DOZE DETECTION METHOD AND APPARATUS THEREOF

• US 20140205149A1
• Filed: 09/04/2012
• Published: 07/24/2014
• Est. Priority Date: 09/05/2011
• Status: Active Grant

• Current Assignee: National University Corporation University of Toyama
• Original Assignee: TOYAMA PREFECTURE
• Inventors: Nakamura, Kiyomi, Takano, Hironobu
• Granted Patent: US 9,286,515 B2
• Time in Patent Office: Days
• US Class Current: 382/103
• CPC Class Codes: A61B 5/0077 Devices for viewing the surface of the body, e.g. camera, magnifying lens
• CPC Class Codes: A61B 5/1103 Detecting eye twinkling
• CPC Class Codes: A61B 5/163 by tracking eye movement, gaze, or pupil change
• CPC Class Codes: A61B 5/18 for vehicle drivers or machine operators
• CPC Class Codes: A61B 5/4809 Sleep detection, i.e. determining whether a subject is asleep or not
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence
• CPC Class Codes: B60K 28/066 actuating a signalling device B60K28/063 takes precedence
• CPC Class Codes: G06V 40/19 Sensors therefor
• CPC Class Codes: G08B 21/06 indicating a condition of sleep, e.g. anti-dozing alarms

Abstract

A doze detection method, which accurately detects a blink burst and improves speed and accuracy of doze detection, includes measuring a state where the eye is substantially open as an open eye time and another state as a closed eye time, defining a time shorter than an average blink interval of a healthy adult in an alert state as a first threshold time; defining a time longer than an average closed eye time of a healthy adult in an alert state as a second threshold time; and defining blinks as a blink burst when detecting an eye opening equal to or shorter than the first threshold time. A doze state is determined when the closed eye time of a blink among the blinks during the blink burst reaches at least the second threshold time, the blink occurring after an open eye time equal to at most the first threshold time.

Claims

1. A doze detection method, comprising:

measuring, among states from an eye closure to an eye opening of a human eye, a state where the eye is substantially open as an open eye time and the other state as a closed eye time;

defining a time that is relatively shorter than an average blink interval of healthy adult in an alert state as a first threshold time;

defining a time that is relatively longer than an average closed eye time of healthy adult in an alert state as a second threshold time;

when detecting an eye opening equal to or shorter than the first threshold time, defining blinks before and after the eye opening as a blink burst; and

determining to be a doze state when a closed eye time of a blink among the blinks during the blink burst reaches the second threshold time or more, the blink occurring after an open eye time equal to or shorter than the first threshold time.

2. The doze detection method according to claim 1, wherein:

it is immediately determined to be a doze state when a closed eye time of a blink among the blinks during the blink burst is equal to or longer than the second threshold time, the blink occurring before an open eye time equal to or shorter than the first threshold time.

3. The doze detection method according to claim 1, wherein:

a closed eye time that is relatively longer than the second threshold time is defined as a third threshold time, and it is immediately determined to be a doze state when a closed eye time of a blink among the blinks during the blink burst reaches the third threshold time or more, the blink occurring after an open eye time equal to or shorter than the first threshold time.

4. The doze detection method according to claim 1, wherein:

a closed eye time that is relatively longer than the second threshold time is defined as a third threshold time, in detecting the open eye time, when detecting an eye opening longer than the first threshold time and when an open eye time before a blink immediately preceding the eye opening occurs is longer than the first threshold time, the immediately-preceding blink is determined to be a blink other than a blink burst, and it is immediately determined to be a doze state when a closed eye time of the blink other than a blink burst is equal to or longer than the third threshold time.

5. The doze detection method according to claim 1, wherein:

a closed eye time that is relatively longer than the second threshold time is defined as a third threshold time, and in detecting the open eye time, when detecting an eye opening longer than the first threshold time and when a closed eye time of a blink immediately after the eye opening reaches the third threshold time or more, it is immediately determined to be a doze state.

6. The doze detection method according to claim 3, wherein:

the third threshold time is a closed eye time relatively longer than an average closed eye time of blinks other than the blink burst of healthy adult in an alert state.

7. The doze detection method according to claim 6, wherein:

it is determined to be a doze state, when a total closed eye time obtained as a sum of the closed eye time of the blink during the blink burst and the closed eye time of the blink other than the blink burst is relatively longer than the third threshold time.

