Flat Lens Promises Possible Revolution In Optics (bbc.com)

An anonymous reader shares a BBC report: A flat lens made of paint whitener on a sliver of glass could revolutionize optics, according to its U.S. inventors. Just 2mm across and finer than a human hair, the tiny device can magnify nanoscale objects and gives a sharper focus than top-end microscope lenses. It is the latest example of the power of metamaterials, whose novel properties emerge from their structure. Shapes on the surface of this lens are smaller than the wavelength of light involved: a thousandth of a millimetre. "In my opinion, this technology will be game-changing," said Federico Capasso of Harvard University, the senior author of a report on the new lens which appears in the journal Science. The lens is quite unlike the curved disks of glass familiar from cameras and binoculars. Instead, it is made of a thin layer of transparent quartz coated in millions of tiny pillars, each just tens of nanometres across and hundreds high.PetaPixel has more details.

Comments

Canon's Diffractive Optics taken to a new level

[dgatwood]

Sounds like they've taken Canon's Diffractive Optics to a new level. Basically, DO uses Fresnel lenses with smaller ribs. This raises the bar to nanoscale features, which should result in even less distortion and other problems. I, for one, welcome our new superzoom overlords. I'm envisioning a lightweight 16-600 that will outperform everything on the market today by a large margin....

Re:Canon's Diffractive Optics taken to a new level

[doublebackslash]

It isn't the same as a Fresnel lens.
The scale of these features are below the wavelength of light. That means that these structures interact with the electromagnetic field in a way that allows for a negative refractive index, which is impossible using conventional optics, rather than bending the light in steps like a Fresnel lens. This is more like an array of phased antennae, but small enough to work with light's high frequency. They have been doing similar things with microwaves for something like a decade or so.
Google image search for microwave metamaterial. It will show you what sort of thing these pillars are mimicking, but on the order of millimeters instead of nanometers.

Monocrhomatic

[Anonymous Coward]

The downside with this type of lens is they are monochromatic. Visual light covers and entire octave (wave length doubles). It is very hard to make a meta material lens that has that big of a range. The actual science paper talks about this and describes how to make a lens in red, blue and green. These lenses need object to be illuminated by lasers. This is amazing stuff, but we are a long ways from cell phone camera lenses, which are talked about in the science "journalism" articles.

actually (meta-material-style) optics

[slew]

...but still the same basic optics solved hundreds of years ago.

Actually, no. More details.

The short story of what is different is described in their paper (preprint here)...

Although visible planar lenses can be realized by diffractive components, high NA and efficiency are not attainable because their constituent structures are of wavelength scale that precludes an accurate phase profile..... To maximize the polarization conversion efficiency, the nanofins should operate as halfwaveplates. This is achieved due to the birefringence arising from the asymmetric cross section of nanofins with appropriately designed height, width, and length

The new idea (well not new, but meta-material approach) is that for each x,y position on the lens, a nanofin is positioned and rotated so that a localized "half-wave-plate" effect created by birefringence of the nanofin crossection modifies the phase profile of incident circularly polarized light to that which propagation through a spherical lens would have produced: All without a refractive component. A fresnel-like lens uses a small refraction (lens) element instead of a nano-sized half-wave plate to accomplish bending, but refraction requires an interface, and you can't make that interface too small without diffractive effects.

The catch? Chromatic aberration will be much worse than a traditional lens because the phase profile is only correct for one wavelength (traditional materials also have a index of refraction that changes with wavelength, but it isn't strictly a linearly proportional geometric effect like rotating nanofins). This new technique would work fine for most scientific purposes where you have monochromatic light, but taking a full color picture with this type of lens might take quite a bit of dsp-post-processing to look reasonable.