need military grade technology for it -- since as a weapon a light saber is quite ineffective, a guy with a 19th century handgun is more dangerous than a guy with a light saber. You'd rather put the huge energy needed for it into action at a distance. Psychologically, The appeal of lightsaber is purely archetypal, it being a sword.

      That said, maybe a tech like this could lead to retractable light blade that looks and glows like a light saber, without any cutt

      • The only reason a light saber is useful in the Star Wars universe is that you can block blaster fire with it but presumably only force users have the reflexes and senses to do that.

        • by kmoser ( 1469707 )

          The only reason a light saber is useful in the Star Wars universe is that you can block blaster fire with it but presumably only force users have the reflexes and senses to do that.

          And only when they are being shot at by one person at a time, from one direction, with a low-power hand-held blaster. Change any of those variables and suddenly a light saber is useless.

      • Now if you had a real light sabre - that would be the most useful thing in the world. Take it apart, reverse engineer the force field technology, and in a few years you'll be building Star Wars machines.. Someone has to think of these things. : )

      • Besides, you still couldn't block one blade with another. And it wouldn't ZWOOM, ZWOOM, ZWOOM right.
    • 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

      • 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,

        • 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.

          I would not describe the power of laser required to do this as "harmless".

  • The smell. (Score:3, Interesting)

    by Anonymous Coward on Sunday December 20, 2015 @01:07PM (#51154291)

    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.

  • by Anonymous Coward
    Uhh, you wanna be careful about calling Femto a fairy. He kicked Guts's ass using only his mind. And you're no Guts.
  • by 140Mandak262Jamuna ( 970587 ) on Sunday December 20, 2015 @01:14PM (#51154321) Journal
    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?

    • by Anonymous Coward

      lasers in beyond visible range, but they interfere with beat frequency in visible range

      They don't. Photons just pass through each other without any kind of interference, unlike sound waves in air, where the medium does actually vibrate at the beat frequency.

      If light interacted like that, you'd probably not be able to see very far, and there would be "funny" effects when additional light sources are turned on.

    • "When sound waves of nearly equal frequencies interfere we hear a beat frequency which is the difference between the two frequencies."

      Unfortunately, that only works if the sound waves by themselves are audible. It won't convert supersonic sound to audible sound, unless the original amplitude is so large that you get significant nonlinear effects (that's essentially how a radio receiver works).

    • Can we think of doing something in light waves, two lasers in beyond visible range, but they interfere with beat frequency in visible range.

      No. First the beat frequency is the frequency at which the amplitude of the wave oscillates. The frequency of the wave itself is the average of the two waves which make it up. So actually what you would want is one higher frequency and one lower frequency beam of waves so say IR and UV at which point the beat frequency will be too high to see.

      The next problem you face is that beats only occur at the precise point where the beams interfere and they are not created and then emitted from that point as a ne

  • by rmdingler ( 1955220 ) on Sunday December 20, 2015 @01:14PM (#51154323) Journal
    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.

    • by cfalcon ( 779563 )

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

      Eh, the level of injury we are willing to tolerate from something is roughly in proportion to how cool it is. Cars? Super cool. Guns? Pretty goddamned cool. Mating with a laser mote? TOTALLY AWESOME!

  • by DarkOx ( 621550 ) on Sunday December 20, 2015 @01:17PM (#51154335) Journal

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

  • Burnt or blinded? (Score:5, Insightful)

    by burtosis ( 1124179 ) on Sunday December 20, 2015 @01:30PM (#51154405)
    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.
    • by Jamlad ( 3436419 )
      You know what else pulsed lasers are great for? Ablation. The vaporization of matter. We're not talking of "burning" away material here. We're bypassing the relatively inefficient method of thermal excitation of molecules (vibration) and going directly to the ejection of matter through excitation into a charged particle plasma flume. The real danger here is that with the pico-/femto-second lasers it becomes athermal, and at low intensities it can be a gradual process. I don't go around leaving my skin exp
    • 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.

      • 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...

        That's actually not the worse problem with a laser lawnmower. If you had tested it on a lawn with a lot of dry grass the resulting grass fire would probably have meant that you would not be here telling us about how it did not work. Still, if you and your house did survive the experience at least you would not need to cut the grass for a while.

  • Once the intensity is sufficiently high to ionize air it can easily ionize a denser medium such as water or the skin. Superficially, yet with every sensatory experience one will loose some piece of skin. Femtosecond lasers are used for Lasic at intensties below the ionization threshold of air, still they ablate cornea. Maybe not child safe...
  • So when can I order a light sabre with a beam shaped like Princess Leia?
  • After the ubiquitous laser warning sign [umd.edu] we also need a sign like "do not touch the hologram with the remaining arm" !

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