Scene change detection in a dimensioner
A package dimensioner is disclosed. A change in the pose of the package dimensioner is detected by background modeling the area of a measurement platform and then determining if a number of points in a scene are different in distance from the background model. Change in the pose can also be detected by comparing a count of support points in a 3D container generated from images taken in a training process with a count of support points in a subsequent images and determining how many support points are different.
1. A method, comprising:
initializing a dimensioning system by:
at a range camera, capturing one or more initial reference images of a measurement platform and surrounding area;
at a processor:
generating a reference depth map from each initial reference image;
generating and storing to a memory a background model from the reference depth maps;
testing the dimensioning system for a scene change by:
at the range camera, capturing a subsequent image of the measurement platform and surrounding area;
at the processor:
generating a current depth map from the subsequent image;
comparing each pixel of the current depth map with a corresponding pixel of the background model; and
counting a number of pixels Pv of the current depth map that differ absolutely from the background model by more than the prescribed threshold THRESH 1 , and if the number of pixels Pv is greater than a threshold THRESH 2 , determining that a significant change in the image has occurred.
2. The method according to claim 1 , where the testing is carried out on a periodic basis.
3. The method according to claim 1 , further comprising executing a dimensioning process to measure the dimensions of an object on the measurement platform.
4. The method according to claim 3 , where the testing is carried out whenever a prescribed period of inactivity in measuring dimensions of an object on the measurement platform.
5. The method according to claim 3 , where the testing is carried out prior to each measurement of dimensions of an object on the measurement platform.
6. The method according to claim 1 , further comprising generating an alert upon determining that a significant scene change has occurred.
7. The method according to claim 1 , further comprising upon determining that a significant scene change has occurred, repeating the initializing.
8. A dimensioning system, comprising:
a measurement platform;
a range camera mounted so as to capture an image of the measurement platform and surrounding area;
a processor programmed to carry out the following actions:
initialize the dimensioning system by:
receiving one or more initial reference images of the measurement platform and surrounding area from the range camera;
generating and storing to a memory a background model from the one or more captured initial reference images;
test the dimensioning system for a scene change by:
receiving a subsequent image of the platform area from the range camera;
generating a current depth map from the subsequent image;
comparing each pixel of the current depth map with a corresponding pixel of the background model; and
counting a number of pixels Pv of the current depth map that differ absolutely from the background model by more than the prescribed threshold THRESH 1 , and if the number of pixels Pv is greater than a threshold THRESH 2 , determining that a significant change in the image has occurred.
9. The system according to claim 8 , where the testing is carried out on a periodic basis.
10. The system according to claim 8 , further comprising the processor executing a dimensioning process to measure dimensions of an object on the measurement platform.
11. The system according to claim 10 , where the testing is carried out whenever a prescribed period of inactivity in measuring dimensions of an object on the measurement platform.
12. The system according to claim 10 , where the testing is carried out prior to each measurement of dimensions of an object on the measurement platform.
13. The system according to claim 8 , further comprising the processor generating an alert upon determining that a significant scene change has occurred.
14. The system according to claim 8 , further comprising upon determining that a significant scene change has occurred, the processor repeating the initializing.
15. A method, comprising:
initializing a dimensioning system by:
at a range camera, capturing an initial reference image of a platform and surrounding area;
at a processor, generating a three-dimensional container around the platform and storing the container to memory; and
at the processor, determining a count of support points in the container from the initial reference image;
testing the dimensioning system for a scene change by:
at the range camera, capturing a subsequent image of the measurement platform and surrounding area;
at the processor:
counting support points in the subsequent image that are in the container;
comparing the count of support points in the container in the subsequent image with the count of support points in the container in the initial reference image;
based on the comparison, determining if a prescribed difference in the counts is present; and
upon determining that a prescribed difference in the counts exists establishing that a significant scene change has occurred.
16. The method according to claim 15 , where the testing is carried out on a periodic basis.
17. The method according to claim 15 , further comprising executing a dimensioning process to measure dimensions of an object on the platform.
18. The method according to claim 17 , where the testing is carried out whenever a prescribed period of inactivity in measuring dimensions of an object on the measurement platform.
19. The method according to claim 17 , where the testing is carried out prior to each measurement of dimensions of an object on the measurement platform.
20. The method according to claim 17 , further comprising generating an alert upon determining that a significant scene change has occurred.
21. The method according to claim 17 , where the container comprises a right prism with a base approximating a convex polygon, where the base is parallel to a congruent convex polygon that bounds the measurement platform, and where the prism's height equals twice a maximum support distance.
22. The method according to claim 15 , where the container comprises a right cylinder with a circular base, where the base is parallel to a congruent circle that bounds the measurement platform, and where the cylinder's height equals twice the maximum support distance.
23. The method according to claim 15 , comprising: when a significant scene change is deemed to have occurred, searching the scene for the measurement platform at a location coplanar therewith.
24. The method according to claim 15 , further comprising upon establishing that a significant scene change has occurred, repeating the initializing.
25. A dimensioning system, comprising:
a measurement platform;
a range camera mounted so as to capture an image of the measurement platform and surrounding area;
a processor programmed to carry out the following actions:
initialize the dimensioning system by:
receiving an initial reference image of a platform area from the range camera;
generating a three-dimensional container around the measurement platform and storing the container to memory; and
determining a count of support points in the container from the initial reference image;
test the dimensioning system for a scene change by:
receiving a subsequent image of the measurement platform and surrounding area from the range camera;
counting support points in the subsequent image that are in the container;
comparing the count of support points in the container in the subsequent image with the count of support points in the container in the initial reference image;
based on the comparison, determining if a prescribed difference in the counts of support points is present; and
upon determining that a prescribed difference in the counts exists establishing that a significant scene change has occurred.
26. The system according to claim 25 , where the testing is carried out on a periodic basis.
27. The system according to claim 25 , further comprising the processor executing a dimensioning process to measure dimensions of an object on the measurement platform.
28. The system according to claim 27 , where the testing is carried out whenever a prescribed period of inactivity in measuring dimensions of an object on the measurement platform.
29. The system according to claim 27 , where the testing is carried out prior to each measurement of dimensions of an object on the measurement platform.
30. The system according to claim 25 , further comprising the processor generating an alert upon determining that a significant scene change has occurred.
31. The system according to claim 25 , where the container comprises a right prism with a base approximating a convex polygon, where the base is parallel to a congruent convex polygon that bounds the measurement platform, and where the prism's height equals twice the maximum support distance.
32. The system according to claim 25 , where the container comprises a right cylinder with a circular base, where the base is parallel to a congruent circle that bounds the measurement platform, and where the cylinder's height equals twice the maximum support distance.
33. The system according to claim 25 , further comprising when a significant scene change is deemed to have occurred, the processor searching the scene for the measurement platform at a location coplanar therewith.
34. The system according to claim 25 , further comprising the processor repeating the initializing upon establishing that a significant scene change has occurred.