Adaptive updating processor for use in an area correlation video tracker
First Claim
1. In an area correlation video tracker including an electro-optical sensor which generates frames of video information representative of an intensity pattern of the field of view of said electro-optical sensor corresponding to discrete intervals in time;
- means for partitioning a preselected portion of said generated video frames into an array of picture elements, the value of each picture element being representative of the gray level intensity corresponding to its index in said array, said array being additionally partitioned into a predetermined number of indexed subarray zones;
means for acquiring the gray level values of the picture element of a selected first subarray zone corresponding to an acquisition video frame; and
correlation means for cross-correlating, based on a predetermined metric correlation function, the gray level values of the picture elements of said selected first subarray zone with the picture element gray level values of said partitioned subarray zones of each of a number of video frames generated subsequent said acquisition video frame to identify a second subarray zone of picture elements in each of said number of subsequently generated video frames and to derive a cross-correlation metric value associated with each of said identified second subarray zones, the improvement of an adaptive updating means comprising;
means operative to perform an autocorrelation of the gray level values of the picture elements of said selected first subarray zone with the gray level value of the picture elements of an at least one predetermined third subarray zone of said acquisition video frame in accordance with said predetermined metric correlation function to derive a reference threshold correlation metric value and to further perform an autocorrelation of the gray level values of the picture elements of said identified second subarray zone with the gray level values of the picture elements of at least one predetermined fourth subarray zone of the same video frame in accordance with said predetermined metric correlation function to derive another threshold correlation metric value, said another threshold correlation metric value being derived for each of said number of subsequently generated video frames;
means operative to render an update condition based on the results of a comparison between one derived cross-correlation metric value and said reference threshold correlation metric value, said update condition causes the gray level values of the picture elements of said selected first subarray to be replaced with the gray level values of the picture elements of said identified second subarray corresponding to said one cross-correlation metric value and causes said reference threshold correlation metric value to take on the value of said another threshold correlation metric value derived from the video frame corresponding to said one cross-correlation metric value, whereby subsequent cross-correlation processing will be performed with the updated gray level values of the picture elements of the selected first subarray and updated threshold correlation metric value.
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Abstract
In an area correlation video tracker, a reference subarray of picture elements acquired from a selected track window array of picture elements of an acquisition video frame is cross-correlated in accordance with a predetermined metric function with the picture elements of the selected track window array of each of a number of video frames generated subsequent the acquisition video frame. From these cross-correlations, a minimum cross-correlation value is derived and a subarray of picture elements associated therewith is identified in the track window array of the subsequently generated video frames. An adaptive threshold processor performs autocorrelations in accordance with the predetermined metric function with the video information of the acquisition frame to derive a reference threshold correlation value and with the video information of each of the number of subsequently generated frames to correspondingly derive another threshold correlation value each. An update condition is rendered in the video frame having a derived one cross-correlation value greater than the reference threshold correlation value. The update condition causes the values of the picture elements of the reference subarray to be replaced with the values of the picture elements of the identified subarray corresponding to the one cross-correlation value and causes the reference threshold correlation value to take on the value of the another threshold correlation value derived in the video frame associated with the one cross-correlation value, whereby subsequent cross-correlations will be performed with the updated values until another update condition is rendered.
