The IIR is the most advanced technology and the design is applicable to many missiles which are projected to exist in the next decade. Infrared technology has replaced the radar-guided missiles. The missile guidance system based on infrared technology or the IIR seekers does not provide any indication that they are tracking the missile and therefore called as passive devices. It has become very necessary to study the defense strategy related to Infrared technology. The effectiveness of the overall missile system is determined by the individual components and the key parameters that describe them. The design equations corresponding to the efficiency of different components used in the substems are discussed. The IIR seeker is a very critical element used in the guidance system of the missiles. Many disciplines related to the IIR missile such as signal processing, optics, microelectronics, manufacturing, and stabilization are integrated together and are discussed in the paper.