The mounted screen (or helmet-mounted screen , for flight applications), both abbreviated HMD , is a display device, imposed on head or as part of a helmet, which has a small optical display in front of one (monocular HMD) or each eye (binocular HMD). HMD has many uses, including in games, flights, techniques, and drugs.
There is also a head-mounted optical screen (OHMD), which is a wearable screen that can reflect the projected image and allow the user to view it.
Video Head-mounted display
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Typical HMDs have one or two small screens, with semi-transparent lenses and mirrors embedded in glasses (also called data glasses, shields or helmets. The display unit is miniature and may include cathode ray tubes (CRT), liquid crystal displays (LCDs), liquid crystals in silicon (LCos), or organic light-emitting diodes (OLEDs). Some vendors use multiple micro-displays to improve the total resolution and field of view.
HMD differs in terms of whether they can only display computer-generated imagery (CGI), or just direct imagery from the physical world, or a combination. Most HMDs can only display computer-generated images, sometimes referred to as virtual images. Some HMDs can allow CGI to be superimposed on a real-world view. This is sometimes referred to as augmented reality or mixed reality. Combining real-world views with CGI can be done by projecting CGI through a partial reflective mirror and seeing the real world directly. This method is often called optical see-through . Combining real-world views with CGI can also be done electronically by receiving video from the camera and mixing it electronically with CGI. This method is often called transparent video .
Maps Head-mounted display
HMD Optics
The optical-headed display uses an optical mixer made of some silver mirrors. This can reflect the artificial image, and let the real picture crosses the lens, and let the user see it.
Various methods exist to see-through HMD, which can be largely summarized into two main families based on curved mirrors or waveguides. The curved mirrors have been used by Laster Technologies, and by Vuzix in their 1200 Star products. Various waveguide methods have been around for years. These include optical diffraction, holographic optics, polarized optics, and reflective optics.
Apps
Major HMD applications include military, government (fire, police, etc.), and civil commercial (drugs, video games, sports, etc.).
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In 1962, Hughes Aircraft Company revealed Electrocular, a compact CRT (7 "long), monocular screen mounted on the head that reflects TV signals to transparent eyepiece.
The ruggedized HMD is increasingly integrated into the modern helicopter cockpit and fighter. These are usually fully integrated with pilot flying helmets and may include protective cover, night vision devices, and other symbology displays.
Military, police, and firefighters use HMD to display tactical information such as maps or hot imaging data when viewing the real scene. The latest applications include the use of HMD for paratroopers. In 2005, Liteye HMD was introduced to ground combat troops as lightweight and lightweight waterproof screens embedded into US military helmet TNM-14 military standards. Organic monocular color light-emitting diode (OLED) displays replace the NVG tube and connect to mobile computing devices. LE has a translucent capability and can be used as a standard HMD or for augmented reality applications. This design is optimized to provide high definition data under all lighting conditions, in closed or transparent operation mode. LE has a low power consumption, operates on four AA batteries for 35 hours or receives power through a standard Universal Serial Bus (USB) connection.
The Agency Agency for Advanced Defense Research (DARPA) continues to fund research in additional HMD realities as part of the Persistent Close Air Support Program (PCAS). Vuzix is ​​currently working on a PCAS system that will use holographic waveguides to produce a transparent augmented reality glasses that are only a few millimeters thick.
Engineering
Engineers and scientists use HMD to provide stereoscopic views of CAD schemes (computer-assisted). Virtual reality, when applied to engineering and design, is a key factor in human integration in design. By allowing engineers to interact with their designs on a full-size scale, the product can be validated for problems that may not have been seen until the physical prototype. The use of HMD for VR is seen as an adjunct to the conventional use of CAVE for VR simulation. HMD is mostly used for one-person interaction with design, while CAVE allows for more collaborative virtual reality sessions.
Head Mounted Display systems are also used in complex system maintenance, as they can provide a simulated x-ray vision technician by combining computer graphics such as system charts and images with the technician's natural vision (plus or modification of reality).
Medicine and research
There are also applications in operation, where a combination of radiographic data (X-ray computed tomography (CAT) scan, and magnetic resonance imaging imaging (MRI)) combined with a surgeon's natural view of surgery, and anesthesia, where patients are vital signs are in the field of anesthesia at all times.
