Changes

[[File:Chromostereopsis.png|thumb|Focal conflict in a [[chromostereogram]]. Look at this image in full screen.]]

[[File:VAC detail.png|thumb|200px|VAC as it can happen in virtual reality]]

A '''vergence-accommodation conflict''', also known as a '''focal conflict''', is when a brain receives mismatching cues between eyes' [[focus]] and angle. It is disorienting and can result in eye and brain pain. The effect can be unpleasant and cause eye strain.

A '''vergence-accommodation conflict''' is when a brain receives mismatching cues between eyes' [[focus]] and angle. It is disorienting and can result in eye and brain pain. The effect can be unpleasant and cause eye strain.

 

This can happen with [[fixed-focus two-view display]]s, such as VR headsets and AR headsets including the [[Meta Quest]], [[Oculus Rift]], and [[Microsoft HoloLens]]. Focal conflict can occur in binocular flat focus autostereoscopic displays.  

This can happen with [[fixed-focus two-view display]]s, such as VR headsets and AR headsets including the [[Meta Quest]], [[Oculus Rift]], and [[Microsoft HoloLens]]. Focal conflict can occur in binocular flat focus autostereoscopic displays.  

Focal conflict can be encountered when viewing flat-focus [[stereogram]]s, [[3D movie]]s, or [[virtual reality]] (VR). It can cause visual fatigue and headaches after a short period of time; It is one of the main contributors to [[virtual reality sickness]]. The phenomenon can make it impossible to focus on objects close to the eye in VR, limiting the development of VR software.<ref name=facebook>{{Citation |title=Vergence-Accommodation Conflict: Facebook Research Explains Why Varifocal Matters For Future VR |url=https://www.youtube.com/watch?v=YWA4gVibKJE |language=en |access-date=2022-09-26| others=This sequence of clips is taken from Douglas Lanman's talk 'Quality Screen Time: Leveraging Computational Displays for Spatial Computing' at the 33d annual Electronic Imaging Symposium (26-30 January 2020)}}</ref>

Focal conflict is difficult to overcome when designing new types of [[3D display]]s.<ref name=facebook /> Overcoming focal conflict requires the use of [[integral imaging]], or [[holographic display]]s or [[sequential lightfield display]]s.

Focal conflict is difficult to overcome when designing new types of [[3D display]]s.<ref name=facebook /> Overcoming focal conflict requires the use of [[integral imaging]], or [[holographic display]]s or [[sequential lightfield display]]s.

Companies including [[CREAL]] and [[VividQ]] have claimed to solve VAC.

__NOTOC__

__NOTOC__

== Effects ==

== Effects ==

Focal conflict is part of why VR and 3D media causes eye strain and is disorienting.<ref>{{Cite web |title=Is it normal the 3DS effect hurt my eyes? - Nintendo 3DS |url=https://gamefaqs.gamespot.com/boards/997614-nintendo-3ds/72524629 |access-date=2022-09-26 |website=gamefaqs.gamespot.com}}</ref> There is not a strong consensus on the extent of visual damage, if any, that may occur due to overexposure to vergence-focal conflict. Even though this is the case, users of classic stereoscopic gadgets report being unable to look at the 3D screen for a long period of time.<ref>{{Cite web |title=Is Your Nintendo 3DS Bad for Your Health? |url=https://www.pcmag.com/archive/is-your-nintendo-3ds-bad-for-your-health-262584 |access-date=2022-09-26 |website=PCMAG |language=en}}</ref>

Focal conflict is part of why VR and 3D media causes eye strain and is disorienting.<ref>{{Cite web |title=Is it normal the 3DS effect hurt my eyes? - Nintendo 3DS |url=https://gamefaqs.gamespot.com/boards/997614-nintendo-3ds/72524629 |access-date=2022-09-26 |website=gamefaqs.gamespot.com}}</ref>

 

