SoylentNews is people
SoylentNews
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.
(Score: 4, Interesting) by dvader on Thursday December 08 2016, @01:11PM
I haven't read the article but the linked abstract says "transform the frequency" which could mean turning invisible light into visible. The image suggests it is up-conversion, from low frequency to higher (from w to 2w), that is from IR to visible (or at least less IR).
Since higher frequency photons carry more energy than lower frequency, it can't be a one-to-one conversion but must be a conversion of at least two low energy photons to one high energy photon. To get a sharp image, the direction of each photon must be preserved which means the momentum of the first photon must be "stored" in the antenna until the second photon arrives and both can be released. I guess the momentum of the outgoing photon is the sum of the ingoing ones. So the antenna itself must be highly directional so it doesn't absorb light from vastly different directions. I also assume each antenna is tuned to a single frequency as well...
That's enough speculation for now. Maybe someone with a bit more knowledge of optics can explain this in detail.
(Score: 0) by Anonymous Coward on Thursday December 08 2016, @01:34PM
Well, while speculating, it could also be that the first photon is simply absorbed (with no information but its energy remaining, minus the energy cost of the recoil, of course) and the second photon then gets the energy of the first added, without changing its direction (again, with an energy correction due to recoil). Assuming the photons are uncorrelated and sufficiently many, that would still give a pretty good sampling of the original photons, that is, a pretty good image.
(Score: 3, Informative) by dlb on Thursday December 08 2016, @01:57PM
Second harmonic generation (also called frequency doubling or abbreviated SHG) is a nonlinear optical process, in which photons with the same frequency interacting with a nonlinear material are effectively "combined" to generate new photons with twice the energy, and therefore twice the frequency and half the wavelength of the initial photons.
There's some clever things going on here in this field...
(Score: 2) by JeanCroix on Thursday December 08 2016, @09:21PM
(Score: 0) by Anonymous Coward on Thursday December 08 2016, @06:45PM
> To get a sharp image,
A sharp image may not be necessary.
Consider modern digital image compression. It works by breaking out chroma (color) and luma (brightness) and the chroma is half the resolution of the luma. For example a typical 1920x1080 hdtv frame will have 1920x1080 pixels of brightness (8-bit) and 960x540 pixels of each Red/Green/Blue. The human eye integrates the higher resolution brightness with the lower-resolution color to get an image that is perceived to be the full resolution.
So, if these are used in low-light conditions, rather than black-out conditions, we might get the same effect where fuzzy infra-red upconverted photons are integrated with the natural-light photons to produce an image the brain perceives as sharp enough.