Optical design of a dual band infrared seeker for precision guided systems

Infrared guided systems are used to track the target and destroy it, by using the radiation emitted from it. The main components of the guided systems can be listed as follows: a dome, a lens-set (or mirrors) and a detector. In this study, the optical design of a seeker, operating in two bands of infrared (MWIR–LWIR), is performed. Dual-band optics design has been developed by using two softwares: Zemax, OpticStudio. Before the design the seeker-optics is started, the commercially available dual-band IR detectors are searched by comparing the performances of the latest detector technologies. By using the optical parameters of the selected detector, the design of the IR imaging seeker is completed for the operation within the wavelength range of 3 – 10 µm. The temperature dependence of the optical design is also examined by using four different body materials, for the large temperature interval ranging from –40 to +80 °C. The defocusing effect caused by using different materials is fixed by passive-optical-athermalization technique. The design is completed evaluating the cost and availability of the materials used in the design. The field of view of the optical system is found to be 16°. MTF value of each field is higher than 50% when the spatial frequency takes a value of 23 lp/mm. The results are analyzed and discussed in terms of spot-diagram, modulation transfer function (MTF), Seidel diagram and encircled energy distribution.