Ivica Kopriva Harold Szu
e­mail: ivica.kopriva@public.srce.hr e­mail: szuh@onr.navy.mil

Reticle systems are considered to be the classical approach for estimating the position of a target in a considered field of view and are widely used in IR seekers. However, the disadvantage of the reticle trackers has been overly sensitivity to man­made clutters. We show that the nonlinear coherent version of Independent Component Analysis (ICA) theory can perhaps help alleviate the problem. When the processing device is redesigned properly by a band­pass filtering, the output signals are linear convolutive of the reticle transmission functions (rtf) considered as the unknown input source s i (t) signals in the context of ICA. That enables ICA neural network to be applied on the optical tracker output signals x i (t) giving on its outputs recovered rtf s (t). Position of each optical source is obtained by applying appropriate demodulation method on the recovered source signals. The contribution of this paper is demonstrating that the coherence between optical sources results in a nonlinear ICA problem that becomes linearized, when the optical fields are incoherent, or, when the proper design of the optical tracker converts the nonlinear coherent model into linear one by band­pass filtering operation. Consequently, the multisource limitation of the reticle based optical trackers can in principle be overcome for both coherent and incoherent optical sources. We therefore conclude that requirements necessary for the ICA theory to work are fulfilled for both coherent and incoherent optical sources.