8. The doze detection method according to claim 7, wherein:

the total closed eye time is obtained by weighting the closed eye time of the blink during the blink burst and the closed eye time of the blink other than the blink burst respectively, and by adding the weighted closed eye times.

19. The doze detection method according to claim 4, wherein:

the third threshold time is a closed eye time relatively longer than an average closed eye time of blinks other than the blink burst of healthy adult in an alert state.

20. The doze detection method according to claim 5, wherein:

the third threshold time is a closed eye time relatively longer than an average closed eye time of blinks other than the blink burst of healthy adult in an alert state.

9. A doze detection apparatus, comprising:

an eye closure detection means that detects states from an eye closure to an eye opening of the eye by recognizing a position of a human eye; and

a blink time measurement means that measures a state where the human eye is substantially open as an open eye time and the other state as a closed eye time by the eye closure detection means, wherein the doze detection apparatus comprises;

defining a time that is relatively shorter than an average blink interval of healthy adult in an alert state as a first threshold time;

defining a time that is relatively longer than an average closed eye time of healthy adult in an alert state as a second threshold time; and

when detecting an eye opening equal to or shorter than the first threshold time, defining blinks before and after the eye opening as a blink burst; and

the doze detection apparatus comprises;

a blink burst discrimination means that discriminates the blink burst on the basis of a time of the blink measured by the blink time measurement means; and

a doze discrimination means that determines to be a doze state when the blink burst is detected, and when a closed eye time of a blink, among the blinks during the blink burst, occurring after an open eye time equal to or shorter than the first threshold time reaches the second threshold time or more.

10. The doze detection apparatus according to claim 9, wherein:

the doze discrimination means immediately determines to be a doze state when a closed eye time of a blink among the blinks during the blink burst detected by the blink burst discrimination means is equal to or longer than the second threshold time, the blink occurring before an open eye time equal to or shorter than the first threshold time.

11. The doze detection apparatus according to claim 9, wherein:

a closed eye time that is relatively longer than the second threshold time is defined as a third threshold time, and the doze discrimination means immediately determines to be a doze state when a closed eye time of a blink among the blinks during the blink burst detected by the blink burst discrimination means reaches the third threshold time or more, the blink occurring after an open eye time equal to or shorter than the first threshold time.

12. The doze detection apparatus according to claim 9, wherein:

a closed eye time that is relatively longer than the second threshold time is defined as a third threshold time, and when detecting an eye opening longer than the first threshold time by the blink time measurement means and when an open eye time before a blink immediately preceding the eye opening occurs is longer than the first threshold time, the immediately-preceding blink is determined to be a blink other than a blink burst, and the doze discrimination means immediately determines to be a doze state when a closed eye time of the blink other than a blink burst is equal to or longer than the third threshold time.

13. The doze detection apparatus according to claim 9, wherein:

a closed eye time that is relatively longer than the second threshold time is defined as a third threshold time, and when detecting an eye opening longer than the first threshold time by the blink time measurement means and when a closed eye time of a blink immediately after the eye opening reaches the third threshold time or more, the doze discrimination means immediately determines to be a doze state.

14. The doze detection apparatus according to claim 11, wherein:

the third threshold time is a closed eye time relatively longer than an average closed eye time of blinks other than the blink burst of healthy adult in an alert state.

15. The doze detection apparatus according to claim 14, wherein:

the doze discrimination means determines to be a doze state, when a total closed eye time obtained as a sum of the closed eye time of the blink during the blink burst detected by the blink burst discrimination means and the closed eye time of the blink other than the blink burst that is detected by the blink time measurement means is relatively longer than the third threshold time.

16. The doze detection apparatus according to claim 15, wherein:

the doze discrimination means obtains the total closed eye time by weighting the closed eye time of the blink during the blink burst and the closed eye time of the blink other than the blink burst respectively, and by adding the weighted closed eye times.

17. The doze detection apparatus according to claim 9, wherein:

the doze detection apparatus comprises an alert means issuing a doze alert on the basis of the determination result of a doze state.

18. A vehicle, comprising the doze detection apparatus according to claim 9.

21. The doze detection apparatus according to claim 12, wherein:

the third threshold time is a closed eye time relatively longer than an average closed eye time of blinks other than the blink burst of healthy adult in an alert state.

22. The doze detection apparatus according to claim 13, wherein:

the third threshold time is a closed eye time relatively longer than an average closed eye time of blinks other than the blink burst of healthy adult in an alert state.