Alertness monitor

• US 20060202841A1
• Filed: 05/19/2006
• Published: 09/14/2006
• Est. Priority Date: 11/08/2001
• Status: Active Grant

• Current Assignee: SDIP Holdings Pty Ltd.
• Original Assignee: Sleep Diagnostics Pty Ltd.
• Inventors: Johns, Murray
• Granted Patent: US 7,616,125 B2
• Time in Patent Office: Days
• US Class Current: 340/575
• CPC Class Codes: A61B 3/113 for determining or recording eye movement
• 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: G06V 20/597 Recognising the driver's state or behaviour, e.g. attention or drowsiness
• 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

An alertness monitoring system uses reflectance measurement of infrared light pulses to monitor eye movement of a vehicle or machine operator. The data is used to measure eye and eyelid movement for presence slow or drifting eye movements, and/or eyelid closure and optionally one or more of, absence of saccadic movement, loss of eye co-ordination, wavering eyelids, partial eye closure, and drooping eyelids as indicators of loss of attention and drowsiness. The eye movements of a subject are analysed using reflected infra red light to obtain measures of the blink amplitude velocity ratio and the saccade amplitude velocity ratio. The readings are continuously compared with eye movement data indicative of degrees of alertness so that the monitor provides an indication of the operator'"'"'s fitness to operate the vehicle or machine from the point of view of drowsiness no matter how it is caused.

Claims

1. An alertness monitoring system which includes

a) means to measure eyelid and eye movement for presence of one or more of relatively slow eye and eyelid movements in relation to their amplitude, wavering eyelids, partial eye closure, drooping eyelids;

slow or drifting eye movements, slow and prolonged eyelid closure, absence of saccadic movement and loss of eye co-ordination

b) storage means to continuously record the measurements

c) a data processor to compare the measurements against a predetermined scale, said scale being averaged measurements of the eye and eyelid movement parameters for a sample population measured against predetermined incremental levels of sleep deprivation

d) a display for showing the alertness measurement based on the scale or

e) an alarm means triggered by the scale reading reaching a predetermined limit based on the blood alcohol level scale.

2. An alertness system as claimed in claim 1 in which the eye and eyelid movements are monitored using a digital camera

3. An alertness system as claimed in claim 1 in which at least one infra red pulse emitter and one infra red detector is mounted on at least one eye.

4. An alertness system as claimed in claim 3 in which the detector measures the total level of light immediately before each pulse is transmitted and subtracts this from combined level of the measured reflectance during the pulse.

5. A method of measuring alertness in which the eye movements of a subject are analysed to obtain measures of the blink amplitude to velocity ratio and/or the saccade amplitude to velocity ratio averaging these over predetermined periods of time and measuring the deviation of the average from a predetermined average for alert subjects.

6. A method as claimed in claim 5 in which the measured blink amplitude to velocity ratio and the saccade amplitude to velocity ratio values are measured using reflected pulses of infra red light.

7. A method as claimed in claim 6 in which the reflected light pulses are detected at two locations on each eye.

8. A method as claimed in claim 5 in which one location detects reflectance associated with eyelid movement and the second location detects reflectance associated with saccadic movement.

9. An alertness measuring system for a subject which includes

a. an infrared pulse emitter adapted to be located adjacent at least one eye of a subject

b. at least one reflected light detector located adjacent said emitter

c. means to transmit the detector signals

d. data processing means to receive the detector signals and to subtract the total level of light immediately before each pulse is transmitted from the combined level of the measured reflectance after the pulse to provide a reflectance measure

e. said data processing means analyzing said reflectance measure to assess eyelid and eye movement for presence of one or more of relatively slow eye and eyelid movements in relation to their amplitude, wavering eyelids, partial eye closure, drooping eyelids;

slow or drifting eye movements, slow and prolonged eyelid closure, absence of saccadic movement and loss of eye co-ordination.

10. An alertness measuring system as claimed in claim 9 in which the reflected light pulses are detected at two locations on each eye.

11. An alertness measuring system as claimed in claim 10 in which one location detects reflectance associated with eyelid movement and the second location detects reflectance associated with saccadic movement.

12. An alertness measuring system as claimed in claim 11 in which the data processing system analyses the reflectance signals to obtain measures of the blink amplitude to velocity ratio and/or the saccade amplitude to velocity ratio, averaging these over predetermined periods of time and measuring the deviation of the average from a predetermined average for alert subjects.

13. An alertness measuring system as claimed in claim 12 which includes a display for displaying the alertness measurement or an alarm triggered by the scale reading reaching a predetermined limit.