Method and apparatus for detecting objects using structured light patterns

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.

1 . A method for detecting an object in a monitored area, the method comprising the steps of: 
 illuminating the monitored area using two or more wavelengths to create at least one pattern on the monitored area;    capturing a live image of the monitored area, including at least a portion of the at least one pattern; and    detecting an object in the monitored area by comparing the live image to a reference image, wherein a change in the at least one pattern between the live and reference images indicates the presence of an object in the monitored area.    
     
     
         2 . The method according to  claim 1 , wherein the pattern comprises a number of dots.  
     
     
         3 . The method according to  claim 1 , wherein each of the two or more wavelengths produces a different pattern.  
     
     
         4 . The method according to  claim 1 , wherein a change in the at least one pattern at both wavelengths indicates the presence of an object in the monitored area.  
     
     
         5 . The method according to  claim 1 , wherein a change in the at least one pattern at either wavelengths indicates the presence of an object in the monitored area.  
     
     
         6 . The method according to  claim 1 , wherein at least one of the wavelengths is in the near infrared or infrared.  
     
     
         7 . A system for monitoring a volume of space, the system comprising: 
 an illumination apparatus placed to illuminate at least a portion of a monitored area with two or more wavelengths; and    an image capture apparatus placed to capture images of at least part of the monitored area, wherein the image capture apparatus is sensitive to each of the two or more wavelengths;    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.    
     
     
         8 . The system according to  claim 7 , wherein the illumination apparatus is adapted to create at least one pattern using the two or more wavelengths and project the at least one pattern onto the monitored area.  
     
     
         9 . The system according to  claim 8 , wherein the illumination apparatus is adapted to create and project a different pattern onto the monitored area with each wavelength.  
     
     
         10 . The system according to  claim 8 , wherein the at least one pattern is not present in the monitored area in the absence of the illumination apparatus.  
     
     
         11 . The system according to  claim 8 , wherein the illumination apparatus is adapted to project the at least one pattern onto a surface in the monitored area, such that an object in the monitored area will have the pattern projected onto its surface.  
     
     
         12 . The system according to  claim 7 , wherein the portion of the monitored area illuminated by the illumination apparatus is not rectangular.  
     
     
         13 . The system according to  claim 7 , wherein the portion of the monitored area extends around at least two sides of a machine.  
     
     
         14 . The system according to  claim 7 , wherein the illumination apparatus illuminates at least a portion of a monitored area with a different pattern for each of the two or more wavelengths.  
     
     
         15 . The system according to  claim 7 , wherein the portion of the monitored area does not include the pattern prior to the illuminating step.  
     
     
         16 . The system according to  claim 7 , wherein at least one of the wavelengths is in the near infrared or infrared.  
     
     
         17 . A method for detecting an object in a monitored area, the method comprising the steps of: 
 creating at least one pattern using two or more wavelengths;    projecting the at least one pattern onto the monitored area;    capturing one or more live images of the monitored area at the two or more wavelengths, including at least a portion of the at least one pattern; and    detecting an object in the monitored area by comparing the one or more live images to one or more reference images, wherein a change in the pattern between the one or more live and reference images indicates the presence of an object in the monitored area.    
     
     
         18 . The method according to  claim 17 , wherein each of the two or more wavelengths produces a different pattern.  
     
     
         19 . The method according to  claim 17 , wherein a change in the at least one pattern at both wavelengths indicates the presence of an object in the monitored area.  
     
     
         20 . The method according to  claim 17 , wherein the monitored area does not include the pattern prior to the projecting step.  
     
     
         21 . The method according to  claim 17 , wherein at least one of the wavelengths is in the near infrared or infrared.