Head-mounted display
Encyclopedia
A head-mounted display or helmet mounted display
Helmet mounted display
A helmet mounted display is a device used in some modern aircraft, especially combat aircraft. HMDs project information similar to that of head-up displays on an aircrew’s visor or reticle, thereby allowing him to obtain situational awareness and/or cue weapons systems to the direction his head...

, both abbreviated HMD, is a display device, worn on the head or as part of a helmet, that has a small display optic in front of one (monocular HMD) or each eye (binocular HMD).

Overview

A typical HMD has either one or two small displays with lenses and semi-transparent mirrors embedded in a helmet, eye-glasses (also known as data glasses) or visor. The display units are miniaturised and may include CRT
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...

, LCDs
Liquid crystal display
A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....

, Liquid crystal on silicon
Liquid crystal on silicon
Liquid crystal on silicon is a "micro-projection" or "micro-display" technology typically applied in projection televisions. It is a reflective technology similar to DLP projectors; however, it uses liquid crystals instead of individual mirrors. By way of comparison, LCD projectors use...

 (LCos), or OLED
Organic light-emitting diode
An OLED is a light-emitting diode in which the emissive electroluminescent layer is a film of organic compounds which emit light in response to an electric current. This layer of organic semiconductor material is situated between two electrodes...

. Some vendors employ multiple micro-displays to increase total resolution and field of view
Field of view
The field of view is the extent of the observable world that is seen at any given moment....

.

Types

HMDs differ in whether they can display just a computer generated image
Computer-generated imagery
Computer-generated imagery is the application of the field of computer graphics or, more specifically, 3D computer graphics to special effects in art, video games, films, television programs, commercials, simulators and simulation generally, and printed media...

 (CGI), show live images from the real world or a combination of both.
  • Most HMDs display only a computer-generated image, sometimes referred to as a virtual image
  • Some HMDs allow a CGI to be superimposed on a real-world view. This is sometimes referred to as augmented reality
    Augmented reality
    Augmented reality is a live, direct or indirect, view of a physical, real-world environment whose elements are augmented by computer-generated sensory input such as sound, video, graphics or GPS data. It is related to a more general concept called mediated reality, in which a view of reality is...

     or mixed reality
    Mixed reality
    Mixed reality refers to the merging of real and virtual worlds to produce new environments and visualisations where physical and digital objects co-exist and interact in real time...

    . Combining real-world view with CGI can be done by projecting the CGI through a partially reflective mirror and viewing the real world directly. This method is often called Optical See-Through. Combining real-world view with CGI can also be done electronically by accepting video from a camera and mixing it electronically with CGI. This method is often called Video See-Through.

Applications

Major HMD applications include military, governmental (fire, police, etc.) and civilian/commercial (medicine, video gaming, sports, etc.).

Aviation and Tactical / ground

Ruggedized HMDs are increasingly being integrated into the cockpit
Cockpit
A cockpit or flight deck is the area, usually near the front of an aircraft, from which a pilot controls the aircraft. Most modern cockpits are enclosed, except on some small aircraft, and cockpits on large airliners are also physically separated from the cabin...

s of modern helicopters and fighter aircraft. These are usually fully integrated with the pilot's flying helmet and may include protective visors, night vision devices and displays of other symbology.

Military, police and firefighters use HMDs to display tactical information such as maps or thermal imaging data while viewing the real scene. Recent applications have included the use of HMD for paratroopers. In 2005, the Liteye HMD was introduced for ground combat troops as a rugged, waterproof lightweight display that clips into a standard US PVS-14 military helmet mount. The self-contained color monocular OLED
Organic light-emitting diode
An OLED is a light-emitting diode in which the emissive electroluminescent layer is a film of organic compounds which emit light in response to an electric current. This layer of organic semiconductor material is situated between two electrodes...

 display replaces the NVG tube and connects to a mobile computing device. The LE has see-through capability and can be used as a standard HMD or for augmented reality
Augmented reality
Augmented reality is a live, direct or indirect, view of a physical, real-world environment whose elements are augmented by computer-generated sensory input such as sound, video, graphics or GPS data. It is related to a more general concept called mediated reality, in which a view of reality is...

 applications. The design is optimized to provide high definition data under all lighting conditions, in covered or see-through modes of operation. The LE has a low power consumption, operating on four AA batteries for 35 hours or receiving power via standard USB
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....

 connection.

DARPA continues to fund research in Augmented Reality
Augmented reality
Augmented reality is a live, direct or indirect, view of a physical, real-world environment whose elements are augmented by computer-generated sensory input such as sound, video, graphics or GPS data. It is related to a more general concept called mediated reality, in which a view of reality is...