Focal conflict generally does not cause long term vision damage. Even though this is the case, users of classic stereoscopic gadgets report being unable to look at the 3D screen for a long period of time.<ref>{{Cite web |title=Is Your Nintendo 3DS Bad for Your Health? |url=https://www.pcmag.com/archive/is-your-nintendo-3ds-bad-for-your-health-262584 |access-date=2022-09-26 |website=PCMAG |language=en}}</ref>

== Measurement ==

== Measurement ==

A vergence-focal conflict is caused due to factors in human physiology like the [[accommodation reflex]]. Focal conflict occurs when the human brain receives mismatching cues between [[vergence]] and [[Accommodation (eye)|accommodation]].<ref name="kramida">{{Cite web |date=2022-09-22 |title=Resolving the Vergence-Accommodation Conflict in Head-Mounted Displays |url=https://3dvar.com/Kramida2016Resolving.pdf |access-date=2022-09-22 |archive-url=https://web.archive.org/web/20220922032435/https://3dvar.com/Kramida2016Resolving.pdf |archive-date=2022-09-22 |url-status=live}}</ref><ref>{{Cite journal |last=Konrad |first=Robert |date=2015-11-06 |title=What is the vergence-accommodation conflict and how do we fix it? |url=https://doi.org/10.1145/2810048 |journal=XRDS: Crossroads, the ACM Magazine for Students |volume=22 |issue=1 |pages=52–55 |doi=10.1145/2810048 |s2cid=9330080 |issn=1528-4972}}</ref><ref name=anses>{{Cite web |date=2014-11-06 |title=3D technologies and eyesight: use not recommended for children under the age of six, use in moderation for those under the age of 13 |url=https://www.anses.fr/en/content/3d-technologies-and-eyesight-use-not-recommended-children-under-age-six-use-moderation-0 |access-date=2022-09-22 |website=Anses |language=en}}</ref> It often causes headaches and visual fatigue.<ref>{{Cite journal |last1=Hoffman |first1=David M. |last2=Girshick |first2=Ahna R. |last3=Akeley |first3=Kurt |last4=Banks |first4=Martin S. |date=2008-03-01 |title=Vergence–accommodation conflicts hinder visual performance and cause visual fatigue |url=https://jov.arvojournals.org/article.aspx?articleid=2122611 |journal=Journal of Vision |language=en |volume=8 |issue=3 |pages=33.1–30 |doi=10.1167/8.3.33 |issn=1534-7362 |pmc=2879326 |pmid=18484839}}</ref> The vergence-accommodation conflict is one of the main causes of [[virtual reality sickness]].<ref>{{Cite journal |last1=Lawson |first1=Ben D. |last2=Stanney |first2=Kay M. |date=2021 |title=Editorial: Cybersickness in Virtual Reality and Augmented Reality |journal=Frontiers in Virtual Reality |volume=2 |doi=10.3389/frvir.2021.759682 |issn=2673-4192|doi-access=free }}</ref>

