Re: diffraction curiosity questions

On Mar 18, 4:58 pm, AES <sieg...@xxxxxxxxxxxx> wrote:
In article (info lost) someone wrote:

Of course it isn't only in optical resonators that this is true. What
most optical designers like me find extraordinary is that for an
optical system which is "useful" (in other words, not too badly
aberrated), the aberrations and hence the diffraction performance, can
be estimated through ray tracing.

Is the explanation perhaps that "useful" systems are essentially always
limited to using low spatial frequencies -- or more accurately, small
spatial frequency spreads if viewed in an appropriately chosen
coordinate system?  

(since what large spatial frequency spreads do is to scatter / diffract
/ refract light at *large* angles, i.e. out of the optical system --
which is seldom useful.)

Or at least, this is another way of viewing the situation.

I think what Brian means is that it is remarkable (and I agree) that
99.9% of lens imaging systems can be designed without the need to
resort to diffraction integrals. All that is needed is ray tracing.

Using ray tracing one can either use transverse aberration for lenses
that do not need to be "diffraction limited" and wavefront aberrations
for those that do. Except in the very rare cases where correction at
only specific spatial frequencies is required, performing the final
optimization on the RMS wavefront error yields results as good as can
be had.

www.richardfisher.com
.

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