Alertness monitor

• US 7,616,125 B2
• Filed: 05/19/2006
• Issued: 11/10/2009
• Est. Priority Date: 11/08/2001
• Status: Active Grant

• Current Assignee: SDIP Holdings Pty Ltd.
• Original Assignee: Optalert Pty Limited
• Inventors: Johns, Murray
• Primary Examiner(s): TRIEU, VAN THANH
• Application Number:
  US11/436,551
• Publication Number:
  US 20060202841A1
• Time in Patent Office: 1,271 Days
• Field of Search: 340/575, 340/576, 340/573.1, 340/439, 340/937, 340/5.81, 600/473, 600/476, 600/558, 382/117, 382/291
• US Class Current: 340/576
• 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 analyzed 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. A computerized method of calculating a measure of alertness which comprises:

a) receiving reflectance signals,

b) using an algorithm to obtain measures of the blink amplitude to velocity ratio and/or the saccade amplitude to velocity ratio,

c) averaging the measures obtained in b) over predetermined periods of time, and

d) measuring the deviation of the average obtained in c) from a predetermined average for alert subjects.

2. A computerized method of calculating a measure of alertness as claimed in claim 1 which displays the deviation as a ranking on a scale.

3. A computerized method of calculating a measure of alertness as claimed in claim 2 which actuates an alarm if the displayed ranking exceeds a predetermined value.

4. A medium storing instructions adapted to be executed by a processor to calculate a measure of alertness which method comprises:

a) receiving reflectance signals,

b) using an algorithm to obtain measures of the blink amplitude to velocity ratio and/or the saccade amplitude to velocity ratio,

c) averaging the measures obtained in b) over predetermined periods of time, and

d) measuring the deviation of the average obtained in c) from a predetermined average for alert subjects.

5. A medium storing instructions adapted to be executed by a processor to calculate a measure of alertness as claimed in claim 4 in which the method displays the deviation as a ranking on a scale.

6. A medium storing instructions adapted to be executed by a processor to calculate a measure of alertness as claimed in claim 5 in which the method actuates an alarm if the displayed ranking exceeds a predetermined value.

7. 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 to collect signals representing blinks and saccades,

c) means to transmit the detector signals,

d) data processing means to receive the detector signals,

e) said data processor using an algorithm to obtain measures of the blink amplitude to velocity ratio and/or the saccade amplitude to velocity ratio,

f) averaging the measures obtained in e) over predetermined periods of time, and

g) measuring the deviation of the average obtained in f) from a predetermined average for alert subjects.

8. An alertness measuring system as claimed in claim 7 which includes a display for displaying the alertness measurement or an alarm triggered by the scale reading reaching a predetermined limit.