What is Head-Mounted Display (HMD)?
A head-mounted display, or HMD, is a visual tool for mixed, enhanced, or virtual reality. It could be as tiny as a set of spectacles or as big as a headgear with a built-in monitor.
HMDs for virtual reality
VR devices, also known as head-mounted displays, are usually bigger than their AR/MR equivalents. Most headsets have a headpiece or a pair of flexible bands to hold them in position. Since VR devices are contained, when the screen is off, the view is totally dark. The headgear creates a 3D world that is responsive to your motions as soon as you switch it on. The Meta Quest and PlayStation VR devices are two examples.
Augmented & Mixed-Reality HMDs
See-through devices with digital pictures superimposed over the actual world are known as head-mounted displays for augmented and mixed reality. Using an AR device, for instance, you could visualize how various items of furnishings would appear in your living room. You can engage with simulated items in a true 3D environment when using mixed reality. Microsoft Hololens and Google Glass are two examples of MR and AR HMDs.