-16- 
Multipliers Nos. 9 and 10 correlate the X and Y parallax signals with 
a reference signal XY produced by multiplying the X and Y reference sig. 
nals together. These multipliers, therefore, sense XY in X and XY in Y 
respectively, giving error signals which are used to control the appropriate 
second-order transformations in the pattern transformation circuitry. 
All of the multipliers in the registration analyzer are, in effect, cor 
relators and each develops an error output or error signal proportional to 
the magnitude of components in the parallax signal coherent with its particu 
lar reference input. Each of these error signals is delivered to the appro 
priate transformation modulator which in turn introduces a transformation in 
the scanning pattern which tends to reduce the magnitude of the particular 
registration error being sensed. There are 10 such feedback loops in the 
registration system plus the two displacement or shift corrections described 
previously. It is necessary that each of these loops be stable both sepa 
rately and in concert and to this end compensating networks are interposed 
in each error channel between the appropriate analyzing discriminator and 
modulator circuits. The operating characteristics of the final instrument 
are determined to a great extent by the manner in which this compensation 
program is carried out. 
IMAGE ENHANCEMENT 
The image enhancement aspects of ARES are modest and are confined to the 
automatic regulation of tone range and to a limited amount of edge enhancement. 
Figure 11 is a block diagram of the video processor and illustrates prin 
cipally the layout of the automatic gain control system used to provide con 
stant image contrast or tone range. The automatic gain control is conventional 
and adjusts amplification in such a manner that the output video amplitude re 
mains substantially constant in spite of variations in input amplitude owing 
to differences in local image contrast. In this way the full range of the 
viewing cathode ray tubes from dark to light is utilized. 
Figure 11.- Video processor (4.0).