 HMDs as part of the Persistent Close Air Support(PCAS) Program. Vuzix
Vuzix
Vuzix is a United States multinational technology firm headquartered in Rochester, New York. Founded in 1997, Vuzix manufactures and sells computer display devices and software...

 is currently working on a system for PCAS that will use holographic waveguides
Waveguide (optics)
An optical waveguide is a physical structure that guides electromagnetic waves in the optical spectrum. Common types of optical waveguides include optical fiber and rectangular waveguides....

 to produce a see-through augmented reality glasses that are only a few milimeters thick .

Engineering, science and medicine

Engineers and scientists use HMDs to provide stereoscopic views of CAD
Computer-aided design
Computer-aided design , also known as computer-aided design and drafting , is the use of computer technology for the process of design and design-documentation. Computer Aided Drafting describes the process of drafting with a computer...

 schematics. These systems are also used in the maintenance of complex systems, as they can give a technician what is effectively "x-ray vision" by combining computer graphics such as system diagrams and imagery with the technician's natural vision. There are also applications in surgery, wherein a combination of radiographic data (CAT scans and MRI
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...

 imaging) is combined with the surgeon's natural view of the operation, and anesthesia, where the patient vital signs are within the anesthesiologist's field of view at all times.
Research universities often use HMDs to conduct studies related to vision, balance, cognition and neuroscience.

Gaming

Low cost HMD devices are available for use with 3D games and entertainment applications.

One of the first commercially available HMDs was the Forte VFX-1
Vuzix
Vuzix is a United States multinational technology firm headquartered in Rochester, New York. Founded in 1997, Vuzix manufactures and sells computer display devices and software...

 which was announced at CES
Consumer Electronics Show
The International Consumer Electronics Show is a major technology-related trade show held each January in the Las Vegas Convention Center, Las Vegas, Nevada, United States. Not open to the public, the Consumer Electronics Association-sponsored show typically hosts previews of products and new...

 in 1994. The VFX-1 had stereoscopic displays, 3-axis head-tracking, and stereo headphones.

Another pioneer in this field was Sony who released the Glasstron
Glasstron
The Sony Glasstron was a portable head-mounted display. The products included two LCD screens and two earphones for video and audio respectively.The Glasstron was released to the U.S. market in 1997....

 in 1997, which had as an optional accessory a positional sensor which permitted the user to view the surroundings, with the perspective moving as the head moved, providing a deep sense of immersion.
One novel application of this technology was in the game MechWarrior 2, which permitted users of the Sony Glasstron or Virtual I/O's iGlasses to adopt a new visual perspective from inside the cockpit of the craft, using their own eyes as visual and seeing the battlefield through their craft's own cockpit.

Sony have announced the release of a fully surround-sound headset for 3D gaming and movies, the Personal 3D Viewer. It is due for a November 2011 release in Japan.

Sports

A HMD system has been developed for Formula One
Formula One
Formula One, also known as Formula 1 or F1 and referred to officially as the FIA Formula One World Championship, is the highest class of single seater auto racing sanctioned by the Fédération Internationale de l'Automobile . The "formula" designation in the name refers to a set of rules with which...

 drivers by Kopin Corp. and the BMW
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...

 Group. According to BMW, “The HMD is part of an advanced telemetry system approved for installation by the Formula One racing committee… to communicate to the driver wirelessly from the heart of the race pit.”

The HMD will display critical race data while allowing the driver to continue focussing on the track. Pit crews control the data and messages sent to their drivers through two-way radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

.

Training and simulation

A key application for HMDs is training and simulation, allowing to virtually place a trainee in a situation that is either too expensive or too dangerous to replicate in a real-life. Training with HMDs cover a wide range of applications from driving, welding and spray painting, flight and vehicle simulators, dismounted soldier training, medical procedure training and more.

Performance parameters

  • Ability to show stereoscopic imagery. A binocular HMD has the potential to display a different image to each eye. This can be used to show stereoscopic
    Stereoscopy
    Stereoscopy refers to a technique for creating or enhancing the illusion of depth in an image by presenting two offset images separately to the left and right eye of the viewer. Both of these 2-D offset images are then combined in the brain to give the perception of 3-D depth...

     images. It should be borne in mind that so-called 'Optical Infinity' is generally taken by flight surgeons and display experts as about 9 metres. This is the distance at which, given the average human eye rangefinder "baseline" (distance between the eyes or Inter-Pupillary Distance
    Pupillary distance
    Pupillary Distance or interpupillary distance is the distance between the centers of the pupils in each eye. This measurement is used when preparing to make prescription eyeglasses...

