>I am working in a lab temporarily which has a Biorad confocal set up
>on an upright Nikon Eclipse.  They use the Nikon confocal water
>immersion lens as a dipping lens on this system.  My impression was
>that these lenses were designed to correct index mismatching, but
>that they were intended to go through a coverslip, since there is a
>correction collar for coverslip thicknesses.  Can someone comment on
>whether one would expect any optical abberations from using it by
>dipping without a coverslip?  Thanks- Dave
>--
>
>************************************************************
>Dr. David Knecht
>Department of Molecular and Cell Biology
>University of Connecticut
>75 N. Eagleville Rd.   U-125
>Storrs, CT 06269-3125
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>860-486-2200      860-486-4331 (fax)
>home page: http://www.sp.uconn.edu/~mcbstaff/knecht/knecht.html
>************************************************************

Just a clarification of Jeff Larson's response.  The problem you get
by using a water coverslip lens without a coverslip (or vice versa)
is MASSIVE spherical aberration. As SA depends on RI mismatch and as
RI varies with wavelength, this problem also generates a small amount
of chromatic aberration but SA is the big problem.

To get an idea of the size of the problem: When using an oil lens to
look into water, you lose about half your signal after say 10
micrometers (i.e., 10 micrometers of glass replaced by water causes
this loss). When you use a coverslip lens W/O a coverslip, you are
replacing 170 micrometers of glass by water, about 17x as much.  You
will still see an image but it will only be formed by those rays
passing through the center of your objective. The others will be so
aberrated that they really only add to the background.

I echo the warnings about measuring the coverslips and being careful
to set the collar so that the image of a point goes out of focus in
the same way whether you are focusing up or down. The adjustment is
far more important (and finicky) on any sort of water lens than on
oil lens.

Cheers,

Jim P.
--
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Prof. James B. Pawley,                             Ph.  608-263-3147
Room 223, Zoology Research Building,               FAX  608-265-5315
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