with its vertical axis offset from the optical or viewing axis,, logic 
is provided to translate the table using the Ferranti metering 
system the proper number of counts to put the point to be marked 
under the proper die. The total distance is approximately 3 inches 
or approximately 75,000 counts. When the marking cycle is complete 
the table is returned to its original position. The marked point is 
visually checked for accuracy of marking. A mechanical adjustment 
to the individual marking units is provided for adjustment in the 
axis perpendicular to the travel of the table and varying the counts 
in the logic adjusts the position of the marking unit in the direction 
of travel. The marking die is rigidly held in a die chuck which, in 
turn, is held in a barrel. The barrel is fixed inside a core which 
is the inner race of the guidance bushing. Because the low pressure 
air is available and because of the stringent accuracy requirements 
for marking, the air is used as the vertical guidance bushing. A 
heating coil is used to apply indirect heat to the die. The coil is 
held in a ceramic coil form which is used because of its thermal, 
electrical, and mechanical properties. The vertical drive consists 
essentially of a spring loaded solenoid and drive wheel. A pin 
which is eccentrically located on the drive wheel is connected to 
the marking unit which provides for the vertical motion of the unit. 
When the solenoid is actuated and the drive wheel rotates, the 
marking unit translates downward, marks the image, and returns. The 
"throw" of drive wheel is larger than necessary for instantaneous 
contact, thereby allowing a finite and controllable contact time 
between the die and the emulsion. 
The scan system is composed of three flying spot scanners, one 
for each comparator table and one for the reference tables, an optical 
system, and photomultiplier tubes. Photomultiplier tubes are used to 
generate the video signals by sensing the light modulated by the 
emulsion of the diapositives or film input material. The optical 
system consists of a folded optical demagnification train with an 
image to object ratio of 1:16, a raster centering system, and a light 
collecting system. A K-mirror image rotating system is included in 
the optical train to rotate the raster through 360°. The prime 
lenses used in the demagnification train are a 2-inch focal length 
f/2 Minicard Ektar lens and a 152-inch focal length f/11 doublet lens. 
This combination gives an overall optical path length of 36.34 inches 
for the total reduction of 1:16. The light collecting system below 
the film emulsion plane consists of a 1.4-inch focal length, f/1.75 
condensing lens system. The raster centering system and intensity 
control systems operate essentially the same as the scan system.