A vergence-focal conflict is caused due to factors in human physiology like the [[accommodation reflex]]. Focal conflict occurs when the human brain receives mismatching cues between [[vergence]] and [[Accommodation (eye)|accommodation]].<ref name="kramida">{{Cite web |date=2022-09-22 |title=Resolving the Vergence-Accommodation Conflict in Head-Mounted Displays |url=https://3dvar.com/Kramida2016Resolving.pdf |access-date=2022-09-22 |archive-url=https://web.archive.org/web/20220922032435/https://3dvar.com/Kramida2016Resolving.pdf |archive-date=2022-09-22 |url-status=live}}</ref><ref>{{Cite journal |last=Konrad |first=Robert |date=2015-11-06 |title=What is the vergence-accommodation conflict and how do we fix it? |url=https://doi.org/10.1145/2810048 |journal=XRDS: Crossroads, the ACM Magazine for Students |volume=22 |issue=1 |pages=52–55 |doi=10.1145/2810048 |s2cid=9330080 |issn=1528-4972}}</ref><ref name=anses>{{Cite web |date=2014-11-06 |title=3D technologies and eyesight: use not recommended for children under the age of six, use in moderation for those under the age of 13 |url=https://www.anses.fr/en/content/3d-technologies-and-eyesight-use-not-recommended-children-under-age-six-use-moderation-0 |access-date=2022-09-22 |website=Anses |language=en}}</ref> It often causes headaches and visual fatigue.<ref>{{Cite journal |last1=Hoffman |first1=David M. |last2=Girshick |first2=Ahna R. |last3=Akeley |first3=Kurt |last4=Banks |first4=Martin S. |date=2008-03-01 |title=Vergence–accommodation conflicts hinder visual performance and cause visual fatigue |url=https://jov.arvojournals.org/article.aspx?articleid=2122611 |journal=Journal of Vision |language=en |volume=8 |issue=3 |pages=33.1–30 |doi=10.1167/8.3.33 |issn=1534-7362 |pmc=2879326 |pmid=18484839}}</ref> The vergence-accommodation conflict is one of the main causes of [[virtual reality sickness]].<ref>{{Cite journal |last1=Lawson |first1=Ben D. |last2=Stanney |first2=Kay M. |date=2021 |title=Editorial: Cybersickness in Virtual Reality and Augmented Reality |journal=Frontiers in Virtual Reality |volume=2 |doi=10.3389/frvir.2021.759682 |issn=2673-4192|doi-access=free }}</ref>

Two ocular responses exist: vergence of eyes, and focus, also known as accommodation. Both of these mechanisms are crucial in stereoscopic vision. Vergence or independent inward/outward rotation of eyes is engaged to fixate on objects and perceive them as single. Incorrect vergence response can cause double vision. Accommodation is the eye’s focusing mechanism and it is engaged to produce a sharp image on a retina. Both of these mechanisms are neurally linked forming the accommodation-convergence reflex<ref>{{Cite web |title=Reflex action {{!}} Definition, Types and Mechanism and Important solved questions |date=11 November 2020 |url=https://www.crackyourtarget.com/reflex-action.html}}</ref> of eyes.

There are two ocular responses: vergence of eyes, and focus, which is also known as accommodation. These mechanisms are linked together. Vergence or independent inward/outward rotation of eyes is engaged to fixate on objects and perceive them as single. Incorrect vergence response can cause double vision. Accommodation is the eye’s focusing mechanism and it is engaged to produce a sharp image on a retina. Both of these mechanisms are neurally linked forming the accommodation-convergence reflex of eyes.<ref>{{Cite web |title=Reflex action {{!}} Definition, Types and Mechanism and Important solved questions |date=11 November 2020 |url=https://www.crackyourtarget.com/reflex-action.html}}</ref>

One can distinguish vergence (a distance of a point towards which both eyes are converging), and an accommodation (a distance of a region in space towards which the focus or refractive power of the crystalline lens has been adjusted to produce a sharp image on the retina).

One can distinguish vergence (a distance of a point towards which both eyes are converging), and an accommodation (a distance of a region in space towards which the focus or refractive power of the crystalline lens has been adjusted to produce a sharp image on the retina).

Most people can tolerate some extent of vergence-focal conflict, without noticeable onset of adverse effects. While it depends on a particular person and viewing distance, vergence-focal conflict of around up to 0.4 Diopters <ref name="Shibata 11–11"/> is within comfort limits of most people.

