Cross-correlation video tracker and method
First Claim
1. A device for deriving a signal indicative of the direction and distance of movement between successive video frames, said device comprising:
- an input for receiving a video signal;
means for storing elements from a frame of the video signal to establish a reference;
means comparing elements from a subsequent frame of the video signal with the stored reference elements for generating a difference signal representing the difference between a pair of cross-correlation signals dependent on the correlations of the subsequent frame elements and the stored reference elements at two predetermined opposite relative shifts;
means for generating a gain control signal;
means responsive to the difference signal and to the gain control signal for generating an error signal indicative of the amount of shift required to center the stored reference frame with respect to the subsequent frame; and
means for outputting the error signal.
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Accused Products
Abstract
A cross-correlation video tracker and method for automatically tracking a relatively moving scene by storing elements from a frame of a video signal to establish a reference frame and comparing elements from a subsequent frame with the stored reference frame to derive signals indicating the direction and angular distance of scene relative movement. A cross-correlation difference signal is generated which represents the difference between a pair of cross-correlation signals dependent on the correlations of the subsequent frame elements and the stored reference elements at two predetermined opposite relative shifts. A circuit is responsive to this difference signal for generating an error signal indicative of the amount of shift required to center the stored reference frame with respect to the subsequent frame. In order to maintain feedback loop stability as the system tracks different scenes which result in varying degrees of decorrelation even with constant shifts in scene position, the circuit responsive to the error signal is also responsive to a gain control signal which represents the difference between a pair of autocorrelation signals dependent upon the correlations of the elements of a representative frame of the video signal at substantially a zero shift and at a fixed predetermined shift. The representative frame of the video signal may be either the subsequent frame or the stored reference frame.
129 Citations
32 Claims
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1. A device for deriving a signal indicative of the direction and distance of movement between successive video frames, said device comprising:
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an input for receiving a video signal; means for storing elements from a frame of the video signal to establish a reference; means comparing elements from a subsequent frame of the video signal with the stored reference elements for generating a difference signal representing the difference between a pair of cross-correlation signals dependent on the correlations of the subsequent frame elements and the stored reference elements at two predetermined opposite relative shifts; means for generating a gain control signal; means responsive to the difference signal and to the gain control signal for generating an error signal indicative of the amount of shift required to center the stored reference frame with respect to the subsequent frame; and means for outputting the error signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A device for deriving a signal indicative of the direction and distance of movement between successive video frames, said device comprising:
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an input for receiving a video signal; means for storing elements from a frame of the video signal to establish a reference; means comparing elements from a subsequent frame of the video signal with the stored reference elements for generating an error signal indicative of the amount of shift required to center the stored reference frame with respect to the subsequent frame, the error signal being dependent upon a signal representative of the difference between a pair of cross-correlation signals dependent on the correlations of the subsequent frame element and the stored reference elements at two predetermined opposite relative shifts, divided by a signal representative of the difference between a pair of autocorrelation signals dependent upon the autocorrelations of the elements of a representative frame of the video signal at substantially zero shift and at a predetermined shift; and means for outputting the error signal. - View Dependent Claims (16, 17, 18, 19, 20)
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21. A cross-correlation video tracker comprising:
- sensing means for generating a video signal representing a scene which may be moving, said sensing means including controllable means responsive to a signal for moving said sensing means to track the scene;
means for receiving and storing elements from a frame of the video signal to establish a reference; means comparing elements from a subsequent frame of the video signal with the stored reference elements for generating an error signal indicative of the amount of shift required to center the stored reference frame with respect to the subsequent frame, the error signal being dependent upon a signal representative of the difference between a pair of cross-correlation signals dependent on the correlations of the subsequent frame elements and the stored reference elements at two predetermined opposite relative shifts, adjusted by a gain control signal; means for effectively moving the stored reference by an amount which is a function of the error signal, whereby the stored reference frame is centered with respect to the subsequent frame; feedback means for supplying the error signal to said controllable means whereby said sensing means follows the scene. - View Dependent Claims (22, 23, 24, 25, 26)
- sensing means for generating a video signal representing a scene which may be moving, said sensing means including controllable means responsive to a signal for moving said sensing means to track the scene;
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27. A method of deriving a signal indicative of the direction and distance of movement between successive frames of a video signal, said method comprising the steps of:
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storing elements from a frame of the video signal to establish a reference; and comparing elements from a subsequent frame of the video signal with the stored reference elements and generating an error signal indicative of the amount of shift required to center the stored reference frame with respect to the subsequent frame, the error signal being dependent upon a signal representative of the difference between a pair of cross-correlation signals dependent on the correlations of the subsequent frame element and the stored reference elements at two predetermined opposite relative shifts, divided by a signal representative of the difference between a pair of autocorrelation signals dependent upon the autocorrelations of the elements of a representative frame of the video signal at substantially zero shift and at a predetermined shift. - View Dependent Claims (28, 29, 30, 31, 32)
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Specification