Participants in a recent study rated the comfort and performance of these so-called near-eye displays as comparable to that of traditional computer monitors. Near-eye displays are like eyeglasses with a monitor built into the lenses.
"The problems with near-eye devices range from motion sickness to the device's weight to poor image resolution," said James Sheedy, a study co-author and an associate professor of optometry at Ohio State University.
"But the design of such devices is improving, and the subjects in our study found the function and usefulness of the near-eye display similar to that of a regular computer screen."
The research appears in a recent issue of the journal Optometry and Vision Science. Sheedy, who is also the director of the computer vision clinic at Ohio State, conducted the study with Neil Bergstrom, the vice president of business development at Iridigm Display Corporation in San Francisco.
At the time of the study, Bergstrom was the chief technology officer of InViso Corporation, a now-defunct startup company specializing in microdisplays. InViso provided support for the study, and Sheedy served as a consultant to InViso during the study. InViso was acquired by the company Three-Five Systems, Inc. in spring 2002.
The researchers asked 22 subjects to participate in a reading experiment and a separate movement experiment.
The subjects used a total of five different displays to complete the tasks in the reading experiment: a hand-held monocular vision display with an attached cover for the non-viewing eye; a binocular vision display with a holder that wrapped around the subject's head; hard copy with printed text; a flat panel computer screen; and a screen on a hand-held computer.
The participants were asked to perform four trials each of three different reading tasks: the first had subjects reading four separate paragraphs of about 325 words in length and answering three to four multiple choice questions at the end of each passage. The second task involved counting the occurrences of an assigned letter in a paragraph of nonsense words. In the final reading experiment, subjects were instructed to find three out of four occurrences of an assigned three-letter word on a spreadsheet filled with various three-letter words.
The researchers measured how long it took each subject to complete each reading task using the respective visual display. After using each type of display, the subjects were asked if they had experienced any of the following symptoms, and to what degree: headache, eyestrain, sore or irritated eyes, blurry vision, dizziness, nausea, disorientation, neck ache or backache.
Results showed that the performance of the monocular vision display was comparable to the performance of the flat panel screen and hard copy text.
"To our surprise, the reading tasks were completed faster with the monocular display than with the binocular display," said Sheedy. "This may have had to do with how each display fit the user, or the design of the respective device."
However, the subjects did complain about eyestrain more with the monocular display than with any of the other displays.
Performance speeds with the binocular display were about 5 to 7 percent slower than for the other displays, the researchers found. Sheedy suspects that this slower speed may have something to do with how the image is aligned along the line of sight in each lens.
The image displayed by a near-eye device may appear to be much farther - up to 6 feet away - from the viewer than an image on a typical computer monitor. The seemingly greater distance makes for easier viewing, Sheedy said. But the image size in a near-eye display is about the size of an average computer screen.
"Traditional displays are constrained by their physical size and are usually about 20 to 30 inches from the eyes," he said.
The second experiment assessed the risk for motion-related symptoms while wearing the binocular head display.
Seated subjects were asked to rotate their heads several times to the left and right, and again up and down. They performed the same task while standing. They were also asked to rotate their head while sitting and while standing.
"Motion-related symptoms were a large problem in previous studies," Sheedy said. "Participants didn't have much problem with motion sickness in this study, probably due in part to the nature of the tasks they were asked to perform.
"Most of the previous studies on near-eye displays used video movement or virtual reality tasks that created movement on the virtual display. These kinds of tasks are more likely to cause queasiness."
Nor were the participants in the current study fully immersed in the image. That is, neither the monocular nor binocular displays blocked the user's peripheral vision, so he could focus on the image in front of him and still see his surroundings.
"Being able to see the real environment while wearing a display gives the user a visual reference that can help lessen confusion when the eye sees the image move," Sheedy said. "For most of the common uses, the user wouldn't want to be fully immersed in the virtual environment."
Although several prototypes exist, near-eye displays have yet to become common. It's only a matter of time before they do, Sheedy said. He doesn't see such devices becoming a commodity in the office, but he does predict that they'll find a place in business and industry.
"From a remote location, a warehouse worker stocking orders can use a wearable display to look up accounts," he said. "A traveling salesperson can pull up email messages, addresses and other vital information en route to his destination."
A user can plug his display into a hand-held computer and see a full-size page, or surf the web from his cell phone and see the entire site, rather than a fraction of the information.
"These portable displays give a viewer complete privacy when viewing a document," Sheedy said. "That goes for confidential documents, email, web pages and so on."
Written by Holly Wagner, 614-292-8310; Wagner.firstname.lastname@example.org