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AUTOMATIC SEARCH SYSTEM
The purpose of the search system is to automatically locate and
follow any stereomodel contours that exist for a particular elevation in
model space.
The search pattern selected is a compromise between efficiency
and ease of instrumentation. The pattern consists of a series of straight-
line searches which radiate (1) from the center of the flying spot scanner
tube during the first mode of operation and (2) from the edges of the scan
ner tube inward toward the center during the second mode of operation. As
a stereomodel contour is printed, as a result of one search line, the search
pattern will resume with the next sequential search line.
Digital circuitry is predominantly used in instrumenting the auto
matic search system. Analog operations on selected digital pulses provide
the required wave shapes for search deflection. The search system instru
mentation provides eight spokes searching outward from the scanner tube
center in a linear fashion, followed by four spokes searching from the edge
of the scan cathode-ray tube inward to center. Crossing a contour inhibits
the search generator so that, when it is restarted, the search sequence is
continued. After the entire search pattern has been completed, the search
system stops; and a visible light indicates to the operator that a new ele
vation setting is required in the stereomodel. The search sequence of the
rosette scan pattern is shown in Figure 4.
CORRELATION TECHNIQUES UTILIZED IN
CONJUGATE IMAGE MATCHING
Correlation techniques are utilized to indicate a match of conju
gate image points from a stereo diapositive pair. The detection of such a
match is fundamental to the problem of locating and tracing stereomodel
contours.
The general correlation function is given by:
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