# Virtual reality headset

A virtual reality headset (or VR headset) is a head-mounted device that uses 3D near-eye displays and positional tracking to provide a virtual reality environment for the user. VR headsets are widely used with VR video games, but they are also used in other applications, including simulators and trainers. VR headsets typically include a stereoscopic display (providing separate images for each eye), stereo sound, and sensors like accelerometers and gyroscopes for tracking the pose of the user's head to match the orientation of the virtual camera with the user's eye positions in the real world. Augmented reality (AR) headsets are VR headsets that enable the user to see and interact with the outside world. Examples of AR headsets include the Apple Vision Pro and Meta Quest 3.
VR headsets typically use at least one MEMS IMU for three degrees of freedom (3DOF) motion tracking, and optionally more tracking technology for six degrees of freedom (6DOF) motion tracking. 6DOF devices typically use a sensor fusion algorithm to merge the data from the IMU and any other tracking sources, typically either one or more external sensors, or "inside-out" tracking using outward facing cameras embedded in the headset. The sensor fusion algorithms that are used are often variants of a Kalman filter. VR headsets can support motion controllers, which similarly combine inputs from accelerometers and gyroscopes with the headset's motion tracking system.
Most headsets are reliant on a personal computer to operate. Some "standalone" headsets are based on a mobile operating system and smartphone-like hardware, allowing VR apps to run directly on the device, while also allowing VR applications to be streamed from a PC over a USB or Wi-Fi connection. Virtual reality headsets and viewers have also been designed for smartphones, where the device's screen is viewed through lenses acting as a stereoscope, rather than using dedicated internal displays.

## History

VPL Research was a company that made early VR headsets in the 1980s.
The Sega VR was announced in 1991 and seen in early 1993 at the Winter CES. It was never released for consoles, but was utilized for the Sega VR-1 motion simulator arcade attraction in 1994. Another early VR headset, the Forte VFX1, was announced at CES in 1994. The VFX-1 has stereoscopic displays, 3-axis head-tracking, and stereo headphones.
Sony released the Glasstron in 1997, which has an optional positional sensor, allowing the wearer to view the surroundings, with the perspective moving as the user's head moves, giving a deep sense of immersion. These VR headsets gave MechWarrior 2 players a new visual perspective of seeing the battlefield from inside the cockpit of their craft. However, these early headsets failed commercially due to their limited technology, and they were described by John Carmack as like "looking through toilet paper tubes".
In 2012, a crowdfunding campaign began for a VR headset known as Oculus Rift; the project was led by several prominent video game developers, including John Carmack who later became the company's CTO. In March 2014, the project's parent company Oculus VR was acquired by Facebook for $2 billion. The final consumer-oriented release of Oculus Rift began shipping on 28 March 2016.
In March 2014, Sony demonstrated a prototype headset for PlayStation 4, which was later named PlayStation VR. In 2014, Valve demonstrated some headset prototypes, which led to a partnership with HTC to produce the Vive, which focuses on "room-scale" VR environments that users can naturally navigate within and interact with. The headset uses Valve's "SteamVR" software platform. The Vive was released in April 2016 and PlayStation VR in October 2016.
Google released a series of specifications and associated DIY kits for virtual reality viewers known as Google Cardboard; these viewers are capable of being constructed using low-cost materials (and a smartphone with a gyroscope), such as cardboard (hence the naming). Samsung Electronics partnered with Oculus VR to co-develop the Samsung Gear VR (which is only compatible with some Samsung Galaxy devices). LG Electronics developed a headset with dedicated displays for its LG G5 smartphone known as LG 360 VR. In March 2017, Microsoft launched a platform for VR and mixed reality headsets running on Windows 10 known as Windows Mixed Reality, with VR headsets from multiple partners including PC makers Acer, Dell, HP Inc., and Lenovo.
In 2018, Oculus released the Oculus Go, a standalone headset running capable of running VR apps on embedded mobile computing hardware, thus not needing a PC or an inserted smartphone to operate. In June 2019, Valve released their own in-house SteamVR headset, the Valve Index. In an October 2019 report, Sony, Facebook (Oculus), and HTC were identified by Trend Force as the three largest manufacturers of VR hardware. 2019 saw Facebook release the first-generation Oculus Quest, a successor to the Oculus Go concept which supports motion controllers and positional tracking with 6DOF.