Most people can tolerate some extent of vergence-focal conflict, without noticeable onset of adverse effects. While it depends on a particular person and viewing distance, vergence-focal conflict of around up to 0.4 Diopters is within comfort limits of most people.<ref name="Shibata 11–11"/>

 

Meta Half Dome prototypes addressed the problem with variable focus lenses that matched focal depth to vergence stereoscopic depth.<ref>{{Cite web |last=VR |first=Oculus |title=Introducing the Team Behind Half Dome—Facebook Reality Labs' Varifocal Prototype {{!}} Meta Quest Blog |url=https://www.oculus.com/blog/introducing-the-team-behind-half-dome-facebook-reality-labs-varifocal-prototype/ |access-date=2023-06-13 |website=www.oculus.com |language=en}}</ref> The first prototype used bulky mechanical actuators to refocus the lens. The third prototype used a stack of 6 liquid crystal lens layers where each layer could be turned on and off by applying a voltage, and this creates 64 discrete focal planes.<ref>{{Cite web |date=2020-07-28 |title=Facebook's Display Research Lead: Varifocal Half-Dome 3 'Almost Ready For Prime Time' |url=https://www.uploadvr.com/half-dome-3-prime-time/ |access-date=2023-06-13 |website=UploadVR |language=en}}</ref> There are currently no production products using this technology.

==Causes==

==Causes==

===Virtual and augmented reality===

===Virtual and augmented reality===

Examples of fixed-focus biscopic gadgets that can cause focal conflict include the [[Oculus Quest 2]], [[HTC Vive]], [[Valve Index]] and the [[Microsoft HoloLens]]. Focal conflict can be experienced by bringing a virtual object very close to one's eyes in the headset and trying to focus on it.<ref>{{Citation |title=Vergence-Accommodation Conflict: Facebook Research Explains Why Varifocal Matters For Future VR |url=https://www.youtube.com/watch?v=YWA4gVibKJE |language=en |access-date=2022-09-22|publisher=VR Trailers & Clips|date =18 July 2020| via=YouTube|format=Video}}</ref>

Examples of fixed-focus biscopic gadgets that can cause focal conflict include the [[Meta Quest 3S]], [[HTC Vive]], [[Valve Index]] and the [[Microsoft HoloLens]]. Focal conflict can be experienced by bringing a virtual object very close to one's eyes in the headset and trying to focus on it.<ref>{{Citation |title=Vergence-Accommodation Conflict: Facebook Research Explains Why Varifocal Matters For Future VR |url=https://www.youtube.com/watch?v=YWA4gVibKJE |language=en |access-date=2022-09-22|publisher=VR Trailers & Clips|date =18 July 2020| via=YouTube|format=Video}}</ref>

Stereoscopic displays such as [[holographic display]]s and [[light field display]]s can remove the problem.<ref name="kramida" />

Stereoscopic displays such as [[holographic display]]s and [[light field display]]s can remove the problem.<ref name="kramida" />

*[[autostereoscopy|autostereoscopic displays]], such as the one found in the [[Nintendo 3DS]]<ref name= anses />

*[[autostereoscopy|autostereoscopic displays]], such as the one found in the [[Nintendo 3DS]]<ref name= anses />

==Mitigations==

==Effect on software==

VR and AR hardware companies often ask software developers not to show virtual content too close to the user in the gadgets.<ref>{{Cite web |title=Comfort - Mixed Reality |url=https://learn.microsoft.com/en-us/windows/mixed-reality/design/comfort |access-date=2022-09-22 |website=learn.microsoft.com |date=19 October 2021 |language=en-us}}</ref><ref>{{Cite web |date=2019-08-26 |title=Magic Leap Developer - Game Design: Best Practices |url=https://ml1-developer.magicleap.com/en-us/learn/guides/best-practices-in-game-design |url-status=live |archive-url=https://web.archive.org/web/20220922071934/https://ml1-developer.magicleap.com/en-us/learn/guides/best-practices-in-game-design |archive-date=2022-09-22 |access-date=2022-09-22 |website=Magic Leap Developer}}</ref> However, this is only a software mitigation and often times the effect can still be noticed.

