14- 
There are, altogether, 10 first- and second-order transformation errors 
which, together with the two X and Y parallax errors comprise 12 errors, 
each of which must be reduced to low value for satisfactory viewing of the 
stereo images. All of the transformations may be controlled manually by the 
application of separate control signals into the transformation modulators. 
Adjustments could be provided which would enable the operator to adjust the 
amplitude and polarity of each control signal as required to produce regis 
tration of the images. In ARES these adjustments are performed automatically, 
the appropriate control signals being generated by the parallax analyzer and 
registration analyzer shown as separate blocks in Figure 6. 
IMAGE CORRELATION 
The primary sensing operation to be performed in image registration is 
the detection of parallax. As mentioned earlier, parallax is detected in 
electronic scanning systems by noting the difference in arrival times between 
corresponding portions of the left and right video signals. Such a time dif 
ference is a measure of the parallax between the images in a direction paral 
lel to the path being traced by the scanning spot at that instant. 
Figure 9 is a block diagram of a parallax analyzer suitable for use in 
the ARES device. As shown, there are four input signals to the parallax ana 
lyzer, namely, the left and right video signals, and the X and Y reference 
signals. 
X PARALLAX 
OUT 
Y PARALLAX 
OUT 
Figure 9.- Parallax analyzer (5.1).