VR Head Mounted Display
Virtual Reality head mounted devices are the most widely used VR display systems. Unlike CAVE systems these are small and can be carried to anywhere and they don't occupy much space. These are the devices worn on the head for experiencing VR. But some of these devices need computer systems for processing.
In HMDs the head movement is tracked by the trackers and the results are processed by CPU and GPU and displayed through the screen of the HMD.
Head tracking is achieved by Rotation tracking and Position tracking
Rotation Tracking: The user's head rotation is tracked by the HMD and the view on the display is updated according to the angle of rotation. The rotation tracking is achieved using the gyroscope and accelerometer within the HMD.
The Position tracking is achieved by using external devices like the IR cameras and the IR sensors. These are capable of tracking user's head, hand and body positions within the range.
VR controllers are used for the purpose of interaction in the virtual world. The haptic feedback provided by these controllers gives a strong sense of immersion.
Types of HMDs
The HMDs can be classified into 3 types:
1. Slide-on HMDs
2. Discrete HMDs
1. Slide - on HMDs:
In this type of HMDs, the mobile phone is inserted into the mount and VR is experienced. This is just a box with lenses. The VR content is made for the mobile and the mobile is inserted into the mount. This doesnot provide with position tracking. Only the rotation is tracked with the help of accelerometer and gyroscope of the mobile. This gives relatively less immersion in VR.
The examples of Slide - on HMDs are Samsung Gear VR, Google cardboard.
2. Discrete HMDs:
These HMDs provide great immersion. The position and rotation tracking is all done by the system itself. For the processing, these should be connected to the computer.
The examples of Discrete HMDs are Oculus Rift, HTC Vive, Playstation VR.
3. Integrated HMDs:
These HMDs are the most sophisticated and expensive. These don't need any external computer systems for processing. Everything is built - in. These HMDs are targeted for high - end tracking and utilize advanced input methods.
The examples of Integrated HMDs are Microsoft HoloLens, Google Glass.
In the next section let us learn about different HMDs available in market..