Selection of balanced-probe sites for 3-D alignment algorithms

Patent metadata

Field	Value
Publication number	US-10417533-B2
Application number	US-201615232766-A
Country	US
Kind code	B2
Filing date	Aug 9, 2016
Priority date	Aug 9, 2016
Publication date	Sep 17, 2019
Grant date	Sep 17, 2019

Abstract

Techniques include systems, computerized methods, and computer readable media for choosing placement of three-dimensional (3D) probes used for evaluating a 3D alignment pose of a runtime 3D image inside a 3D alignment system for estimating the pose of a trained 3D model image in that 3D runtime image. A plurality of features associated with a first plurality of points of interest from a 3D image are generated, wherein each feature includes data indicative of 3D properties of an associated point from the plurality of points of interest. A second plurality of points of interest are selected from among the first plurality of points of interest, based at least in part on the plurality of features associated with the first plurality of points of interest. Placements of a plurality of 3D probes are determined based at least in part on the second plurality of points of interest.

First claim

The invention claimed is:

1. A system for choosing placement of three-dimensional (3D) probes used for evaluating a 3D alignment pose of a runtime 3D image inside a 3D alignment system for estimating the pose of a trained 3D model image in that 3D runtime image, comprising:
a processor in communication with a memory, wherein the processor is configured to run a computer program stored in the memory that is configured to:
generate a plurality of features associated with a first plurality of points of interest from a 3D image, wherein each feature comprises data indicative of 3D properties of an associated point from the plurality of points of interest;
determine a target distribution of placements of a plurality of 3D probes based on the plurality of features associated with the first plurality of points of interest;
select a second plurality of points of interest from among the first plurality of points of interest, based at least in part on the target distribution; and
determine placements of the plurality of 3D probes based at least in part on the second plurality of points of interest.

2. The system of claim 1 , wherein each of the plurality of features incorporates at least one measure of usefulness of an associated point from among the first plurality of points for alignment in at least one translational degree of freedom.

3. The system of claim 1 , wherein each of the plurality of features incorporates at least one measure of usefulness of an associated point from among the first plurality of points for alignment in at least one rotational degree of freedom.

4. The system of claim 1 , wherein the placement of the plurality of 3D probes provides an increase in ensemble alignment ability in at least one less represented translational degree of freedom provided by a placement on each of the first plurality of points of interest.

5. The system of claim 1 , wherein the placement of the plurality of 3D probes provides an increase in ensemble alignment ability in at least one less represented translational degree of freedom and in a less represented rotational degree of freedom provided by a placement on each of the first plurality of points of interest.

6. The system of claim 1 , wherein the placement of the plurality of 3D probes provides an increase in ensemble alignment ability in at least one less represented rotational degree of freedom provided by placement on each of the first plurality of points of interest.

7. The system of claim 1 , wherein the processor is further configured to:
determine a center of rotation that minimizes a sum of rotational moments of the plurality of features; and
determine a first, second, and third axis of rotation that minimizes the sum of rotational moments of the plurality of features.

8. The system of claim 1 , wherein a center of rotation and rotational axes that fit a subset of the first plurality of points are determined such that the center of rotation and rotational axes are associated with rotationally symmetric features of a pattern.

9. The system of claim 8 , where finding the center of rotation and rotational axes from a subset of the first plurality of points comprises using a RANSAC technique.

10. The system of claim 8 , where finding the center of rotation and rotational axes from a subset of the first plurality of points comprises using a Monte Carlo technique.

11. The system of claim 1 , wherein the plurality of features includes a plurality of surface normal vectors.

12. The system of claim 1 , wherein the plurality of features includes a plurality of edge proximity vectors.

13. The system of claim 1 , wherein the plurality of features includes a plurality of edge direction vectors.

14. The system of claim 1 , wherein the plurality of features includes a plurality of surface curvature vectors.

15. The system of claim 1 , wherein selecting the second plurality of points of interest from among the first plurality of points of interest based at least in part on the target distribution comprises fitting a probability distribution to the first plurality of points and determining the target distribution, wherein the target distribution is indicative of a desired placement of the plurality of 3D probes on one or more of the first plurality of points of interest; and
wherein determining the placements of the plurality of 3D probes based at least in part on the second plurality of points of interest comprises determining placements of the plurality of 3D probes at least in part by utilizing relative probabilities of the fitted probability distribution and the target distribution.

16. The system of claim 15 , wherein fitting the probability distribution to the first plurality of points comprises fitting the first plurality of interest points to the probability distribution comprising a mixture model, wherein the probability distribution is indicative of at least a distribution of orientations measured at the first plurality of interest points.

17. The system of claim 16 , wherein the processor is further configured to determine a number of components of the mixture model of the probability distribution by clustering the first plurality of interest points into at least one cluster.

18. The system of claim 1 , wherein the processor is further configured to:
identify one or more horizon points from the first plurality of interest points; and
remove from consideration the one or more horizon points such that the second plurality of interest points does not comprise the one or more horizon points.

19. The system of claim 1 , wherein selecting the second plurality of points of interest comprises using a Monte Carlo technique.

20. A method for choosing placement of three-dimensional (3D) probes used for evaluating a 3D alignment pose of a runtime 3D image inside a 3D alignment system for estimating the pose of a trained 3D model image in that 3D runtime image, the method comprising:
generating a plurality of features associated with a first plurality of points of interest from a 3D image, wherein each feature comprises data indicative of 3D properties of an associated point from the plurality of points of interest;
determining a target distribution of placements of a plurality of 3D probes based on the plurality of features associated with the first plurality of points of interest;
selecting a second plurality of points of interest from among the first plurality of points of interest, based at least in part on the target distribution; and
determining placements of the plurality of 3D probes based at least in part on the second plurality of points of interest.

21. The method of claim 20 , wherein each of the plurality of features incorporates at least one measure of usefulness of an associated point from among the first plurality of points for alignment in at least one translational degree of freedom.

22. The method of claim 20 , wherein each of the plurality of features incorporates at least one measure of usefulness of an associated point from among the first plurality of points for alignment in at least one rotational degree of freedom.

23. The method of claim 20 , wherein the placement of the plurality of 3D probes provides an increase in ensemble alignment ability in at least one less represented translational degree of freedom provided by a placement on each of the first plurality of points of interest.

24. The method of claim 20 , wherein the placement of the plurality of 3D probes provi

Assignees

• Cognex Corp

Inventors

• Barker Simon
• Hoelscher Drew

Classifications

• G06T7/75 Primary

  involving models · CPC title

• G06F18/2321

  using statistics or function optimisation, e.g. modelling of probability density functions · CPC title

• G06V10/245

  by locating a pattern; Special marks for positioning · CPC title

• G06V10/44

  Local feature extraction by analysis of parts of the pattern, e.g. by detecting edges, contours, loops, corners, strokes or intersections; Connectivity analysis, e.g. of connected components · CPC title

• G06V10/758

  Involving statistics of pixels or of feature values, e.g. histogram matching · CPC title