Head-mounted display: Difference between revisions

A [[head-mounted display]] ('''HMD''') is a [[display]] [[device]], worn on the head or as part of a [[helmet]] (see [[Helmet-mounted display]]), that has a small display optic in front of one ([[monocular]] HMD) or each eye ([[binocular]] HMD). HMDs serve various purposes, including gaming, aviation, engineering, medicine, and are the primary delivery systems for [[Virtual Reality]] (VR), [[Augmented Reality]] (AR), and [[Mixed Reality]] (MR) experiences, particularly when supporting a seamless blend of physical and digital elements.<ref name="Sutherland1968">Sutherland, Ivan E. (1968-12-09). "A head-mounted three dimensional display". ACM Digital Library. Retrieved 2023-10-27. [https://dl.acm.org/doi/10.1145/1476589.1476686 Link]</ref><ref name="idc2025">IDC (25 March 2025). "Growth Expected to Pause for AR/VR Headsets, according to IDC". Retrieved 2025-05-15. [https://www.idc.com/getdoc.jsp?containerId=prUS53278025 Link]</ref>

HMDs function by presenting imagery, data, or a combination thereof directly to the wearer's visual field. Many modern HMDs are [[stereoscopic]], featuring separate displays or distinct images rendered for each eye to create a sense of depth through [[binocular disparity]]. Examples include VR headsets like the [[Meta Quest 3]] and [[Valve Index]]. Other HMDs, particularly earlier AR devices or specialized notification displays like the original [[Google Glass]], may be monocular, presenting information over only one eye.<ref name="GoogleGlassPatent">Heinrich, Jerome (assignee: Google Inc.) (2014-07-29). "Wearable display device". Google Patents. Retrieved 2023-10-27. [https://patents.google.com/patent/US8791879B1/en Link]</ref>

The vast majority of consumer and enterprise VR and AR systems rely on HMDs. In AR applications, the display system is typically designed to be see-through, allowing digital information to be superimposed onto the user's view of the real world. These are often specifically termed [[Optical head-mounted display]]s (OHMDs), utilizing technologies like [[Waveguide (optics)|waveguides]] or [[beam splitter]]s.<ref name="AROpticsReview">Kress, Bernard C. & Starner, Thad (2018-11-01). "Optical see-through head-mounted displays: a review". ''Applied Optics''. '''57''' (31): 9311-9325. doi:10.1364/AO.57.009311. Retrieved 2023-10-27. [https://www.osapublishing.org/ao/abstract.cfm?uri=ao-57-31-9311 Link]</ref> In VR applications, the display system is opaque, completely blocking the user's view of the real world and replacing it with a computer-generated virtual environment, aiming for high levels of [[immersion]] and [[presence]].<ref name="VRBookSlater">Slater, Mel & Sanchez-Vives, Maria V. (2016). "Chapter 1: Immersive Virtual Reality". ''Enhancing Our Lives with Immersive Virtual Reality''. Elsevier. ISBN 978-0128046377.</ref> Some modern VR HMDs incorporate external [[camera]]s to provide [[video passthrough]] capabilities, enabling a form of AR or "Mixed Reality" where the real world is viewed digitally on the opaque screens with virtual elements overlaid.

The concept of a head-mounted display dates back further than often realized. One of the earliest precursors was Morton Heilig's "Telesphere Mask" patented in 1960, a non-computerized, photographic-based stereoscopic viewing device intended for individual use.<ref name="HeiligPatent">Heilig, Morton L. (1960-10-04). "Stereoscopic-television apparatus for individual use". Google Patents. Retrieved 2023-10-27. [https://patents.google.com/patent/US2955156A/en Link]</ref><ref name="heilig1960">USPTO (28 June 1960). "US 2,955,156 — Stereoscopic-television apparatus for individual use". Retrieved 2024-05-15. [https://patents.google.com/patent/US2955156A Link]</ref>

However, the first true HMD connected to a computer is widely credited to [[Ivan Sutherland]] and his student Bob Sproull at Harvard University and later the University of Utah, around 1968. Dubbed the "[[Sword of Damocles]]" due to its imposing size and the heavy machinery suspended from the ceiling required to support its weight and track head movement, it presented simple wireframe graphics in stereo. This system pioneered many concepts still fundamental to VR and AR today, including head tracking and stereoscopic viewing.<ref name="Sutherland1968"/><ref name="sutherland1968">Wikipedia (20 April 2025). "The Sword of Damocles". Retrieved 2024-05-15. [https://en.wikipedia.org/wiki/The_Sword_of_Damocles_(virtual_reality) Link]</ref>

Throughout the 1970s and 1980s, HMD development continued primarily in military (especially for aviator helmet-mounted displays) and academic research labs, driven by organizations like the US Air Force and [[NASA]].<ref name="NASA_HMD">Fisher, S. S.; McGreevy, M.; Humphries, J.; Robinett, W. (1986-01-01). "Virtual Environment Display System". NASA Technical Reports Server. Retrieved 2023-10-27. [https://ntrs.nasa.gov/citations/19860018487 Link]</ref> The late 1980s and early 1990s saw a "first wave" of commercial VR interest, with companies like VPL Research, founded by [[Jaron Lanier]], popularizing the term "Virtual Reality" and developing HMDs like the "[[EyePhone]]". However, technology limitations (low [[resolution]], high [[latency]], limited processing power, high cost) prevented widespread adoption.<ref name="RheingoldVR">Rheingold, Howard (1991). ''Virtual Reality''. Simon & Schuster. ISBN 978-0671693633.</ref> Nintendo's [[Virtual Boy]] (1995), while technically an HMD, used red LED displays and lacked head tracking, failing commercially but remaining a notable early attempt at consumer VR.<ref name="VirtualBoyHistory">Edwards, Benj (2015-08-21). "Unraveling The Enigma Of Nintendo’s Virtual Boy, 20 Years Later". Fast Company. Retrieved 2023-10-27. [https://www.fastcompany.com/3050016/unraveling-the-enigma-of-nintendos-virtual-boy-20-years-later Link]</ref>

