Depth Artifacts Caused by Spatial Interlacing in Stereoscopic 3D Displays

Abstract

Most spatially interlacing stereoscopic 3D displays display odd and even rows of an image to either the left or right eye of the viewer. The visual system then fuses the interlaced image into a single percept. This row-based interlacing creates a small vertical disparity between the images; however, interlacing may also induce horizontal disparities, thus generating depth artifacts. Whether people perceive the depth artifacts, and if so, what is the magnitude of the artifacts, are unknown. In this study, we hypothesized and tested if people perceive interlaced edges on different depth levels. We tested oblique edge orientations ranging from 2• to 32• and pixel sizes ranging from 16 to 79 arcsec of visual angle in a depth probe experiment. Five participants viewed the visual stimuli through a stereoscope under three viewing conditions: non-interlaced, interlaced, and row-averaged (i.e., where even and odd rows are averaged). Our results indicated that people perceive depth artifacts when viewing interlaced stereoscopic images and that these depth artifacts increase with pixel size and decrease with edge orientation angle. A pixel size of 32 arcsec of visual angle still evoked depth percepts, whereas 16 arcsec did not. Rowaveraging images effectively eliminated these depth artifacts. These findings have implications for display design, content production, image quality studies, and stereoscopic games and software.

Stereoscopic 3D display technique using spatiotemporal interlacing has improved spatial and temporal properties

“…Thus, depth distortions due to the vertical offsets in spatial-interlacing displays should not occur with this technique. We did not test this possibility because Hakala et al [3] have already shown that this type of distortion occurs with spatial interlacing and there is no reason to believe that it should occur with the hybrid protocols proposed here.…”

“…Because the left-and right-eye views are offset vertically by one pixel, the eyes make a vertical vergence eye movement to binocularly fuse the rows (bright rows aligned in the two eyes and dark rows also aligned). The vertical eye movement causes a change in the horizontal disparity at the retinas for off-vertical and off-horizontal edges, so those edges appear at unintended depths [3]. Interestingly, some spatial-interlacing displays eliminate this effect by presenting data rows alternately [23,24].…”

“…The alternation rate is sufficiently high for the alternating images to be temporally averaged by the visual system. This verticalaveraging algorithm eliminates the depth distortion [3], but at the cost of reduced spatial resolution.…”

“…Temporal interlacing is prone to temporal artifacts such as flicker, unsmooth motion appearance, and distortions of perceived depth [1]. Spatial interlacing results in lower spatial resolution at typical viewing distances [2] and can also cause distortions of perceived depth [3]. We sought a technique that would combine the better features of the two protocols-spatial resolution with temporal interlacing and temporal performance with spatial interlacing-while minimizing their shortcomings.…”

An overview of depth distortion in stereoscopic 3D displays

“…Hakala et al measured how spatial interlacing affects depth distortion [13]. The stimulus was an edge between the white and black regions.…”