World Library  
Flag as Inappropriate
Email this Article

Interpupillary distance

Article Id: WHEBN0022446275
Reproduction Date:

Title: Interpupillary distance  
Author: World Heritage Encyclopedia
Language: English
Subject: Binocular neurons, Binocular disparity, HMZ-T1, Head-mounted display, Display technology
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Interpupillary distance

Interpupillary distance (IPD) is the distance between the center of the pupils of the two eyes. IPD is critical for the design of binocular viewing systems, where both eye pupils need to be positioned within the exit pupils of the viewing system.[1] These viewing systems include binocular microscopes, night vision devices or goggles (NVGs), and head-mounted displays (HMDs). IPD data are used in the design of such systems to specify the range of lateral adjustment of the exit optics or eyepieces. IPD is also used to describe the distance between the exit pupils or optical axes of a binocular optical system.

Pupillary distance (PD) also describes the distance between the two pupils, but is an optometric term used to specify prescription eyewear. The PD of a patient is used to specify prescriptive eyewear for that patient. The distinction with IPD is the importance of anthropometric databases and the design of binocular viewing devices with an IPD adjustment that will fit a targeted population of users.

Measurement

IPD can be precisely measured with a pupilometer. This device presents a simple binocular target that can be set from a close viewing distance out to optical infinity. Closer settings will result in an IPD reduction associated with convergent eyepieces.[2] Some pupilometers provide a separate distance readout for the left- and right-eye—taking ocular asymmetry into account.

Databases

Anthropometric databases are available that include IPD.[3][4] These include Military Handbook 743A and the 1988 Anthropometric Survey of US Army Personnel.[5] These databases express the IPD for each gender and sample size as the mean and standard deviation, minimum and maximum, and percentiles (e.g., 5th and 95th; 1st and 99th, 50th or median). Representative data from the 1988 Anthropometric Survey are shown in the following table.

IPD values (mm) from 1988 Army Survey
Gender Sample
size
Mean Standard
deviation
Minimum Maximum Percentile
1st 5th 50th 95th 99th
Male 1771 64.7 3.7 52 78 57 59 65 71 74
Female 2205 62.3 3.6 52 76 55 57 62 69 71

Viewing devices

Devices such as stereo microscopes have small exit pupils, and adjustment for user IPD is necessary.[2] These devices can be designed to fit a large range of IPDs as factors such as size and weight of the adjusting mechanism are not overly critical. A Blue Light Industry stereo microscope is a typical device, and has an adjustment range of 55 to 75 mm. In contrast to microscopes, the weight and bulk of NVGs and HMDs are large factors for wearing comfort and usability. The ANVIS NVG has an adjustment range of 52 to 72 mm.[6] The Rockwell-Collins Optronics XL35 and XL50 binocular HMDs have a range of 55 to 75 mm. The 1988 Army Survey can be used to evaluate the percentage of the Army population captured by these ranges.

Binocular HMDs can be designed with a fixed IPD to minimize weight, bulk and cost. The fixed-IPD design strategy assumes that the exit pupil will be large enough to capture the IPD range of a targeted population. An adjustable IPD design assumes that the lateral adjustment range in conjunction with the exit pupil size is required to capture the targeted population.

Other applications

IPD is also used in binocular vision science. For example, a bench-top haploscope may require setting the mirror separation for each experimental subject. Other experimental presentations may require the use of IPD to control for ocular convergence and binocular depth.

Several binocular HMDs that support night vision position the sensors on the sides of the helmet, effectively extending the IPD by approximately 4x and creating hyperstereopsis.[7] Hyperstereopsis increases ocular convergence and causes near objects to appear closer and with exaggerated depth and slant.

References

  1. ^ Moffitt, K. (1997). Designing HMDs for viewing comfort. In J. E. Melzer & K. Moffitt (eds.), Head mounted displays: Designing for the user. New York: McGraw-Hill.
  2. ^ a b Farrell, R. J., & Booth, J. M. (1975). Design handbook for imagery interpretation equipment. Seattle WA: Boeing Aerospace Company.
  3. ^ Dodgson, N. A. (2004). Variation and extrema of human interpupillary distance. In A. J. Woods, J. O. Merritt, S. A. Benton and M. T. Bolas (eds.), Proceedings of SPIE: Stereoscopic Displays and Virtual Reality Systems XI, Vol. 5291, pp. 36–46. San Jose CA.
  4. ^ Smith, G., & Atchison, D. A. (1997). The eye and visual optical instruments. Cambridge UK: Cambridge University Press.
  5. ^ Gordon, C. C., Bradtmiller, B., Clauser, C.E., Churchill, T., McConville, J.T., Tebbetts, I., and Walker, R.A. (1989). 1987–1988 Anthropometric Survey of U.S. Army Personnel: Methods and Summary Statistics. TR-89-044. Natick MA: U.S. Army Natick Research, Development and Engineering Center.
  6. ^ Rash, C. E. (2001). Introductory overview. In C. E. Rash (ed.), Helmet-mounted displays: Design issues for rotary-wing aircraft. Ft. Rucker AL: US Army Aeromedical Research Laboratory.
  7. ^ Temme, L. A., Kalich, M. E., Curry, I. P., Pinkus, A. R., Task, H. L., & Rash, C. E. (2009). Visual perceptual conflicts and illusions. In C. E. Rash, M. B. Russo, T. R. Letowski, & E. T. Schmeisser (eds.), Helmet-mounted displays: Sensation, perception and cognition issues. Ft. Rucker AL: U.S. Army Aeromedical Research Laboratory.
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.