Here's the Wiki on it:

http://en.wikipedia.org/wiki/AN/PAS-13

The original version was being developed by Hughes Aircraft Company & looked nothing like what it does now. That was circa 1990's.

The version used by Caddy was the Raytheon version circa early 2000's. Or maybe it was the Texas Instruments version from that same era ... can't remember now.

IIRC BAE Systems got the final production contract for the Army.

It's been 10 years since I've worked with the Thermal Imagers so the details are kinda fuzzy.