## Technology
### Resolution and display quality

There are different optics and visual qualities that affect how an individual perceives the image quality and how they experience the virtual world. The image clarity depends on the display resolution, optic quality, refresh rate, and field of view.
Because virtual reality headsets stretch a single display across a wide field of view (up to 110° for some devices according to manufacturers), the magnification factor makes flaws in display technology much more apparent. One issue is the so-called screen-door effect, where the gaps between rows and columns of pixels become visible, kind of like looking through a screen door. This was especially noticeable in earlier prototypes and development kits, which had lower resolutions than the retail versions.

### Optics

The lenses of the headset are responsible for mapping the up-close display to a wide field of view, while also providing a more comfortable distant point of focus. One challenge with this is providing consistency of focus: because eyes are free to turn within the headset, it is important to avoid having to refocus to prevent eye strain.
Fresnel lenses are commonly used in virtual reality headsets due to their compactness and lightweight structure. The lenses do not use multiple pieces of material in their lenses like other lenses, but the lens will be broken down into sections, allowing the individual to have a wider range of view. The issue seen with the lens consists of seeing the ridges of the lenses when the headset is not properly aligned on the head.
The lenses introduce distortion and chromatic aberration, which are typically corrected in software. The lenses can also be adjusted dynamically to account for a user's eyeglass prescription so that the user can use the headset without corrective eyeglasses.

### Latency requirements

Virtual reality headsets have significantly higher requirements for latency—the time it takes from a change in input to have a visual effect—than ordinary video games. If the system is too sluggish to react to head movement, then it can cause the user to experience virtual reality sickness, a kind of motion sickness. According to a Valve engineer, the ideal latency would be 7–15 milliseconds.
The graphics processing unit (GPU) also needs to be powerful enough to render the required amount of frames. Oculus cited the limited processing power of Xbox One and PlayStation 4 as the reason why they targeted the PC gaming market with their first devices.
Foveated rendering is a new technique to reduce the rendering workload. It uses eye tracking hardware to determine at what point the user is looking and reduces rendering resolution farther from the user's gaze. This can be unnoticeable to the user because human peripheral vision is far less sensitive than the fovea.

## Uses in various fields
### Medical training and diagnostics

Virtual reality headsets are being currently used as a means to train medical students for surgery. It allows them to perform essential procedures in a virtual, controlled environment. Students perform surgeries on virtual patients, which allows them to acquire the skills needed to perform surgeries on real patients. It also allows the students to revisit the surgeries from the perspective of the lead surgeon.
Traditionally, students had to participate in surgeries and often they would miss essential parts. Now, with the use of VR headsets, students can watch surgical procedures from the perspective of the lead surgeon without missing essential parts. Students can also pause, rewind, and fast-forward surgeries. They also can perfect their techniques in a real headset, mounted in a risk-free environment.
Besides training purposes, augmented reality headsets are also already being used for image-guided surgery.
VR headset mounted smartphones have been used to capture high-quality videos and images of the retina for documenting peripheral retinal lesions.

### Military training

Virtual reality headsets have been used by the United States Armed Forces. It is a particularly useful tool for training military personnel without putting them in harm's way.
The virtual reality headset allows military personnel to interact with virtual reality people to make it feel real. They can talk to one another and do varying actions to make the virtual reality world feel like they are actually in the real world. There are also disadvantages and advantages when military personnel use the headset. The disadvantage is the headset is made for an indoor area, with a cool environment, and away from any heat, so when military personnel has just the headset on, no military equipment, it is not like their basic training. The advantages consist of repeating the situations multiple times and the cost of having the headset is less, due to no military equipment being needed.