Segmentation method for use against moving objects
First Claim
1. A method of detecting a moving object in a plurality of image frames taken at different times, each image frame containing the object and background clutter, the method comprising the steps of:
- a) registering the background of at least three image frames;
b) determining a median pixel value for each pixel position of the registered image frames to construct a registered image frame representative of only the background of the three image frames without the object;
c) subtracting the median pixel values from pixels in a selected one of the image frames to form a difference image; and
d) applying a threshold to the difference image whereby pixel values exceeding a given threshold level are associated with the position of the moving object.
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Abstract
Three image frames containing an object of interest and background clutter are taken at successive time intervals and stored in memory. The background of images A, B and C are registered preferably using an area correlator 12. A median filter 16 is used to select a median value from the registered image frames. Then, subtractor 18 serves to subtract the median pixel values from one of the image frames. This difference output is then thresholded to provide a binary signal whose pixel values exceeding the threshold levels are generally associated with the position of the moving object.
142 Citations
17 Claims
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1. A method of detecting a moving object in a plurality of image frames taken at different times, each image frame containing the object and background clutter, the method comprising the steps of:
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a) registering the background of at least three image frames; b) determining a median pixel value for each pixel position of the registered image frames to construct a registered image frame representative of only the background of the three image frames without the object; c) subtracting the median pixel values from pixels in a selected one of the image frames to form a difference image; and d) applying a threshold to the difference image whereby pixel values exceeding a given threshold level are associated with the position of the moving object. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of detecting moving objects in cluttered images, said method comprising the steps of:
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a) sensing a first scene at a given time which contains the moving object and background and storing the first scene in a memory; b) sensing substantially the same scene at a subsequent time and storing it as a second image frame in a memory; c) sensing substantially the same scene and storing it as a third image frame in a memory; d) using an area correlator to substantially register the image frames; e) selecting a median pixel value for each pixel position of the registered image frames to construct a registered image frame representative of only the background of the of three image frames without the object; f) subtracting the median pixel values from pixel values in the third image frame to thereby form a difference image; and g) generating a binary output signal by thresholding the difference image against preselected positive and negative threshold levels chosen as a function of noise in the image frames whereby pixel values in the difference image exceeding the positive and negative threshold values are generally associated with dark and bright portions of the moving object, respectively. - View Dependent Claims (10)
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11. Apparatus for detecting a moving object in a plurality of image frames taken at different times, each image frame containing the object and background clutter, the apparatus comprising:
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means for registering the background of at least three image frames; means for determining a median pixel value for each pixel position of the registered images to construct a registered image frame representative of only the background of the three image frames without the object; means for subtracting the median pixel values from pixels in a selected one of the image frames to form a difference image; and means for applying a threshold to the difference image whereby pixel values exceeding a given threshold level are associated with the position the moving object. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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Specification