· String Theory Ping List ·
· Join · Bookmark · Topics · Google ·
· View or Post in 'blog · post a topic · subscribe ·
Posted on 10/03/2018 2:56:16 PM PDT by BenLurkin
Columbia Engineering researchers have created the first flat lens capable of correctly focusing a large range of colors of any polarization to the same focal spot without the need for any additional elements. Only a micron thick, their revolutionary "flat" lens is much thinner than a sheet of paper and offers performance comparable to top-of-the-line compound lens systems. The findings of the team, led by Nanfang Yu, associate professor of applied physics , are outlined in a new study, published today by Light: Science & Applications.
A conventional lens works by routing all the light falling upon it through different paths so that the whole light wave arrives at the focal point at the same time. It is manufactured to do so by adding an increasing amount of delay to the light as it goes from the edge to the center of the lens. This is why a conventional lens is thicker at its center than at its edge.
With the goal of inventing a thinner, lighter, and cheaper lens, Yu's team took a different approach. Using their expertise in optical "metasurfaces"—engineered two-dimensional structures—to control light propagation in free space, the researchers built flat lenses made of pixels, or "meta-atoms." Each meta-atom has a size that is just a fraction of the wavelength of light and delays the light passing through it by a different amount. By patterning a very thin flat layer of nanostructures on a substrate as thin as a human hair, the researchers were able to achieve the same function as a much thicker and heavier conventional lens system. Looking to the future, they anticipate that the meta-lenses could replace bulky lens systems, comparable to the way flat-screen TVs have replaced cathode-ray-tube TVs.
(Excerpt) Read more at phys.org ...
Coming to a cell phone near you
From the article:
Now that the meta-lenses built by Yu and his colleagues are approaching the performance of high-quality imaging lens sets, with much smaller weight and size, the team has another challenge: improving the lenses’ efficiency. The flat lenses currently are not optimal because a small fraction of the incident optical power is either reflected by the flat lens, or scattered into unwanted directions. The team is optimistic that the issue of efficiency is not fundamental, and they are busy inventing new design strategies to address the efficiency problem. They are also in talks with industry on further developing and licensing the technology.
...
The images in the video from this lens look terrible. This will probably never be commercialized which is why they are doing press releases instead of starting a company.
Expect more devices than ever to have cameras on them. Privacy is dead. The only protection we have is that the amount of data will swamp the spymasters’ abilities to sort, sift, understand, and act.
Possibly a very big deal, but article says so far they’ve only made it work in the near infrared: 1.2 to 1.7 microns, which is somewhat less than the bandwidth of the visible spectrum.
Also they don’t give the “speed” (or “f-number”) of the lenses they’ve produced. If they can make f/2.8 or f/2, that would be revolutionary. If they’re at f/60 or f/120, they’re not much better than a pinhole camera.
Still, interesting, and potentially a game changer.
When everybody is bugged....nobody is bugged.
Contrary to what would seem to be common sense. If you defeated all bugs you would stand out and come to the unwanted attention of the spy masters.
The visible spectrum is from 390nm to 750nm, a range of 360nm.
These lenses work in the near infrared, from 1200nm to 1700nm, a range of 500nm. That is a bandwidth somewhat GREATER than the visible spectrum.
These lenses work in the near infrared, from 1200nm to 1700nm, a range of 500nm. That is a bandwidth somewhat GREATER than the visible spectrum.
That's true, but the difficulty lies in getting a given bandwidth as a percentage of center wavelength.
500 nm bandwidth with a center of 1450 nm is a lot easier than 360 nm bandwidth with a center of 570 nm.
Fair point. It also looks like the structures act as waveguides. Making a 570nm waveguide will be more difficult than a 1400nm waveguide.
On a slightly different note, these things somewhat remind me of a Fresnel.
Eyglasses will be changed.
Yes, except with much small features, so they rely on diffraction instead of refraction. I think they're basically a computed hologram of a convex lens, but somehow made to work with non-coherent broadband light.
Ping
Are there no longer any native born Americans in these positions?
Seems I never see western names associated with such articles anymore.
The average Caucasian human hair is about 100 microns thick. This is 100 times smaller.(10,000 angstroms)
A camera placed anywhere to spy on you.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.