System and method for image registration based on variable region of interest

• US 8,620,086 B2
• Filed: 02/09/2012
• Issued: 12/31/2013
• Est. Priority Date: 02/16/2007
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Lam, Eric P., Parks, Harrison A., Leddy, Christopher A., Nash, Stephen R.
• Primary Examiner(s): Desire, Gregory M
• Application Number:
  US13/369,914
• Publication Number:
  US 20120134592A1
• Time in Patent Office: 691 Days
• Field of Search: 348/135, 348/142, 348/159, 382/128, 382/133, 382/143, 382/173, 382/190, 382/294, 382/300
• US Class Current: 382/190
• CPC Class Codes: G06T 7/337 involving reference images or patches

Abstract

An image registration system for aligning first and second images. The novel system includes a first system for extracting a region of interest (ROI) from each image and a second system for coarsely aligning the regions of interest. The first system determines the size and location of the ROI based on the number of features contained within the region. The size of the ROI is enlarged until a number of features contained in the ROI is larger than a predetermined lower bound or until the size is greater than a predetermined upper bound. The second system computes a cross-correlation on the regions of interest using a plurality of transforms to find a coarse alignment transform having a highest correlation. The image registration system may also include a third system for performing sub-pixel alignment on the regions of interest.

Claims

1. A system for finding a region of interest in an image comprising:

a first system for detecting features in said image;

a second system for determining a location for said region of interest; and

;

a third system for determining a size of said region of interest based on a number of features contained within a region of said size and at said location in said image, wherein the third system includes a system for enlarging said size until a number of features contained in said region is larger than a predetermined lower bound or until said size is greater than a predetermined upper bound.

2. The system of claim 1 wherein said location is fixed.

3. The system of claim 2 wherein said location is at a center of said image.

4. The system of claim 1 wherein said location is dependent on a number of features contained in said region of interest.

5. The system of claim 4 wherein said second system includes a system for counting a number of features in each row and each column of said image.

6. The system of claim 5 wherein said second system further includes a system for finding a first subset of rows having a large number of features.

7. The system of claim 6 wherein said second system further includes a system for finding a second subset of columns having a large number of features.

8. The system of claim 7 wherein said location is at an intersection of said first and second subsets.

9. A method executed by one or more processors for finding a region of interest in an image including the steps of:

detecting features in said image;

determining a location for said region of interest;

determining a size of said region of interest based on a number of features contained within a region of said size and at said location in said image; and

enlarging said size until a number of features contained in said region is larger than a predetermined lower bound or until said size is greater than a predetermined upper bound.

10. The method of claim 9 wherein said location is determined by counting a number of features in each row and each column of said image, finding a first subset of rows having a large number of features and a second subset of columns having a large number of features, and choosing said location at an intersection of said first and second subsets.

11. A method executed by one or more processors for aligning a first image and a second image including the steps detecting features in one of said images;

determining a location for a region of interest;

determining a size of said region of interest based on a number of features contained within a region of said size and at said location in said image;

enlarging said size until a number of features contained in said region is larger than a predetermined lower bound or until said size is greater than a predetermined upper bound;

applying said size and location to said first and second images to extract a region of interest from each image; and

cross-correlating said regions of interest using a plurality of transforms to find a first transform that coarsely aligns said regions of interest.

12. The method of claim 11 wherein said method further includes interpolating said regions of interest.

13. The method of claim 12 wherein said method further includes crosscorrelating the interpolated regions of interest using a plurality of transforms to find a second transform that sub-pixel aligns said regions of interest.

14. The method of claim 13 wherein said method further includes applying said first and second transforms to one or both of said first and second images.