Patent ID: 7830266

Claim:
A drowsy state determination device that determines a drowsy state of a driver of a vehicle, comprising: an eye-closure detection device that detects a closure degree of an eye of the driver to generate an eye-closure signal indicating an eye-closure period from an eye closure to a subsequent eye opening of the driver; a first storage device that stores a first threshold in accordance with a drowsiness level to be determined; an eye-closure period storage device that stores the eye-closure period that is indicated by the eye-closure signal, and that is equal to or above the first threshold as a result of comparison between the eye-closure period indicated by the eye-closure signal and the first threshold, in a prescribed measurement period for which the eye-closure signal is measured; a calculation device that calculates an eye-closure value representing the duration of a time for which the driver closes his/her eyes during the measurement period based on the eye-closure period stored in the eye-closure period storage device; a second storage device that stores a second threshold corresponding to the first threshold; and a drowsy state determination device that determines whether a drowsiness level of the driver is equal to or above the drowsiness level, based on whether the eye-closure value is equal to or above the second threshold as a result of comparison between the eye-closure value and the second threshold, wherein the first storage device stores a plurality of first thresholds for a plurality of drowsiness levels; the second storage device stores a plurality of second thresholds corresponding to the respective first thresholds; the eye-closure period storage device performs a process of storing the eye-closure period using the first threshold for each corresponding drowsiness level, for the plurality of drowsiness levels; the calculation device performs a process of calculating the eye-closure value based on the stored eye-closure period, for the plurality of drowsiness levels; the drowsy state determination device performs a process of determining whether or not the eye-closure value is equal to or above the second threshold, for the plurality of drowsiness levels, and determines the highest drowsiness level at which the determination result is positive, as the drowsiness level of the driver; and the calculation device calculates the eye-closure value by accumulating every integer portion of a quotient obtained by dividing each eye-closure period stored in the eye-closure period storage device by the first threshold used to store that eye-closure period.