A new device aims to make augmented reality (AR) technology easier on the eyes. Developed by researchers at the University of Arizona and the University of Connecticut, the OST-HMD (optical see-through head-mounted display) device is similar to Google Glass in that it superimposes 2-D computer-generated images in the user’s direct view. However, transitioning between 2-D images and the 3-D physical world can cause strain on the eyes, particularly at short distances as a result of what’s called the accommodation-convergence mismatch problem: essentially the eye’s inability to focus simultaneously on a 2-D screen and the 3-D world. The new device alleviates this by superimposing the images in 3-D, rather than 2-D. A 3-D depiction of the characters “3D” is decomposed into various perspective views in the micro integral imaging display. Images courtesy of Optics Express. “Minimizing visual discomfort involved in wearing AR displays remains an unresolved challenge,” said Hong Hua of the University of Arizona, a lead researcher. “The eyes are going back and forth between the screen and the three-dimensional scene away from the screen, causing conflicting depth perception cues and visual fatigue.” The researchers created the 3-D images using a microscopic integral imaging display, a technology they also developed. In this technique, a tiny, high-resolution screen produces views from different perspectives of the 3-D image that is to be superimposed onto “a direct view of reality.” The artificial 3-D image behaves as if it were a real object in front of the user. When the position of the camera moves, the perspective of “3D” also slightly shifts. The views then combine to reconstruct a 3-D scene that is sent into the eye through an eyepiece. The lens is based on freeform optics, the researchers said, which allows users to directly view virtual images as real-life scenes. Hau said the device could become “a transformative technology to redefine the way we perceive and interact with digital information.” Potential applications include medical imaging — for example, CT images could be overlaid on a patient during surgery — and enhanced military operations, such as incorporation of 3-D virtual objects into real-world environments for training purposes. Before commercialization of the new OST-HMD device is possible, additional studies are needed, Hua said. Improvements in its depth and spatial resolution, the viewing angle of the microscopic integral imaging technology and the freeform eyepiece also need to be made. The research is published in Optics Express (doi: 10.1364/OE.22.013484).