[ATM] Ghosts

["Richard F.L.R. Snashall" <rflrs@rcn.com>]

How do you determine whether a ghost is objectionable?
In a traditional design, a field flattener can be used
near the focal plane.  However, every time I come to a
design like that, the nearness to the image plane also
makes the ghost near the image plane  --  the result a
small ghost spot size (sub-millimeter).   When does it
go bad enough to throw the design out.  Here's a small
example  (75 mm f/4.2):

    http://users.rcn.com/rflrs/calcn-74x.atm
    http://users.rcn.com/rflrs/calcn-74x.len
    http://users.rcn.com/rflrs/calcn-74x.txt
    http://users.rcn.com/rflrs/calcn-74x.zmx

While the ghosts from the first two groups do not have
problems, the ghosts from the image plane and the last
group are getting small.
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