Digital output can be provided for all three axes so that a digitizer can be connected for 
  
recording the profile data on magnetic tape. A punch card readout can be used but this 
limits the readout speed considerably. 
In order to obtain maximum accuracy and stability the x, y and z carriages are driven by 
long life ball-bearing lead screws capable of sustaining high acceleration. Instead of providing a 
separate orthophoto carriage, the orthophoto print and contour segment cathode ray tubes 
are mounted together with the Z-carriage drive and Z-readout on the X-carriage. This | 
assures a minimal error between the space rod intersection and the orthophoto centre. 
The addition of an independent orthophoto link necessitated the use of an optical multi- 
plexer in the right hand side optical path. A blue pass characteristic is used as in the B8 
Stereomat for the correlation flying spot scanner, but the viewing light band is limited 
to a green pass with the orthophoto flying spot scanner occupying the yellow/red part of e eo 
the visible spectrum. The left hand side optics utilizes the correlation and viewing optics 
only. Careful light filtering has realized an interference free signal for both the correlation 
and the orthophoto link. 
An optical reduction of six from the ortho CRT to the diapositive is used to obtain a reso- 
lution of 60 lines per mm at the diapositive plane. For improved operation in areas of small 
detail an optical reduction of three rather than two in the B8 Stereomat is used for the 
correlation scan. 
The location of the ortho and contour segment print CRT's on the X-carriage required the 
construction of the plotter inside a darkroom environment for protection of the film during 
exposure. 
The electronic control circuitry located in bays underneath the plotter has been built on 
sliding racks, so that all parts are easily accessible for service. 
Electronics 
The main parts of the electronic control circuitry are: | 
The correlator: 'The correlator uses a combination random noise — circular scan for the 
extraction of the x and y parallax, slope direction, magnitude signal and the correlation 
level signal. 
The x parallax signal is used to control the z motor for continuous removal of the x parallax. 
The y parallax signal is used during orientation to null the y parallax and during the pro-