Stereo vision system for counting items in a queue
First Claim
1. A method for counting a plurality of objects currently present in a substantially linear queue, comprising:
- obtaining a stereo image of a scene including said substantially linear queue from a vantage point area in close proximity to one end of said substantially linear queue, wherein said stereo image comprises a first image and a second image, each of said plurality of objects in said first image being shifted relative to said second image;
obtaining depth information from said stereo image for portions of said scene relative to said vantage point, comprising correlating patches in said first image with patches in said second image; and
interpreting said depth information to determine areas of said stereo image substantially corresponding to a given depth range, each of said plurality of objects corresponding to a particular determined area, wherein said step of interpreting comprises;
creating a depth map for said correlated patches,interpreting said depth map to identify one or more regions corresponding to said given depth range, each of said plurality of objects corresponding to one of said one or more regions, andfiltering out said depth information for objects in said scene other than said plurality of objects.
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Abstract
A number of items present in a substantially linear queue are counted by examining two images of a scene including the queue that are taken from vantage points offset relative to each other. Depth information for portions of the scene is obtained by correlating equal sized patches in the images at a predetermined number of offsets, since closer objects will require more of an offset to align one image relative to the other than objects further away from video cameras creating the two images. A match score is determined at each offset. The best offset and the number of offsets to achieve it are stored for each patch. A plot is then created for offsets versus the number of patches at each offset having the best match. Peaks in the plot indicate the number of objects in the queue.
211 Citations
30 Claims
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1. A method for counting a plurality of objects currently present in a substantially linear queue, comprising:
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obtaining a stereo image of a scene including said substantially linear queue from a vantage point area in close proximity to one end of said substantially linear queue, wherein said stereo image comprises a first image and a second image, each of said plurality of objects in said first image being shifted relative to said second image; obtaining depth information from said stereo image for portions of said scene relative to said vantage point, comprising correlating patches in said first image with patches in said second image; and interpreting said depth information to determine areas of said stereo image substantially corresponding to a given depth range, each of said plurality of objects corresponding to a particular determined area, wherein said step of interpreting comprises; creating a depth map for said correlated patches, interpreting said depth map to identify one or more regions corresponding to said given depth range, each of said plurality of objects corresponding to one of said one or more regions, and filtering out said depth information for objects in said scene other than said plurality of objects. - View Dependent Claims (2, 3, 4, 5)
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6. A method for counting a plurality of objects currently present in a substantially linear queue, comprising:
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obtaining a stereo image of a scene including said substantially linear queue from a vantage point area in close proximity to one end of said substantially linear queue, comprising obtaining said stereo image from a pair of video cameras, said stereo image comprising a first image and a second image, wherein said pair of video cameras are separated such that each of said plurality of objects in said first image appears at an offset relative to said second image, wherein said pair of video cameras are parallel such that said offset is horizontal, wherein each said image comprises pixels arranged in rows and columns, and wherein said separation of said cameras is a function of a predetermined maximum length for said substantially linear queue, an expected spacing between each of said plurality of objects, a common field of view for each of said pair of video cameras and a number of pixels in a row of said stereo image; obtaining depth information from said stereo image for portion of said scene relative said vantage point; and interpreting said depth information to determine areas of said stereo image substantially corresponding to a given depth range, each of said plurality of objects corresponding to a particular determined area. - View Dependent Claims (7)
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8. A method for counting a plurality of objects currently present in a substantially linear queue, comprising:
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(a) obtaining a stereo image of a scene including said substantially linear queue from a vantage point area in close proximity to one end of said substantially linear queue, wherein said stereo image comprises a first image and a second image offset from said first image; (b) initializing a shift counter for counting a number of shifts of said first image relative to said second image; (c) correlating a patch of predetermined size from said first image with a patch of said predetermined size from said second image to determine a correlation indicator therefor; (d) storing said determined correlation indicator of step (c) as a maximum indicator for said patch from said first image and storing said initialized shift counter as a corresponding shift indicator for said maximum indicator; (e) shifting said first image relative to said second image; (f) incrementing said shift counter; (g) correlating said patch from said first image with a different patch of said predetermined size from said second image to determine a correlation indicator therefor; (h) comparing said determined correlation indicator of step (g) with said maximum indicator and replacing both said maximum indicator with said determined correlation indicator of step (g) and said corresponding shift number with said incremented shift counter if said determined correlation indicator of step (g) indicates a greater correlation than said maximum indicator; (i) repeating steps (e) through (h) for a predetermined number of shifts; (j) repeating steps (b) through (i) for a predetermined number of different patches from said first image; (k) creating a plot of depth frequency information, said plot plotting for each possible shift counter number a match indicator indicating a number of maximum indicators with a corresponding shift number equal thereto; and (l) determining relative peaks in said plot, each of said plurality of objects corresponding to a particular relative peak. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. Apparatus for counting a plurality of objects currently present in a substantially linear queue, comprising:
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means for obtaining a stereo image comprising a pair of images of a scene including said substantially linear queue; means for correlating patches of said pair of images to determine depths for corresponding areas of said scene relative to said obtaining means; means for providing depth frequency information for said correlated patches from which said plurality of objects is counted; and means for filtering out said depth frequency information corresponding to portions of said scene other than said plurality of objects. - View Dependent Claims (23, 24, 25)
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26. Apparatus for counting a plurality of objects currently present in a substantially linear queue, comprising:
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means for obtaining a stereo image of a scene including said substantially linear queue from a vantage point area in close proximity to one end of said substantially linear queue, wherein said stereo image comprises a first image and a second image, each of said plurality of objects in said first image being shifted relative to said second image; means for obtaining depth information from said stereo image for portions of said scene relative to said vantage point, comprising means for correlating patches in said first image with patches in said second image; and means for interpreting said depth information to determine areas of said stereo image substantially corresponding to a given depth range, each of said plurality of objects corresponding to a particular determined area, wherein said interpreting means comprises; means for creating a depth map for said correlated patches, means for interpreting said depth map to identify one or more regions corresponding to said given depth range, each of said plurality of objects corresponding to one of said one or more regions, and means for filtering out said depth information for objects in said scene other than said plurality of objects. - View Dependent Claims (27, 28, 29, 30)
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Specification