     (IPD)) of between 2.5 and 3 inches (6 and 8 cm), the angle of an object at that distance becomes essentially the same from each eye. At smaller ranges the perspective from each eye is significantly different and the expense of generating two different visual channels through the Computer-Generated Imagery (CGI) system becomes worthwhile.
  • Inter-Pupillary Distance
    Pupillary distance
    Pupillary Distance or interpupillary distance is the distance between the centers of the pupils in each eye. This measurement is used when preparing to make prescription eyeglasses...

     (IPD). This is the distance between the two eyes, measured at the pupils, and is important in designing Head-Mounted Displays.
  • Field of view
    Field of view
    The field of view is the extent of the observable world that is seen at any given moment....

     (FOV) – Humans have an FOV of around 180°, but most HMDs offer considerably less than this. Typically, a greater field of view results in a greater sense of immersion and better situational awareness. Most people do not have a good feel for what a particular quoted FOV would look like (e.g. 25°) so often manufacturers will quote an apparent screen size. Most people sit about 60 cm away from their monitors and have quite a good feel about screen sizes at that distance. To convert the manufacturer's apparent screen size to a desktop monitor position, just divide the screen size by the distance in feet, then multiply by 2. Consumer-level HMDs typically offer a FOV of about 30-40° whereas professional HMDs offer a field of view of 60° to 150°.
  • Resolution – HMDs usually mention either the total number of pixels or the number of pixels per degree. Listing the total number of pixels (e.g. 1600×1200 pixels per eye) is borrowed from how the specifications of computer monitors are presented. However, the pixel density, usually specified in pixels per degree or in arcminutes per pixel, is also used to determine visual acuity. 60 pixels/° (1 arcmin/pixel) is usually referred to as eye limiting resolution, above which increased resolution is not noticed by people with normal vision. HMDs typically offer 10 to 20 pixels/°, though advances in micro-displays help increase this number.
  • Binocular overlap - measures the area that is common to both eyes. Binocular overlap is the basis for the sense of depth and stereo, allowing humans to sense which objects are near and which objects are far. Humans have a binocular overlap of about 100° (50° to the left of the nose and 50° to the right). The larger the binocular overlap offered by an HMD, the greater the sense of stereo. Overlap is sometimes specified in degrees (e.g. 74°) or as a percentage indicating how much of the visual field of each eye is common to the other eye.
  • Distant focus ('Collimation'). Optical techniques may be used to present the images at a distant focus, which seems to improve the realism of images that in the real world would be at a distance.

Support of 3D video formats

Depth perception inside an HMD requires different images for the left and right eyes. There are multiple ways to provide these separate images:
  • Use dual video inputs, thereby providing a completely separate video signal to each eye
  • Time-based multiplexing. Techniques such as frame sequential combine two separate video signals into one signal by alternating the left and right images in successive frames.
  • Side by side or top/bottom multiplexing. This method allocated half of the image to the left eye and the other half of the image to the right eye.


The advantage of dual video inputs is that it provides the maximum resolution for each image and the maximum frame rate for each eye. The disadvantage of dual video inputs is that it requires separate video outputs and cables from the device generating the content.

Time-based multiplexing preserves the full resolution per each image, but reduces the frame rate by half. For example, if the signal is presented at 60 Hz, each eye is receiving just 30 Hz updates. This may become an issue with accurately presenting fast-moving images.

Side-by-side and top/bottom multiplexing provide full-rate updates to each eye, but reduce the resolution presented to each eye. Many 3D broadcasts, such as ESPN
ESPN
Entertainment and Sports Programming Network, commonly known as ESPN, is an American global cable television network focusing on sports-related programming including live and pre-taped event telecasts, sports talk shows, and other original programming....

, chose to provide side-by-side 3D which saves the need to allocate extra transmission bandwidth and is more suitable to fast-paced sports action relative to time-based multiplexing techniques.

Not all HMDs provide depth perception. Some lower-end modules are essentially bi-ocular devices where both eyes are presented with the same image.

3D video players sometimes allow maximum compatibility with HMDs by providing the user with a choice of the 3D format to be used.

