8 
The printer exhibits a capability for excellent 
modulation transfer, essentially limited only by the 
numerical aperture of the lens system. The system has 
provided 72 line pairs per millimeter high contrast 
image transfer, which essentially establishes the limiting 
resolution of the present unit. 
With a relatively wide bandwidth light source the 
printer is capable of producing its outputs on color 
emulsions (Figure 16) . The experiments at RADC resulted 
in a choice of Ektachrome 6116 emulsion. The best color 
reproduction was achieved after several trials of varying 
the light intensity, a simple control provided on the 
printer. The colored orthophoto of Figure 16 is presented 
to demonstrate the color handling capability of the 
printer. The quality of this sample is not indicative 
of the present printer performance as the orthophoto was 
generated in 1970, before the modifications were made. 
DETAIL DESCRIPTION - OPTICAL SYSTEM 
Figure 4 depicts the optical schematic of the 
printer as it now exists, after a number of modifications 
of the original OMI unit. The upper portion of the 
optical train, consisting of a collecting lens and an 
imaging lens, comprises the slit forming optics. This 
system forms a 50 micron wide element of illumination 
upon the input photo with the long dimension of the line 
element being approximately 4 millimeters. The light 
filament is a line filament, exhibiting a near linear 
energy output. The filament can be rotated about the 
optical axis, and is mechanically linked to the dove 
prism rotation assembly. The filament is aligned with 
the local photo X direction and the dove prism is 
rotated to align the projected line element image along 
the output drum's Model X direction - which is always 
normal to the drum axis. As the input and output stages 
are translated, the filament alignment is controlled by 
the computer, based upon local photogeometry and com 
puted terrain slope. 
The viewing mirror, relay lens and screen comprise 
the means for viewing the fiducials in the interior 
orientation process. The mirror flips up out of the 
optical path when this is completed. 
The transfer optics are located below the input 
photo carriage and comprise elements to collect the 
rays from the illuminated line element and to collimate