Retroreflection Suppression Plate

Abstract

Infrared sensors have been called “the eyes of the digital battlefield” [1]. Military applications dominate the requirements today, especially for IRFPAs (infrared focal plane arrays, which are optical sensors placed at the focal plane of an IR optical system such as a camera, night vision system or night gun sight). In addition to the many military applications for IR systems such as target acquisition, search and track and missile seeker guidance, there is also great potential for IR systems in the commercial marketplace. IR systems can enhance automobile and aircraft safety, medical diagnosis and manufacturing quality and control. Uncooled long wavelength infrared range (LWIR) FPA’s, i.e. those not requiring cryogenic cooling equipment, have enjoyed significant recent advances, making them lighter, simpler and easier to install and maintain. These sensors are now being considered for many “Future Combat System” platforms to meet target acquisition, navigation and surveillance requirements. However, the reflectivity of current uncooled LWIR sensor technology is unacceptably high due to high refractive index semiconductors used in the FPA: If they are used in an otherwise “invisible” airplane, they can be seen, e.g. by CW search lasers as illustrated in Figure 10.1. In military applications it is therefore very important to minimize the signature of sensors in certain wavelength regions without compromising performance. Thus, it is highly desirable to reduce the reflectivity of uncooled imaging sensors.