EyesDrive is a new, non-invasive, human interface assistive device that uses eyes movement to control any compatible electronic device, such as a wheelchair, the mouse pointer, or a car steering wheel. The project is based upon the Electrooculography technique, already known in medical fields for diagnosis.
The eye is home to an electric potential, independent from luminous stimuli: it is a fixed dipole, with the positive end on the cornea and the negative one on the retina. The corresponding potential difference is called corneo-retinal standing potential. This voltage is attributed mainly to physiological processes taking place on the retina.
The corneo-retinal standing potential and the eye movement allow the measurement of a signal known as Electrooculogram.
With the eye pointing straight, the electrodes have the same electric potential, so any signal isn't recorded. Moving eyes leads to an electric potential difference between both eyes: the electrode facing the rotation side is positive relative to the other electrode.
Electrooculography has both advantages and disadvantages compared to other eyes position detection systems: the main advantage is the ability of this method to sense eye movement in all scenarios: with or without light and in every environment with the lowest interference.
The EyesDrive system was developed with ALS and other movement diseases in mind: it permits, after various signal elaboration processes, eyes movement mapping and makes it understandable to a computer. The EyesDrive heart is its frontend: it transmits the acquired EOG signal via a Bluetooth interface to any connected compatible device. Its distinctive and easy to implement protocol permits to implement EyesDrive assistive technology theoretically to any device possible.
The signal acquisition chain begins from the EOG signal amplification: an Instrumentation Amplifier increases the corneo-retinal potential until the wanted result is reached. The other stages of the analog chain filter and adjust the signal for an optimal quantization of the signal by the microcontroller ADC.
To reduce the 50 Hz hum from the power grid, the common-mode rejection ratio of the instrumentation amplifier isn't enough: an additional circuit, called "Reference Driver" was added and, as the name says, "drives" the user skin to a known potential to reduce the hum present in the body.
The EyesDrive system finds use in several "old-style" assistive medical devices: the frontend can control a wheelchair direction, making the use of it more natural. Another use is speech synthesis: the eyes movement can select characters and buttons on a computer screen without the use of the mouse, making more straightforward the control of computers for paralyzed people.