Eye%20Tracking%20With%20Stereoscopic%20Images

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Eye Tracking With Stereoscopic Images
Eamon Moore, Punit Seth, Dhaval Shah Clemson
University
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Introduction

• Stereoscopic image optical illusion of depth
  seen by focusing ones eyes in front of or behind
  an image 7
• Each eye views an image differently which gives
  the perception of depth.

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Eye Tracking

• Eye Trackers Can be used to track eye movements
  and gaze coordinates
• Gaze coordinates Helps in understanding why
  some people see stereo images and some do not

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Divergence and Convergence

• Divergence and Convergence the methods that
  people use to view stereograms
• Divergence Moving your eyes outward in the
  opposite direction
• Convergence Moving your eyes inward

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Why Use Stereograms?

• Marketers and researchers Attempts are being
  made to utilize ones ability to see
  three-dimensional images and use them in
  advertising.
• Stereograms can enhance vividness, clarity,
  realism, and depth.

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The Experiment

• Analyzing the behavior of the eyes to view
  stereograms dependant variable
• Convergence
• Divergence
• Looking for significant differences in Placebo
  and Experimental group independent variable

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Hypothesis

• Null Hypothesis There will be no significant
  change in the distance of the eyes when viewing
  stereograms, regardless of experimental
  condition.
• Alternate Hypothesis There will be significant
  results that indicate divergence of the eyes in
  both conditions.

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Background

• Brain processing The brain accepts two images
  that are seen by each eye and creates a
  completely different three-dimensional picture
  called stereo 6.

Figure 1 Image processing

• Stereo allows you to see objects as solids
• in dimension of width, height, and depth.

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When Stereoscopy Started

• Idea of stereoscopy preceded photography
• Paintings were made by Giovanni Porta in the late
  1500s by placing images side by side. This showed
  his understanding of binocular vision.

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Three-Dimensional Glasses

• Three-Dimensional Glasses red filter for left
  eye, blue filter for right eye 11
• When looked at images that have depth, a
  three-dimensional image could be seen.

Figure 2 Red-blue Stereo Image
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Modern Stereogram

• First modern stereogram created in 1959 by Julesz
  11
• Original image viewed by left eye
• Modified version of original image viewed by
  right eye
• Brain fuses both images creating the final image

Figure 3 Modern Stereogram
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Single Image Stereogram

• Created in 1979 by a student of Julesz, Tyler
• Found that the offset idea could be applied to a
  single image to create a black and white random
  dot stereogram

Figure 4 Single Image stereogram
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Colored Stereogram Program

• In 1991 Smith improved on the research of Julesz
  by creating stereogram modeling software.
• Eliminated the need for dots and provided color

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Tracking of Eye Movements and Visual Attention

• Study conducted by Neuroinformatics Group,
  Bielefield University 8
• Concentrated on vergence eye movements using
  stereograms similar to the ones used in this
  experiment

Figure 5 Coarse Granularity Image (left)
Stereogram (right)
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Neuroscience Institute

• Gave insight about vergence eye movements
• Discussed dynamics of horizontal and vertical
  vergence
• Study indicated that horizontal eye movements
  were of more importance.

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Program to Create Stereograms

• School of Electrical and Electronic Engineering
  at the University of Nottingham 3
• Created program that produces stereograms
• Examined how stereograms were viewed

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Experimental Design
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Apparatus

• Tobii Eye Tracker 16 Video-based combined
  pupil and
• corneal
  reflection eye tracker
• 2.4 GHz
• 256 MB RAM
• Windows XP
• Red Hat Linux Release 9,
• Version 2.4.20
• Sampling Rate 50 Hz
• Accuracy 1º visual angle

Figure 6 Tobii System
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Experimental Design

• Between subjects
• Two conditions
• Experimental group Stereogram
• Placebo group Nonstereo Image
• 10 Participants

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Stimulus - Control Image
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Stimulus - Stereogram
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The Hidden Image
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Stimulus Nonstereo Image
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Salient Features

• Reduced calibration points
• An organized file structure
• Validity 0
• Timer
• Shortcut keys
• Analysis option

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Algorithm

• Record XL, XR, YL, YR.
• Distance
• Control distance
• Experimental distance

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Algorithm

• If (Experimental distance lt Control
  distance)
• If (XL lt XR)
• Convergence
• Else Convergence with crossover.
• else If (Experimental distance gt Control
  distance)
• Divergence
• else No difference.

