4 ms·

What controls the distance? You shine a laser beam in some direction in order to create an image/flashbang/whatever twenty meters away. Why does it ionize the

What controls the distance? You shine a laser beam in some direction in order to create an image/flashbang/whatever twenty meters away. Why does it ionize the air twenty meters away but not ten meters away (along the same ray from the laser to the projection)?

thechao 5y ago
There are two ways off the top of my head (assuredly there are more): (1) use two lasers; or, (2) the geometry of a laser is hour-glassed shaped, so only the “neck” may have sufficient energy density.
maxden 5y ago
This page linked earlier [0] relates one possibility to the 'Bethe formula', where depending on the energy of the beam (proton in their example) you can control where the burst appears. [0] https://www.otherhand.org/home-page/area-51-and-other-strange-places/bluefire-main/bluefire/particle-beams-and-saucer-dreams/ https://www.otherhand.org/home-page/area-51-and-other-strang...
- KirillPanov 5y ago
  Maybe. But that article is talking about beams of massive particles -- not beams of massless photons, which is what lasers are. The fact that the particles have mass and decelerate is what produces the sharp drop in velocity: the slower it goes the more it slows down per unit of time or of distance traveled. Like a bullet travelling through water. So you get that nice sharp asymptote in the position-vs-time graph. I don't think that webpage is applicable to light or other photon beams. Photons can't slow down unless they encounter a change of medium -- but that's basically projecting onto a physical "screen"... the laser operator can't influence the depth position of the screen. But thanks for the link, it's the first time I've seen a "3D projection technology" that had a coherent answer to the depth-control question. Maybe the Navy is using massive-particle beams instead of lasers and the Forbes journalist just doesn't know the difference. Or maybe it's deliberate disinformation, like how fusion weapons were named "hydrogen" bombs.
jcun4128 5y ago
It was called Aerial 3D [0] it was mentioned in OP article in a link. [0] https://www.google.com/amp/s/techcrunch.com/2011/11/15/aerial-3d-amazing-system-shows-3d-objects-in-mid-air-with-no-screen-video/amp/ https://www.google.com/amp/s/techcrunch.com/2011/11/15/aeria...
- KirillPanov 5y ago
  Yeah that link has zero explanation of depth control.
  - jcun4128 5y ago
    My guess/assumption is intersecting beams. Or maybe it is just an energy distance thing. Not sure what happened to this company. Aerial Burton 3D is the name

thechao 5y ago

There are two ways off the top of my head (assuredly there are more): (1) use two lasers; or, (2) the geometry of a laser is hour-glassed shaped, so only the “neck” may have sufficient energy density.

maxden 5y ago

This page linked earlier [0] relates one possibility to the 'Bethe formula', where depending on the energy of the beam (proton in their example) you can control where the burst appears. [0] https://www.otherhand.org/home-page/area-51-and-other-strange-places/bluefire-main/bluefire/particle-beams-and-saucer-dreams/ https://www.otherhand.org/home-page/area-51-and-other-strang...

KirillPanov 5y ago
Maybe. But that article is talking about beams of massive particles -- not beams of massless photons, which is what lasers are. The fact that the particles have mass and decelerate is what produces the sharp drop in velocity: the slower it goes the more it slows down per unit of time or of distance traveled. Like a bullet travelling through water. So you get that nice sharp asymptote in the position-vs-time graph. I don't think that webpage is applicable to light or other photon beams. Photons can't slow down unless they encounter a change of medium -- but that's basically projecting onto a physical "screen"... the laser operator can't influence the depth position of the screen. But thanks for the link, it's the first time I've seen a "3D projection technology" that had a coherent answer to the depth-control question. Maybe the Navy is using massive-particle beams instead of lasers and the Forbes journalist just doesn't know the difference. Or maybe it's deliberate disinformation, like how fusion weapons were named "hydrogen" bombs.

jcun4128 5y ago

It was called Aerial 3D [0] it was mentioned in OP article in a link. [0] https://www.google.com/amp/s/techcrunch.com/2011/11/15/aerial-3d-amazing-system-shows-3d-objects-in-mid-air-with-no-screen-video/amp/ https://www.google.com/amp/s/techcrunch.com/2011/11/15/aeria...

KirillPanov 5y ago
Yeah that link has zero explanation of depth control.
- jcun4128 5y ago
  My guess/assumption is intersecting beams. Or maybe it is just an energy distance thing. Not sure what happened to this company. Aerial Burton 3D is the name