Head-Mounted Display

A head-mounted display [ hedmaʊntɪd dɪspleɪ ] (literally " head-mounted display " ), short HMD is worn on the head of a visual output device. It presents images either on a near- eye display or projected directly onto the retina (see virtual retinal display). Depending on how it is called HMD and video glasses, helmet display or VR helmet.

Molding

Video Glasses

The simplest form of a head- mounted display consisting of a video glasses without additional sensors. These glasses consists of a headband, two small screens, headphones or earplugs, and usually additional screens that allow to view video information undisturbed by external visual stimuli. Video glasses are used in the private sector for watching DVDs or TV programs, as well as for computer games. In the medical field, the systems on the one hand to fear or pain distraction, for example, the dentist or other outpatient therapies are used.

VR glasses

A virtual reality glasses ( glasses, data ) or a corresponding helmet additionally has sensors for detecting movement of the head. So that the display of the calculated graphic can be adapted to the movements of the user. As another input device data gloves or a 3D mouse can be used. Some systems also use non-contact control via gesture recognition that can work with techniques of machine vision.

A special form of HMDs is the Helmet Mounted Display. In such a system is part of the HMD of a helmet, such as a helmet for the pilot.

Impact and benefits

Due to the physical closeness, the image surfaces of head- mounted displays seem to be much larger than the free-standing screens and cover in extreme cases, the entire field of view of the user from. Because the display by the head mount all the head movements of the wearer follows, he gets the feeling to move directly into the image landscape generated by the computer. Some head-mounted displays seal off their support from other visual impressions of the environment and let him thereby completely immerse in a virtual reality. Other blend outer and computer- generated images and let her slide by perceive artificial objects augmented reality as part of the tangible world.

Head - mounted displays can in principle serve as a convenient screen replacement, including the ability to view and edit video material with extremely large image dimensions. By immerse the user in the virtual reality, they can aspiring pilots and tank drivers can practice on the computer the complex vehicle operation and medical risky surgery techniques and offer players of 3D computer games, the far greatest form of realism. The semi-translucent augmented reality offers the possibility to display all kinds of information directly into the environment, from tourist information on attractions over -turn directions on the road up to the next step in the heater assembly; combined with other systems, the sense of sight to heat perception or the " X-ray vision " to be expanded.

History

Technology

The main components of HMDs are a display unit, and an HMD optics. The display unit provides the image from a connected data source. This can be a laptop, a pocket computer or a standalone player be. The HMD optics passes the image and projects it in front of the eye. However, the display for defective vision (short - or long-sighted ) must be adapted to the eye.

The first data generation glasses were each equipped with a cathode ray tube attached in front of each eye.

Today HMDs are usually equipped with one or two LCD monitors (Liquid Crystal Displays ). These are integrated into a pair of glasses or a data helmet. Displays of this type have in the commercial sector a resolution of about 320 × 240 pixels and the approximate image size of a 50 cent coin.

Modern HMDs are equipped with a Virtual Retinal Display ( VRD ). This technique projects an image directly onto the retina. Thus, an image, as if the data were floating before your eye. Along with a transparent or translucent glasses, the eye can detect the environment as well as the representations of the glasses at the same time. A further advantage is that the image can be scaled and then the entire field of view is used. Modern HMDs are available with an image resolution of 1280 × 1024 pixels.

Equipped with a head tracker (German: , head - tracker '), the image can be adjusted to the current viewing direction. On the basis of reference points on the HMD, the head tracker grasp the head movement. With the collected position data of the head of the projected image in real- time can be changed. Thus arises even when moving the feeling to be part of the application. Delayed and fuzzy representation can lead to unpleasant side effects such as the Simulator Sickness (simulator sickness ) and a reduction in the presence and / or degree of immersion.

Main technical parameter besides stereoscopic ability, weight, resolution of the screens etc. especially the field of view (English: Field of View, short FOV) that is specified in well-documented devices as horizontal and vertical FOV.