7 
other applications suggested the development of an auto 
mated generator with a flexible range of ellipsoidal axes 
and eccentricities. Bausch & Lomb Inc. of Rochester, N.Y. 
undertook and success 
fully completed the 
development of a machine 
which permits the gene 
ration of ellipsoidal 
masters from 0° to 200mm 
separation of foci and 
with major axes from 
8-14 inches. (Figure 3). 
It utilizes a modified 
version of the principle 
of constructing an 
ellipse of given major 
and minor axes by means 
of a right angle whose vertex is guided along the circle 
scribed with a diameter equal to the major axis, and 
whose one leg is confined to pass through one of the focal 
points of the ellipse. The second leg is then always 
tangent to the curve. In some textbooks this principle 
of ellipse construction is called ”Gullstrand mechanism.” 
The machine is hydraulically operated and generates 
the master according to the design parameters. It starts 
with a coarsely preshaped terraced work piece and pro 
ceeds through a sequence of grinding stages to the final 
surface polish. By a special gaging method the shape of 
the rotational body is rigidly checked. In the final 
stage of polishing deviations from a true ellipsoidal 
shape are reduced to the order of .0001”. 
Replication from the convex master surface yields 
immediately a concave metal backed segment which after 
Figure 3