Shun-nan Yang

Stereoscopic Viewing and Reported Perceived Immersion and Symptoms

Purpose. Stereoscopic 3D displays heighten perceived immersion but elevate viewing symptoms for some viewers. The present study measured prevalence and magnitude of perceived immersion and viewing symptoms in stereoscopic viewing, and related them to viewers characteristics and viewing position. Methods. Two hundred three teens and adults viewed a movie in 2D or 3D while sitting at different angles and distances. Their prior viewing symptoms, as well as visual and physical discomfort immediately before and after viewing, were measured with questionnaires. They were also asked to report their perceived immersion after the viewing. Results. Twelve percent and twenty-one percent of 2D and stereoscopic 3D participants reported increases of measured symptoms during and/or after viewing. Stereoscopic 3D viewing incurred greater and more frequent perception of blurred vision, double vision, dizziness, disorientation, and nausea than 2D viewing. Reported ocular and physical symptoms were negatively correlated to perceived immersion in 3D viewing. Older viewers (age 46 years or older) reported greater ocular, visual, and motion sickness symptoms in 2D viewing, and younger viewers (age 24–34 years) reported greater visual and motion sickness symptoms in 3D viewing. Sitting in an oblique position attenuated perceived immersion but also reduced motion symptoms in 3D viewing. Prior viewing symptoms in 2D tasks also predicted ocular and physical symptoms in 2D but less so in 3D viewing. Conclusions. Stereoscopic 3D viewing provides greater immersion, but it can also lead to heightened visual and motion sickness symptoms. Viewers with prior symptoms in viewing TV and computer screen are not more likely to have increased ocular and physical symptoms in 3D viewing. Young viewers incurred higher immersion but also greater visual and motion sickness symptoms in 3D viewing; both will be reduced if a farther distance and a wider viewing angle are adopted.

Comparative effect of lens care solutions on blink rate, ocular discomfort and visual performance

Citation information: Yang N, Tai C, Sheedy JE, Kinoshita B, Lampa M & Kern JR. Comparative effect of lens care solutions on blink rate, ocular discomfort and visual performance. Ophthalmic Physiol Opt 2012, 32, 412–420. doi: 10.1111/j.1475‐1313.2012.00922.x

Effects of gaze-contingent text changes on fixation duration in reading.

In reading, a text change during an eye fixation can increase the duration of that fixation. This increased fixation duration could be the result of disrupted text processing, or from the effect of perceiving the brief visual change (a visual transient). The present study was designed to test those two hypotheses. Subjects read multiple-line text while their eye movements were monitored. During randomly selected saccades, the text was masked with an alternate page, which was then replaced with a second alternate page, 75 or 150 ms after the onset of the subsequent (critical) fixation. The effect of the initial masking page, the text change during fixation, and the content of the second page on the likelihood of saccade initiation during the critical fixation, was measured. Results showed that a text change during fixation resulted in similar bilateral (forward and regressive) saccade suppression regardless of the nature of the first and second pages, or the timing of text change. This result likely reflects the effect of a low-level visual transient caused by text change. In addition, there was delay effect reflecting the content of the initial masking. How the suppression dissipated after text change depended on the nature of the first and second pages. These effects are attributed to high-level text processing. The present results suggest that in reading, visual and cognitive processes both can disrupt saccade initiation. The combination of processing difficulty and visually-induced saccade suppression is responsible for the change in fixation duration when gaze-contingent display change is utilized. Therefore, it is prudent to consider both factors when interpreting the effect of text change on eye movement patterns.

Depth perception from stationary and moving stereoscopic three-dimensional images

Purpose: The study evaluated the accuracy of depth perception afforded by static and dynamic stereoscopic three-dimensional (S3D) images with proportional (scaled to disparity) and constant size cues. Methods: Sixty adult participants, 18 to 40 years (mean, 24.8 years), with good binocular vision participated in the study. For static S3D trials, participants were asked to indicate the depth of stationary S3D images rendered with 36, 48 and 60 pixels of crossed disparity, and with either proportional or a constant size. For dynamic S3D trials, participants were asked to indicate the time when S3D images, moving at 27, 32 and 40 pixels/sec, matched the depth of a reference image which was presented with 36, 48 and 60 pixels of crossed image disparity. Results: Results show that viewers perceived S3D images as being closer than would be predicted by the magnitude of image disparity, and correspondingly they overestimated the depth in moving S3D images. The resultant depth perception and estimate of motion speed were more accurate for conditions with proportional and larger image size, slower motion-in-depth and larger image disparity. Conclusion: These findings possibly explain why effects such as looming are over stimulating in S3D viewing. To increase the accuracy of depth perception, S3D content should match image size to its disparity level, utilize larger depth separation (without inducing excessive discomfort) and render slower motion in depth.

