Virtual Reality (VR) hardware and handset

Displays (output)

Physical perception of the virtual world is based entirely on what the computer display. Display is a method of presenting information to any of the senses (Visual, Aural and Haptic).

There are three basic arrangement for all sensory displays.

Stationary displays (like rear projection screens and audio speakers ) are fixed in a place. The output is rendered to reflected the changing position of user's input sensory organs. Example : Monitor based VR, Projection VR
Head based displays are worn on or attached to the user's head and move along with the head. Here the display move and remain in a fixed position relative to body's sensory inputs. Example : Occlusive HMDs, Noninclusive HMDs

Hand based display move in conjunction with the user's hand. All senses can not receive stimuli from all type of displays. Example : Palm VR

Visual depth cues : Humans, whiles visualizing, perceive information regarding the relative distance of object in various ways ; these indicators of distance are called depth cues.

Monoscopic image depth cues : These can be seen in a single static view of a scene, as in photographs and paintings.
Stereoscopic image depth cues : These on parallax, which is the apparent displacement of objects viewed from different location.
Motion depth cues : These depends on parallax created by the changing relative position between the head and the objects being observed (one or both may be in motion).
Physiological depth cues : These are generated by the eye's muscle to bring an object into clear view.

Vision : DLP (digital light Processing) projector, LCd (liquid crystal display), and LcoS (liquid crystal on Silicon) are the latest display technologies which are customized for VR. Example : Google Glass, Microsoft Hololens, and Avegant Glyph
Sound : speaker technology. Latest technology includes bone conduction methods which vibrate the skull and propagate the waves to the inner car. Example : Google Glass
Touch : Haptic displays. These feedback can be given in the form of vibration, pressure or temperature.

Interface to the virtual world (input)

VR system needs hardware devices that monitor the user in order to provide the user information necessary to make a display physically immersive. Inputs from the user also enable them to interact with the virtual world.
There ate two types of input to a VR application: user monitoring and world monitoring
User monitoring

# It includes the continuous tracking of both user movements and user initiated actions.

# Active user monitoring - user inputs information into the system Example Use of spoken commands, physical control like wands, joysticks, steering wheels, keyboards

# Passive user monitoring - Information is supplied to the computer about where and how user is moving and where they are looking.

Example : Body tracking (Hands, eyes and feet) and position tracking (user's location and orientation)

Computers

A computer executes the virtual world generator.
The location of the PC is important for body fixed displays. If separate PC is needed to power the system, fast and reliable communication must be provided between headset and PC.
Specialized computing hardware like graphical processing unit (GPUs) have been optimized for quickly rendering graphics to a screen and they are adapted to handle specific performance demands of VR.
Display interface chip are used to convert the input video into display commands.
Micro controllers are frequently used to gather information from sensing devices and send them to main computer using standard protocol, such as USB.

Taxonomy of VR/AR Input Devices