Variable focus skinny lens designed for augmented and digital actuality headsets

Researchers developed a really skinny lens with a constantly tunable focal size and confirmed that it could possibly assist overcome vergence-accommodation battle in an AR system. Credit score: Yan Li, Shanghai Jiao Tong College

Researchers have developed a skinny lens with a constantly tunable focal size. The brand new lens may someday make visible fatigue from augmented and digital actuality (AR/VR) gadgets a factor of the previous.

“Lots of the 3D shows utilized in at the moment’s AR/VR gadgets trigger discomfort after long-term use as a result of vergence-accommodation battle,” stated analysis staff chief Yan Li from Shanghai Jiao Tong College in China. “Our lens, which is called an Alvarez lens, can be utilized to alleviate this downside. This might present a extra snug and extra lifelike 3D expertise that might allow extra widespread use of AR/VR headsets.”

The researchers describe their new lens in Optics Categorical. It’s created from two flat, or planar, liquid crystal parts that may be moved in relation to one another to constantly change the lens’s focal size. To exhibit the brand new Alvarez lens, they integrated it into an AR show system that displayed digital pictures on a real-world view at totally different depths.

“This lens has a steady and enormous tuning vary, a skinny formfactor, is light-weight and might be made utilizing a easy low-cost fabrication course of,” stated Li, who collaborated with Shin-Tson Wu’s lab on the College of Central Florida School of Optics and Photonics. “Along with AR/VR gadgets, the sort of compact tunable lens could possibly be helpful for microscopic imaging, machine imaginative and prescient, laser processing and ophthalmology.”

Bettering the digital expertise

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

Variable focus thin lens designed for augmented and virtual reality headsets
The researchers used their new lens to create a benchtop augmented actuality system. The photographs present the lens sub-elements shifted laterally -5 mm, 0 mm and 5 mm after which imaged at totally different depths. Irrespective of the imaging depth, the digital picture confirmed the identical in-and-out of focus impact as the true 3D objects. Credit score: Yan Li, Shanghai Jiao Tong College

It is attainable 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 totally different depths in numerous moments. An alternative choice 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 downside is suppressed as a result of the human eye can concentrate on the proper depths of the digital objects.

Vari- or multi-focal show methods want a tunable lens that may change focus constantly inside a wide range whereas additionally being compact and light-weight sufficient to be helpful in head-mounted AR/VR gadgets. Li has been engaged on fatigue-free AR shows and liquid crystal gadgets for about 10 years and just lately developed a option to fabricate a liquid crystal based mostly diffractive optical element often called a Pancharatnam-Berry (PB) optical ingredient that can be utilized to create a tunable lens that meets these necessities.

“Our methodology allows Pancharatnam-Berry optical parts with the sophisticated and irregular section profiles wanted to create an Alvarez lens with excessive precision, low value and unprecedented comfort,” stated Li. “We wished to see if this ultracompact Alvarez tunable lens may provide an answer to the long-standing vergence-accommodation battle downside in VR and AR shows.”

AR show demonstration

The researchers used their new method to create a tunable Alvarez lens manufactured 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 have been capable of constantly tune the depth of the digital picture from close to to far distances.

“Irrespective of the depth, the digital picture exhibited the identical in-and-out of focus impact as the true 3D objects in the true world,” stated Li. “This meant that the human eye may at all times concentrate on the depth of the digital 3D picture appropriately, thus overcoming the vergence-accommodation battle downside.”

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. In addition they need to undertake an digital methodology for controlling the lateral displacement between the optical parts, which was carried out manually on this analysis.

Researchers use flat lenses to increase viewing distance for 3D show

Extra data:
Shuyi Chen et al, Planar Alvarez tunable lens based mostly on polymetric liquid crystal Pancharatnam-Berry optical parts, Optics Categorical (2022). DOI: 10.1364/OE.468647

Variable focus skinny lens designed for augmented and digital actuality headsets (2022, September 8)
retrieved 9 September 2022

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