Dual mode video tracker
First Claim
1. A method of establishing a size of a correlation tracking gate in a correlation tracking system of a type which generates tracking error signals from input electromagnetic video signals Vi,j (k) utilized to form one video frame k of a two dimensional image plane having coordinates (ε
- ,η
) where ε
represents an elevation and η
represents an azimuth, said image plane being defined by a plurality of pixels each having a discrete location (i,j) in the image plane along coordinates ε and
η
respectively and wherein said tracking gate is defined by N×
M pixels along coordinates η and
ε
respectively, said method comprising the steps of;
(a) generating a reference map value for each pixel according to the relationship
space="preserve" listing-type="equation">MAP.sub.ij (k)=W.sub.1 V.sub.ij (k)+(1-W.sub.1)MAP.sub.ij (k-1)where W1 is a weighting factor having a value 0≦
W1 ≦
1;
(b) generating a first weighting function Weij (k) related to relative values of pairs of pixels along the ε
coordinate;
(c) generating a second weighting function Wdij (k) related to relative values of pairs of pixels along the η
coordinate;
(d) generating first and second respective correlation error signals δ
'"'"'d (k) and δ
'"'"'e (k) for each image plane frame using the first and second weighting functions Weij (k) and Wdij (k);
(e) generating a gradient function GFij (k) for each pixel within a gradient gate defined by YxZ pixels, according to the relationship
space="preserve" listing-type="equation">GF.sub.ij (k)=[We.sub.ij (k)].sup.2 +[Wd.sub.ij (k)].sup.2,said gradient function GFij (k) representing a measure of information content within the tracking gate; and
(f) altering the size of said tracking gate using the gradient function GFij (k) generated in step (e).
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Abstract
Point and area target tracking are employed by a dual mode video tracker which includes both a correlation processor (30) and a centroid processor (32) for processing incoming video signals representing the target scene (20) and for generating tracking error signals over an entire video frame. A microcomputer (26) controls the operation of the correlation and centroid processors, as well as a preprocessor (28) which preconditions the incoming video signals. The tracker operates in any of several modes in which the correlation and centroid processors function either independently or cooperatively with each other. The correlation processor generates a reference map in pixel format which is used to produce azimuth and elevation optimal weighting values for each pixel in the field-of-view. The reference map is recursively updated. The track gate for the correlation processor is automatically sized using a gradient function derived from the optimal weighting values. The gradient function is also employed along with difference video to determine correlation tracking status. The correlation and centroid tracking errors may be combined to form a composite signal defining a true complementary function.
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Citations
16 Claims
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1. A method of establishing a size of a correlation tracking gate in a correlation tracking system of a type which generates tracking error signals from input electromagnetic video signals Vi,j (k) utilized to form one video frame k of a two dimensional image plane having coordinates (ε
- ,η
) where ε
represents an elevation and η
represents an azimuth, said image plane being defined by a plurality of pixels each having a discrete location (i,j) in the image plane along coordinates ε and
η
respectively and wherein said tracking gate is defined by N×
M pixels along coordinates η and
ε
respectively, said method comprising the steps of;(a) generating a reference map value for each pixel according to the relationship
space="preserve" listing-type="equation">MAP.sub.ij (k)=W.sub.1 V.sub.ij (k)+(1-W.sub.1)MAP.sub.ij (k-1)where W1 is a weighting factor having a value 0≦
W1 ≦
1;(b) generating a first weighting function Weij (k) related to relative values of pairs of pixels along the ε
coordinate;(c) generating a second weighting function Wdij (k) related to relative values of pairs of pixels along the η
coordinate;(d) generating first and second respective correlation error signals δ
'"'"'d (k) and δ
'"'"'e (k) for each image plane frame using the first and second weighting functions Weij (k) and Wdij (k);(e) generating a gradient function GFij (k) for each pixel within a gradient gate defined by YxZ pixels, according to the relationship
space="preserve" listing-type="equation">GF.sub.ij (k)=[We.sub.ij (k)].sup.2 +[Wd.sub.ij (k)].sup.2,said gradient function GFij (k) representing a measure of information content within the tracking gate; and (f) altering the size of said tracking gate using the gradient function GFij (k) generated in step (e). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- ,η
-
9. A method of determining correlation track quality in a correlation tracking system of a type which generates tracking quality error signals from input electromagnetic video signals Vij (k) utilized to form one video frame k of a two dimensional image plane having coordinates (ε
- ,η
) where ε
represents an elevation and η
represents an azimuth, said image plane being defined by a plurality of pixels each having a discrete location (i,j) in the image plane along coordinates ε and
η
respectively, and wherein correlation is performed over a track gate defined by NxM pizels along coordinates and respectively, said method comprising the steps of;(a) recursively generating a reference map value for each pixel according to the relationship
space="preserve" listing-type="equation">MAP.sub.ij (k)=W.sub.1 V.sub.ij (k)+(1-W.sub.1)MAP.sub.ij (k-1)where W1 is a weighting factor having a value of 0≦
W1 ≦
1;(b) subtracting reference map values MAPij (k) from the video signals Vij (k) of a subsequent frame to produce a difference video Δ
Vij (k);(c) generating a first weighting function Weij (k) related to pixels along the ε
coordinate;(d) generating a second weighting function Wdij (k) related to pixels along the η
coordinate;(e) generating first and second respective correlation error signals δ
'"'"'d (k) and δ
'"'"'e (k) for each image plane frame using said first and second weighting functions Weij (k) and Wdij (k);(f) defining border gates outside of and adjacent to said track gate, summing a value of the difference video Δ
Vij (k) over said track gate for each image plane frame to produce a track gate sum; and
summing the difference video Δ
Vij (k) over said border gates for each image plane frame to produce a border gate sum;(g) generating a gradient function GFij (k) for each pixel in a gradient gate defined by YxZ pixels according to the relationship
space="preserve" listing-type="equation">GF.sub.ij (k)=[We.sub.ij (k)].sup.2 +[Wd.sub.ij (k)].sup.2 ;(h) summing the gradient function GFij (k) over the gradient gate for each image plane to produce a gradient function sum; and
,(i) generating an indication of track quality using the track gate sum, border gate sum and gradient function sum. - View Dependent Claims (10, 11, 12, 13)
- ,η
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14. In a method of determining correlation track quality in a correlation tracking system wherein difference video signals are accumulated over a track gate and used as an indicator of track quality status, the improvement wherein the method further comprises:
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defining at least one border gate that is outside of and adjacent to said track gate; accumulating said difference video signals over said defined border gate to generate a border gate sum; and using the border gate sum as an additional indicator of track quality status. - View Dependent Claims (15, 16)
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Specification