VR and AR hardware companies often ask software developers not to show virtual content too close to the user.<ref>{{Cite web |title=Comfort - Mixed Reality |url=https://learn.microsoft.com/en-us/windows/mixed-reality/design/comfort |access-date=2022-09-22 |website=learn.microsoft.com |date=19 October 2021 |language=en-us}}</ref><ref>{{Cite web |date=2019-08-26 |title=Magic Leap Developer - Game Design: Best Practices |url=https://ml1-developer.magicleap.com/en-us/learn/guides/best-practices-in-game-design |url-status=live |archive-url=https://web.archive.org/web/20220922071934/https://ml1-developer.magicleap.com/en-us/learn/guides/best-practices-in-game-design |archive-date=2022-09-22 |access-date=2022-09-22 |website=Magic Leap Developer}}</ref> However, this is only a software mitigation and often times the effect can still be noticed.

==Solutions==

==Solutions==

In VR and AR, new types of displays have been developed since the 2010s that can minimize or eliminate focal conflict to non-issue levels. These displays include varifocal, multifocal,<ref>{{Cite journal |last1=Zhan |first1=Tao |last2=Xiong |first2=Jianghao |last3=Zou |first3=Junyu |last4=Wu |first4=Shin-Tson |date=2020-03-30 |title=Multifocal displays: review and prospect |journal=PhotoniX |volume=1 |issue=1 |pages=10 |doi=10.1186/s43074-020-00010-0 |s2cid=214754949 |issn=2662-1991|doi-access=free }}</ref> holographic, [https://www.youtube.com/watch?v=LowxBE6iKQk pin-mirror] and [https://www.youtube.com/watch?v=p5trOS3NaHw light field displays].<ref name=lanman>{{Citation |title=Douglas Lanman (Nvidia) - Light Field Displays at AWE2014 |url=https://www.youtube.com/watch?v=8hLzESOf8SE |language=en |access-date=2022-09-26}}</ref>

In VR and AR, new types of displays have been developed since the 2010s that can minimize or eliminate focal conflict to non-issue levels. These displays include varifocal, multifocal,<ref>{{Cite journal |last1=Zhan |first1=Tao |last2=Xiong |first2=Jianghao |last3=Zou |first3=Junyu |last4=Wu |first4=Shin-Tson |date=2020-03-30 |title=Multifocal displays: review and prospect |journal=PhotoniX |volume=1 |issue=1 |pages=10 |doi=10.1186/s43074-020-00010-0 |s2cid=214754949 |issn=2662-1991|doi-access=free }}</ref> holographic, pin-mirror and light field displays.<ref name=lanman>{{Citation |title=Douglas Lanman (Nvidia) - Light Field Displays at AWE2014 |url=https://www.youtube.com/watch?v=8hLzESOf8SE |language=en |access-date=2022-09-26}}</ref>

Varifocal displays are a concept explored mainly in VR display solutions. The basic principle relies on dynamically adjusting focal distance of displays based on the gaze direction. The technique requires an eye-tracking solution and means of modulating focal distance of a screen. Modulation of a focal distance can be, for example, [https://www.youtube.com/watch?v=JdM5SnSnuyQ&t=4s physical actuation of the screen] in relation to a fixed eyepiece optics, alternatively it can be utilization of varifocal<ref>{{Cite journal |doi=10.1364/OE.27.015627 |title=Design and demonstration of a vari-focal optical see-through head-mounted display using freeform Alvarez lenses |year=2019 |last1=Wilson |first1=Austin |last2=Hua |first2=Hong |journal=Optics Express |volume=27 |issue=11 |pages=15627–15637 |pmid=31163757 |bibcode=2019OExpr..2715627W |s2cid=174815078 |hdl=10150/633572 |hdl-access=free }}</ref><ref>{{Cite book |last1=Stevens |first1=R. E. |last2=Rhodes |first2=D. P. |last3=Hasnain |first3=A. |last4=Laffont |first4=P.-Y. |title=Digital Optics for Immersive Displays |chapter=Varifocal technologies providing prescription and VAC mitigation in HMDS using Alvarez lenses |editor-first1=Bernard C |editor-first2=Hagen |editor-first3=Wolfgang |editor-last1=Kress |editor-last2=Stolle |editor-last3=Osten |date=2018-05-21 |chapter-url=https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10676/106760J/Varifocal-technologies-providing-prescription-and-VAC-mitigation-in-HMDs-using/10.1117/12.2318397.full |publisher=SPIE |volume=10676 |pages=142–158 |doi=10.1117/12.2318397|bibcode=2018SPIE10676E..0JS |isbn=9781510618787 |s2cid=173178593 }}</ref> lens element(s). While varifocal approach mitigates or entirely solves VAC, it cannot convey realistic monocular focus cues. To try to add realism, these techniques rely on [https://www.cl.cam.ac.uk/~rkm38/pdfs/march2022_impact_of_focus_cues.pdf image processing techniques to simulate focus cues].    

