Vergence-accommodation conflict: Difference between revisions
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[[File:Vergence accommodation conflict image.png|thumb|right|250px|Vergence-accommodation conflict in VR compared to real-world vision]] | |||
'''Vergence-accommodation conflict''' ('''VAC'''), also known as '''accommodation-vergence conflict''' or sometimes '''accommodation-vergence mismatch''', is a visual and perceptual phenomenon that occurs when the [[Brain|brain]] receives mismatching cues between the distance to which the eyes are pointed or converged ([[Vergence|vergence]]) and the distance at which the eyes' lenses are focused ([[Accommodation (eye)|accommodation]]).<ref name="Hoffman2008">Hoffman D M, Girshick A R, Akeley K, Banks M S. (2008). “Vergence–accommodation conflicts hinder visual performance and cause visual fatigue.” ''Journal of Vision'', 8 (3): 33 (1‑30). doi:10.1167/8.3.33. PMID 18484839. https://pubmed.ncbi.nlm.nih.gov/18484839/</ref> | '''Vergence-accommodation conflict''' ('''VAC'''), also known as '''accommodation-vergence conflict''' or sometimes '''accommodation-vergence mismatch''', is a visual and perceptual phenomenon that occurs when the [[Brain|brain]] receives mismatching cues between the distance to which the eyes are pointed or converged ([[Vergence|vergence]]) and the distance at which the eyes' lenses are focused ([[Accommodation (eye)|accommodation]]).<ref name="Hoffman2008">Hoffman D M, Girshick A R, Akeley K, Banks M S. (2008). “Vergence–accommodation conflicts hinder visual performance and cause visual fatigue.” ''Journal of Vision'', 8 (3): 33 (1‑30). doi:10.1167/8.3.33. PMID 18484839. https://pubmed.ncbi.nlm.nih.gov/18484839/</ref><ref name="Kreylos2014VAC">{{cite web |last=Kreylos |first=Oliver |title=Accommodation and Vergence in Head-mounted Displays |url=http://doc-ok.org/?p=1602 |website=Doc-Ok.org |date=2014-04-13}}</ref> Because natural viewing conditions tightly couple these two mechanisms, breaking that link is a primary cause of visual discomfort and performance issues in modern [[Virtual reality|virtual reality]] (VR), [[Augmented reality|augmented reality]] (AR), and other [[Stereoscopy|stereoscopic]] 3-D displays, including nearly all mainstream [[Head-Mounted Display|head-mounted displays]] (HMDs).<ref name="Hoffman2008" /> | ||
<ref name="Kreylos2014VAC">{{cite web |last=Kreylos |first=Oliver |title=Accommodation and Vergence in Head-mounted Displays |url=http://doc-ok.org/?p=1602 |website=Doc-Ok.org |date=2014-04-13}}</ref> Because natural viewing conditions tightly couple these two mechanisms, breaking that link is a primary cause of visual discomfort and performance issues in modern [[Virtual reality|virtual reality]] (VR), [[Augmented reality|augmented reality]] (AR), and other [[Stereoscopy|stereoscopic]] 3-D displays, including nearly all mainstream [[Head-Mounted Display|head-mounted displays]] (HMDs).<ref name="Hoffman2008" /> | |||
==Physiological Basis== | ==Physiological Basis== | ||
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* '''Fixed-focus HMDs''': Nearly all consumer VR and many AR headsets use internal display screens (like OLED or LCD) viewed through lenses. These lenses create a [[virtual image]] of the screens, making them appear to be located at a fixed focal distance, typically between 1.3 and 2 meters (though this varies).<ref name="Kreylos2013HMD">{{cite web |last=Kreylos |first=Oliver |title=Head-mounted Displays and Lenses |url=http://doc-ok.org/?p=1360 |website=Doc-Ok.org |date=2013-07-24}}</ref> Consequently, viewers must accommodate (focus their eyes) to this fixed plane to see a sharp image, regardless of the perceived depth of virtual objects. However, stereoscopic rendering creates virtual objects that appear at various depths by presenting slightly different images to each eye, requiring the viewer's eyes to converge or diverge (vergence). Objects rendered virtually nearer than the fixed focal plane induce a ''positive VAC'' (eyes converge more than they accommodate), while objects rendered virtually farther induce a ''negative VAC'' (eyes converge less than they accommodate).<ref name="Shibata2011">Shibata T, Kim J, Hoffman D M, Banks M S. (2011). “The zone of comfort: Predicting visual discomfort with stereo displays.” ''Journal of Vision'', 11 (8): 11. doi:10.1167/11.8.11. PMC 3369815. https://pmc.ncbi.nlm.nih.gov/articles/PMC3369815/</ref> | * '''Fixed-focus HMDs''': Nearly all consumer VR and many AR headsets use internal display screens (like OLED or LCD) viewed through lenses. These lenses create a [[virtual image]] of the screens, making them appear to be located at a fixed focal distance, typically between 1.3 and 2 meters (though this varies).<ref name="Kreylos2013HMD">{{cite web |last=Kreylos |first=Oliver |title=Head-mounted Displays and Lenses |url=http://doc-ok.org/?p=1360 |website=Doc-Ok.org |date=2013-07-24}}</ref> Consequently, viewers must accommodate (focus their eyes) to this fixed plane to see a sharp image, regardless of the perceived depth of virtual objects. However, stereoscopic rendering creates virtual objects that appear at various depths by presenting slightly different images to each eye, requiring the viewer's eyes to converge or diverge (vergence). Objects rendered virtually nearer than the fixed focal plane induce a ''positive VAC'' (eyes converge more than they accommodate), while objects rendered virtually farther induce a ''negative VAC'' (eyes converge less than they accommodate).<ref name="Shibata2011">Shibata T, Kim J, Hoffman D M, Banks M S. (2011). “The zone of comfort: Predicting visual discomfort with stereo displays.” ''Journal of Vision'', 11 (8): 11. doi:10.1167/11.8.11. PMC 3369815. https://pmc.ncbi.nlm.nih.gov/articles/PMC3369815/</ref> | ||
