Inverse design of a spatial filter in edge enhanced imaging

A spatial filter, as a key element in edge enhanced imaging, determines the resolution and the contrast of imaging. However, the conventional spiral phase filter (SPF) results in background noise near the edges of objects in the formed images due to the fact that the point spread function (PSF) of the SPF has sub-oscillations that decrease the edge resolution. In this Letter, we propose a method for inversely designing the spatial filter, aiming to achieve high-resolution images. We show that the sub-oscillations in the PSF of the filter can be, in principle, completely suppressed. Further, we experimentally demonstrate the edge enhancement, with high resolution, for both amplitude and phase objects by using our own designed filter. Our method may find potential applications in fingerprint identification and image processing.