SLEEP MONITORING SYSTEM AND METHOD

• US 20160310046A1
• Filed: 12/04/2014
• Published: 10/27/2016
• Est. Priority Date: 12/13/2013
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: VAN VUGT, HENRIETTE CHRISTINE, HEINRICH, ADRIENNE, JEANNE, VINCENT
• Granted Patent: US 10,058,272 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2503/04 Babies, e.g. for SIDS detection
• CPC Class Codes: A61B 5/0077 Devices for viewing the surface of the body, e.g. camera, magnifying lens
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/1128 using image analysis A61B5/1127 takes precedence
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/1176 Recognition of faces
• CPC Class Codes: A61B 5/4806 Sleep evaluation A61B5/4821 takes precedence; devices for inducing sleep A61M21/02
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B

Abstract

The sleep monitoring system uses a motion vector estimator to determine motion vectors as a function of location in camera images. A signal processing system with an input coupled to the motion vector estimator computes a measure of turning motion, by summing motion vectors from respective locations within an image. Pose changes are detected based on the measure of turning motion. The measure of turning motion may be computed from a sum of components of the motion vectors that are normal to the major axis of a body area in the image, which is determined based on image content changes in a set of images from the camera. To avoid false turning detection due to leg kicking or similar motion the detected turning motion may be reduced to zero if it is not detected in a sufficiently large part of the body area.

Claims

1. A monitoring system for monitoring a person on a bed, the system comprising

a camera for obtaining images of a person on the bed;

a motion vector estimator with an input coupled to the camera, configured to determine motion vectors as a function of location in the image;

a signal processing system with an input coupled to the motion vector estimator;

wherein the signal processing system is configured to

determine image locations associated with a body area and determine a direction of a major axis of the body area from the determined image locations;

compute a measure of turning motion, the computation comprising summing components of the motion vectors that are normal to the major axis from respective locations within an image;

detect pose changes based on the measure of turning motion.

2. A monitoring system according to claim 1, wherein the signal processing system is configured to

determine the image locations associated with the body area based on image content changes in a set of images from the camera, captured during a time window including a time point of capturing said image or adjacent to said time point.

3. A monitoring system according to claim 1, wherein the signal processing system is configured to

detect time intervals wherein the measure of turning motion indicates less than a predetermined amount of motion;

assign different pose states to successive ones of the detected time intervals, each based on signs of the measure of turning motion in further time intervals surrounding the time interval, and/or on a position of the time interval in a sequence of time intervals in which the detected time intervals occur.

4. A monitoring system according to claim 3, wherein the pose states include an on the belly pose state, an on the back pose state and an on the side pose state, and wherein the signal processing system is configured to use accumulated sizes of the measure of turning motion between the time intervals and/or time duration between the time intervals to select between using direct transitions between the on the belly pose state and the on the back pose state and transitions from the on the belly pose state or the on the back pose state to the on the side pose state.

5. A monitoring system according to claim 4, wherein the signal processing system is configured to use a sign of the measure of turning motion between the time intervals to select between using transitions to an on the left side pose state and an on the right side pose state.

6. A monitoring system according to claim 3, wherein the signal processing system is configured to perform face detection and/or breathing detection based on images from the camera and to set part of the assigned pose states based on results of face detection and/or breathing detection.

7. A monitoring system according to claim 3, wherein the signal processing system is configured to generate an alert signal when a predetermined pose state has been assigned and/or when a same pose state remains assigned for more than a predetermined time interval.

8. A monitoring system according to claim 7, wherein the signal processing system is configured to perform breathing detection based on images from the camera and to generate the alert signal on condition that no breathing with parameters within a predetermined range has been detected and/or a change of detected breathing parameters has been detected while the predetermined pose state has been assigned.

9. A monitoring system according to claim 1, wherein the signal processing system is configured to detect whether motion vectors in at least a predetermined fraction of the image locations in the body area or a part thereof exceed a threshold size and, if not, to decrease the measure of turning motion.

10. A monitoring system according to claim 1, wherein the signal processing system is configured to detect whether motion vectors in at least a first predetermined fraction of the image locations in the body area exceed a threshold size, and motion vectors in at least a second predetermined fraction of the image locations in a first end part of the body area along the major axis exceed the threshold size and, if not both, to decrease the measure of turning motion.

11. A monitoring system according to claim 1, wherein the signal processing system is configured to determine the measure of turning motion by accumulating sums of motion vectors from respective locations as a function of time and low pass filtering the accumulated sums.

12. A monitoring system according to claim 2, wherein the signal processing system is configured to select a region of interest in images from the camera for face detection and or heart beat detection dependent on a direction of the major axis.

13. A computer implemented method of monitoring a person on a bed, the method comprising

obtaining images of the person on the bed;

determine motion vectors as a function of location in the image;

wherein the method further comprises

determine image locations associated with a body area;

determine a direction of a major axis of the body area from the image locations;

compute a measure of turning motion, the computation comprising summing components of the motion vectors that are normal to the major axis from respective locations within an image;

detect pose changes based on the measure of turning motion.

14. A method according to claim 13, comprising

determine image locations associated with a body area based on image content changes in a set of images from the camera, captured during a time window including a time point of capturing said image or adjacent to said time point;

determine a direction of a major axis of the body area;

determine the measure of turning motion from a sum of components of the motion vectors that are normal to the major axis.

15. A computer program product, comprising a program of instructions for a programmable computer that, when executed by the programmable computer will cause the programmable computer to execute the method of claim 13.