Peripherals

  • The most rudimentary HMDs simply project an image or symbology on a wearer’s visor or reticle. The image is not slaved to the real world (i.e., the image does not change based on the wearer’s head position).
  • More sophisticated HMDs incorporate a positioning system
    Positioning system
    A positioning system is a mechanism for determining the location of an object in space. Technologies for this task exist ranging from worldwide coverage with meter accuracy to workspace coverage with sub-millimetre accuracy.- Interplanetary systems :...

     that tracks the wearer’s head position and angle, so that the picture or symbology displayed is congruent with the outside world using see-through imagery.
  • Head tracking – Slaving the imagery. Head-mounted displays may also be used with tracking sensors that allow changes of angle and orientation to be recorded. When such data is available in the system computer, it can be used to generate the appropriate computer-generated imagery (CGI) for the angle-of-look at the particular time. This allows the user to "look around" a virtual reality
    Virtual reality
    Virtual reality , also known as virtuality, is a term that applies to computer-simulated environments that can simulate physical presence in places in the real world, as well as in imaginary worlds...

     environment simply by moving the head without the need for a separate controller to change the angle of the imagery. In radio-based systems (compared to wires), the wearer may move about within the tracking limits of the system.
  • Eye tracking – Eye trackers measure the point of gaze, allowing a computer to sense where the user is looking. This information is useful in a variety of contexts such as user interface navigation : by sensing the user's gaze, a computer can change the information displayed on a screen, bring additional details to attention, etc.

HMD manufacturers (alphabetically)

Companies that have produced HMDs include:
  • Atari
    Atari
    Atari is a corporate and brand name owned by several entities since its inception in 1972. It is currently owned by Atari Interactive, a wholly owned subsidiary of the French publisher Atari, SA . The original Atari, Inc. was founded in 1972 by Nolan Bushnell and Ted Dabney. It was a pioneer in...

     (Jaguar VR headset
    Atari Jaguar
    The Atari Jaguar is a video game console that was released by Atari Corporation in 1993. It was the last to be marketed under the Atari brand until the release of the Atari Flashback in 2004. It was designed to surpass the Mega Drive/Genesis, Super Nintendo Entertainment System, and the Panasonic...

    )
  • Canon
  • Cybermind
  • EMagin
    EMagin
    eMagin Corporation positions itself as a leader in personal display systems and Organic light-emitting diode microdisplay technologies. The company manufactures its microdisplays on silicon wafers, which also accommodate signal processing and data-buffering...

     (EMAN)
  • Kopin Corporation (created Golden-i
    Golden-i
    Golden-i is a Head Mounted Computer developed by Kopin Corporation featuring a monocular head mounted display. Utilising a speech controlled user interface and head-tracking functionality, Golden-i enables the user to carry out common computer functions whilst keeping their hands free.Kopin...

    )
  • The Link simulation division of L-3 Communications
    L-3 Communications
    L-3 Communications Holdings, Inc. is a company that supplies command and control, communications, intelligence, surveillance and reconnaissance systems and products, avionics, ocean products, training devices and services, instrumentation, space, and navigation products. Its customers include...

  • LASTER Technologies
    LASTER Technologies
    Laster Technologies develops augmented reality eyewear using its patented EnhancedView technology. The company is based near Paris, France and was co-founded in January 2005 by its CEO and principal shareholder Zile Liu....

  • Motorola
    Motorola
    Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...

     (Wearable PC)
  • MyVu
    MyVu
    Myvu Personal Media Viewer refers to a product family of wearable video display glasses released by Myvu Corporation.Founded in 2001 as The MicroOptical Corporation. Company reported raising $11.5 million USD in 2006. Company reported raising $3.25 million USD in 2009. Company seems to be out...

     (formerly MicroOptical)
  • Nintendo
    Nintendo
    is a multinational corporation located in Kyoto, Japan. Founded on September 23, 1889 by Fusajiro Yamauchi, it produced handmade hanafuda cards. By 1963, the company had tried several small niche businesses, such as a cab company and a love hotel....

     (Created the Virtual Boy
    Virtual Boy
    The was a video game console developed and manufactured by Nintendo. It was the first video game console that was supposed to be capable of displaying "true 3D graphics" out of the box. Whereas most video games use monocular cues to achieve the illusion of three dimensions on a two-dimensional...

     video game platform
    Video game console
    A video game console is an interactive entertainment computer or customized computer system that produces a video display signal which can be used with a display device to display a video game...

    )
  • novero
    Novero
    -Background:Novero is a wireless company making Bluetooth products for consumer and automotive clients. Novero has customers including Audi, Bentley, BMW, Ford of Europe, Jaguar, Land Rover, Mercedes-Benz, Volkswagen, Nokia and others....

