7 October 2014 Evaluation of super-resolution imager with binary fractal test target
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Today, new generation of powerful non-linear image processing are used for real time super-resolution or noise reduction. Optronic imagers with such features are becoming difficult to assess, because spatial resolution and sensitivity are now related to scene content. Many algorithms include regularization process, which usually reduces image complexity to enhance spread edges or contours. Small important scene details can be then deleted by this kind of processing. In this paper, a binary fractal test target is presented, with a structured clutter pattern and an interesting autosimilarity multi-scale property. The apparent structured clutter of this test target gives a trade-off between a white noise, unlikely in real scenes, and very structured targets like MTF targets. Together with the fractal design of the target, an assessment method has been developed to evaluate automatically the non-linear effects on the acquired and processed image of the imager. The calculated figure of merit is to be directly comparable to the linear Fourier MTF. For this purpose the Haar wavelet elements distributed spatially and at different scales on the target are assimilated to the sine Fourier cycles at different frequencies. The probability of correct resolution indicates the ability to read correct Haar contrast among all Haar wavelet elements with a position constraint. For the method validation, a simulation of two different imager types has been done, a well-sampled linear system and an under-sampled one, coupled with super-resolution or noise reduction algorithms. The influence of the target contrast on the figures of merit is analyzed. Finally, the possible introduction of this new figure of merit in existing analytical range performance models, such as TRM4 (Fraunhofer IOSB) or NVIPM (NVESD) is discussed. Benefits and limitations of the method are also compared to the TOD (TNO) evaluation method.
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Stéphane Landeau, Stéphane Landeau, "Evaluation of super-resolution imager with binary fractal test target", Proc. SPIE 9249, Electro-Optical and Infrared Systems: Technology and Applications XI, 924909 (7 October 2014); doi: 10.1117/12.2067499; https://doi.org/10.1117/12.2067499

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