Page 161 - Chalcogenide Glasses for Infrared Optics

Unconventional Lens Fabrication, Aspheric Surfaces, and Kinos 137

FIGURE 6.2 Infrared image made using the LTC camera with DPT lenses.

Figure 6.2 shows an infrared image produced by the camera using
the DPT lenses. The image was made in the AMI parking lot. Notice
the fence wire is clearly resolved and the hot tires on the vehicle are
prominent. Presently, AMI has only two infrared cameras for experi-
mental use. The first is an Agema 210, a 3- to 5-µm camera that has
proved useful in our infrared imaging bundle work. The second is a
Raytheon Palm IR BST uncooled bolometer 8- to 12-µm camera that
has been most valuable in evaluating lens performance. Both repre-
sent early technology and are not considered high-performance
cameras. But they were all AMI could afford for this purpose.
Adapter plates were required for every different lens we wanted
to evaluate. AMI wanted to use the 100-mm molded lens with our 8- to
12-µm camera. Unfortunately, the Palm IR has an optical chopper
blade in front of the detector array. The design of the 100-mm lens
was for the LTC camera; the back focal length of the camera was too
long to be in focus, the lens would hit the light chopper. Fortunately,
we could use that same mold with Amtir 5 to shorten the back focal
length. Our molding skills had improved to the point we did not hes-
itate to use different glasses with the same mold. So lens number 1
remained molded with Amtir 4 and lens number 2 was molded with
Amtir 5. An adapter plate was made and the lens was placed on the
Palm IR. A photograph of the camera with lens is shown in Fig. 6.3.
One may notice the coated lens does not look bright and shiny. The
reason is the fact the Amtir 4 must be coated at a low temperature