Head-mounted display

A head-mounted display (HMD) is an electronic near-eye display device that is worn on the head, either on its own or built into a helmet. It places one or two small display optics directly in front of the user's eyes so that the image fills a large part of the field of view. Because the display is fixed to the head, its outer shell shares a coordinate system with the user's head, and adding head positional tracking lets the rendered image respond to where the wearer is looking. This combination of a near-eye display and head tracking is the basic building block of virtual reality and many augmented reality systems.

Head-mounted displays range from large opaque VR headsets that block out the real world to lightweight smart glasses that overlay a small amount of information on the wearer's view. The term covers both consumer entertainment devices and specialised hardware such as the helmet-mounted displays used in military aviation.

Most modern VR HMDs are binocular: two slightly different images, one for each eye, are channeled into the eyes so the human perceptual system can perceive binocular disparity and see depth. An HMD is most useful when it presents visual content across a large portion of both eyes, which is what separates an immersive headset from a simple wearable screen.

History

Sutherland's 1968 display

The first head-mounted display is widely credited to computer scientist Ivan Sutherland, who built it in 1968 with his students Bob Sproull, Quintin Foster, and Danny Cohen. The system is part of Ivan Sutherland's head-mounted 3D display project and is often considered the first functional augmented reality display. It projected a computer-generated wireframe object, the first being a simple cube, onto half-silvered mirrors in front of the eyes, so the object appeared to hang in the air in the middle of the room.

The device was nicknamed the "Sword of Damocles". According to Sutherland the name actually referred only to the bulky mechanical arm that hung from the ceiling of the lab, not to the display itself. The arm was needed partly because of the headset's weight and primarily to track the user's head movement through mechanical linkages, so the rendered perspective could update as the wearer moved. Sutherland's project established both the core idea of the head-mounted display and, by some accounts, the first recorded use of the term.

Military helmet-mounted displays

For several decades after Sutherland's work, head-mounted displays advanced mainly in military aviation, where they are called helmet-mounted displays. In 1984 the U.S. Army fielded the AH-64 Apache with the Integrated Helmet and Display Sighting System (IHADSS), the first HMD developed as an integrated helmet-and-optics system. IHADSS used a monocular display with a 40 by 30 degree field of view and infrared head tracking, so a slewable sensor on the aircraft nose could be slaved to the pilot's head movements.

More recent systems are far more capable. The Helmet-Mounted Display System on the F-35 Lightning II, developed by the Elbit Systems and Rockwell Collins joint venture Vision Systems International, lets the pilot "see through" the aircraft using imagery from external cameras and presents flight and targeting symbology directly on the visor. The F-35 was the first tactical fighter in decades designed to fly without a separate head-up display.

Early consumer and research headsets

Consumer-oriented headsets appeared in the late 1980s and 1990s. The LEEP Cyberface from LEEP Systems was an early commercial VR headset. It had flat focus, was monochromatic, and offered a very high horizontal field of view; it originally shipped as part of a complete telepresence system. The later Cyberface4 used a single LCD panel and was an upgraded version of the Cyberface3. Other devices from this era include the 1994 Forte VFX1 and Sony's 2011 HMZ-T1 personal viewer. These early products suffered from low resolution, narrow field of view, high latency, and high cost, which kept the technology out of the mainstream.

The modern consumer era

The modern wave of head-mounted displays began with the Oculus Rift. On August 1, 2012 a Kickstarter campaign for the headset, led by Palmer Luckey, raised about 2.4 million dollars from more than 9,500 backers, roughly ten times its goal. The resulting developer kit, the Oculus Rift DK1, shipped on March 29, 2013 with a single 7-inch panel driving 640 by 800 pixels per eye, a roughly 90 degree or wider field of view, a 60 Hz refresh rate, and rotational (3 degrees of freedom) tracking.

The year 2016 brought the first mass-market consumer headsets. The Oculus Rift CV1 launched at 599 dollars with two 90 Hz OLED panels at 1080 by 1200 per eye, alongside the HTC Vive, which added external "Lighthouse" base stations for room-scale tracking, and Sony's PlayStation VR, whose panel reached up to 120 Hz. Standalone headsets that ran without a PC, full-color passthrough mixed reality, and high-resolution microdisplays followed over the next decade, exemplified by the Meta Quest 3 and the Apple Vision Pro.

Types by function

Head-mounted displays are grouped by how they relate the virtual image to the real world.

• Virtual reality HMDs are opaque. They block the wearer's view of the physical surroundings and replace it entirely with rendered imagery, so the goal is full immersion.
• Optical see-through AR headsets use transparent or partially reflective optics. The wearer looks through the optics at the real world while computer-generated imagery is added on top. Devices such as the Microsoft HoloLens use diffractive waveguides to route light from a side-mounted microdisplay into the see-through lens; the original HoloLens had a narrow field of view of about 30 by 17 degrees.
• Video see-through or passthrough mixed reality devices are opaque, but outward-facing cameras capture the real world and the headset electronically mixes that video with rendered content before showing it on the internal displays. Modern VR headsets increasingly use this approach to blend physical and virtual objects.
• Smart glasses are lightweight head-worn displays that overlay limited information, such as notifications or navigation, rather than aiming for full immersion. As computing has become more power efficient, this glasses form factor has grown alongside the larger headset.