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Citations
16 Claims
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1. In an area correlation video tracker including an electro-optical sensor which generates frames of video information representative of an intensity pattern of the field of view of said electro-optical sensor corresponding to discrete intervals in time;
- means for partitioning a preselected portion of said generated video frames into an array of picture elements, the value of each picture element being representative of the gray level intensity corresponding to its index in said array, said array being additionally partitioned into a predetermined number of indexed subarray zones;
means for acquiring the gray level values of the picture element of a selected first subarray zone corresponding to an acquisition video frame; and
correlation means for cross-correlating, based on a predetermined metric correlation function, the gray level values of the picture elements of said selected first subarray zone with the picture element gray level values of said partitioned subarray zones of each of a number of video frames generated subsequent said acquisition video frame to identify a second subarray zone of picture elements in each of said number of subsequently generated video frames and to derive a cross-correlation metric value associated with each of said identified second subarray zones, the improvement of an adaptive updating means comprising;means operative to perform an autocorrelation of the gray level values of the picture elements of said selected first subarray zone with the gray level value of the picture elements of an at least one predetermined third subarray zone of said acquisition video frame in accordance with said predetermined metric correlation function to derive a reference threshold correlation metric value and to further perform an autocorrelation of the gray level values of the picture elements of said identified second subarray zone with the gray level values of the picture elements of at least one predetermined fourth subarray zone of the same video frame in accordance with said predetermined metric correlation function to derive another threshold correlation metric value, said another threshold correlation metric value being derived for each of said number of subsequently generated video frames; means operative to render an update condition based on the results of a comparison between one derived cross-correlation metric value and said reference threshold correlation metric value, said update condition causes the gray level values of the picture elements of said selected first subarray to be replaced with the gray level values of the picture elements of said identified second subarray corresponding to said one cross-correlation metric value and causes said reference threshold correlation metric value to take on the value of said another threshold correlation metric value derived from the video frame corresponding to said one cross-correlation metric value, whereby subsequent cross-correlation processing will be performed with the updated gray level values of the picture elements of the selected first subarray and updated threshold correlation metric value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- means for partitioning a preselected portion of said generated video frames into an array of picture elements, the value of each picture element being representative of the gray level intensity corresponding to its index in said array, said array being additionally partitioned into a predetermined number of indexed subarray zones;
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10. In an area correlation video tracker including an electro-optical sensor which generates frames of video information representative of an intensity pattern of the field of view of said electro-optical sensor corresponding to discrete intervals in time;
- means for partitioning a preselected portion of said generated video frames into an array of picture elements, the value of each picture element being representative of the gray level intensity corresponding to its index in said array, said array additionally being partitioned into a predetermined number of indexed subarray zones;
means for acquiring the gray level values of the picture elements of a selected first subarray zone corresponding to an acquisition video frame; and
correlation means for cross-correlating, based on a predetermined metric correlation function, the gray level values of the picture elements of said selected first subarray zone with the picture element gray level values of said additional subarray zones of each of a number of video frames generated subsequent said acquisition video frame to identify a second subarray zone of picture elements in each of said number of subsequently generated video frames and to derive a cross-correlation metric value associated with each of said identified second subarray zones, the improvement of an adaptive updating means comprising;means operative to perform autocorrelations in accordance with a predetermined metric function between (a) the gray level values of the picture elements of said selected first subarray zone and the gray levels of corresponding picture elements of said predetermined subarray zones in said preselected array of said acquisition frame to derive an autocorrelation metric value for each autocorrelation, and between (b) the gray level values of the picture elements of said identified second subarray zone and the gray level values of corresponding picture elements of said predetermined subarray zones in said preselected array of a video frame generated subsequent said acquisition frame to derive an autocorrelation metric value for each autocorrelation, whereby a group of autocorrelation metric values is derived for each of said number of subsequently generated frames corresponding to the subarray video information generated in each of said number of frames; means for segregating from the autocorrelation metric values derived from said acquisition video frame an initial set of autocorrelation metric values based on a first predetermined relationship between the indexes of the autocorrelated subarray zones and the index of said selected first subarray zone in the preselected array of said acquisition frame, and for selecting one autocorrelation metric value from said segregated initial set to be a reference threshold correlation metric value; and
for segregating from each of said groups of autocorrelation metric values correspondingly derived from the video information of each of said number of subsequently generated frames another set of autocorrelation metric values based on a second predetermined relationship between the index of said identified second subarray zone and the indexes of the autocorrelated subarray zones corresponding to the video frame from which said second subarray was identified, and for selecting one autocorrelation metric value from each of said another sets to each be an another threshold correlation metric value; andmeans for generating an update signal corresponding to the one of said number of subsequently generated video frames which has a derived cross-correlation metric value substantially greater than said reference threshold correlation metric value, said update signal causing the gray level values of the picture elements of said selected first subarray zone to be replaced with the gray level values of the picture elements of said second subarray zone identified from said one subsequently operated video frame and causes said reference threshold correlation value to take on the value of said selected another threshold correlation metric value corresponding to said one subsequently generated video frame, whereby subsequent cross-correlation processing will be performed with the updated gray level values of said first subarray zone and the updated threshold correlation metric value. - View Dependent Claims (11, 12, 13, 14, 15, 16)
- means for partitioning a preselected portion of said generated video frames into an array of picture elements, the value of each picture element being representative of the gray level intensity corresponding to its index in said array, said array additionally being partitioned into a predetermined number of indexed subarray zones;
Specification