4 
In order to achieve high uniformity of performance 
in production, pairing of elements, truing and spacing 
have to be rigidly controlled with newly developed 
retroflective centering equipment by which the location 
of centers of curvature of all elements relative to an 
accepted system axis are observed and corrected. Since 
these lens systems are used for projection in anaglyphic 
colors they are specially corrected for the spectral 
range in which they are to be used. 
Optical bench methods are employed to compensate 
radial distortion at the given magnification ratio. The 
nominal residual distortion curve is shown in Figure 1. 
10° 20° 30P 40° 50° 60° 
Figure 1 
A new method of internal reciprocal air spacing creates 
the possibility to compensate the lens system for any 
given magnification ratio, including infinity application. 
A Super Wide Angle Illumination System 
Conventional optical condensing systems of the re 
fractive variety become quite cumbersome and heavy if 
designed to illuminate a 120° field. They are very 
useful in applications of partial field illumination as 
exemplified by a number of plotter designs as e.g. 
Gallus Ferber, the Zeiss Stereoplanigraph, the Kelsh, 
Nistri and Williamson plotters, where physical dimensions 
and weight are limited. They, however, require mechani 
cal linkages and a motive force to place the light source- 
condenser system in an ever changing operational position 
while the stereomodel is being scanned with the measuring