These categories overlap. A single product line can offer both immersive VR and camera-based passthrough, and the boundary between AR, MR, and VR is often a matter of how much of the real world the device lets through.

Binocular, monocular, and biocular

The number and arrangement of displays defines three configurations.

Configuration	Description	Typical use
Monocular	A single display optic in front of one eye.	Aviation symbology, smart glasses, data readouts
Binocular	A separate display and optic for each eye, presenting slightly different images to enable stereoscopic depth.	Immersive virtual reality and high-end AR
Biocular	Two eyepieces that show the same single image to both eyes, with no stereo depth.	Lower-cost or simpler viewers

Binocular HMDs are the basis of immersive VR because binocular disparity between the two images is what lets the visual system perceive 3D depth.

Key components

Displays

The image source is usually a small, dense panel called a Microdisplay. Common panel technologies include LCD, OLED, liquid crystal on silicon (LCoS), and Micro-OLED, which builds OLED pixels directly on a silicon backplane to reach very high pixel densities. The Apple Vision Pro, for example, uses a pair of roughly 1.4-inch micro-OLED panels with about 7.5 micron pixels for a combined total near 23 million pixels.

Optics

Because the display sits only centimeters from the eye, lenses are needed to let the eye focus on it and to magnify the image across the field of view. Early consumer VR headsets used Fresnel lenses, which collapse a thick lens into concentric prism rings to save weight and cost but tend to produce glare and "god rays" against high-contrast scenes. Many newer headsets use pancake lenses, which fold the optical path by bouncing light between thin reflective layers. A pancake lens can be far thinner than an equivalent Fresnel lens and reduces stray light and chromatic aberration, but it passes only a small fraction of the light, so it needs a much brighter display to compensate. The Meta Quest 3 adopted pancake optics, which sharpened the image and slimmed the headset compared with the Meta Quest 2.

Tracking

Positional tracking reports the position and orientation of the head so the rendered scene stays locked to the real world as the user moves. Simple headsets track only rotation (3 degrees of freedom); fully immersive headsets track both rotation and translation (6 degrees of freedom), using either external base stations such as the HTC Vive Lighthouse system or inside-out cameras built into the headset. Low latency between head motion and display update is essential to comfort.

Interpupillary distance adjustment

The lenses work best when their optical centers line up with the wearer's pupils, so many HMDs allow interpupillary distance (IPD) adjustment. IPD is the distance in millimeters between the centers of the two pupils. Adult IPD averages about 63 mm and commonly ranges from roughly 50 to 75 mm. If the IPD setting does not match the user, the image is less sharp and the wearer can experience eye strain, double vision, or an incorrect sense of scale.

Display metrics

Three figures are commonly used to compare head-mounted displays.

• Field of view is the angular extent of the visible image. Human vision spans roughly 180 to 200 degrees horizontally, while many VR headsets cover only about 90 to 110 degrees; the Valve Index reaches around 130 degrees diagonally. A wider field of view increases immersion.
• Resolution is the pixel count of the display, often quoted per eye. Higher per-eye resolution and pixels-per-degree reduce the visible "screen-door" gaps between pixels.
• Refresh rate is how many times per second the display updates, measured in hertz. VR generally targets at least 90 Hz, and studies suggest 120 Hz further reduces VR sickness, because a faster refresh shortens how long each frame persists and lowers motion-to-photon latency.

Representative head-mounted displays

The table below lists devices across eras to show how the technology has changed. Specifications are per eye unless noted.

Device	Year	Type	Display / per-eye resolution	Field of view	Refresh rate
Sutherland HMD	1968	Optical see-through, wireframe	CRT, vector graphics	Narrow	N/A
IHADSS (AH-64 Apache)	1984	Monocular helmet display	Video with symbology	40° by 30°	N/A
Oculus Rift DK1	2013	VR (opaque)	640 by 800	~90°+	60 Hz
Oculus Rift CV1	2016	VR (opaque)	1080 by 1200 (OLED)	~110°	90 Hz
Microsoft HoloLens	2016	Optical see-through AR (waveguide)	Waveguide	~30° by 17°	60 Hz
Valve Index	2019	VR (opaque)	1440 by 1600 (LCD)	~130° diagonal	up to 144 Hz
Meta Quest 3	2023	VR with color passthrough	2064 by 2208 (pancake optics)	~110°	up to 120 Hz
Apple Vision Pro	2024	Video see-through MR	Micro-OLED, ~23M pixels total	Wide	up to 100 Hz

Applications

Head-mounted displays are used wherever a hands-free, head-tracked, or immersive view is valuable.

• Gaming and entertainment is the largest consumer use, with immersive VR titles and 360-degree video driving headset sales since 2016.
• Aviation and defense use helmet-mounted displays for targeting, navigation symbology, and night-vision imagery slaved to head movement.
• Medicine uses HMDs to overlay imaging data during surgery and for rehabilitation and training.
• Engineering and design use stereoscopic headsets to review CAD models and digital prototypes at full scale.
• Training and simulation use VR to rehearse hazardous or expensive scenarios, from flight and military drills to industrial safety, in a controlled environment.

See also

• Virtual reality
• Augmented reality
• VR headset
• AR headset
• Smart glasses
• Near-eye display
• Field of view
• Interpupillary distance
• Positional tracking