Page 105 - Chalcogenide Glasses for Infrared Optics
P. 105
Glass Pr oduction 83
10 ×
3
10 × Experimental data
2
Viscosity (p)
10 ×
1
Prior estimate
(extrapolated from 10 7.6
p & 10 4.7 p data points)
0
10 ×
500 600 700 800
Temperature (°C)
FIGURE 3.11 Viscosity of TI 1173 glass measured in liquid range.
two average results were compared, the recast index increased by
about +0.0040. The increase was thought to be due to loss of Se and
Ge-Se vapors. The optical designer could then decide if glass could be
recast once, twice, or even 3 times and used based on the index change
and system design parameters such as focus. The dispersion param-
eters for the glass were left relatively unchanged.
Figure 3.12 shows the final configuration of the casting furnace
used at TI for TI 1173 glass. The chamber enclosure is round and large
with a single door in front. Inside is a large quartz crucible that holds
all the glass to be cast. Heaters are provided to melt and control the
temperature of the glass. Provisions are made for a powered stirring
device controlled from the top. A rod from the top is connected to the
ball joint in the bottom of the crucible that allows glass to flow into
the mold in the bottom chamber. Provisions are made for heating the
