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Nanotechnology Researchers Are One Step Closer to the Perfect ‘Meta-lens’ for AR/VR Headsets

Nanotechnology Researchers Are One Step Closer to the Perfect ‘Meta-lens’ for AR/VR Headsets

AR and VR headsets of the future could have clearer, lighter, and wafer thin lenses, thanks to a new manufacturing process that uses nanotechnology to not only shrink the thickness of the lens, but also correct for the sort of color distortions common to the lenses currently used in VR headsets.

 Update (4/24/18): Harvard researchers shared new developments in their meta-lens research this week in an article in The Conversation.

 

Unimaginably small, discrete nanostructures in the meta-lens bend incoming light to varying degrees. | Image courtesy Capasso Group, Harvard University (CC BY-ND)

While 1mm thick meta-lenses capable of bending incoming light to a singular focal point have been previously demonstrated, the researchers say they’ve refined their design, allowing for arbitrarily adjustments to the transmission speed of light passing through different points on the lens. By modulating the transmission speed, the light can be made to arrive simultaneously at the focal point, resulting in a sharper image, the researchers say.

To [reach the focal point at the same time], [light from the edges of the lens] has to travel faster [than light from the center]. So we built some nanostructures that transmit the light more quickly, and others that do so more slowly. We put the faster-transmitting nanostructures at the edges of the lens, so light travels through them faster than in those in the middle. This effectively helps the light from the meta-lens edges catch up with light at the center, so that all the rays focus together.

 Though nanotechnology sounds exotic (and expensive), the researchers say that this approach could lead to better and cheaper lenses, and specifically suggest head mounted displays as one potential application:

Once designed, meta-lenses can be created as part of a wider mass production process: for instance, of VR headsets or augmented reality glasses. They can also be used in place of more expensive ground-glass camera lenses on smartphones and laptops, reducing weight, thickness and cost of portable devices.

Original Article (2/26/15): The news came out of Harvard’s School of Engineering and Applied Sciences (SEAS), detailing a technical improvement on a prototype ‘flat lens’, which now uses what they call a “glass substrate and tiny, light-concentrating silicon antennas” to redirect light.

The updated design differs from ‘flat lenses’ of the past by using nano-sized silicon antennas to immediately bend incoming light, that thanks to the recent introduction of the electrically insulating material, can now redirect red, green, and blue (the three colors used in displays) light in the visible spectrum at variable angles.

What this now means is that complicated effects like color correction, which in a conventional optical system would require light to pass through several thick lenses in sequence, can be achieved in one extremely thin, miniaturized device,” said principal investigator Professor Federico Capasso of SEAS.

Taking out the bulky lenses of modern VR headsets and replacing them with the new generation of ‘flat lenses’ could not only significantly reduce the headset’s physical size and weight, but could also entirely remove ‘chromatic aberration’, a misalignment of colors caused by the fact that lenses bend light of different colors at slightly different angles.

The phenomenon has traditionally been corrected by adding a number of lenses to create a bulky achromatic lens setup to shift red, green and blue colors of the spectrum closer to the center focal point. The more lenses, the closer you are to ‘perfect’, but the solution is adds cost, weight, and size with each addition of corrective lenses.

Another less weighty method of chromatic aberration correction can be achieved by digitally shifting colors in the software, the method primarily used in consumer VR headsets currently in development that use a single lens, like the Oculus Rift. But it isn’t perfect, and works only when the eye is looking directly into the center of the lens, revealing artifacts of chromatic aberration when users look elsewhere on the lens (as they tend to do naturally when presented with a wide field of view).

An example of chromatic aberration correction from Oculus. Notice the separation of colors toward the edge of this scene. Through the Rift’s lenses, the colors are aligned.

Founder of Oculus VR Palmer Luckey, said this a little over a year ago in regards to another compact lens solution, the fresnel lens, and oft-proposed solution to reduce the bulk and weight of VR optics:

they kill contrast, add a variety of annoying artifacts, and don’t actually save all that much weight. They don’t help with form factor, either; Fresnels cannot come close to matching the focal length/magnification of other optics tech.”

There’s no word yet on when the lens tech will be ready for production—or for what cost—but it’s possible that upgrades of this type could follow a similar path set out for future VR headset displays. As demand for VR grows, the co-opted smartphone screens taken from the mobile ecosystem could give way to more robust, custom-built displays that would offer higher refresh rates, resolution, and a wider field of view.

Demand would likely also increase for VR-specific tech in optics, eventually giving lens manufacturers a good reason to throw their chips in with the virtual reality crowd too, but only as soon as the ‘flat lens’ is safely out of the R&D labs and into the marketplace.

However, established fields like photography, astronomy, and microscopy could make good use of the new, slimmed down optics, and help bring the technology to market. So VR might have to play second fiddle and keep rummaging through the parts bins of other industries for a while longer—but you know what they say about good things and waiting.

                                    Courtesy; www.roadtovr.com