Point-spread function (PSF)

Point-spread function (PSF) — how an imaging system spreads the information from one ideal point across nearby pixels. Spanish: función de dispersión de punto.

In microscopy, astronomy and medical imaging a measured image is often blurred by such an optical response. The notebook builds a known one: a normalized 9×9 box, so each pixel becomes the average of its neighbourhood.

An average like that multiplies frequencies by a sinc-shaped response that shrinks fine detail and has zeros in it. Where the response is zero, there is nothing left to recover — the hard limit on any deconvolution.