  • Olympus
    Olympus Corporation
    is a Japan-based manufacturer of optics and reprography products. Olympus was established on 12 October 1919, initially specializing in microscope and thermometer businesses. Its global headquarters are in Shinjuku, Tokyo, Japan, while its USA operations are based in Center Valley, Pennsylvania,...

  • Philips
    Philips
    Koninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....

     (SCUBA) introduced 1998
  • Recon Instruments
    Recon Instruments
    Recon Instruments is a technology company that specializes in developing Global Positioning System based products that focus on providing direct-eye communication of live performance statistics. Currently Recon has integrated its technology with Ski/Snowboard goggles...

  • Rockwell Collins
    Rockwell Collins
    Rockwell Collins, Inc. is a large United States-based international company headquartered in Cedar Rapids, Iowa, primarily providing aviation and information technology systems and services to governmental agencies and aircraft manufacturers.- History :...

     Optronics (formerly Kaiser Electro-Optics). Note that SEOS, now part of Rockwell Collins, also produced HMDs in the UK
    United Kingdom
    The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

    .
  • SEGA
    Sega
    , usually styled as SEGA, is a multinational video game software developer and an arcade software and hardware development company headquartered in Ōta, Tokyo, Japan, with various offices around the world...

     Sega VR
    Sega VR
    Sega, flush with funds from the Sega Mega Drive , announced the Sega VR add-on in 1991. It was based on an IDEO virtual reality headset with LCD screens in the visor and stereo headphones...

  • Sensics
    Sensics
    Sensics corporation describes itself as a leader in panoramic virtual reality displays, also known as head-mounted displays. In contrast to most other head-mounted displays that use a single display element for each eye, Sensics often combines multiple displays to form an image that has unusually...

  • Sony
    Sony
    , commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....

     in Japan
  • Takara
    Takara
    Takara Co., Ltd. was a Japanese toy company founded in 1955, that merged with another prominent Japanese toy company, Tomy Co., Ltd., on March 1, 2006 to form Takara Tomy, also known in English as TOMY Company Ltd....

     (Dynovisor) introduced 1996
  • TDVision
    TDVision
    TDVision Systems Inc is a company that has designed products and system architectures for Stereoscopic Video Coding, Stereoscopic Video Games, and Head Mounted Display...

  • Vuzix
    Vuzix
    Vuzix is a United States multinational technology firm headquartered in Rochester, New York. Founded in 1997, Vuzix manufactures and sells computer display devices and software...


See also

  • Helmet mounted display
    Helmet mounted display
    A helmet mounted display is a device used in some modern aircraft, especially combat aircraft. HMDs project information similar to that of head-up displays on an aircrew’s visor or reticle, thereby allowing him to obtain situational awareness and/or cue weapons systems to the direction his head...

  • Augmented reality
    Augmented reality
    Augmented reality is a live, direct or indirect, view of a physical, real-world environment whose elements are augmented by computer-generated sensory input such as sound, video, graphics or GPS data. It is related to a more general concept called mediated reality, in which a view of reality is...

     (AR)
  • Computer-mediated reality
  • Mixed reality
    Mixed reality
    Mixed reality refers to the merging of real and virtual worlds to produce new environments and visualisations where physical and digital objects co-exist and interact in real time...

     (MR)
  • Eyetap
    Eyetap
    An EyeTap is a device that is worn in front of the eye that acts as a camera to record the scene available to the eye as well as a display to superimpose a computer-generated imagery on the original scene available to the eye....

  • Stereoscopy
    Stereoscopy
    Stereoscopy refers to a technique for creating or enhancing the illusion of depth in an image by presenting two offset images separately to the left and right eye of the viewer. Both of these 2-D offset images are then combined in the brain to give the perception of 3-D depth...

  • Virtual reality
    Virtual reality
    Virtual reality , also known as virtuality, is a term that applies to computer-simulated environments that can simulate physical presence in places in the real world, as well as in imaginary worlds...

     (VR)
  • Virtual retinal display
    Virtual retinal display
    A virtual retinal display , also known as a retinal scan display or retinal projector , is a display technology that draws a raster display directly onto the retina of the eye. The user sees what appears to be a conventional display floating in space in front of them...

  • Head-up display
    Head-Up Display
    A head-up display or heads-up display is any transparent display that presents data without requiring users to look away from their usual viewpoints...

     (HUD)
  • Positioning technologies
    Positioning technologies
    Positioning systems will use positioning technology to determine the position and orientation of an object or person in a room, building or in the world.-Time of flight:...

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