Discernible difference and change in object depth afforded by stereoscopic three-dimensional content

Purpose: Stereoscopic three-dimensional (S3D) viewing enhances depth perception of two-dimensional (2D) images. The present study measured viewer’s ability to discern depth differences and depth change afforded by image disparities presented on an S3D display. Methods: Sixty adults (age 24.8 +/- 3.4 years, 28% male) with binocular acuity better than 20/25 and stereoacuity better than 60 arcsec viewed test images presented on a 55” 3D TV (1920 x 1080 pixels) at 2.4m distance. In each trial, three of the four circles in the test image were with the same crossed baseline disparity of 12, 24, 36, 48, and 60 pixels, and the other (target) circle with added crossed disparity (delta disparity) of 2, 4, and 6 pixels. A subsequent change in delta disparity of the target circle (+/-2 pixels) was presented. Participants response time and accuracy for identifying the target circle and its direction of depth change, as well as their vergence eye position, was recorded. Results: Larger baseline disparity resulted in lower accuracy and longer response times in identifying the target circle. The change of delta disparity was more accurately discerned when the delta disparity was larger and the change resulted in increased crossed disparity. Direction of vergence change and the final vergence error reflected an averaging of screen and image depths. Conclusion: S3D-induced depth difference and motion in depth is more easily discerned with smaller crossed disparity for background objects (< 43.3 arcmin or 48 pixels) and larger separation between image disparities (>3.6 arcmin or 4 pixels).

Effects of ocular transverse chromatic aberration on near foveal letter recognition

Transverse chromatic aberration (TCA) smears retinal images of peripheral stimuli. In reading, text information is extracted from both foveal and near fovea, where TCA magnitude is relatively small and variable. The present study investigated whether TCA significantly affects near foveal letter identification. Subjects were briefly presented a string of five letters centered one degree of visual angle to the left or right of fixation. They indicated whether the middle letter was the same as a comparison letter subsequently presented. Letter strings were rendered with a reddish fringe on the left edge of each letter and a bluish fringe on the right edge, consistent with expected left periphery TCA, or with the opposite fringe consistent with expected right periphery TCA. Effect of the color fringing on letter recognition was measured by comparing the response accuracy for fringed and non-fringed stimuli. Effects of lateral interference were examined by manipulating inter-letter spacing and similarity of neighboring letters. Results demonstrated significantly improved response accuracy with the color fringe opposite to the expected TCA, but decreased accuracy when consistent with it. Narrower letter spacing exacerbated the effect of the color fringe, whereas letter similarity did not. Our results suggest that TCA significantly reduces the ability to recognize letters in the near fovea by impeding recognition of individual letters and by enhancing lateral interference between letters.

Assessment of lossy images with visual detection and saccadic eye movements

This study investigated a novel method of evaluating visually lossy images based on saccadic eye movements. In each trial, participants with normal vision were asked to indicate any visible changes in the image while their gaze positions were being monitored. The original image was replaced with compressed or blurred versions of the same image 150ms after the onset of each eye fixation, and the parameters of the immediately following saccades were assessed. These outcomes were compared to those with a constant rate of image switch (5 Hz flicker) and without switch (control). The resultant rate of visual detection was higher with blurred and constant flickering images than compressed images. Changes in fixation duration, saccade amplitude and peak saccade velocity suggest disrupted visuomotor processes associated with image switch. These disruptions occurred with or without conscious detection. The use of flickering images likely overestimates the probability of detecting lossy image. Analysis of eye movements might be more useful in discerning lossy images in situations where various form factors and visuomotor contexts need to be evaluated.

Industry and business perspectives on the distinctions between visually lossless and lossy video quality: Mobile and large format displays.

This paper will explore the mobile and business perspectives of visually lossless image quality, as well as review recent scientific advances. It is the outcome from the Special Session on Visually ...