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Data Analysis
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Data Analysis Experimental Group (Individual)
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Data Analysis Placebo Group (Individual)
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Data Analysis Experimental Group (Aggregate)
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Data Analysis Placebo Group (Aggregate)
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One Way Analysis of Variance (ANOVA)
Levene Statistic df1 df2 Sig.
3.335 1 8 .105

• Assumptions of an ANOVA
• Independence
• Homogeneity of Variance
• Normality

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Descriptive Statistics

• Randomly Assigned Groups
• Placebo
• - Five Men
• Experimental
• - Three Men, Two Women

N Min Max. Mean Statistic Mean Std. Error Std. Dev. Variance
Distance 10 -599.35 33.28 -133.4980 60.4466 191.1490 36537.957
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ANOVA

• Not a significant difference between the Placebo
  (M -36.048,
• S 86.891) and Experimental Group (M
  -230.949,S 225.562)

Sum of Squares df Mean Square F Sig.
Between Groups 94965.981 1 94965.981 3.248 .109
Within Groups 233875.629 8 29234.454
Total 328841.610 9
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ANOVA and Power Analysis
N Mean Std. Deviation Std. Error 95 Confidence Interval for Mean 95 Confidence Interval for Mean Minimum Maximum
N Mean Std. Deviation Std. Error Lower Bound Upper Bound Minimum Maximum
Placebo 5 -36.0475 86.8910 38.8589 -143.9370 71.8419 -163.99 33.28
Experimental 5 -230.9485 225.6521 100.9147 -511.1326 49.2355 -599.35 -48.72
Total 10 -133.4980 191.1490 60.4466 -270.2378 3.2418 -599.35 33.28

• Post Hoc G-Power Analysis
• power of .1077 indicates approximately 11 percent
  chance
• that the null hypothesis could have been
  rejected.

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Discussion
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Discussion

• Stereograms are viewed by using
• convergence regardless of stimuli.
• No significant results
• Experimental group shows trend towards
• divergence near the end.
• Placebo group shows a lesser trend
• towards convergence

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Experimental Group (Aggregate)
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Placebo Group (Aggregate)
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Limitations

• Low Power
• - Priori Power Analysis
• Tobii Eye Tracker
• Stereograms are harder to view on a
• computer screen.

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Future Work

• Larger sample size
• Introduce Z coordinate for the distance from the
  screen
• Measure characteristics such as the diameter of
  the pupil while studying its behavior.

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Conclusion

• Our hypothesis was incorrect however, we were
  correct in believing both groups would behave
  similarly.
• Stereograms are viewed by converging ones eyes
  however, a higher power study may prove
  otherwise.
• More research can now be conducted to understand
  how stereograms can be used for advertising,
  marketing, and other practical applications.

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Acknowledgements

• Dr. Andrew Duchowski, PhD.,
• Associate Professor, Clemson University.
• Ms. Puja Seth, M.A.
• Doctoral Student, University of Georgia
• Mr. Jacob Hicks
• Undergraduate Student, Clemson University.

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References

• 1 Academy of Marketing Science Review.
  Three-Dimensional Stereographic Visual displays
  in Marketing and Consumer Research. Available
  at http//www.vancouver.wsu.edu/amsrev/theory/hol
  brook11- 97t.htm.
• Last Accessed 10 October, 2004.
• 2 Annals of the New York Academy of Sciences
  2002. Binocular Eye Movement Responses to
  Dichoptically
• Presented Horizontal and/or Vertical
  Stimulus Steps. Available at http//www.annalsnya
  s.org/cgi/content/full/956/1/487. Last Accessed
  December 2, 2004.
• 3 BBC, Nottingham. SIRDS An optical illusion.
  
• Available at http//www.bbc.co.uk/notting
  ham/features/2003/08/sirds.shtmlwhat
• Last Accessed December 2, 2004.
• 4 CIT,Cornell University. How To See A Magic
  Eye Poster.
• Available At http//instruct1.cit.cornell.e
  du/courses/psych470/To_Be_Edited/How20To20See20
  A20Magic20Eye20Poster20(MVW).doc. Last
  Accessed December 2, 2004.
• 5 C. Rashbass G. Westheimer J. Physiol.
  Disjunctive Eye Movements. 159, 339-360, 1961
• 6 Cooper, Rachel. What is Stereo Vision?.
  2004. Available At http//www.vision3d.com/ster
  eo.html.
• Last Accessed16 September 2004.
• 7 Dictionary.com. Available at
  http//dictionary.reference.com/search?qstereogra
  m

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References

• 9 Faul, F., Erdfelder, E. (1992). G-Power A
  priori, post- hoc, and compromise power analyses
  for MS-DOS
• (computer program). Bonn, FRGBonn
  University, Department of Psychology.
• 10 History of Photography and the Camera.
• Available At http//inventors.about.com/li
  brary/inventors/blphotography.htm
• Last Accessed December 2, 2004.
• 11 Magic Eye Inc. Frequently Asked Questions.
  2004.
• Available at http//magiceye.com/faq.htm.
  Last Accessed 16 September 2004.
• 12 Mowforth, P. et al. Vergence Eye Movements
  Made in Response to Spatial-Frequency-Filtered
  Random-Dot-
• Stereograms. Perception, 10, 299-304, 1981
  
• 13 Patrick Hahn. The History of Stereograms
  1996.
• Available Athttp//www2.vo.lu/homepages/p
  hahn/rds/history.htm. Last Accessed December 2,
  2004.
• 14 Robert Leggat. Stereoscopic photography
  2003.
• Available At http//www.rleggat.com/phot
  ohistory/history/stereosc.htm.
• Last Accessed December 2, 2004.

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Questions