Re: diffraction curiosity questions

In article
<81645c03-81c9-4b93-8680-c2c821f1fdbd@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Brian <brian4052003@xxxxxxxxxxx> 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. In other words, starting with the
assumption that light only travels in straight lines, you can come up
with a very good approximation to the distribution of intensity in the
diffraction pattern in the image plane, which is based on the fact
that it doesn't! And because it is the image plane that you are most
interested in most of the time, the fact that these approximations
fall apart in the intervening spaces is irrelevant. What is
particularly stunning about this is that it made the design of
excellent lenses possible long before we had today's computing power.
The earliest calculations of diffraction patterns were carried out
when rays were traced using 7-figure tables.

Can you be confusing aberration with diffraction? Almost all lens design
is based upon geometric optics. The wave nature of light is unimportant.
The pathlength differences from aberrations are usually much greater
than those involving diffraction. Nevertheless, the diffraction integral
will show the effects of diffraction and aberration.

Bill
.

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