Depth Artifacts in Passive 3D Displays

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.

Row interlacing

Left, an interlaced stereoscopic image pair for parallel viewing. The oblique edge of the dark object is highlighted with a white rectangle. Right, the interlaced oblique edge displayed such that the odd pixel rows are intended for the right eye (R) and the even pixel rows are intended for the left eye (L). The white edges highlight the segment endpoints and the arrows point to the closest matches in the left eye image for the specific feature in the right eye image.

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.

4 thoughts on “Depth Artifacts in Passive 3D Displays

  1. Jim Krisvoy

    This doesn’t appear to be a significant problem on the latest generation of passive 4K uhd Tv’s, particularly LG’s 4K oled models. With high color dot panels coming up, it should represent an even more dramatic improvement in stereo imaging.

    Reply
  2. Jussi Post author

    Thanks for the comment, Jim Krisvoy! 4K definitely alleviates the problem. At least the vertical resolution loss from row-averaging does not hurt so much. Our results show that 4K resolution at three times screen height viewing distance is not quite high enough to entirely solve the issue.

    Reply
    1. marni

      Most discouraging. Shutterspex tech seems stalled, and passive tech, as you’ve elucidated, is in even worse shape.
      4K, in addition to not quite solving the vertical rez problem, introduces its own problems [higher power use, backward compatibility issues].
      The real bottleneck for 3D is legacy media compatibility: there’s little enough standard [1080p] 3D media, so 4K is a sour joke. To make a prediction: until adequate at least offline 2D > 3D upscalers arrive, consumer 3D will languish. Sigh.

      Reply
      1. Jussi Post author

        Lack of content is definitely a major issue. My prediction is that the screen based viewing paradigm will become secondary to head mounted virtual reality displays in entertainment quite soon. And then, finally, there will be no excuse to make 2D content. More about this in an upcoming post on the future of display technology 😉

        Reply

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