Abstract
New forms of stereoscopic 3-D technology offer vision scientists new opportunities for research, but also come with distinct problems. Here we consider autostereo displays where the two eyes' images are spatially interleaved in alternating columns of pixels and no glasses or special optics are required. Column-interleaved displays produce an excellent stereoscopic effect, but subtle changes in the angle of view can increase cross talk or even interchange the left and right eyes' images. This creates several challenges to the presentation of cyclopean stereograms (containing structure which is only detectable by binocular vision). We discuss the potential artifacts, including one that is unique to column-interleaved displays, whereby scene elements such as dots in a random-dot stereogram appear wider or narrower depending on the sign of their disparity. We derive an algorithm for creating stimuli which are free from this artifact. We show that this and other artifacts can be avoided by (a) using a task which is robust to disparity-sign inversion—for example, a disparity-detection rather than discrimination task—(b) using our proposed algorithm to ensure that parallax is applied symmetrically on the column-interleaved display, and (c) using a dynamic stimulus to avoid monocular artifacts from motion parallax. In order to test our recommendations, we performed two experiments using a stereoacuity task implemented with a parallax-barrier tablet. Our results confirm that these recommendations eliminate the artifacts. We believe that these recommendations will be useful to vision scientists interested in running stereo psychophysics experiments using parallax-barrier and other column-interleaved digital displays.
Highlights
Technical advances are offering vision scientists new ways of displaying stereo images
The parallax barrier is one of the oldest autostereoscopic techniques (Sexton & Surman, 1999): In 1838, Wheatstone proposed a simple version of this technique in order to help fuse two disparate images when the naked eyes are used
In the Appendix, we present an algorithm for creating randomdot patterns containing a disparate target with a specified parallax relative to the background, so as to avoid crosstalk de-camouflage on column-interleaved displays
Summary
Technical advances are offering vision scientists new ways of displaying stereo images. These are related by DI 1⁄4 2DH þ 1 ð1Þ where D is the distance in pixels between left and right images This distinction is important because, to avoid cross-talk de-camouflage on a column-interleaved display, it is the I-parallax, not the H-parallax, that must be applied symmetrically. We wanted to verify empirically that the cross-talk de-camouflage artifact provides a visible monocular cue if parallax is applied incorrectly on a columninterleaved display, and at the same time confirm that our proposed solution eliminates the artifact To this end, we asked two stereoblind observers and four controls to perform the stereoacuity task described under Methods. In Experiment 1, H-parallax was applied symmetrically, meaning that the target and background dots could be distinguished monocularly by their width when the tablet was held so that the two half-images were each visible to both eyes. In Experiment 2, I-parallax was applied symmetrically, with the intention of removing this dot-width artifact
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