Varifocal displays are a concept explored mainly in VR display solutions. The basic principle relies on dynamically adjusting focal distance of displays based on the gaze direction. The technique requires an eye-tracking solution and means of modulating focal distance of a screen. Modulation of a focal distance can be, for example, physical actuation of the screen in relation to a fixed eyepiece optics, alternatively it can be utilization of varifocal<ref>{{Cite journal |doi=10.1364/OE.27.015627 |title=Design and demonstration of a vari-focal optical see-through head-mounted display using freeform Alvarez lenses |year=2019 |last1=Wilson |first1=Austin |last2=Hua |first2=Hong |journal=Optics Express |volume=27 |issue=11 |pages=15627–15637 |pmid=31163757 |bibcode=2019OExpr..2715627W |s2cid=174815078 |hdl=10150/633572 |hdl-access=free }}</ref><ref>{{Cite book |last1=Stevens |first1=R. E. |last2=Rhodes |first2=D. P. |last3=Hasnain |first3=A. |last4=Laffont |first4=P.-Y. |title=Digital Optics for Immersive Displays |chapter=Varifocal technologies providing prescription and VAC mitigation in HMDS using Alvarez lenses |editor-first1=Bernard C |editor-first2=Hagen |editor-first3=Wolfgang |editor-last1=Kress |editor-last2=Stolle |editor-last3=Osten |date=2018-05-21 |chapter-url=https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10676/106760J/Varifocal-technologies-providing-prescription-and-VAC-mitigation-in-HMDs-using/10.1117/12.2318397.full |publisher=SPIE |volume=10676 |pages=142–158 |doi=10.1117/12.2318397|bibcode=2018SPIE10676E..0JS |isbn=9781510618787 |s2cid=173178593 }}</ref> lens element(s). While varifocal approach mitigates or entirely solves VAC, it cannot convey realistic monocular focus cues. To try to add realism, these techniques rely on image processing techniques to simulate focus cues.    

 

Meta Half Dome prototypes addressed the problem with variable focus lenses that matched focal depth to vergence stereoscopic depth.<ref>{{Cite web |last=VR |first=Oculus |title=Introducing the Team Behind Half Dome—Facebook Reality Labs' Varifocal Prototype {{!}} Meta Quest Blog |url=https://www.oculus.com/blog/introducing-the-team-behind-half-dome-facebook-reality-labs-varifocal-prototype/ |access-date=2023-06-13 |website=www.oculus.com |language=en}}</ref> The first prototype used bulky mechanical actuators to refocus the lens. The third prototype used a stack of 6 liquid crystal lens layers where each layer could be turned on and off by applying a voltage, and this creates 64 discrete focal planes.<ref>{{Cite web |date=2020-07-28 |title=Facebook's Display Research Lead: Varifocal Half-Dome 3 'Almost Ready For Prime Time' |url=https://www.uploadvr.com/half-dome-3-prime-time/ |access-date=2023-06-13 |website=UploadVR |language=en}}</ref> There are currently no production products using this technology.

