One interesting feature of diffraction is that the image of a point source that is imaged by a system with a circular aperture is typically a large central lobe and a series of concentric but less intense rings (lobes). Interestingly, if the aperture were not a hard stop, but instead were composed of a graded density ring of gaussian transmission profile the image of a point source would not have rings but would instead be a gaussian blur, i.e. one central lobe with a rapidly decreasing intensity when moving away from the main part of the lobe.

Laser physicists and chemists actually produce good approximations to gaussian beam profiles in the laboratory, but their methods are not useful for producing two dimensional images.

I just thought you might want to know that bit of optical esoterica.