for 
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le 
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f 
6 
Min à = X 
P Jd 
xP yj AS AX xj yj Ri(xj, yi) 
!withp*q-k. 
The area A; and the M,;, My; of Equations (12) are thus the zero order and first order moments 
respectively. By means of the first moments, the centroid for R;(x;, y;) is determined. By means of the 
second moments the principal axes and the principal radii of gyration can be determined. 
The implementation of this process, on-line with the scan, is shown in Figure 15 for the ith 
window. Here, the discrimination of points x¢, y; within the window aperture is controlled by the 
signals Xp;, yp; Where: 
If xp; = 1 and yg; = 1, then the point is a member of the set of points of window 
aperture i. 
or 
If xp; = 0 and yg; = 0, then the point does not belong to the set of points of 
% window aperture i. 
Within the sample signal gating module, this test for conjunction of xg; = 1, yg; = 1 serves 
two functions: 
#1) It provides the basis for generating the corresponding x;, y; control signals for the x;, y; 
points within the window. 
2) It provides the sampling control for the conversion of the level discriminated video signal 
R;(t) into control signal R;(x;, y;), which is shown as R;(x;), since y; is constant during the 
scan line. 
These x;, ÿ;, R;(x;) signals then go to the arithmetic unit modules where À, , M,; M,; are 
derived. The control signal F/F designates the odd or even field of the frame and accordingly goes 
to the y-moment arithmetic unit. 
By means of these control signals, this process of discrimination and arithmetic takes place 
on-line with the scan at the clock frequency of the horizontal oscillator. 
Each it^ window aperture discrimination-arithmetic unit is independent. They can (by 
design) be individually assigned to different video cameras (V4 , Vg, Vc), each with its own level 
dizerimination condition, and as a consequence the system can be extended to real-time two camera 
(s. Teo) or three camera applications. 
Since the initial development was for the single camera application, only one level comparator 
is used for the four units of the laboratory prototype. 
* To provide information to the operator as to where a window aperture is located in the frame, 
the window discrimination logic is used to provide enhancement of the perimeter of the window aperture 
in the video display. By means of other discrimination logic, the set of axes defined by Equations (7) 
are also displayed as shown in Figures 16, 17. With the insertion of these “cross hair" axes, whose 
origin is referred to as the “optical center”, one now has the analogy with a typical optical instrument. 
With knowledge of the defining basis for the set of points x;, y;, which for the laboratory 
prototype is; 
0 & x; < Ax; 
0 < y, € Ay, 
one can, by calculation, determine the A;, M,;, My; for all points in the window aperture i. 
25