* '''[[3D television|3D Cinema and Television]]''': VAC also occurs here, but symptoms are often milder. The screen is typically farther away, the [[Field of view|field of view]] is smaller, and content creators can limit disparities to keep virtual objects within a "zone of comfort" relative to the screen distance.<ref name="ISO2015">International Organization for Standardization. (2015). ''ISO 9241‑392: | * '''[[3D television|3D Cinema and Television]]''': VAC also occurs here, but symptoms are often milder. The screen is typically farther away, the [[Field of view|field of view]] is smaller, and content creators can limit disparities to keep virtual objects within a "zone of comfort" relative to the screen distance.<ref name="ISO2015">International Organization for Standardization. (2015). ''ISO 9241‑392:2015 - Ergonomics of human‑system interaction – Part 392: Ergonomic requirements for the reduction of visual fatigue from stereoscopic images''. https://www.iso.org/standard/60317.html</ref> | ||
* '''[[Optical see-through display|Optical See-Through (OST) AR]]''': In OST AR glasses, virtual images (often at a fixed focus) are overlaid onto the real world. This creates a conflict not only between vergence and accommodation for virtual objects but also a potential mismatch between focusing on real-world objects at various distances and the fixed focus of the virtual overlay. This can introduce depth discontinuities, reduce the perceived registration accuracy of virtual objects, and cause discomfort.<ref name="Zhou2021">Zhou Y, Li X, Yuan C. (2021). “Vergence‑accommodation conflict in optical see‑through display: Review and prospect.” ''Results in Optics'', 5: 100160. doi:10.1016/j.rio.2021.100160. https://doi.org/10.1016/j.rio.2021.100160</ref> | * '''[[Optical see-through display|Optical See-Through (OST) AR]]''': In OST AR glasses, virtual images (often at a fixed focus) are overlaid onto the real world. This creates a conflict not only between vergence and accommodation for virtual objects but also a potential mismatch between focusing on real-world objects at various distances and the fixed focus of the virtual overlay. This can introduce depth discontinuities, reduce the perceived registration accuracy of virtual objects, and cause discomfort.<ref name="Zhou2021">Zhou Y, Li X, Yuan C. (2021). “Vergence‑accommodation conflict in optical see‑through display: Review and prospect.” ''Results in Optics'', 5: 100160. doi:10.1016/j.rio.2021.100160. https://doi.org/10.1016/j.rio.2021.100160</ref> | ||
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! [[Light field display|Light Field]] | ! [[Light field display|Light Field]] | ||
| Attempts to reconstruct the 4D light field of the scene (rays of light with position and direction). This allows the eye's lens to naturally focus at different depths within the reproduced volume. | Research using lenslet | | Attempts to reconstruct the 4D light field of the scene (rays of light with position and direction). This allows the eye's lens to naturally focus at different depths within the reproduced volume. | Research using [[lenslet array]]s, parallax barriers, holographic optical elements, super-multi-view displays. | Potentially provides true continuous focus cues without eye-tracking. Challenges include extremely high resolution and bandwidth requirements, computational complexity, limited field of view, and tradeoffs between spatial and angular resolution. | ||
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! [[Holography|Holographic Displays]] | ! [[Holography|Holographic Displays]] | ||
| Aims to fully reconstruct the wavefront of light from the virtual scene using diffraction patterns generated by [[Spatial light modulator|spatial light modulators]]. | Research by Microsoft Research, VividQ, Light Field Lab. | Theoretically the ultimate solution, providing all depth cues including accommodation correctly. Challenges include high computational cost ("speckle" noise), limited field of view, and hardware complexity for real-time, high-quality HMDs. | | Aims to fully reconstruct the wavefront of light from the virtual scene using diffraction patterns generated by [[Spatial light modulator|spatial light modulators]]. | Research by Microsoft Research, [[VividQ]], Light Field Lab. | Theoretically the ultimate solution, providing all depth cues including accommodation correctly. Challenges include high computational cost ("speckle" noise), limited field of view, and hardware complexity for real-time, high-quality HMDs. | ||
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! [[Retinal projection|Retinal Projection / Scanning]] | ! [[Retinal projection|Retinal Projection / Scanning]] | ||
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* '''Perceptual Modeling''': Research using large-sample studies to better understand individual variability in the accommodation-vergence relationship, potentially enabling personalized comfort settings or adaptive display parameters.<ref name="Lin2022" /> | * '''Perceptual Modeling''': Research using large-sample studies to better understand individual variability in the accommodation-vergence relationship, potentially enabling personalized comfort settings or adaptive display parameters.<ref name="Lin2022" /> | ||
==See | ==See also== | ||
* [[Depth perception]] | * [[Depth perception]] | ||
* [[Eye tracking]] | * [[Eye tracking]] | ||
* [[Light field display]] | * [[Light field display]] | ||
* [[Stereoscopy]] | * [[Stereoscopy]] | ||