The modern era of consumer VR HMDs was effectively kickstarted by [[Palmer Luckey]]'s prototype [[Oculus Rift]] in the early 2010s, which demonstrated that high-quality, low-latency VR was becoming feasible with modern mobile display panels and [[sensor]]s. Its subsequent Kickstarter success and acquisition by [[Facebook]] (now [[Meta Platforms|Meta]]) spurred renewed industry-wide investment.<ref name="OculusKickstarter">Kickstarter. "Oculus Rift: Step Into the Game". Retrieved 2023-10-27. [https://www.kickstarter.com/projects/1523379957/oculus-rift-step-into-the-game Link]</ref> This led to the release of numerous consumer HMDs:

*2014 - [[Google Cardboard]] popularised low-cost, smartphone-driven VR viewers.<ref name="cardboard2014">Time Magazine (28 Jan 2016). "Google’s New Head of Virtual Reality on What They’re Planning Next". Retrieved 2024-05-15. [https://time.com/4193755/google-cardboard-virtual-reality-clay-bavor-vr/ Link]</ref>

*2015 - [[Samsung Gear VR]] improved on the smartphone HMD concept with better optics and integrated controls.<ref name="gearvr2015">Wikipedia (24 Apr 2025). "Samsung Gear VR". Retrieved 2024-05-15. [https://en.wikipedia.org/wiki/Samsung_Gear_VR Link]</ref>

*2016 - The consumer [[Oculus Rift]] (CV1) and [[HTC Vive]] established high-end, PC-tethered VR with wide FOV and robust external tracking systems.<ref name="rift2016">Wikipedia (15 Apr 2025). "Oculus Rift". Retrieved 2024-05-15. [https://en.wikipedia.org/wiki/Oculus_Rift Link]</ref><ref name="lighthouse">Valve Software (12 Feb 2025). "Valve Index Base Stations". Retrieved 2024-05-15. [https://www.valvesoftware.com/index/base-stations Link]</ref> [[PlayStation VR]] brought tethered VR to the console market.

*2019 - [[Oculus Quest]] pioneered high-quality standalone (untethered) 6DoF VR using inside-out camera tracking (Oculus Insight).<ref name="insight2019">Meta Reality Labs (14 Aug 2019). "The Story Behind Oculus Insight Technology". Retrieved 2024-05-15. [https://tech.facebook.com/reality-labs/2019/8/the-story-behind-oculus-insight-technology/ Link]</ref> [[Valve Index]] pushed fidelity in the PC VR space.

*2024 - [[Apple Vision Pro]] launched as a premium "spatial computer" featuring high-resolution Micro-OLED displays, advanced eye and hand tracking, and spatial video capabilities.<ref name="visionpro">Apple Newsroom (08 Jan 2024). "Apple Vision Pro available in the U.S. on February 2". Retrieved 2024-05-15. [https://www.apple.com/newsroom/2024/01/apple-vision-pro-available-in-the-us-on-february-2/ Link]</ref>

#*[[Distortion Correction]]: Simple magnification often introduces optical distortion (like pincushion distortion). The rendered image is typically pre-distorted (barrel distortion) in software to counteract the lens distortion, resulting in a geometrically correct view for the user.<ref name="LensDistortionVR">Oculus Developer Documentation. "Distortion Correction". Retrieved 2023-10-27. [https://developer.oculus.com/documentation/native/pc/dg-render-distortion/ Link]</ref>

Tracking the user's head movement is fundamental to creating immersive and interactive experiences, particularly in VR. As the user moves their head, the system updates the rendered images accordingly, making the virtual world appear stable and allowing the user to look around naturally. Failure to track accurately and with low latency can lead to disorientation and [[Motion sickness]] (often termed "cybersickness" in VR/AR contexts).<ref name="LaViolaMotionSickness">LaViola Jr., Joseph J. (2000). "A discussion of cybersickness in virtual environments". ''ACM SIGCHI Bulletin''. '''32''' (1): 47-56. doi:10.1145/333329.333033. Retrieved 2023-10-27. [https://ieeexplore.ieee.org/document/947376 Link]</ref> Tracking operates in multiple [[Degrees of Freedom]] (DoF):

*[[Magnetometer]]: Measures the local magnetic field (like a compass), used to correct for gyroscope drift, especially in yaw. [[Sensor fusion]] algorithms combine data from these sensors to provide a stable orientation estimate.<ref name="IMU_VR">Pell, Oliver (2017-07-12). "Use of IMU in Virtual Reality Systems". Analog Dialogue, Analog Devices. Retrieved 2023-10-27. [https://www.analog.com/en/technical-articles/imu-in-virtual-reality-systems.html Link]</ref><ref name="imu">Wikipedia (20 Apr 2025). "Inertial measurement unit". Retrieved 2024-05-15. [https://en.wikipedia.org/wiki/Inertial_measurement_unit Link]</ref>