When the eyes move, biopotentials are generated. These corneo-retinal potentials (from the back of the eye to the front of the eye) biopotentials are generated by the retinal dipole, and variously called the EOG (Electro-oculogram), ERG (Retinogram) or ENG (Nystagmogram). The potentials vary with a number of factors, e.g. light level, blinking, and tends to drift.
- Use electrodes on the forehead, under the eyes on the cheek, and behind the right ear (mastoid) for the grounding point.
- These three electrodes could be mounted on the eyeglass frame
- Design and build a suitable instrumenattion amplifier to detect the EOG
- Suggested circuit schematic - 3-op-amp differential amplifier + 3-pole Butterworth lowpass filter + Inverting amplifier
- Characteristics of EOG signal and requirements for mouse
- Frequency Range DC – 10 Hz
- Voltage Range 0.05 – 3.5 mV
- Gain needed ~5,000
- Approximately linear over 30 degree arc
- Accurate to 1 degree
- Use a TTL comparator to generate a 1 or 0, or generate a signal proportional to the eye angle.
- Couple to mouse port of PC
CIRCUIT DIAGRAM