Multifocal displays are a way of overcoming focal conflict. The principle of operation relies on availability of multiple image focal planes (screens), which from the perspective of a viewer are available simultaneously at all times. This gives the ability to accommodate eyes within the available range of focal distances and perceive realistic monocular focus (image blur) cues similarly to natural viewing conditions. Essentially multifocal displays discretize the depth dimension and split or slice the 3D content according to the available configuration of depth planes to minimize focal conflict. The topic of multifocal displays has been generously researched for at least several [http://bankslab.berkeley.edu/publications/Files/stereo_display_prototype04.pdf decades],<ref>{{Cite journal |last1=MacKenzie |first1=Kevin J. |last2=Hoffman |first2=David M. |last3=Watt |first3=Simon J. |date=2010-07-01 |title=Accommodation to multiple‐focal‐plane displays: Implications for improving stereoscopic displays and for accommodation control |url=https://jov.arvojournals.org/article.aspx?articleid=2191682 |journal=Journal of Vision |language=en |volume=10 |issue=8 |pages=22 |doi=10.1167/10.8.22 |pmid=20884597 |issn=1534-7362|doi-access=free }}</ref><ref>{{Cite journal |doi=10.1364/AO.39.003209 |title=Multifocal planes head-mounted displays |year=2000 |last1=Rolland |first1=Jannick P. |last2=Krueger |first2=Myron W. |last3=Goon |first3=Alexei |journal=Applied Optics |volume=39 |issue=19 |pages=3209–3215 |pmid=18349886 |bibcode=2000ApOpt..39.3209R |s2cid=16434842 }}</ref> nevertheless, there is only a limited offering of commercially available [https://lightspace3d.com/ multifocal] near-eye displays.

Multifocal displays are a way of overcoming focal conflict. The principle of operation relies on availability of multiple image focal planes (screens), which from the perspective of a viewer are available simultaneously at all times. This gives the ability to accommodate eyes within the available range of focal distances and perceive realistic monocular focus (image blur) cues similarly to natural viewing conditions. Essentially multifocal displays discretize the depth dimension and split or slice the 3D content according to the available configuration of depth planes to minimize focal conflict. The topic of multifocal displays has been generously researched for at least several [http://bankslab.berkeley.edu/publications/Files/stereo_display_prototype04.pdf decades],<ref>{{Cite journal |last1=MacKenzie |first1=Kevin J. |last2=Hoffman |first2=David M. |last3=Watt |first3=Simon J. |date=2010-07-01 |title=Accommodation to multiple‐focal‐plane displays: Implications for improving stereoscopic displays and for accommodation control |url=https://jov.arvojournals.org/article.aspx?articleid=2191682 |journal=Journal of Vision |language=en |volume=10 |issue=8 |pages=22 |doi=10.1167/10.8.22 |pmid=20884597 |issn=1534-7362|doi-access=free }}</ref><ref>{{Cite journal |doi=10.1364/AO.39.003209 |title=Multifocal planes head-mounted displays |year=2000 |last1=Rolland |first1=Jannick P. |last2=Krueger |first2=Myron W. |last3=Goon |first3=Alexei |journal=Applied Optics |volume=39 |issue=19 |pages=3209–3215 |pmid=18349886 |bibcode=2000ApOpt..39.3209R |s2cid=16434842 }}</ref> nevertheless, there is only a limited offering of commercially available [https://lightspace3d.com/ multifocal] near-eye displays.

Light field displays are one of the best ways to solve the vergence-focal conflict.<ref name="lanman" /> They share features with [[integral imaging]] displays.

Light field displays are one of the best ways to solve the vergence-focal conflict.<ref name="lanman" /> They share features with [[integral imaging]] displays.

[http://www.creal.com CREAL], a near-eye display manufacturer for AR headsets/glasses, developed a light field display technology that projects the light rays just like they exist in the real world. This way, the virtual content has a real depth, and each eye can change focus naturally between the virtual objects, from up close to infinity.

