The design of a saccade-size predictor for eye communication

A method for predicting the end position of a saccade, based on the peak velocity/amplitude relationship, was studied for application in eye communication. An analogue delay line of the bucket brigade type was implemented for measuring the saccadic velocity on-line. The magnitude of the differentiated saccade-signal had been subdivided in discrete values, corresponding to the distances between the neighbouring LEDs at the characters in a row of the communication board. An up-down counter started one by one the successive switching-on of the LEDs at each step in the saccadic velocity staircase. A single emitting LED corresponded finally to a predicted eye position. The signal-to-noise ratio of the detecting transistors of the infrared limbus-reflection method determined the confidence limits in prediction of the saccadic sizes. Predictions turned out to be reliable over 6 characters at 3 degrees equidistant locations in a horizontal row. It is concluded in a discussion that the feasibility of a two-dimensional fast eye keyboard system can be studied by one saccade-size predictor in combination with the magnetic field scleral search coil technique.