In recent years, numbers of traffic accidents have been caused by drivers' drowsiness. For preventing traffic accidents, such a system as to detect the drowsiness level without putting any sensor on the driver was developed. According to various reports, as the drowsiness level of a driver decreases, the blinking duration becomes longer than his normal arousal level. In this report, thesefore, we propose a highly reliable method of noncontact measurement for the driver's drowsiness level during driving. The our method consists of the following three parts : 1. We have devised an imaging unit which is less affected by ambient light. We provided an infrared light source which lights the driver's face; this light source emits pulses of light synchronizing with the storage time of a TV camera in electronic shutter mode. 2. We have devised a method of measuring the blinking duration which is independent of the driver's facial features. The blinking duration is calculated from the result of eye-opening measurement using simple gray scale processing. 3. We have proposed a method of estimating the drowsiness level from a change in blinking duration. In this method, the regression line for estimation is repeatedly renewed during driving to respond to individual drivers' differences.
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