Overview of VR headsets Technology in 2022
Introduction
We are now in 2022 and the number of VR headsets available on the market keeps growing. Even though I only own the Oculus Quest 2, I was wondering what are the characteristics that differentiate various VR headsets.
In this article, we are looking at the most important aspects which ultimately also drive the cost of the device.
Characteristics
One characteristic I will not delve into is the VR and AR headsets. AR headsets provide augmented reality features. It means that you see your environment with the added bonus of overlaid VR rendered content. In this article, I only focus on VR headsets.
Target Market
One characteristic that is fairly obvious is the market orientation of the device. Some of them are aimed at consumers and some are aimed at professionals. Obviously, there is a blurry zone in-between.
The table below summarizes some headsets and their price point:
Below $500, the headset is considered to be consumer-oriented with the exception of the Valve Index where the target market is either professional or consumers with disposable income.
Refresh Rate
The refresh rate represents the speed at which the image can be displayed on the VR headset LCD screens. All modern headsets provide a refresh rate of at least 60 Hertz which guarantees a minimum of comfort. As the human eye is requiring between 30 and 60 images per second, it is considered good enough.
However, increasing this refresh rate to a higher value generally leads to better visual comfort and the user experience is improved with better immersion.
A lot of VR headsets are now providing a minimum of 70 Hz. If we take the Oculus Quest 2, it initially shipped with a 72 Hz refresh rate that was increased to 90 and then 120 Hz through firmware upgrades.
However, for this refresh rate to be significant, the application running in your headset must be able to deliver the same framerate which is not always the case.
For the Oculus Quest 2:
- there is an optimization technique called SpaceWarp that lets the application render half the frames and use some tricks to generate the other half. If you want to learn more, go to the Oculus page.
2. Meta does not allow games to run lower than 72 Hz framerate. However, for an application like Go Clubbing VR where media (video) is displayed, Meta allows a minimum framerate of 60 Hz.
Field of View
Another interesting aspect is the Field of View (FOV). It represents how much you can see left to right without moving your head or eyes and similarly top to bottom.
The human eyes, together, have a horizontal FOV of over 210 degrees but more importantly, only 114 degrees are used for depth perception (this is the area where both eyes’ vision overlap which is a requirement for being able to measure depth). Vertically, the FOV is about 150 degrees.
To have the best immersive experience, the VR device must provide as much visual coverage as possible, especially where depth can be felt.
The Pimax Vision 5K Super offers an advertised horizontal FOV of 200 degrees but most VR headsets on the market have a much lower FOV. If we take the Oculus Quest 2, the FOV is about 90 degrees.
You can get a comparison of various models on the Infinite database.
Display Resolution
As we’ve seen with the refresh rate and field of view, the display is the cornerstone of a VR headset. The display resolution is another element that is important. And because we have two eyes, a VR headset will have two displays.
The higher the resolution per eye, the better the immersion will be. The highest resolution available today is the Pimax 8K with 3,840 x 2,160 per eye. They even announced the Pimax 12K which is estimated to have the 5,760 x 3,240 resolution.
The consumer model Oculus Quest 2 has a resolution of 1,832 x 1,920.
See the Comparison of virtual reality headsets Wikipedia page for a comparison of various models.
But comparing displays between devices is a bit more complicated as we should also take into consideration:
- PPD (Pixels Per Degree): it indicates the number of pixels per horizontal degree that makes up the image. The higher the better.
- Multi-Resolution: some devices have a different pixel density in different areas. For instance, the Varjo VR-3 has 70 PPD for the focus area (center) and 30 PPD for the rest. More density where we care!
- Distance: the distance between the eye and the display is also important. The closer you get to the display the higher the density of pixels has to be but the wider the FOV is.
- Color Accuracy: similar to monitors, different displays render color more or less accurately.
- Lens Shape: because the lens doesn’t have a square shape (usually Fresnel lenses are used) and our eye has a ball shape, the image to be displayed requires warping and corrections.
Standalone vs Tethered VR Headset
Some headsets embed a CPU & GPU and can function without a computer. The obvious advantage is that they don’t have to be connected to anything.
The processing capability of those VR headsets is an important factor as it impacts their rendering capability. Latest standalone VR headsets tend to embed the Qualcomm Snapdragon XR2 which is a dedicated CPU/GPU for XR applications.
However, the tethered headsets have the advantage of getting their processing capability directly dependent on the computer’s hardware. If you connect the VR headset to a very performant computer, you can render very complex scenes.
Tracking
I want to mention one last aspect which impacts the user’s immersive experience. The tracking of the VR headset and the hand controllers is also important. They all provide 6 DOF (degree of freedom) and must be tracked correctly for the VR scene to be rendered according to the user’s interactions.
There are various solutions but I will mention only two:
- Base stations: your devices are tracked using base stations. Those are boxes placed in your environment that emit a signal (e.g. Infrared) that is received by the headset to determine where it is located in space. This is called outside-in tracking. The major drawback of this solution is occlusion where the signal is blocked and the device loses tracking. HTC Vive and Steam Valve Index use this type of approach.
- Optical Tracking: using cameras mounted on the VR headset, the position of the user in space is determined using two elements:
- Inertial tracking: using an accelerometer and a gyroscope, the device is tracked based on its movement. This is the same technology that is used inside mobile phones. This technology is not sufficient as the measurement contains errors that drift measurements over time.
- SLAM (Simultaneous Localization and Mapping): using cameras on the headset, the device generates feature points of your environment. It then constantly measure the distance between those points giving an indication of the device in space. This is similar to another technique called photogrammetry. This is called inside-out tracking and this does not require any external device. Note that you need the room to be lit in order to use the device as this technology uses visible light.
Each controller on the Oculus Quest 2 uses 15 infrared LEDs that are tracked by the headset. By using a laptop camera, you can easily see the LEDs but note that some cameras fail to capture infrared light:
Conclusion
We have seen the most important aspects that distinguish various VR headsets and their pricing. Technology is constantly evolving so it will not be a surprise if tomorrow’s 4K headsets become mainstream. This is currently a rapidly growing market so we can expect a lot of innovation in the coming years!