Volumetric display

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A volumetric display device is a graphical display device that forms a visual representation of an object in three physical dimensions, as opposed to the planar image of traditional screens that simulate depth through a number of different visual effects. One definition offered by pioneers in the field is that volumetric displays create 3-D imagery via the emission, scattering, or relaying of illumination from well-defined regions in (x,y,z) space. Though there is no consensus among researchers in the field, it may be reasonable to admit holographic and highly multiview displays to the volumetric display family if they do a reasonable job of projecting a three-dimensional light field within a volume.

Most, if not all, volumetric 3-D displays are autostereoscopic; that is, they create 3-D imagery visible to the unaided eye. Note that some display technologists reserve the term “autostereoscopic” for flat-panel spatially-multiplexed parallax displays, such as lenticular-sheet displays. However, nearly all 3-D displays other than those requiring headwear, e.g. stereo goggles and stereo head-mounted displays, are autostereoscopic. Therefore, a very broad group of display architectures are properly deemed autostereoscopic.

Volumetric 3-D displays embody just one family of 3-D displays in general. Other types of 3-D displays are: stereograms / stereoscopes, view-sequential displays, electro-holographic displays, parallax "two view" displays and parallax panoramagrams (which are typically spatially-multiplexed systems such as lenticular-sheet displays and parallax barrier displays), re-imaging systems, and others.

Although first postulated in 1912, and a staple of science fiction, volumetric displays are still under development, and have yet to reach the general population. With a variety of systems proposed and in use in small quantities — mostly in academia and various research labs — volumetric displays remain accessible only to adademics, corporations, and the military.

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[edit] Types of volumetric displays

Many different attempts (US Patent Office) have been made to extend the dynamic 2D representation of the cathode ray tube to three dimensions. There is no officially accepted "taxonomy" of the variety of volumetric displays, an issue which is complicated by the many permutations of their characteristics. For example, illumination within a volumetric display can either reach the eye directly or via an intermediate surface; likewise, the surface, which need not be tangible, can undergo motion such as reciprocation or rotatation. One categorization is as follows:

[edit] Swept-surface

Swept-surface (or "swept-volume") volumetric 3-D displays rely on the human persistence of vision to fuse a time-series of regions of the ultimate 3-D region into a single 3-D image. A variety of swept-volume displays have been created.

Fast-moving LEDs create a 360 degree object in air in this prototype by University College Sedaya International
Enlarge
Fast-moving LEDs create a 360 degree object in air in this prototype by University College Sedaya International

For example, the 3-D scene is computationally decomposed into a series of "slices," which can be rectangular, disc-shaped, or helical cross-sectioned, whereupon they are projected onto or from a display surface undergoing motion. The image on the 2D surface (created by projection onto the surface, LEDs embedded in the surface, or other techniques) changes as the surface rotates. Due to the persistence of vision humans perceive a volume of light. The display surface can be reflective, transmissive, or a combination of both.

Another type of 3-D display which is a candidate member of the class of swept-volume 3-D displays is the varifocal mirror architecture. One of the first references to this type of system is in 1966, in which a vibrating mirrored drumhead re-images a series of patterns from a high frame rate 2-D image source, such as a vector display, to a corresponding set of depth surfaces.

[edit] Static volume

So-called static volume volumetric 3-D displays create imagery without any macroscopic moving parts in the image volume. It is unclear if the rest of the system must remain stationary for membership in this display class to be viable.

This is probably the most 'direct' form of volumetric display. In the simplest case, an addressable volume of space is created out of active elements that are transparent in the off state but are either opaque or luminous in the on state. When the elements or voxels are activated they show a solid pattern within the space of the display.

  • Simple systems with LEDs in a 3D matrix.
    • The 3D Display Cube, patented by James Clar & Associates, is a commercially available device that uses a sparse matrix of single-color LEDs to create crude three-dimensional imagery. As the 3D Display Cube relies on a network of wires among the LEDs, one cannot reach into the viewing volume.
    • A similar cube with much wider color depth is the Hypnocube, which is sold finished or as a kit.
  • Static volume 3-D display with specialized fiber-optic illumination — University of Texas Prototype with 76,000 voxels (U.S. Patent 5,801,666 )
  • Static volume multiplanar displays generate 3-D imagery by, for example, projecting light onto an electo-optical surface that undergoes periodic translational motion. See LightSpace Technologies, Inc., whose product includes a high-speed projector that illuminates a series of diffuse liquid crystal panels.

