In scene-based nonuniformity correction (NUC) methods for infrared focal-plane array cameras, the problem of ghosting artifacts widely affects the sensitivity of the imaging system and visibly decreases the image quality. Ghosting artifacts can also degrade the performance of several applications, such as target detection and tracking. We carried out a detailed analysis of the problem using a well-established NUC technique: the least mean square Scribner's algorithm. In order to solve some drawbacks of the original Scribner's algorithm, we introduced in the scheme a new technique that mitigates ghosting. Such technique relies on the employment of an edge-preserving spatial filter for the purpose of computing reliable spatial estimates. We tested the effectiveness of the new technique applying the improved NUC method to an experimental IR sequence of frames acquired in the laboratory. Finally, the performance of the proposed method was discussed and compared to that yielded by a well-established deghosting technique. c 2010 Society of Photo-Optical Instrumentation Engineers. [DOI:10.1117/1.3425660

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The LMS-based adaptive non-uniformity correction (NUC) technique, known in the literature as Scribner's algorithm, is an efficient method to mitigate the presence of fixed pattern noise in video sequences acquired by thermal cameras. Unfortunately, ghosting artefacts can be generated from the process of NUC depending on the edges that characterise the scene inside the sensor's field of view. Introduced is a de-ghosting technique based on the computation of the statistics of the error signal employed in the Scribner's algorithm. Such a technique is characterised by a small computational load which is the most important requirement for real-time applications. Experimental results demonstrate its good performance and de-ghosting capabilitie

Software design and development in Free/Open Source projects are analyzed through the lens of the theory of modularity applied to complex systems. We show that both the architecture of the artifacts (software) and the organization of the projects benefited from the paradigm of modularity in an original and effective manner. In particular, our analysis on empirical evidence suggests that three main shortcuts to modular design have been introduced and effectively applied. First, some successful projects inherited previously existing modular architecture, rather than designing new modular systems from scratch. Second, popular modular systems, like GNU/Linux kernel, evolved from an initial integrated structure through a process of evolutionary adaptation. Third, the development of modular software took advantage of the violation of one fundamental rule of modularity, that is, information hiding. Through these three routines, the projects can exploit the benefits of modularity, such as concurrent engineering, division of labor, decentralized and parallel development; at the same time, these routines lessen some of the problems posed by the design of modular architectures, namely imperfect decompositions of interdependent components. Implications and extensions of Free/Open Source projects experience are discussed in the conclusions.

The paper introduces the analysis carried out by Selex ES (SE) for the development of a third generation IRST system based on large format MWIR sensors, separable in blue and red bands. In the feasibility study, physical constraints have been evaluated relying on different optics and scanning options. The goal is a system based on distributed heads to cover 360 with a resolution better than 0.3 mrad and high frame rate that allow to take advantage of the typical atmospheric phenomena of the maritime environment as scintillation and super and sub refraction. Two critical aspects were investigated: (i) the setting of an adequate scanning mechanism to assure a high frame rate and (ii) the stitching of the collected images while maintaining the bit-depth so as to avoid abrupt changes of SNR at the seams between two subsequent images