Design of a cryogenic IR detector with integrated optics

Cryogenically cooled IR detectors, which are used in applications such as situational awareness, search & track, missile launch and approach warning, typically use wide angle, single field of view optical systems. We describe a complete IR imaging optical assembly for such applications, which is mounted inside a cold shield and is maintained at a stabilized cryogenic temperature inside the dewar. A typical system houses two to four lenses and a cold filter, and weighs 5 grams or less. Despite this integration and added complexity, the resulting Detector-Dewar-Cooler Assembly (DDCA) has overall dimensions similar to those of equivalent-performing DDCAs without integrated optics. Moreover, Compact designs integrating wide-angle optics and a warm, high-magnification, telescope module for narrow FOV applications are seen as a straightforward extension of our system. We conclude with an in-depth, technical overview describing the design considerations for a typical wide-field imaging system.