Virtual reality (VR) content doesn’t need to look like real life to be immersive yet ultimately that is one end goal looking to be achieved. There are various factors and problems that need to be solved to get there, one of which are the big and heavy lenses needed in each head-mounted display (HMD). Well those clever folks over at Harvard University’s John A. Paulson School of Engineering and Applied Sciences may have come up with a possible solution, creating a tiny metalens that can focus the entire visible spectrum of light — including white light — in the same spot.
Due to the way metalenses work they are thin, easy and cheap to make, meaning that if they were to be used inside a VR headset, not only would it be lighter and more comfortable to wear, the actual visual experience would be even better.
“Metalenses have advantages over traditional lenses,” says Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS and senior author of the research in a statement. “Metalenses are thin, easy to fabricate and cost effective. This breakthrough extends those advantages across the whole visible range of light. This is the next big step.”
The problem when focusing the entire visible spectrum and white light is that each wavelength moves through materials at different speeds. So with a traditional lens each colour wavelength will hit the eye at different times, causing an issue called chromatic aberration. To get around this conventional lenses have to be stacked, increasing cost and weight.
So the Harvard team has created a metalens that feature arrays of titanium dioxide nanofins to equally focus wavelengths of light and eliminate chromatic aberration.
“One of the biggest challenges in designing an achromatic broadband lens is making sure that the outgoing wavelengths from all the different points of the metalens arrive at the focal point at the same time,” said Wei Ting Chen, a postdoctoral fellow at SEAS and first author of the paper. “By combining two nanofins into one element, we can tune the speed of light in the nanostructured material, to ensure that all wavelengths in the visible are focused in the same spot, using a single metalens. This dramatically reduces thickness and design complexity compared to composite standard achromatic lenses.”
While this is certainly an interesting step towards better looking VR don’t expect anything just yet as the researchers next goal is to scale up the lens, to about 1 cm in diameter for VR and augmented reality (AR) applications. That being said, the intellectual property relating to this project has been protected and licensed to a startup for commercial development. As development continues, VRFocus will keep you updated.