Campus researchers find cause of discomfort in some 3-D displays

Derek Remsburg/Staff
A campus research team found a reason that viewing 3-D stereo imagery on mobile devices can cause discomfort such as headaches.

Researchers at UC Berkeley have recently pinpointed a cause of visual discomfort, headaches, eyestrain, and blurry vision when viewing 3-D stereo imagery, according to a study published Friday.

Displays utilizing 3-D stereo imagery, including those on mobile devices  do not optimally present 3-D stereo imagery, which results in visual discomfort, according to a recent study led by Martin Banks, a campus professor of optometry and vision science.

According to the study, depending on size — ranging from mobile devices to movie theater screens — and viewing distance for 3-D stereo imagery, content should either come toward or move away from the viewer.

Joohwan Kim, a co-author of the study, said that usually when the movie industry translates a 3-D film from the theaters onto a smaller platform, like a mobile phone, they scale the depth range uniformly while not thinking about the biological visual issues.

This type of scaling can cause what is called the vergence-accommodation conflict in viewers, resulting in discomfort, Kim said.

According to Kim, the conflict arises “when you fix your accommodation (where the light source is) but change your vergence, which depends on the shifting depth of the 3-D content.”

There are various means of increasing viewier comfort when looking at 3-D content, according to the study.

When a 3-D stereo device is fairly close, such as in a mobile device or laptop screen, viewers experience more visual comfort when the content appears to move past the screen rather than out toward the viewer, the study states.

Conversely, when viewing 3-D stereo imagery at a farther distance like in a movie theater or on a television screen, viewers are more visually comfortable when the 3-D content appeared to move out of the screen toward them, the study found.

Bill Sprague, a third-year campus graduate student working with Banks, added that the conflict is not one people experience naturally. In the natural world, a typical person would not experience the vergence-accommodation conflict because the place where the eye receives light and where the eye focuses on the object in space are continuously linked together, he said.

According to Kim, age is a factor when considering levels of viewer discomfort. The study focused on young adults ranging from the age of 19 to 33, because by the age of 50, people begin to lose the ability to change accommodation, which is what stereo 3-D images require, he said.

When individuals approach the age of 50, Kim said he would expect that they will likely experience less discomfort from 3-D stereo imaging than their younger counterparts.

Brian Barsky, a campus professor of computer science and vision science, said this study brought to light one of many factors that cause discomfort when observing 3-D imagery.

“Although discomfort experienced in viewing stereo displays arises due to a myriad of causes, this valuable study shows that one of the factors is the dissonance between the converging movements of both eyes to fuse a single binocular vision and the accommodation, or focusing, of the crystalline lens inside each eye,” he said.

According to Banks, the study will hopefully impact future 3-D imagery technology.

“We hope that content providers will use this information to help design future 3-D content, assist display manufacturers and will help design displays.”