The point spread function (PSF) describes the response of an imaging system to a point source or point object. A more general term for the PSF is a system's impulse response, the PSF being the impulse response of a focused optical system. The PSF in many contexts can be thought of as the extended blob in an image that represents an unresolved object. In functional terms it is the spatial domain version of the modulation transfer function. It is a useful concept in Fourier optics, astronomical imaging, electron microscopy and other imaging techniques such as 3D microscopy (like in Confocal laser scanning microscopy) and fluorescence microscopy. The degree of spreading (blurring) of the point object is a measure for the quality of an imaging system. In incoherent imaging systems such as fluorescent microscopes, telescopes or optical microscopes, the image formation process is linear in power and described by linear system theory. This means that when two objects A and B are imaged simultaneously, the result is equal to the sum of the independently imaged objects. In other words: the imaging of A is unaffected by the imaging of B and vice versa, owing to the non-interacting property of photons. The image of a complex object can then be seen as a convolution of the true object and the PSF. However, when the detected light is coherent, image formation is linear in the complex field. Recording the intensity image then can lead to cancellations or other non-linear effects.
Read more about Point Spread Function: Introduction, Theory, History and Methods, PSF in Microscopy, The PSF in Astronomy, Point Spread Functions in Ophthalmology
Famous quotes containing the words point, spread and/or function:
“I laugh when I think that all of Rome made it a point not to pronounce Drusilla’s name. Because Rome was mistaken for all those years. Love is not enough for me, and I understood that then.... To love someone is to accept to grow old with her. An old Drusilla is far worse than a dead one.”
—Albert Camus (1913–1960)
“Cows sometimes wear an expression resembling wonderment arrested on its way to becoming a question. In the eye of superior intelligence, on the other hand, lies the nil admirari spread out like the monotony of a cloudless sky.”
—Friedrich Nietzsche (1844–1900)
“Morality and its victim, the mother—what a terrible picture! Is there indeed anything more terrible, more criminal, than our glorified sacred function of motherhood?”
—Emma Goldman (1869–1940)