Research universities often use HMD to conduct studies related to vision, balance, cognition and neuroscience. In 2010, the use of predictive visual tracking measurements to identify mild traumatic brain injury is being studied. In a visual tracking test, the HMD unit with eye tracking capability indicates the object is moving in a regular pattern. People without brain injury can keep track of moving objects with fine motion and fine track motion .
Games and videos
Low cost HMD devices are available for use with 3D games and entertainment applications. One of the first commercially available HMD was Forte VFX1 which was announced at the Consumer Electronics Show (CES) in 1994. VFX-1 has a stereoscopic display, 3-axis head tracking, and stereo headphones.
Another pioneer in this field is Sony, which released Glasstron in 1997. It has an optional accessory as a position sensor that allows the user to see the surroundings, with a moving perspective as the head moves, giving a deep profound feel. One of the new applications of this technology is in the MechWarrior 2 game, which allows users from Sony Glasstron or IGlasses Virtual I/O to adopt a new visual perspective from within the cockpit of a plane, using their own. eyes as visually and sees the battlefield through their own craft cockpit.
In 2013, many brands of video glasses can be connected to video cameras and DSLRs, making it usable as a new age monitor. As a result of the ability of glasses to block ambient light, filmmakers and photographers can see a clearer picture presentation of their lives.
Oculus Rift is a head-mounted virtual reality screen (VR) created by Palmer Luckey that Oculus VR company is developing for virtual reality simulations and video games. HTC Vive is a virtual reality screen mounted on the head. The headset is manufactured by a collaboration between Valve and HTC, with features that define it are precision space scale tracking, and high precision movement controllers. PlayStation VR is the only virtual reality headset for game consoles, for the PlayStation 4.
Sports
The HMD system has been developed for Formula One drivers by Kopin Corp. and BMW Group. According to BMW, " HMD is part of a sophisticated telemetry system approved for installation by the Formula One racing committee... to communicate with drivers wirelessly from the center of the racing pit. " HMD will display temporary critical race data allowing the driver to continue to focus on the track. Pit crew controls the data and messages sent to their drivers via two-way radio.
Recon Instruments released on November 3, 2011 installed two heads for skiing goggles, MOD and MOD Live, the latter based on the Android operating system.
Training and simulation
The main applications for HMD are training and simulation, allowing to place a trainee in a situation that is too expensive or too dangerous to imitate in real life. Training with HMD covers a wide range of applications ranging from driving, welding and spray painting, flight and vehicle simulators, army training, medical procedure training, and more. However, a number of undesirable symptoms have been caused by long-term use of certain types of head-mounted monitors, and these problems must be solved before training and optimal simulations can be performed.
Performance parameters
- Ability to display stereoscopic imagery. Binocular HMD has the potential to display different images for each eye. This can be used to display stereoscopic images. Keep in mind that the so-called 'Optical Infinity' is generally taken by a flight surgeon and screen expert about 9 meters. This is the distance where, given the average "baseline" (distance between the eye or the interpupillary distance (IPD)) between 2.5 and 3Ã, inch (6 and 8Ã, cm), the angle of an object at that distance becomes basically the same from each eye. In smaller ranges, the perspective of each eye is very different and the cost of generating two different visual channels through a computer-generated imagery (CGI) system becomes useful.
- Interpupillary distance (IPD). This is the distance between the two eyes, measured on the pupil, and important in designing the display mounted on the head.
- Field of view (FOV) - Humans have a FOV of about 180 °, but most of the HMD offers much less than this. Typically, the larger field of view results in greater immersion and better situational awareness. Most people do not have good feelings for what a particular FOV would cite (eg, 25  °) so manufacturers often cite visible screen sizes. Most people sit about 60 cm from their monitors and quite feel good about the screen size at that distance. To convert the manufacturer's display size to the desktop monitor position, divide the screen size by foot distance, then multiply it by 2. Consumer level HMD usually offer FOV around 30-40Ã,  ° whereas professional HMD offers field of view from 60Ã, ° to 150Ã,  °.
- Resolution - HMD usually specifies the total number of pixels or number of pixels per degree. Lists the total number of pixels (for example, 1600ÃÆ'â € "1200 pixels per eye) borrowed from how computer monitor specifications are presented. However, pixel density, usually specified in pixels per degree or in arcminutes per pixel, is also used to define visual acuity. 60 pixels/Ã, Â ° (1 arcmin/pixel) is usually referred to as an eye limiting resolution, above that the resolution increase is not noticed by people with normal vision. HMD typically offers 10 to 20 pixels/Â °, though advances in micro screens help increase this amount.
