ALLPCB
Overview
As VR technology has matured, VR experience venues have appeared in shopping centers and pedestrian areas. When using a VR headset, you will typically find a gyroscope inside the device. What is this gyroscope and what role does it play in VR systems?
Gyroscope as a sensor
A gyroscope is a type of sensor that detects dynamic changes in the position and orientation of the headset. If the gyroscope has poor performance or slow response, latency increases and the displayed image can stutter, which may cause discomfort or motion sickness. Modern systems commonly use a 9-axis sensor, which is a combination of three types of 3-axis sensors: a 3-axis accelerometer, a 3-axis gyroscope, and a 3-axis magnetometer (also called an electronic compass).
Accelerometer
The accelerometer measures acceleration along each axis. It uses a proof mass whose inertia produces forces on the X, Y, and Z axes when the sensor moves. A piezoelectric element or similar transducer converts those forces into electrical signals. As the device moves, the pressures on each axis change and the electrical output varies accordingly, allowing the system to infer acceleration direction and magnitude. For example, a sudden forward push of a phone registers as forward acceleration.
Gyroscope
The gyroscope measures angular rate and helps maintain orientation. In applications such as flight simulators, sports games, and first-person shooters, it enables accurate tracking of the user’s head or hand rotation so that in-game movements map closely to real motions.
Magnetometer (electronic compass)
By combining data from the accelerometer and gyroscope, a system can describe most of the device motion, but long-term integration of rotational rates produces accumulated drift that degrades orientation accuracy. The magnetometer measures the Earth’s magnetic field and provides an absolute heading reference to correct that drift. Using this absolute reference, the system can compensate for accumulated error and improve estimates of direction, attitude angles, and motion parameters.
Smartphone sensors versus VR-grade sensors
Typical gyroscopes in phones are adequate for many mobile applications but often do not meet the latency and precision requirements of immersive VR. Dedicated VR headsets frequently include higher-quality, built-in 9-axis sensors to reduce latency and image stutter, which helps minimize motion sickness.
Six degrees of freedom in VR
VR scenes must simulate the positions of virtual objects after head motion, so the system needs the head pose relative to the world in real time. Head pose has six parameters: three for rotation and three for translation, giving six degrees of freedom. A 9-axis sensor can detect the headset attitude and provide pose data to the virtual environment, enabling a head pose that matches the real world.
