Electro-oculograph(EOG)

and Eye Blink

The Electro-oculograph or EOG is a signal that can be sensed across the human eye based on the location of the gaze. A typical EOG arrangement involves electrodes placed across the eyes, both Vertically (across one eye), and Horizontally (across both eyes). Evaluated together, the two EOG signals can be used to infer eye position, and so, gaze direction and movement.

Using the EOG for eye position tracking requires D.C response from the two EOG signal conditioners. A typical slow drift in the baseline of the EOG signal makes this aspect quite challenging. To address this, UFI has designed and implemented a microprocessor controlled recentering scheme which automatically adjusts the baseline of a D.C. Fetrode amplifier, when the output signal approaches either end of the amplifier's response range.

An alternative for eye tracking is a video camera. The rapid growth of digital cameras have made this seem an attractive alternative. The cost of digital cameras has dropped very low, and a small camera is easy to find. The down side with the camera based eye tracking solution is that a complex and computationally intensive algorithm is necessary in order to recognize the eyes and extract gaze direction information, in real time, from the video stream from the camera.

And a single, vertical EOG channel can be used to supply Eye Blink information. For this setup, A.C. coupling is preferred for the signal conditioner, since this approach removes the D.C. component of the EOG associated with Eye Position, and leaves just the higher frequency Eye Blink pulse.

We recommend the use of our Fetrodes for all EOG signal conditioning and recording systems.

Both our Biolog ambulatory recorders, and our SC-2000 Simple Scope data collection platforms can accommodate the microprocessor recentering scheme, and record / supply 1 or 2 channels of EOG data with D.C. low frequency response. The EOG channel can be included with our Multi-Subject Data Collection System as well.

If you still have questions, or if you don't see what you need, drop us a line, and we will see how we can help you!