Posted by
Guy Cox-2 on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Southeastern-Microscopy-Society-meeting-tp4640594p4643943.html
I don't think that is true. A lot of published versions start out from
an objective forming an image of a point object.
Many years ago I got a bit incensed at a diagram in a textbook,
purporting to show SA introduced by a coverslip. The rays leaving the
coverslip were not parallel to those entering it! I wanted a diagram to
show my students, and this obviously wasn't it.
So I sat down with pencil, paper and ruler. First of all I drew a
perfect lens forming an image of a point. Then I drew a coverslip in
the way, looked up the sines of the angles as measured, and constructed
the ray paths. Lo and behold, there was the classic caustic curve.
(And, need I say, the rays exited the coverslip at the same angle they
entered.) So I traced it on OHP film and used it in my lectures
thereafter (long before Powerpoint!). And the students were much more
willing to take it on board since it was constructed without any complex
formulae - nothing more than Snell's Law.
Guy
-----Original Message-----
From: Confocal Microscopy List [mailto:
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On Behalf Of MODEL, MICHAEL
Sent: Saturday, 27 February 2010 7:55 AM
To:
[hidden email]
Subject: tube lens and spherical aberration
(I apologize if this is a second post, I got some strange errors from
the first one)
Dear List
It's not a confocal question, it's strictly a wide-field question...
When people talk about spherical aberration they typically start with a
parallel beam falling on an objective, and then, for whatever reason,
the objective fails to bring all the rays into a common focus. In
wide-field, one has a luminous spot in the object space, and the effect
of spherical aberration would be a failure of the objective to collect
all the rays into a single parallel beam. Some rays will form a
converging (or diverging) cone instead. Then, this cone will be received
(I suspect that in the case of a diverging cone, some light may even get
lost on its way) by a tube lens and form a blurry spot on the image
plane. My question is, Is this situation really equivalent to the
standard one considered in all books? (I suspect, it's not because even
the distance to the tube lens should make a difference). But I would be
very interested in the opinion of those who understand optics better
than I do. Thanks!
Mike Model
Michael Model, Ph.D.
Confocal Microscopy,
Dpt Biological Sciences,
1275 University Esplanade,
Kent State University, Kent, OH 44242
tel. 330-672-2874
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