While traditional lens is made from glass, metalenses use flat surfaces made up of nanostructures to focus light. These simple, flat surface lenses could replace bulky, curved lenses currently used in optical devices.
The biggest drawback with metalenses has been their inability to focus the full spectrum of light. That’s not the case anymore. Early in 2018, scientists at Harvard University unveiled a metalens that has the potential to shrink the size of any device that uses a camera, while at the same time improving performance. The team at Harvard’s Paulson School of Engineering and Applied Science have developed a metalens that can focus the entire visible spectrum of light – including white light – at a focal point, with high resolution.
One advantage metalenses have over conventional lens systems is that multiple elements are not needed to correct for aberrations. Multiple elements make lenses thick, therefore devices are thicker.
According to Federico Capasso, a professor of applied science at Harvard and author of the research paper on the new metalens, “Our lens is a flat lens, so it’s thinner than a conventional lens.” He went on to say that if this lens was to be used in a cellphone, the phone would be much thinner.
By correcting chromatic aberration, the metalens developed by the researchers at Harvard addresses the problem facing virtual and augmented reality hardware developers.
Chromatic aberration – color focal point mismatch resulting from the propagation speed of different light frequencies – is one of the many visual artifacts causing the lack of visual fidelity and realism in VR and AR. To correct this issue, high-end VR or AR hardware often uses advanced computational techniques to adjust focal points on a color-by-color bases.
The metalenses developed by Capasso and his team use arrays of titanium dioxide nanofins to equally focus wavelengths of light and eliminate chromatic aberration. Previous research demonstrated that different wavelengths of light could be focused but at different distances by optimizing the shape, width, distance, and height of the nanofins. The researchers created units of paired nanofins that control the speed of different wavelengths of light simultaneously. The paired nanofins control the refractive index on the metasurface and are tuned to result in different time delays for the light passing through different fins, ensuring that all wavelengths reach the focal spot at the same time.
The researcher’s goal is to upscale the lens to about 1cm in diameter. This would open a host of new possibilities, including applications in virtual and augmented reality.
“With a metalens, we can have the same foundry that makes the sensor chip make the metalenses for the camera module,” Capasso said. “That’s why so many companies are excited about this. There is a chance to disrupt the business model anywhere cameras are used.
However, don’t expect to see a cellphone with metalenses two years from now. This is in the research stages, but it’s a big step forward, according to Capasso.
At Universe Optics, we pride ourselves on manufacturing the highest quality, precision lenses available. As technology changes, you can be assured that our team of engineers, along with our manufacturing facilities, will deliver exceptional results when it comes to your specifications.