Modulation transfer function assessment for sampled imaging system: application of the generalized line spread function to a widespread infrared camera

摘要

Abstract: The line spread function (LSF) is a classical figure ofmerit used to derive the modulation transfer function(MTF) of an imaging system. However this test cannot bedirectly applied to cameras based on an infrared focalplane array (IRFPA), as these sampled systems exhibitaliasing effects. ONERA has proposed a new techniquecalled generalized line spread function allowing MTFassessment for sampled imaging systems. A testing ofspatial frequency filtering becomes possible until atleast twice the Nyquist frequency. The purpose of thispaper is to show that this method is well-adapted toIRFPA cameras. In particular, the effects of bad apriori estimation of the characteristics of the cameraare discussed. Secondly, we have carried on alaboratory experiment with a widespread infraredimaging system. The purpose is to demonstrateexperimentally the advantages of this new method, notonly in terms of performances but also in terms ofsimplicity of implementation and robustness. Theinfrared imaging system tested is a 512 by 512 Si:PtIR5120C Mitsubishi camera equipped with a F/1.2Angenieux lens. !4