The Use of the Wigner Distribution Function for Deflning the Concept of Quasi-point Source, and the Application of this Concept to the Restoration of Defocused Images

We introduce the concept of quasi-point source (QPS) by means of the sampled Wigner distribution function (WDF), as applied to the detected image of a small incoherent disc object. A QPS is realized when the WDF of such image is always positive within the extended bandwidth corresponding to this function. To substantiate this concept, we employed a conventional microscope with Kohler illumination. We made use of a QPS to obtain an estimation of the defocused point spread function of an speciflc optical system. This function was employed next to construct the corresponding Wiener fllter, in order to restore defocused images of extended objects.