re: diffraction

[P3D Richard M. Koolish <koolish@xxxxxxx>]

Joshua Rubin writes:

> If diffraction is caused by edges, what if the aperture were a small
> circular gradient on a transparent film where the diaphragm would otherwise
> be, instead of a sharply-defined hole?  Then there wouldn't be an edge per
> se.  Would that eliminate or minimize the diffraction?


    Astronomers call this an "apodising mask" and usually make them
    out of window screen, using multiple layers to get the graduated
    density.  Some people claim that it increases the ability to
    see fine planetary detail.


------------------------------