Device provides two-dimensional correlation of video data. Operation is reliable, accurate, and predictable

Cornwell, D. F.

Geise, P. E.

Petcher, M.

English

NASA Technical Reports Server

.October 1975
NASA TECH BRIEF 
Marshall Space Flight Center
B75-10265 
rNj 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington. D.C. 20546. 
Real-Time Video Correlator 
The problem: 
Two-dimensional correlation of video data is a 
complicated and slow procedure. Some of the 
standard methods include the use of optical sources, 
video disks, and sequential digital calculations. These 
methods are expensive; none operates in real time. 
The solution: 
A new real-time video correlator is fast and 
inexpensive.
How it's done: 
The correlator as shown in the illustration includes 
11 line delays and 12 line correlators. The real-time 
digitized video (TTL logic level) is fed into the line 
delays (MOS 64-bit shift registers) serially. At the 
same time, any information available at the input of 
each line correlator is clocked through. During the 
first line cycle, the first line of live video data is 
clocked through line correlator 1. During the second 
line cycle, the first line of live video data is clocked 
through line correlator 2, and the second line through 
correlator 1, etc. 
.
______ 	 _________	 _______ 	 I Line Delay ILine 
	
C.Video In ______I Lower 	 ___
11 
	
Cutoff	 1	 1 
Threshold I	
.j Line Delay 
J	 f 
Line Delay 
	
I	 Line	 I	 I	 Line	 I	 Line 
	
I	 Corretator	 I Correlator	 Correlator 
	
I	 12	 3 I	 1 1	 2 
Clock
Summing Network 
Horizontal Vertical 
Sync	 Sync
Analog 
Correlation 
Value 
Position
 
I Peak Sense I Correlation I	 and	 I	 Peak Counter	 I	 Hold	 I 
Position
of
Correlation Peak 
Real-Time Video Correlator
(continued overleaf) 
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https://ntrs.nasa.gov/search.jsp?R=19750000265 2020-03-19T20:14:37+00:00Z
The input video entering a line correlator is 
available to a series of 12 paired shift registers. One 
side of the paired series is continuously clocked during 
the correlation. This permits the physical translation 
of a line of live data relative to a line of stationary 
reference data, namely, that stored in the remaining 
side of the paired series. The outputs of each of the 12 
pairs of registers are put through EXCLUSIVE-OR 
gates and are summed. This corresponds to the 
output of the single line correlator, which is 
one-twelfth of the total input to the summing 
network. 
Basically, the 11 line delays serve to translate the 
real-time image vertically (Y direction) with respect to 
the stored image, whereas each line correlator serves 
the function of horizontal translation (X direction). 
The stationary line of data (reference) is one of the 12 
lines of the stored reference scene. If the operator 
desires to update or change the reference, the memory 
update clock is enabled, and the incoming video is fed 
through both sides of the paired series of registers in 
each line correlator but is frozen into one side only at 
the designated point. At that time the memory update 
clock is disabled. 
The outputs of all 12 line correlators are summed 
with each clock pulse and are fed into a peak 
sense-and-hold module. At that point the operator 
can monitor the analog correlation values. The peak 
detector tracks the correlation value and holds the 
peak value per frame. A free-running synchronous 
position counter assigns a count (coordinate) to each 
successive value of the correlation output and also 
registers per frame the coordinate assigned to the 
maximum correlation value attained at that frame.
A prototype correlator has undergone rigorous 
testing and has been the subject of numerous 
demonstrations. Its operation has been extremely 
reliable, accurate (within present constraints on 
resolution and memory, which are easily removed), 
and quite predictable. Manual operation of the unit 
also has been made easy. 
Note: 
Requests for further information may be directed in 
writing to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code ATO1 
Marshall Space Flight Center, Alabama 35812 
Reference: B75-10265 
Patent status: 
Inquiries concerning rights for the commercial use 
of this invention should be addressed to: 
Patent Counsel 
Marshall Space Flight Center 
Code CCO1 
Marshall Space Flight Center Alabama 35812 
Source: P. E. Geise, Jr., M. Petcher, 
and D. F. Cornwell of
Sperry Rand Corp.
(MFS-23200)
. 
Categories: 02 (Electronics Systems) 
B75-10265	 03 (Physical Sciences)


Real-time video correlator

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