HMDS

Head-mounted displays (HMDs) are wearable devices that place visuals in the user's field of view by sitting on the head and often blocking the external environment. They present images to each eye through displays or optical elements, creating depth and immersion while tracking head motion to adjust the view.

HMDs are commonly categorized by optical arrangement and whether they render virtual imagery exclusively or augment the real world. Immersive VR HMDs enclose the eyes and render synthetic environments, while AR or MR HMDs provide see-through lenses or pass-through cameras to overlay digital content with the real scene. Configurations described as video see-through or optical see-through refer to how the real world combines with virtual imagery.

Tracking methods vary. Inside-out systems use built-in sensors and cameras on the headset for position and orientation, while outside-in setups rely on external sensors or base stations to determine position in space.

Displays typically use OLED or LCD microdisplays, with resolutions ranging widely and refresh rates from about 60 Hz to 120 Hz or higher. Lenses such as Fresnel or aspheric elements shape the image, and some devices employ light guides or waveguides to direct the display to the eye. Some HMDs use transparent optics for AR or MR, while others are fully enclosed for VR.

The earliest head-mounted displays emerged in the 1960s, with Ivan Sutherland’s Sword of Damocles being a notable milestone. Modern consumer HMDs include VR headsets such as Oculus Rift, HTC Vive, Valve Index, and PlayStation VR, and AR/MR devices such as Microsoft HoloLens and Magic Leap.

Applications span gaming, professional simulations for training and design, medical visualization, and remote collaboration. Limitations include weight and comfort, cost, latency, resolution, and potential motion sickness for some users.

See also: Virtual reality, Augmented reality, Mixed reality, Head-mounted display.