Several static-volume volumetric 3-D displays use laser light to encourage visible radiation in a solid, liquid, or gas. For example, some researchers have relied on two-step upconversion within a rare earth-doped material when illuminated by intersecting infrared laser beams of the appropriate frequencies.

A pulsed laser creates points of glowing plasma in air
A pulsed laser creates points of glowing plasma in air

Another technique uses a focused pulsed infrared laser (about 100 pulses per second; each lasting a nanosecond) to create balls of glowing plasma at the focal point in normal air. The focal point is directed by two moving mirrors and a sliding lens, allowing it to draw shapes in the air. Each pulse creates a popping sound, so the device crackles as it runs. Currently it can generate dots anywhere within a cubic metre. It is thought that the device could be scaled up to any size, allowing for 3D images to be generated in the sky.

[edit] Candidate: Highly multiview displays

Parallax panoramagrams, such as parallax barrier displays, generate an approximation of a desired 3-D light field. For a sufficient angular density of "view" directions, the synthesized 3-D light field becomes nearly equivalent to a volumetric image. Some researchers state that even a flat-panel 3-D display that projects over 30 views within a 30-degree horizontal field of view evokes an accommodation response in the viewer. Therefore, multiview displays with a high angular view density might be rightful members of the class of volumetric 3-D displays.

[edit] Candidate: Holograms and electro-holographic

The realistic imagery of holograms and electro-holographic displays make them contenders for membership in the class of volumetric 3-D displays, as well.

[edit] Human-computer interfaces

The unique properties of volumetric displays, which may include: 360-degree viewing, agreement of converge and accommodation cues, and their inherent "three-dimensionality," enable new human-computer interface techniques. There is recent work investigating the speed and accuracy benefits of volumetric displays (Van Orden et al, 2000), new graphical user interfaces (Grossman et al, 2004), and medical applications enhanced by volumetric displays (Med., 2005; Wang et al, 2005).

Also, software platforms exist which deliver native and legacy 2-D and 3-D content to volumetric displays (Chun et al, 2005).

[edit] Drawbacks

Known volumetric display technologies also have several drawbacks that are exhibited depending on trade-offs chosen by the system designer.

It is often claimed that volumetric displays are incapable of reconstructing scenes with viewer-position-dependent effects, such as occlusion and opacity. This is a misconception; a display whose voxels have non-isotropic radiation profiles are indeed able to depict position-dependent effects. To-date, occlusion-capable volumetric displays require two conditions: (1) the imagery is rendered and projected as a series of "views," rather than "slices," and (2) the time-varying image surface is not a uniform diffuser. For example, researchers have demonstrated spinning-screen volumetric displays with reflective and/or vertically diffuse screens whose imagery exhibits occlusion and opacity. One system (Cossairt et al, 2004; Favalora, 4 Aug. 2005) created HPO 3-D imagery with a 360-degree field of view by oblique projection onto a vertical diffuser; another (Otsuka et al, 2004) projects 24 views onto a rotating controlled-diffusion surface; and another (Tanaka et al, 2006) provides 12-view images utilizing a vertically oriented louver.

So far, the ability to reconstruct scenes with occlusion and other position-dependent effects have been at the expense of vertical parallax, in that the 3-D scene appears distorted if viewed from locations other than those the scene was generated for.

One other consideration is the very large amount of bandwidth and processing power required to feed imagery to a volumetric display: for example, a 24-bit 70 volume/sec 1024×1024×768 display might need up to 180 GB/s transferred to the electro-optic modulator components.

