Effectiveness in Monitoring Sleep: Graphic Displays

These figures show the effectiveness of the APL drowsy driver detection system in monitoring the onset of sleep. The system is capable of detecting the change in activity with increasing levels of fatigue. Once the person becomes fatigued, the system can detect the eyelid behavior and eye blinks. Eyelid behavior such as the eyes opening, closing, and the period of time the eyes remain closed can be measured.

In the first screen, below, an eye closure takes place, which is indicated on the microwave data by the unique bipolar waveform. This bipolar waveform time correlates well with the eye closure seen on the video frame. A bipolar waveform is characteristic of either a rapid blink, or an eye closure. Differences in the bipolar waveform allow differentiation of a rapid blink from an eye closure.

The second screen captures the characteristic, negative unipolar signal seen when an eye re-opens if it has been closed for longer than a blink. This difference in waveform allows a critical feature to be measured, the duration of eye closure.



The measurements are not limited to side views. The following figure is an example of measurements made from the front. Once again a characteristic waveform for a rapid eye blink is easily identifiable in the microwave signal and correlates well with the video data.