Impact of focus cue presentation on perceived realism of 3-D scene structure: Implications for scene perception and for display technology

Stereoscopic imagery often aims to evoke three-dimensional (3-D) percepts that are accurate and realistic-looking. The "gap" between 3-D imagery and real scenes is small, but focus cues typically remain incorrect because images are displayed on a single focal plane. Research has concentrated on the resulting vergence-accommodation conflicts. Yet, incorrect focus cues may also affect the appearance of 3-D imagery. We investigated whether incorrect focus cues reduce perceived realism of 3-D structure ("depth realism"). Experiment 1 used a multiple-focal-planes display to compare depth realism with correct focus cues vs. conventional stereo presentation. The stimuli were random-dot stereograms, which isolated the role of focus cues. Depth realism was consistently lower with incorrect focus cues, providing proof-of-principle evidence that they contribute to perceptual realism. Experiments 2 and 3 examined whether focus cues play a similar role with realistic objects, presented with an almost complete set of visual cues using a high-resolution, high-dynamic-range multiple-focal-planes display. We also examined the efficacy of approximating correct focus cues via gaze-contingent depth-of-field rendering. Improvements in depth realism with correct focus cues were less clear in more realistic scenes, indicating that the role of focus cues in depth realism depends on scene content. Rendering-based approaches, if anything, reduced depth realism, which we attribute to their inability to present higher-order aspects of blur correctly. Our findings suggest future general 3-D display solutions may need to present focus cues correctly to maximise perceptual realism.

Expert and Novice Performers Respond Differently to Attentional Focus Cues for Speed Jump Roping

Directing attention to an external focus has been shown to facilitate motor performance. For expert performers, however, results have been mixed. Additionally, little is currently known about how focus cues affect the performance of complex continuous whole-body coordination tasks involving object manipulation such as jump roping. The purpose of this study was to examine the effects of attentional focus cues on single-rope speed jumping by experts and novices. The cues directed attention toward the upper (UP) or lower (LB) body and either internally (IN) or externally (EX). Participants (N = 30) completed bouts of speed jumping during a baseline trial and under experimental conditions (UPIN, UPEX, LBIN, LBEX). Jumps and errors were recorded for each trial. Number of jumps (NJ) and errors (NE) were analyzed using separate Friedman's Tests comparing for each group to compare trials, with Wilcoxon Signed-Rank Tests for post hoc comparisons. Cumulative number of jumps (CNJ) and errors (CNE) for each condition were compared using separate Friedman's Tests with Wilcoxon Signed-Rank Tests for post hoc comparisons. For experts, baseline NJ was significantly higher than NJ for each trial under the UPIN, UPEX, and LBIN conditions. No differences between baseline NE and any trials were detected. Additionally, no differences were detected between conditions for NJ or NE. For novices, baseline NJ and NE were significantly higher and lower, respectively, compared to Trial 1 under the LBEX condition. Both the UPIN and UPEX conditions produced higher CNJ and lower CNE than the LBIN and LBEX conditions, respectively. Results showed that experts and novices responded in distinctly different patterns to the four conditions. Experts showed degraded performance under the UPIN, UPEX, and LBIN conditions whereas novices only showed temporarily degraded performance under the LBEX condition. These findings may reflect differences in mastery of whole-body coordination and are partially consistent with the Constrained Action Hypothesis (CAH) despite not supporting specific predictions related to the benefit of external focus cues.

Induction of Monocular Stereopsis by Altering Focus Distance: A Test of Ames's Hypothesis

Viewing a real three-dimensional scene or a stereoscopic image with both eyes generates a vivid phenomenal impression of depth known as stereopsis. Numerous reports have highlighted the fact that an impression of stereopsis can be induced in the absence of binocular disparity. A method claimed by Ames (1925) involved altering accommodative (focus) distance while monocularly viewing a picture. This claim was tested on naïve observers using a method inspired by the observations of Gogel and Ogle on the equidistance tendency. Consistent with Ames’s claim, most observers reported that the focus manipulation induced an impression of stereopsis comparable to that obtained by monocular-aperture viewing.

Stereo display with time-multiplexed focal adjustment

In stereo displays, binocular disparity creates a striking impression of depth. However, such displays present focus cues-blur and accommodation-that specify a different depth than disparity, thereby causing a conflict. This conflict causes several problems including misperception of the 3D layout, difficulty fusing binocular images, and visual fatigue. To address these problems, we developed a display that preserves the advantages of conventional stereo displays, while presenting correct or nearly correct focus cues. In our new stereo display each eye views a display through a lens that switches between four focal distances at very high rate. The switches are synchronized to the display, so focal distance and the distance being simulated on the display are consistent or nearly consistent with one another. Focus cues for points in-between the four focal planes are simulated by using a depth-weighted blending technique. We will describe the design of the new display, discuss the retinal images it forms under various conditions, and describe an experiment that illustrates the effectiveness of the display in maximizing visual performance while minimizing visual fatigue.