Perlin, et al “An Autostereoscopic Display”

1. Perlin, et al“An Autostereoscopic Display” • Goals: • 3D display for single viewer • unrestricted viewer movement • autostereoscopic • low cost • Success? • Contribution?

2. Outline • Stereoscopic display techniques • Other recent autostereoscopic work • Description of proposed system • Contributions of proposed system • Conclusion

3. Stereoscopic Displays • Humans use binocular disparity (stereopsis) as a depth cue • Stereoscopic displays exploit this by presenting a different image to each eye • Many kinds of stereoscopic displays have been developed, each with unique advantages and disadvantages

5. Stereoscopic Displays • Location-multiplexed displays • e.g. HMDs • Color-multiplexed displays • Polarization-multiplexed displays • Time-multiplexed displays • e.g. ImmersaDesk, CAVE

6. Autostereoscopic Displays • Autostereoscopic displays exploit stereopsis without special eyewear • Holography is promising but not yet feasible • Direction-multiplexed displays: project the left/right images in different directions, toward each eye

7. Refraction-based autostereopsis • Interleave left/right images in alternating columns • Place lenticular sheet over display • Effect is that each eye sees a different image

8. Refraction-based autostereopsis

9. Refraction problems • Horizontal resolution is halved • Need precise alignment between R, G, B components of display pixels and lenticular grating • Need precise eye alignment • Need to track head and adjust geometry accordingly

10. Recent refraction work • Borner in March 2000 Trans. Circuits & Systems for Video Technology presents several refractive-based alternatives: • robotic boom ensures alignment with eyes • mechanically move lenticular plate • mechanically move projector wrt lenticular plate

11. Parallax barrier-based stereopsis • Interleave left/right images in alternating columns • Parallax barrier has alternating transparent/opaque columns • Effect is that each eye sees different image

12. Recent parallax barrier work: Cambridge Display • Combines time-multiplexing and parallax barrier to provide several discrete views • Viewer’s eyes must be in different view windows

13. Perlin, et al.“An Autostereoscopic Display” • Uses parallax barrier principle with time multiplexing • LCD panel is used as barrier, so transparent/opaque stripe width is electronically controllable • Feedback from eye tracker dynamically varies stripe widths • Can handle head rotation with non-uniform stripe widths

14. “An Autostereoscopic Display” • Barrier is placed relatively far from display, so stripes are large and visible • Three-phase time multiplexing prevents viewer from seeing stripes (“picket-fence effect”) while allowing room for tracker error

15. Implementation • Custom pi-cell LCD panel for barrier • FPGA syncs barrier with projector • Digital Light Processor (DLP) used for display; projects R, G, B sequentially • Eye tracker emits infrared light and tracks reflection from eyeball • Main CPU handles stripe width calculations and left/right image rendering

18. Results • Displays grayscale 3-D images in 30-60 frames per second (could be extended to color) • Comments from SIGGRAPH attendees • Accuracy of tracker is very important • Some “ghosting” due to timing imperfections

19. Contributions • Use of adjusting, electronic parallax barrier based on viewer tracking • Use of stripes with dynamic widths to permit head rotation • Use of time-multiplexed stripes • Relatively low cost • Adaptable to portable devices

20. Conclusion • Paper presents a very flexible, novel autostereoscopic display • An important contribution • Some of authors’ claims seem somewhat unfounded