Method and apparatus for detecting objects using structured light patterns

• US 20040256541A1
• Filed: 06/19/2003
• Published: 12/23/2004
• Est. Priority Date: 01/19/2001
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Hamza, Rida M., Cofer, Darren D.
• Granted Patent: US 7,176,440 B2
• Time in Patent Office: Days
• US Class Current: 250/221
• CPC Class Codes: F16P 3/142 using image capturing devices
• CPC Class Codes: G01B 11/25 by projecting a pattern, e.g. one or more lines, moiré fringes on the object G01B11/255 takes precedence ; image analysis for depth or shape recovery G06T7/50
• CPC Class Codes: G06T 7/20 Analysis of motion motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51
• CPC Class Codes: G06T 7/254 involving subtraction of images
• CPC Class Codes: G06V 10/145 Illumination specially adapted for pattern recognition, e.g. using gratings
• CPC Class Codes: G06V 20/52 Surveillance or monitoring of activities, e.g. for recognising suspicious objects recognising microscopic objects G06V20/69
• CPC Class Codes: G08B 13/18 Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength
• CPC Class Codes: G08B 13/19602 Image analysis to detect motion of the intruder, e.g. by frame subtraction
• CPC Class Codes: G08B 13/19604 involving reference image or background adaptation with time to compensate for changing conditions, e.g. reference image update on detection of light level change
• CPC Class Codes: G08B 13/19652 Systems using zones in a single scene defined for different treatment, e.g. outer zone gives pre-alarm, inner zone gives alarm
• CPC Class Codes: G08B 13/19686 Interfaces masking personal details for privacy, e.g. blurring faces, vehicle license plates

Abstract

An object detection system is provided that projects one or more patterns onto a monitored area, captures one or more live images of the monitored area, and detects objects that enter the monitored area by detecting changes in the one or more patterns in the live images. Such an object detection system may be less susceptible to dynamic lighting conditions, and more sensitive to object intrusions. One illustrative example projects a pattern of dots onto an area to be monitored, and captures images corresponding to the monitored area, comparing live images to reference images to determine whether an object has intruded a defined area. The area to be monitored does not consist solely of the area captured in the images and may include a volume illuminated by the pattern as well as a volume corresponding to the captured image area. Objects not in the field of view may be detected by the disclosed systems and methods. Several illustrative analytical methods are disclosed as well.

Claims

1. A method for detecting an object in a monitored area, the method comprising the steps of:

illuminating the monitored area with a pattern;

capturing a live image of the monitored area, including at least a portion of the pattern; and

detecting an object in the monitored area when a change is detected in the pattern in the live image, the change being noted by comparing a reference image showing at least a portion of the pattern to the live image to determine whether any part of the pattern has moved, been removed, or undergone some deformation.

2. The method according to claim 1 wherein the detecting step detects an object in the monitored area when the change in the pattern exceeds a predetermined threshold.

3. The method according to claim 1 wherein the monitored area is illuminated with a static pattern.

4. The method according to claim 1 wherein the monitored area is illuminated with a dynamic pattern.

5. The method according to claim 1 wherein the reference image and the live image each have a number of mask windows, and wherein the comparing step compares selected mask windows of the reference image to selected mask windows of the live image.

6. The method according to claim 5 wherein the comparing step compares the selected mask windows of the reference image and the live image using one or more comparing algorithms.

7. The method according to claim 6 wherein the comparing step compares two or more of the selected mask windows using different comparing algorithms.

8. The method according to claim 5 further comprising the step of performing a predefined action if the detecting step detects an object in one of the selected mask windows.

10. The method according to claim 1 wherein the pattern defines a number of spaced dots.

11. The method according to claim 1 wherein the pattern defines a number of stripes.

12. The method according to claim 1 wherein the pattern is projected using an infrared wavelength of light.

13. The method according to claim 1 wherein the pattern includes at least two discrete wavelengths of light.

9. The method according to claim 9 wherein the predefined action is different depending on the mask window in which an object is detected.

14. A method for detecting an object in a monitored area, the method comprising the steps of:

capturing a live image of the monitored area using an image capture apparatus having a field of view; and

detecting an object in the monitored area by comparing the live image to a reference image, wherein the object need not lie within the field of view of the image capture apparatus.

15. The method according to claim 14 further comprising the step of:

illuminating the monitored area with a pattern.

16. The method according to claim 15 wherein the pattern comprises a number of dots.

17. The method according to claim 15 wherein the pattern includes a first pattern illuminated using a first wavelength and a second pattern illuminated using a second wavelength.

18. The method according to claim 17 wherein the step of detecting an object in the monitored area by comparing the live image to a reference image includes making a first comparison using the first wavelength and a second comparison using the second wavelength.

19. The method according to claim 18 further comprising comparing the first comparison to the second comparison to determine whether a difference between the pattern in the live image and the pattern in the reference image is due to an object entering the area of interest.

20. A system for monitoring a volume of space, the system comprising:

an image capture apparatus placed to capture images of a monitored area; and

an illumination apparatus placed to illuminate the monitored area;

wherein the volume of space monitored includes a volume corresponding to the space defined between the illumination apparatus and the monitored area; and

wherein the volume of space monitored includes a volume corresponding to the space defined between the monitored area and the image capture apparatus.

21. The system of claim 20 wherein the illumination apparatus is adapted to project a pattern on the monitored area.

22. The system of claim 21 wherein the illumination apparatus is adapted to project the pattern using light of a selected wavelength.

23. The system of claim 21 wherein the pattern is a dynamic pattern.

24. A system for detecting an object in a monitored area, the system comprising:

an illumination device adapted to illuminate the monitored area with a pattern;

an image capture device adapted to capture a live image of the monitored area, including at least a portion of the pattern; and

detection electronics adapted to detect an object in the monitored area when a change is detected in the pattern in the live image, the change being noted by comparing a reference image showing at least a portion of the pattern to the live image to determine whether any part of the pattern has moved or been removed.