Page 159 - Chalcogenide Glasses for Infrared Optics

Unconventional Lens Fabrication, Aspheric Surfaces, and Kinos 135

bundles produced at AMI. Later, a second low-softening glass was
2
developed for molding, Amtir 5, similar to Amtir 4 but with a thermal
change in refractive index of essentially zero in both the 3- to 5-µm
and 8- to 12-µm bands. Also, the glass had a thermal expansion that
matches that of aluminum. The glass confirmed an opinion expressed
3,4
by the author many years ago that such a unique composition could
be selected. The AMI Amtir 5 glass composition is protected by U.S.
Patent 6,984,598.
Early experiments carried out with Lockheed Martin personnel
involved slump molding of Amtir 4 glass using Pyrex spherical molds.
Results showed that less than one wave rms was easily achieved on
one surface. Attention turned to precision pressure molding. The first
AMI unit was built, and efforts turned to developing the molding pro-
cess. A photograph of the first unit is shown in Fig. 6.1. The design is
simple and relatively inexpensive, built from parts obtained locally.

FIGURE 6.1 Photograph of the AMI lens molding unit.