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posted by Fnord666 on Thursday December 08 2016, @09:21AM   Printer-friendly
from the but-don't-look-into-the-light dept.

Night vision goggles do a great job of countering the human eye's poor ability to see in the dark, but the devices are usually bulky, requiring several layers of lenses and plenty of power. But thanks to research from the Australian National University (ANU), a new type of nanocrystal could grant night vision powers to a standard pair of specs, without adding any weight.

Darkness, as we perceive it, is the absence of light on the visible spectrum that our eyes can detect, but there's still plenty of light at other frequencies that we can't use. Night vision goggles make use of the near-infrared spectrum, and convert the photons from that light into electrons that light up a phosphor screen inside the device to create the image. But all that makes for a chunky, power-hungry device.

The ANU team's nanocrystal can be used to create night vision devices that forgo electricity completely, by converting incoming photons from infrared light into other photons on the visible spectrum, to allow the human eye to see in the dark.


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  • (Score: 2) by Foobar Bazbot on Thursday December 08 2016, @04:40PM

    by Foobar Bazbot (37) on Thursday December 08 2016, @04:40PM (#438758) Journal

    They're brilliantly using the energy of the photons themselves to power the change in frequency.

    Which means no amplification; in fact there's less photons out than in. So it won't let you see by skyglow/starlight/etc. like current NV gear; it'll only be usable with active NIR illumination, which means batteries.

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  • (Score: 2) by takyon on Thursday December 08 2016, @04:56PM

    by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Thursday December 08 2016, @04:56PM (#438764) Journal

    You could use a gene therapy on yourself to make your eyes more sensitive to low light conditions.

    kek

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    [SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
  • (Score: 3, Interesting) by dlb on Thursday December 08 2016, @06:12PM

    by dlb (4790) on Thursday December 08 2016, @06:12PM (#438786)
    Yes, the photon intensity would be less because of using photons to convert photons. As stated in the news article, "...currently, the nanoparticle requires intense light to make the conversion..." So maybe batteries are in the future for any practical application of the technology.

    However as the lead author of the study implied in the article, embedding millions of these nanocrystals inito a thin film on a pair of glasses would open up a wide swath of invisible frequencies, including "near-infrared illumination," to our vision. Think of all the invisible EMR bouncing around out there. If so, then the glasses wouldn't need additional energy.

    Either way, wearing a pair of those glasses at night, or even during the day, is going to be an experience I'd love to have.
    • (Score: 0) by Anonymous Coward on Friday December 09 2016, @03:56AM

      by Anonymous Coward on Friday December 09 2016, @03:56AM (#439005)

      Either way, wearing a pair of those glasses at night, or even during the day, is going to be an experience I'd love to have.

      Replying back-to-front, I absolutely agree -- the abiity to have full color vision at frequencies one, two, or three (or more? but losses multiply, so I'm afraid not) octaves down from visible wavelength would be fascinating. I'm not sure this is the most practical realization of such IR-seeing goggles, but it's absolutely a cool idea.

      embedding millions of these nanocrystals inito a thin film on a pair of glasses would open up a wide swath of invisible frequencies, including "near-infrared illumination," to our vision. Think of all the invisible EMR bouncing around out there. If so, then the glasses wouldn't need additional energy.

      But it doesn't open a wide swath -- if you absorb two photons, and reemit one photon with half the wavelength, you're basically just shifting the human eye's 400-750 THz (750-400nm) range down an octave to 200-375 THz (1500-800nm). (While you should be able to stack them in series to go two or three octaves down, it's not clear whether you can do this in a way that, as Immerman suggests, would add all those bands together. For now, let's just consider a single-octave filter.)

      We can consider this in two ways -- I find frequency easier for this particular problem, as that graph is better-behaved in the region of interest, but wavelength is more commonly used, and of course they'll both yield the same answer.

      • In wavelength terms, that's twice the bandwidth, so you'll only break even if the spectral radiation density (W/m2/nm) over that range is at least half that in the visible range. (Of course, we should properly use a weighted-average using the sensitivity of the human eye [wikipedia.org].)
      • In frequency terms, that's half the bandwidth, so you'll only break even if the spectral radiation density (W/m2/Hz) over that range is at least double that in the visible range. (Of course, we should properly use a weighted-average using the sensitivity of the human eye.)

      The discrepancy, of course, is due to the different types of spectral density -- it's analogous to the difference between a world map using Mercator vs. Gall-Peters projections.

      So now all we need is a spectrum of our light source. While we're not likely to use sunlight directly, starlight is basically comparable (despite some stars being redder and some bluer), and moonlight is simply reflected sunlight, so it's a decent first approximation, and it's easy to get data on. Here's a nice page with both graphs shown [sciencequestionswithsurprisinganswers.org] -- though that refers to sunlight in space, or as it enters the atmosphere; I couldn't quickly find a similar pair of graphs with atmospheric absorption included, but NIR is attenuated more than visible. I think you'll agree, using either method with the corresponding graph, that the power in the NIR band is not quite enough to break even. (Though as Immerman points out, if these add to, rather than obscuring, visible light, that may still be helpful.)

      Airglow, for what it's worth, is much higher in NIR than visible -- not sure that's enough to make this viable, since it's very dim in the visible, but it's an interesting angle I hadn't considered.

      However, if we're talking about stray light generated on or near Earth's surface (e.g. skyglow from a nearby city or highway), we have to consider two types of light. First, we have blackbody radiation -- whether from a fire or an incandescent lamp, this will tend to be comparatively cool, and have less visible light; in fact, these light sources should do much better than break even. On the other hand, we have LEDs, fluorescent lights, discharge lamps of various sorts, etc. -- these all have non-blackbody spectra selected or designed to provide visible light, and thus very likely to have little NIR content. (The rather bright sodium line at 819nm might seem like a counterexample, but of course that ends up at a barely-visible 410nm.) I believe these non-blackbody sources, taken together, already dominate generic city skyglow and lighted highways, and with the growth of LED and HID headlights, even unlit highways are trending this way.

  • (Score: 2) by Immerman on Thursday December 08 2016, @07:22PM

    by Immerman (3985) on Thursday December 08 2016, @07:22PM (#438811)

    Fewer photons, but probably roughly the same power, which is likely the more important consideration (not knowing the exact physics powering the human eye). Still, you're right, while they might brighten a borderline starlit scene a bit (assuming they don't attenuate visible light) they're probably not going to do a whole lot for you if you can't see anything to begin with. On the other hand, if you give your eyes a chance to adjust you can actually see quite a bit by starlight, especially using your peripheral vision which has more low-light sensitive rods, o they could still be useful.

    There's also the possibility, depending on efficiency and the range of frequency response they can engineer, that you could "stack" 4 layers of crystals to achieve a 16x frequency shift of the "easily seen" frequency range from 390-700nm down to 6240-11200nm, which substantial overlaps the thermal imaging range of 8000nm-15000nm, in which range people will all glow like 100W lightbulbs. You could even add in an 5th layer with a very fine "checkerboard" of additional doubling so that you could add the 12480-22400nm range, fully spanning the thermal range at the expense of halving the apparent brightness and "double-mapping" the color spectrum so each color could correspond to two different temperatures.