Method, System and Apparatus for Object Detection in Point Clouds

Abstract

A method of detecting objects on a support structure includes: obtaining a point cloud of the support structure supporting an object; obtaining a position of a back of the support structure in the point cloud; discarding a portion of the point cloud based on the position of the back of the support structure; generating a three-dimensional occupancy grid from the point cloud, the occupancy grid having a plurality of cells each indicating whether the cell is one of occupied and unoccupied; identifying a contiguous region of occupied cells in the occupancy grid corresponding to the object; and generating a detected object position based on the contiguous region.

1 . A method of detecting objects on a support structure, the method comprising:
 obtaining a point cloud of the support structure supporting an object;   obtaining a position of a back of the support structure in the point cloud;   discarding a portion of the point cloud based on the position of the back of the support structure;   generating a three-dimensional occupancy grid from the point cloud, the occupancy grid having a plurality of cells each indicating whether the cell is one of occupied and unoccupied;   identifying a contiguous region of occupied cells in the occupancy grid corresponding to the object; and   generating a detected object position based on the contiguous region.   
     
     
         2 . The method of  claim 1 , wherein the detected object positions comprises a bounding box. 
     
     
         3 . The method of  claim 1 , wherein obtaining the position of the back of the support structure includes:
 obtaining (i) a plane definition corresponding to a front of the support structure, and (ii) a depth from the plane definition to the back of the support structure.   
     
     
         4 . The method of  claim 3 , wherein discarding the portion of the point cloud at the position of the back of the support structure includes discarding points within a threshold depth matching the depth from the plane definition to the back of the support structure. 
     
     
         5 . The method of  claim 3 , wherein the point cloud defines a plurality of points according to a common frame of reference; the method further comprising:
 before discarding the portion, transforming the points from the common frame of reference to a secondary frame of reference defining, for each point, a position on the plane definition and a depth orthogonal to the plane definition.   
     
     
         6 . The method of  claim 5 , wherein generating the occupancy grid comprises, for each position on the plane definition:
 determining a first depth of a point nearest to the plane definition; and   storing, in a cell of the occupancy grid containing the point, an occupied indicator, and storing, in each cell of the occupancy grid having the position on the plane definition and a greater depth than the first depth, an unoccupied indicator.   
     
     
         7 . The method of  claim 6 , wherein identifying the contiguous region comprises:
 in a first set of cells having a first common depth, identifying a first contiguous sub-region;   in a second set of cells having a second common depth, identifying a second contiguous sub-region;   determining whether to merge the first and second contiguous sub-regions; and   when the determination is affirmative, merging the first and second contiguous sub-regions to generate the contiguous region.   
     
     
         8 . The method of  claim 7 , wherein determining whether to merge the first and second contiguous sub-regions comprises: determining whether a first position on the plane definition of the first contiguous sub-region abuts a second position on the plane definition of the second contiguous sub-region. 
     
     
         9 . The method of  claim 1 , further comprising:
 prior to identifying the contiguous region, discarding a portion of the cells corresponding to support structure edge positions.   
     
     
         10 . A computing device for detecting objects on a support structure, comprising:
 a memory storing (i) a point cloud of the support structure supporting an object, and (ii) a position of a back of the support structure in the point cloud;   an imaging controller connected to the memory, the imaging controller configured to:
 retrieve, from the memory, the point cloud and the position of the back of the support structure in the point cloud; 
 discard a portion of the point cloud based on the position of the back of the support structure; 
 generate a three-dimensional occupancy grid from the point cloud, the occupancy grid having a plurality of cells each indicating whether the cell is one of occupied and unoccupied; 
 identify a contiguous region of occupied cells in the occupancy grid corresponding to the object; and 
 generate a detected object position based on the contiguous region. 
   
     
     
         11 . The computing device of  claim 10 , wherein the detected object positions comprises a bounding box. 
     
     
         12 . The computing device of  claim 10 , wherein the imaging controller is further configured, to obtain the position of the back of the support structure, to:
 retrieve from the memory (i) a plane definition corresponding to a front of the support structure, and (ii) a depth from the plane definition to the back of the support structure.   
     
     
         13 . The computing device of  claim 12 , wherein the imaging controller is further configured, to discard the portion of the point cloud at the position of the back of the support structure, to: discard points within a threshold depth matching the depth from the plane definition to the back of the support structure. 
     
     
         14 . The computing device of  claim 12 , wherein the point cloud defines a plurality of points according to a common frame of reference; and wherein the imaging controller is further configured to:
 before discarding the portion, transform the points from the common frame of reference to a secondary frame of reference defining, for each point, a position on the plane definition and a depth orthogonal to the plane definition.   
     
     
         15 . The computing device of  claim 14 , wherein the imaging controller is further configured, to generate the occupancy grid, to:
 for each position on the plane definition:
 determine a first depth of a point nearest to the plane definition; and 
 store, in a cell of the occupancy grid containing the point, an occupied indicator, and storing, in each cell of the occupancy grid having the position on the plane definition and a greater depth than the first depth, an unoccupied indicator. 
   
     
     
         16 . The computing device of  claim 15 , wherein the imaging controller is further configured, to identify the contiguous region, to:
 in a first set of cells having a first common depth, identify a first contiguous sub-region;   in a second set of cells having a second common depth, identify a second contiguous sub-region;   determine whether to merge the first and second contiguous sub-regions; and   when the determination is affirmative, merge the first and second contiguous sub-regions to generate the contiguous region.   
     
     
         17 . The computing device of  claim 16 , wherein the imaging controller is further configured, to determine whether to merge the first and second contiguous sub-regions, to:
 determine whether a first position on the plane definition of the first contiguous sub-region abuts a second position on the plane definition of the second contiguous sub-region.   
     
     
         18 . The computing device of  claim 10 , wherein the imaging controller is further configured to:
 prior to identifying the contiguous region, discard a portion of the cells corresponding to support structure edge positions.   
     
     
         19 . A non-transitory computer-readable medium storing a plurality of computer-readable instructions executable by a processor of a computing device, wherein execution of the instructions configures the computing device to:
 obtain a point cloud of a support structure supporting an object;   obtain a position of a back of the support structure in the point cloud;   discard a portion of the point cloud based on the position of the back of the support structure;   generate a three-dimensional occupancy grid from the point cloud, the occupancy grid having a plurality of cells each indicating whether the cell is one of occupied and unoccupied;   identify a contiguous region of occupied cells in the occupancy grid corresponding to the object; and   generate a detected object position based on the contiguous region.   
     
     
         20 . The non-transitory computer-readable medium of  claim 19 , wherein the detected object positions comprises a bounding box.