Abstract
Fourier Filtering is a well-known technique that found multiple practical applications such as e.g. radio frequency selection [1], noise reduction on images [2]. It has also be studied in fundamental research and leads to, for instance, transverse pattern stabilization [3]. To do so, some temporal or spatial frequencies are killed or diminished symmetrically with respect to the zero frequency (DC). Negative frequencies have, a priori, no sense physically except for analytical calculations, so that the notion of asymmetrical Fourier filtering would have no meaning. This is not true in optics, since spatial the Fourier transform of an input field coincides with its field distribution located in the focal plane of a lens, and negative frequencies correspond to one half of the Fourier picture. Thus, the concept of positive and negative frequencies holds in spatial optics and so asymmetrical Fourier filtering can be implemented.
© 2015 IEEE
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