Can 3D images be made to look more realistic? York University vision researchers have discovered how a to keep our eyes on the prize, so to speak.
In order to see 3D images properly, our left and right eyes have to view separate images. Because 3D display technology isn’t perfect, there are times when images intended for one eye become contaminated by images meant for the other. Researchers have uncovered a link between this phenomenon, dubbed “crosstalk”, and the amount of depth in the images we see onscreen.
“Our study found that the more interference from crosstalk, the less depth you’ll see. This reduction in depth can make 3D images appear less realistic,” says Inna Tsirlin, a PhD student in psychology working in York’s Centre for Vision Research, part of the Faculty of Health.
Right: An image that is undistorted by crosstalk
To minimize such visual distortions, crosstalk should be kept at levels of four per cent or lower, the study recommends. “For viewers to see as much depth as intended, 3D displays should ensure that less than four per cent of the left image leaks into the right eye, and vice versa,” Tsirlin says.
Tsirlin and her collaborators conducted experiments using a custom-built display. They introduced precise amounts of crosstalk to a pair of lines presented separately to participants’ left and right eyes. The brain combines these 2D images to perceive them as one image in 3D.
Participants were asked to indicate the amount of depth they perceived using a virtual ruler. The study showed that crosstalk was detrimental at even the smallest depths tested, and became more disruptive as depth increased.
Right: The same image showing the distortion caused by crosstalk
“For example, instead of seeing two objects at ten centimetres apart in depth, you would see them at five centimetres apart if the crosstalk is high enough. We also found that the detrimental effect of crosstalk on the perceived amount of depth is stronger when there is a larger depth range in a 3D image. So, there will be more disruption for objects at one millimetre apart than for objects at ten centimetres apart in depth,” says Tsirlin.
Previous research has established that crosstalk causes viewing discomfort, which can include eye strain, headaches and dizziness. Tsirlin says optimizing hardware for a crosstalk level below four per cent may resolve these issues as well.
Tsirlin is supervised by York Professors Robert Allison and Laurie Wilcox, who co-authored the study. Their initial findings were recently presented at the international Stereoscopic Displays and Applications 2011 conference in San Francisco.
The research was conducted as part of the 3D Film Innovation Consortium (3D FLIC), an interdisciplinary collaboration of scientists, filmmakers and industry partners such as Cinespace Studios, IMAX, Christie Digital and Starz Animation. 3D FLIC is funded by the Ontario Media Development Corporation (OMDC) and the Ontario Centres of Excellence (OCE).
Tsirlin’s research is supported by a Natural Sciences & Engineering Research Council of Canada (NSERC) graduate scholarship. She was among the first cohort of students to complete York’s Neuroscience Graduate Diploma Program.