The subject of signal theory was developed particularly after the Second World War [Shannon, Wiener]; developments in telecommunications, sonar and radar opened numerous fields of applications. Using this theory, the ability of a System to transmit Information may be quantitatively evaluated. About the same time, optical engineers had the idea of treating an optical image as a 2-D spatial message and to evaluate the quantity of Information that it contained. In 1947, Duffieux1 developed on a theoretical and experimental basis the harmonic analysis of images; optical instruments could be evaluated by their ability to reproduce periodic test patterns of shorter and shorter spatial periods, that is to say, of higher and higher spatial frequency, until a cut-off frequency is reached beyond which the image is no longer reproduced.
KeywordsSpatial Frequency Radiation Pattern Signal Theory Main Lobe Visible Domain
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