Page 172 - Chalcogenide Glasses for Infrared Optics

148 Cha pte r S i x

for the same small lens in place both top and bottom. This approach
is much more productive from the standpoint of the number of
operators and molding units. Mold cost will still be a major factor.
The business volume must be there to support the effort.
Now, AMI is often asked about producing parts in terms of a
hundred thousand or more. Our molding approach will lend
itself to producing hundreds or a few thousand perhaps, but not
a hundred thousand. A small independent company such as
Amorphous Materials lacks the resources and the desire for such
an undertaking.

6.6 Problem of Refractive Index Change
When Pressure Molding
When a glass is pressure-molded, it must be heated above its glass
transition temperature. One must remember that below that tem-
perature, glass acts as a solid and will break if pressure is applied
to reshape it. As for any liquid, if enough pressure is applied, the
liquid is very slightly compressed. Since refractive index is a mea-
sure of the concentration of atoms per centimeter cubed, the index
increases in a positive sense. In optics, a small change in refractive
index is important, The change needs to be measured to see how
large a problem exists. Also, a way to avoid the problem may be
found.

AMI Infrared Refractometer
Previous discussions concerning the AMI infrared refractometer have
pointed out that measurements of a single prism in a single orienta-
tion are reproducible to a small number in the fourth decimal place.
In each instance of the data presented, the prism has been removed
and measured in the same orientation on different days. The data
presented in Table 6.2 support the claimed accuracy.
Previous discussions have pointed out that the lack of perfection
in the fabricated prism is overcome by measuring the prism in each of

Date N @ 3 µm N @ 4 µm N @ 5 µm
8/4/04 2.7616 2.7565 2.7533
8/6/04 2.7621 2.7569 2.7535
8/9/04 2.7621 2.7565 2.7534
Average 2.7619 2.7566 2.7534
±0.00016 ±0.00016 ±0.00007
TABLE 6.2 Amtir 5 Prism 03-1B, Orientation LD