Variable focus skinny lens designed for augmented and digital actuality headsets

Researchers have developed a skinny lens with a repeatedly tunable focal size. The new lens might one day make visible fatigue from augmented and digital actuality (AR/VR) units a factor of the previous.

“Many of the 3D displays used in today’s AR/VR devices cause discomfort after long-term use due to the vergence-accommodation conflict,” stated analysis group chief Yan Li from Shanghai Jiao Tong University in China. “Our lens, which is known as an Alvarez lens, can be used to alleviate this problem. This could provide a more comfortable and more realistic 3D experience that would enable more widespread use of AR/VR headsets.”

The researchers describe their new lens in Optics Express. It is produced from two flat, or planar, liquid crystal parts that may be moved in relation to one another to repeatedly change the lens’s focal size. To reveal the brand new Alvarez lens, they integrated it into an AR show system that displayed virtual images on a real-world view at completely different depths.

“This lens has a continuous and large tuning range, a thin formfactor, is lightweight and can be made using a simple low-cost fabrication process,” stated Li, who collaborated with Shin-Tson Wu’s lab on the University of Central Florida College of Optics and Photonics. “In addition to AR/VR devices, this type of compact tunable lens could be useful for microscopic imaging, machine vision, laser processing and ophthalmology.”

Improving the digital expertise

In AR/VR units, the vergence-accommodation battle happens as a result of the left and proper eyes obtain two barely completely different pictures that the mind places collectively to type a digital 3D picture. To see the picture clearly, every eye focuses on the mounted 2D aircraft the place the picture is displayed. This causes the merged 3D picture and the one eye focus on the 2D aircraft to be inconsistent, resulting in dizziness and visible fatigue.

It’s doable to minimize the vergence-accommodation battle with a vari-focal show, which dynamically adjustments the depth of single-plane digital objects in order that digital objects seem to exist at completely different depths in numerous moments. Another possibility is a multi-focal show system, which renders a number of 2D cross-sections of a digital object at a number of depths concurrently to reconstruct a 3D quantity. In each instances, the VAC drawback is suppressed as a result of the human eye can concentrate on the proper depths of the digital objects.

Vari- or multi-focal show programs want a tunable lens that may change focus repeatedly inside a wide range whereas additionally being compact and light-weight sufficient to be helpful in head-mounted AR/VR units. Li has been engaged on fatigue-free AR shows and liquid crystal units for about 10 years and not too long ago developed a option to fabricate a liquid crystal primarily based diffractive optical part generally known as a Pancharatnam-Berry (PB) optical ingredient that can be utilized to create a tunable lens that meets these necessities.

“Our method enables Pancharatnam-Berry optical elements with the complicated and irregular phase profiles needed to create an Alvarez lens with high precision, low cost and unprecedented convenience,” stated Li. “We wanted to see if this ultracompact Alvarez tunable lens could offer a solution to the long-standing vergence-accommodation conflict problem in VR and AR displays.”

AR show demonstration

The researchers used their new method to create a tunable Alvarez lens made from two planar Pancharatnam-Berry liquid crystal parts. In every ingredient, an ultrathin polymetric liquid crystal layer only a few hundred nanometers thick is coated onto a 1-mm-thick glass substrate. They integrated this Alvarez lens into an AR show system constructed utilizing off-the-shelf optical parts on an optical desk. By laterally shifting the 2 parts of the Alvarez lens, they had been capable of repeatedly tune the depth of the digital picture from close to to far distances.

“No matter the depth, the virtual image exhibited the same in-and-out of focus effect as the real 3D objects in the real world,” stated Li. “This meant that the human eye could always focus on the depth of the virtual 3D image correctly, thus overcoming the vergence-accommodation conflict problem.”

The Alvarez lens demonstrated on this work was optimized for single-color operation at 532 nm, however the researchers are engaged on methods to make use of it for a full-color show. They additionally need to undertake an digital methodology for controlling the lateral displacement between the optical parts, which was carried out manually on this analysis.