- Binoculars overlap - measuring areas common to both eyes. Binocular overlap is the basis for a sense of depth and stereo, allowing humans to sense close objects and distant objects. Humans have overlapping binoculars around 100 ° (50 ° to left nose and 50 ° to right). The larger the binoculars overlap offered by HMD, the greater the sense of stereo. Overlaps are sometimes specified in degrees (for example, 74 Â °) or as a percentage indicating how many visual fields of each eye are common to other eyes.
- Focus far (collimation). The optical method can be used to present images at a distant focus, which seems to increase the realism of images that in the real world will be at a great distance.
- On-board process and operating system. Some HMD vendors offer on-board operating systems like Android, allow apps to run locally on HMD, and eliminate the need to be tethered to external devices to produce video. This is sometimes referred to as smart glasses . To make the HMD manufacturer a lighter construction can move the processing system to a connected intelligent necklace form factor that will also offer the added benefit of a larger battery pack. Such a solution would make it possible to design a HMD of light with sufficient energy supply for multiple video inputs or higher frequency time-based multiplexing (see below).
Support 3D video formats
Depth perception inside the HMD requires different images for the left and right eyes. There are several ways to provide this separate image:
- Use multiple video inputs, giving a completely separate video signal for each eye
- Time-based multiplexing. Methods such as sequential frames combine two separate video signals into one signal by alternating left and right images in a sequential frame.
- Side-by-side or top-down multiplexing. This method allocates half of the image to the left eye and the other half from the image to the right eye.
The advantage of multiple video inputs is that it provides maximum resolution for each image and maximum frame rate for each eye. The disadvantage of multiple video inputs is that it requires separate video and wired output from the device that generates the content.
Time-based multiplexing retains full resolution per image, but reduces frame rate by half. For example, if a signal is presented at 60 Hz, each eye receives only 30 Hz updates. This may be a problem with presenting fast moving images accurately.
Side-by-side and top-bottom multiplexing provide full level updates to each eye, but reduce the resolution presented to each eye. Many 3D broadcasts, such as ESPN, choose to provide 3D side-by-side which saves the need to allocate additional transmission bandwidth and is better suited for fast-track action relative to time-based multiplexing methods.
Not all HMDs provide deep perceptions. Some lower-end modules are basically bi-ocular devices in which both eyes are presented with the same image.
3D video players sometimes allow maximum compatibility with HMD by providing users with a choice of 3D formats to use.
Peripherals
- The simplest HMD only projects an image or symbology on the user's visor or reticle. Images are not shifted to the real world, ie the image does not change based on the header position of the wearer.
- A more sophisticated HMD incorporates a positioning system that tracks the head and angle position of the wearer, so that the displayed image or symbology is in harmony with the outside world using transparent imagery.
- Head tracking - Creating imagery. Head-mounted displays can also be used with a tracking sensor that detects angular change and orientation. When the data is available on a computer system, it can be used to generate an appropriate computer-generated image (CGI) for a viewing angle at any given time. This allows users to view virtual reality environments simply by moving the head without the need for a separate controller to change the image angle. In radio-based systems (compared to cables), users can move within the limits of system tracking.
- Eye tracking - The eye tracker measures the angle of view, allowing the computer to sense where the user is searching. This information is useful in a variety of contexts such as user interface navigation: By feeling the user's gaze, the computer can change the information displayed on the screen, bring additional details to attention, etc.
- Hand tracking - tracking hand movements from an HMD perspective enables natural interaction with playful content and playback mechanisms
See also
- Virtual reality headset
- Virtual reality (VR)
- Augmented reality (AR)
- Computer-mediated realities
- Eyetap
- Head view (HUD)
- Smartglasses
- Installed helmet display
- optical-formula
- Mixed reality (MR)
- Positioning technology
- No screen
- Stereoscopy
- Virtual retinal display
- List of head-optic display manufacturers
References
Bibliography
- Head Mounted Displays: Designing for users; Melzer and Moffitt; McGraw Hill, 1997.
- O. Cakmakci and J.P. Rolland. Head-Worn Displays: Overview. IEEE Journal of Display Technology, Vol. 2, No. 3, September 2006..
Source of the article : Wikipedia
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