[[CREAL]], a near-eye display manufacturer for AR headsets/glasses, developed a light field display technology that projects the light rays just like they exist in the real world. This way, the virtual content has a real depth, and each eye can change focus naturally between the virtual objects, from up close to infinity.

[[SeeReal Technologies]], a manufacturer of displays for 3D-enabled mobile gadgets, claim that their displays can generate visuals that do not have fixed focus.<ref>{{Cite book|chapter-url=https://www.spiedigitallibrary.org/conference-proceedings-of-spie/6803/68030M/Large-holographic-displays-as-an-alternative-to-stereoscopic-displays/10.1117/12.766163.full|chapter=Large holographic displays as an alternative to stereoscopic displays|first1=R.|last1=Häussler|first2=A.|last2=Schwerdtner|first3=N.|last3=Leister|editor-first1=Andrew J |editor-first2=Nicolas S |editor-first3=John O |editor-last1=Woods |editor-last2=Holliman |editor-last3=Merritt |title=Stereoscopic Displays and Applications XIX |date=29 February 2008|publisher=SPIE|volume=6803|pages=219–227|via=www.spiedigitallibrary.org|doi=10.1117/12.766163|s2cid=62176480 }}</ref> The company developed the display used in the [[Takee 1]] smartphone.<ref>{{Cite web |last=Kano3D |date=2020-12-29 |title=Takee 1: The first Holographic Smartphone gets a new Update after 6 Years! |url=https://www.tridimensional.info/2020/12/takee-1-the-first-holographic-smartphone-gets-a-new-update-after-6-years/ |access-date=2022-09-28 |website=Tridimensional.info |language=en-US}}</ref> However, SeeReal's solution requires [[eye tracking]], which can limit the 3D capabilities of the displays such as the [[field of view]] of the 3D effect.{{citation needed|date=October 2022}}

[[SeeReal Technologies]], a manufacturer of displays for 3D-enabled mobile gadgets, claim that their displays can generate visuals that do not have fixed focus.<ref>{{Cite book|chapter-url=https://www.spiedigitallibrary.org/conference-proceedings-of-spie/6803/68030M/Large-holographic-displays-as-an-alternative-to-stereoscopic-displays/10.1117/12.766163.full|chapter=Large holographic displays as an alternative to stereoscopic displays|first1=R.|last1=Häussler|first2=A.|last2=Schwerdtner|first3=N.|last3=Leister|editor-first1=Andrew J |editor-first2=Nicolas S |editor-first3=John O |editor-last1=Woods |editor-last2=Holliman |editor-last3=Merritt |title=Stereoscopic Displays and Applications XIX |date=29 February 2008|publisher=SPIE|volume=6803|pages=219–227|via=www.spiedigitallibrary.org|doi=10.1117/12.766163|s2cid=62176480 }}</ref> The company developed the display used in the [[Takee 1]] smartphone.<ref>{{Cite web |last=Kano3D |date=2020-12-29 |title=Takee 1: The first Holographic Smartphone gets a new Update after 6 Years! |url=https://www.tridimensional.info/2020/12/takee-1-the-first-holographic-smartphone-gets-a-new-update-after-6-years/ |access-date=2022-09-28 |website=Tridimensional.info |language=en-US}}</ref> However, SeeReal's solution requires [[eye tracking]], which can limit the 3D capabilities of the displays such as the [[field of view]] of the multifocality.{{citation needed|date=October 2022}}

==See also==

==See also==

* [[Accommodative convergence]]

* [[Accommodative convergence]]

* [[Binocular vision]]

* [[Binocular vision]]

* [[Depth perception]]

* [[Depth perception]]

* [[Multiscopy]]

* [[Multiscopy]]

* [[Polarized 3D system]]

* [[Polarized 3D system]]

== References ==

== References ==

{{reflist}}

{{reflist}}

[[Category:Visual]]

[[Category:Visual]]

[[Category:Human vision]]

[[Category:Human vision]]