The key factor for the success of virtual reality is immersion, which is the condition where the user loses awareness of being in an environment which is not real. Immersion is achieved by replicating human senses. In this context, introducing eye-tracking into VR can increase the immersion and open up a wide variety of applications. Among eye-tracking methods, ElectroOculoGraphy (EOG) has the big advantage of having low requirements in terms of processing power and energy. This allows an efficient integration also in less powerful VR headsets.
EOG eye-tracking exploits a property of the eye which behaves as an electric dipole. When the eyes rotate, the dipole vector rotates accordingly. Signals that are a measure of the rotations can be obtained with the EOG technique by placing electrodes on the skin around the eyes.
It is recognised that these electrodes can be efficiently integrated on a VR headset on the foam mask surface which is contacting the user’s face. With a minimum total of five electrodes it is possible record signals that are a measure of horizontal and vertical conjugate (parallel) eye rotations, which can be converted into coordinates of the user’s gaze point in the virtual reality environment.
In order to receive EOG signals, a stable contact between electrodes and the user’s skin must be assured. Standard VR headset masks do not provide uniform contact for all users, due to high variability of the human face shape. For this reason, the foam mask piece was re-designed by creating multiple sizes that could better accommodate different face shapes.
An anthropometric analysis was conducted on a database of 3D scans of European subjects, with the aim of identifying three clusters of face shapes. Such results were then used to create digital mannequins to be exploited in the design of three mask sizes, with the ultimate purpose of improving the contact with the face and the overall comfort.
Electronics and materials were researched and a final prototype with the desired characteristics was built with the purpose of demonstrating the integration of EOG into a VR headset and conduct user-tests. Finally, testing was successful to prove that the with such sizing system there is at least one size out of three that ensures stable contact with EOG electrodes for each subject tested.