Page 166 - Chalcogenide Glasses for Infrared Optics

142 Cha pte r S i x

FIGURE 6.9 Photograph demonstrating the performance of the molded Amtir
4-Amtir 5 100-mm FL IR lens mounted on the Palm IR camera.

is not visible at all in the narrow mode but shows up slightly in the
wide field. Figure 6.9 shows a photograph taken of the same scene
only using the molded Amtir 4-Amtir 5 100-mm FL IR lens again
mounted on the Palm IR camera. Notice the machinery against the
wall is now clearly visible. The image of the person is larger and
more detailed. Figure 6.10 shows in the bottom photograph a visible
image of the high school track. Look closely and you will see a small
white image of a person at the far end of the track. The person is
about 170 yd from the camera. The top image was taken using the
218-mm IR lens mounted on the Palm IR very early in the morning.
The cool background makes the warm person very visible as a white
object. The person is the author. In this case, the camera was on a tripod
aimed at the distant location. The camera was turned on, and the
author walked to the distant point. Being alone made best focus
adjustments impossible. Nevertheless, the shape of a person was clearly
distinguishable.
The composition of Amtir 5 was precisely selected to provide a
near-zero thermal change in refractive index in both bands, 3 to 5 µm
and 8 to 12 µm. The unique value of Amtir 5 was the fact that athermal
systems can be designed and built without the need for mechanical
thermal compensating parts. Such devices were an extra complica-
tion and expense to infrared system designers. After the glass was
developed, LMCO built a wide field of view airborne system and
confirmed by Dan Woody of LMCO a less than 1 percent change in