[edit] References

  • Blundell, B. & Schwarz, A. (2000). Volumetric Three-Dimensional Display Systems, John Wiley & Sons. ISBN 0-471-23928-3
  • Chun, W.-S., Napoli, J., Cossairt, O. S., Dorval, R. K., Hall, D. M., Purtell II, T. J., Schooler, J. F., Banker, Y., & Favalora, G. E. (2005). Spatial 3-D Infrastructure: Display-Independent Software Framework, High-Speed Rendering Electronics, and Several New Displays. In Stereoscopic Displays and Virtual Reality Systems XII, ed. Andrew J. Woods, Mark T. Bolas, John O. Merritt, and Ian E. McDowall, Proc. SPIE-IS&T Electronic Imaging, SPIE Vol. 5664, (pp. 302-312). San Jose, California: SPIE-IS&T.
  • Cossairt, O. S. and Napoli, J. (2004), Radial multiview three-dimensional displays, U.S. Pat. App. 2005/0180007 A1. Provisional (Jan. 16, 2004). Nonprovisional (Jan. 14, 2005). Published (Aug. 18, 2005)
  • Downing, E., Hesselink, L., Ralston, J., & Macfarlane, R. (1996). A Three-Color, Solid-State, Three-Dimensional Display, Science, 273, 1185–1189.
  • Favalora, G. E. (2005, Aug.). "Volumetric 3D Displays and Application Infrastructure," Computer, 38(8), 37-44. Illustrated technical survey of contemporary and historic volumetric 3-D displays. IEEE citation via ACM
  • Favalora, G. E. (2005, 4 Aug.). "The Ultimate Display: What Will It Be?," presented at ACM SIGGRAPH, Los Angeles, California.
  • Grossman, T., Wigdor, D., & Balakrishnan, R. (2004). "Multi-finger gestural interaction with 3D volumetric displays," Proceedings of UIST, ACM Symposium on User Interface Software and Technology, (pp. 61-70). PDF at author site
  • Halle, M. (1997). "Autostereoscopic displays and computer graphics," Computer Graphics, ACM SIGGRAPH, vol. 31, no. 2, (pp. 58-62). A thoughtful and concise overview of the field of 3-D display technologies, particularly non-volumetric displays. HTML and PDF
  • Hartwig, R. (1976). Vorrichtung zur Dreidimensionalen Abbildung in Einem Zylindersymmetrischen Abbildungstraum, German patent DE2622802C2, filed 1976, issued 1983. One of the earliest patent references for the rotating helix 3-D display.
  • Honda, T. (2000). Three-Dimensional Display Technology Satisfying 'Super Multiview Condition.' In B. Javidi & F. Okano (Eds.), Proc. Three-Dimensional Video and Display: Devices and Systems, vol. CR76, SPIE Press, (pp. 218-249). ISBN 0-8194-3882-0
  • Langhans, K., Bezecny, D., Homann, D., Bahr, D., Vogt, C., Blohm, C., & Scharschmidt, K.-H.(1998). "New Portable FELIX 3D Display," Proc. SPIE, vol. 3296, SPIE — Int'l Soc. for Optical Eng., (pp. 204-216). Includes a thorough literature review of volumetric displays.
  • Lewis, J. D., Verber, C. M., & McGhee, R. B. (1971). A True Three-Dimensional Display, IEEE Trans. Electron Devices, 18, 724-732. An early investigation into so-called solid-state 3-D displays.
  • Otsuka, R., Hoshino, T., and Horry, Y. (2004), "Transpost: all-around display system for 3D solid image," in Proc. of the ACM symposium on virtual reality software and technology, (Hong Kong, 2004), pp. 187-194.
  • "Exploring Cutting-Edge 3D Imaging System for Cancer Treatment Planning, Rush University Medical Center," Medical News Today, (29 Apr 05).
  • Tanaka, K. and Aoki, S. (2006). "A method for the real-time construction of a full parallax light field," in Stereoscopic Displays and Virtual Reality Systems XIII, A. J. Woods, N. A. Dodgson, J. O. Merritt, M. T. Bolas, and I. E. McDowall, eds., Proc. SPIE 6055, 605516.
  • Van Orden, K. F. & Broyles, J. W. (2000, March). Visuospatial task performance as a function of two- and three-dimensional display presentation techniques, Displays, 21(1), 17-24. PDF: Mirror, with permission
  • Wang, A. S., Narayan, G., Kao, D., & Liang, D. (2005). "An Evaluation of Using Real-time Volumetric Display of 3D Ultrasound Data for Intracardiac Catheter Manipulation Tasks," Eurographics / IEEE Workshop on Volume Graphics, Stony Brook.

[edit] See also

[edit] External links

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