The passive vs. active 3D TV debate is ongoing. Both technologies have their advantages, and neither one is perfect. On one hand, active glasses provide full resolution, but are heavy, require a sync signal from the TV, and consume batteries. On the other hand, passive displays halve the vertical resolution of the TV, but the glasses are more comfortable. Furthermore, the horizontal interlacing rows of the passive display are still visible at the recommended viewing distance. Horizontal interlacing causes other problems, too, as we discovered in a recent study, published in ACM Transactions on Applied Perception.
One could argue that by displaying half the pixels of the image to each eye, the resulting perceived resolution would be that of the full image. Intuitively, it would thus be beneficial to display every other pixel row of the image to the viewer. However, the visual system does not align the rows as neatly as we would like. Instead, it searches for matching features in the images from the left and right eyes. As a result, if we have an oblique edge as in the figure above, the visual system faces a choice whether to match the feature to the row above or below the feature.
In our study, some participants’ visual system preferred the match above, and others’ below. Whichever the direction was, all participants perceived depth where there should be none. The depth artifact was still visible at very small pixel sizes. To eliminate the depth artifact, the viewing distance for a 46″ HD resolution TV would have to be 7 meters (23 ft.) A more feasible solution to the problem is to average the even and odd rows of the image, effectively halving the vertical image resolution.