| Date | 28th, Jan 2021 |
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Unlike the rest of technologies available to modern consumers, the design and underlying physics of optical lenses have remained, for the most part, unchanged. In fact, the lenses that we have today are nearly identical to those developed and used roughly 3,000 years ago.
One of the consequences of such technological stagnation is the bottlenecks it leads to with regards to next-generation optical systems like wearable displays for virtual/augmented reality (VR/AR). For best results, the components of such devices need to be compact, lightweight, and cost-effective.
Next-gen metalenses could revolutionise the field field of VR/AR. Image: Nan Palmero via flickr.com, CC BY 2.0
After many years of hard work, a team of researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) might finally spur some genuine innovation in the field.
Led by Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, the team has developed two-millimetre achromatic metalens capable of focusing RGB colours without aberrations, and a miniaturised display for VR and AR applications.
Results are published in the journal Science Advances.
“Using new physics and a new design principle, we have developed a flat lens to replace the bulky lenses of today’s optical devices,” said senior author Zhaoyi Li. “This is the largest RGB-achromatic metalens to date and is a proof of concept that these lenses can be scaled up to centimetre size, mass produced, and integrated in commercial platforms.”
The new metalens uses arrays of titanium dioxide nanofins that enable them to equally focus wavelengths of light and eliminate chromatic aberration. Engineered to have a particular shape, and arranged in a specific pattern, these nanoarrays enable the researchers to control the focal length of red, green, and blue colour of light.
But what’s a lens if it can’t be incorporated in to an actual VR/AR system? For this purpose, the team also developed a near-eye display inspired by fibre-scanning-based endoscopic bioimaging techniques.
The display uses an optical fibre through a piezoelectric tube which, upon exposure to a voltage, makes the fibre tip begin scanning left and right, as well as up and down, to display patterns – essentially giving form to a small screen.
Image courtesy of Harvard John A. Paulson School of Engineering and Applied Sciences
When integrated into an actual VR/AR platform, the metalens would be situated directly in front of the eye, and the display would sit within the focal plane of the metalens. The virtual image would then form on the retina, projected by the pattern-scanning display, giving the appearance of being a part of the landscape, not too far from the eye.
Up next, Capasso and his colleagues plan to increase the size of the metalens, thereby enabling mass production at reasonable cost.
Source: seas.harvard.edu
