Multiaccommodative Stimuli in VR Systems: Problems & Solutions

Abstract

Virtual reality environments can introduce multiple and sometimes conflicting accommodative stimuli. For instance, with the high-powered lenses commonly used in head-mounted displays, small discrepancies in screen lens placement, caused by manufacturer error or user adjustment focus error, can change the focal depths of the image by a couple of diopters. This can introduce a binocular accommodative stimulus or, if the displacement between the two screens is unequal, an unequal (anisometropic) accommodative stimulus for the two eyes. Systems that allow simultaneous viewing of virtual and real images can also introduce a conflict in accommodative stimuli: When real and virtual images are at different focal planes, both cannot be in focus at the same time, though they may appear to be in similar locations in space. In this paper four unique designs are described that minimize the range of accommodative stimuli and maximize the visual system's ability to cope efficiently with the focus conflicts that remain: pinhole optics, monocular lens addition combined with aniso-accommodation, chromatic bifocal, and bifocal lens system. The advantages and disadvantages of each design are described and recommendation for design choice is given after consideration of the end use of the virtual reality system (e.g., low or high end, entertainment, technical, or medical use). The appropriate design modifications should allow greater user comfort and better performance.

Get full access to this article

View all access options for this article.

References

Behar, I. , Wiley, R. W. , Levine, R. R. , Rash, C. E. , Walsh, D. J. , & Cornum, R. L. S. (1990). Visual survey of Apache aviators (Tech. Report 90–15). Fort Rucker, AL: U.S. Army Aeromedical Research Laboratory.

Harris, M. G. , Sheedy, J. E. , & Gan, C. M. (1992) Vision and task performance with monovision and diffractive bifocal contact lenses. Optometry and Vision Science, 69, 609–614.

Kenyon, R. V. , DeFanti, T. A. , & Sandin, D. J. (1995) Visual requirements for virtual-environment generation. Society for Information Display Digest, 3, 357–360.

Koetting, R. A. (1970) Stereopsis in presbyopes fitted with single vision contact lenses. American Journal of Optometry and Archives of American Academy of Optometry, 47, 557–561.

Kotulak, J. C. , & Morse, S. E. J. (1994) Relationship among accommodation, focus, and resolution with optical instruments. Journal of the Optical Society of America, 11, 71–79.

Kotulak, J. C. , & Morse, S. E. (1995) Oculomotor responses with aviator helmet-mounted displays and their relation to in-flight symptoms. Human Factors, 37, 699–710.

Kruger, P. B. , & Pola, J. (1986) Stimuli for accommodation: Blur, chromatic aberration and size. Vision Research, 26, 957–971.

Leibowitz, H. W. , & Owens, D. A. (1974) Anomalous myopias and the intermediate dark focus of accommodation. Science, 189, 646–648.

Levy, N. S. , & Glick, E. B. (1974) Stereoscopic perception and Snellen visual acuity. American Journal of Ophthalmology, 78, 722–724.

10.

Marran, L., & Schor, C. M. (in press). Lens induced aniso-accommodation. Vision Research.

11.

Mon-Williams, M. , Wann, J. P. , & Rushton, S. (1993) Binocular vision in a virtual world: Visual deficits following the wearing of a head-mounted display. Ophthalmic and Physiological Optics, 13, 387–392.

12.

Robinett, W. , & Rolland, J. P. A. (1992) A computational model for the stereoscopic optics of a head-mounted display. Presence, 1, 45–61.

13.

Schober, H. A. W. , Dehler, H. , & Kassel, R. (1970) Accommodation during observations with optical instruments. Journal of the Optical Society of America, 60, 103–107.

14.

Schor, C. M. , & Erickson, P. (1988) Patterns of binocular suppression and accommodation in monovision. American Journal of Optometry and Physiological Optics, 65, 853–861.

15.

Wann, J. P. , Rushton, S. , & Mon-Williams, M. (1995) Natural problems in the perception of virtual environments. Vision Research, 35, 2731–2736.

16.

Westheimer, G. (1966) The Maxwellian view. Vision Research, 6, 669–682.