>From the classical literature I gather what is wanted is really a pinhole
and not a pin tunnel. To exaggerate: if one had a piece of 5 mil stock and
drilled a hole through it, one would have two diffraction edges to form
images, the entry edge and the exit edge. This is why the art of making a
pinhole has one first dimpling, and then sanding the metal as thin as
possible, so when the hole is made it is like this >< and not like this ][.
Laser holes aren't the answer either as they tend to be like this )( as
there is some rolling on the edges. George is right, the nature of the hole
is more critical than its size.
Dick
Bostick & Sullivan
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