Thursday, October 30, 2014

Electro-oculogram (EOG) based device control

        Controlling devices with just eye movements is a very fascinating area in bio-medical electronics. Very recent research includes controlling wheelchair for disabled, controlling display power based on gaze of user, video game control using eye movements and even just for fun in case of normal people.  
        Considering this I have added one to my list accomplished projects(which you can find at ).

What is Electro-oculogram?
         There exists a potential between cornea and retina, whose amplitude is proportional to movement of eye from resting position and duration of pulse so produced is proportional to the rate at which eye movement happens. Here resting position is the front gaze of user. This small potential difference which is in the range of 1 to 100uV can be caught by placing Ag-AgCl pads on two sides of the face, just above ears and near to the eyes (This placement  is critical). The reference electrode is placed at the forehead. Any potential measured is with respect to ground electrode.

          This signal when properly amplified and filtered can indicate eye movement with respect to resting position. Thus we can distinguish left/right eye movement from the  (EOG) electrical signal.
          This signal with proper processing can be sensed using microcontroller and suitable control signal can be generated.

          Very interesting power device control applications can be developed using the same theme. Or as mentioned before, motors of wheelchair can be controlled, which becomes a boon for paralyzed people. One of the interesting applications includes controlling display power consumption using eye gaze direction. Also simple demo purpose video games can be done using EOG.
Following are some images of circuit on breadboard, I happened to setup during experimentation. In one of the images you can see led lit as it is controlled using eye movement.

EOG sensor setup on BB

LED lit when eye rolls to right

Following is the real time plot of EOG data for horizontal channel, which clearly shows Left-Right movement of eye.

Real time plot of EOG data