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HI Gabor
I agree with you assessment with regard to my resolution problems with
PMT 3.
We had the slider in front of  PMT 3 replaced
Since that time we have observed that the spectral pattern with this PMT
sometimes had  jagged as opposed to smooth curves observed on the same
sample with the other two PMTs.  This suggests that the sliders are not
working in a smooth orderly fashion ( mechnaical problem) or there may
be some diffraction off the edge of the slider that is causing this
widening pattern due to the combination of the very narrow slit width
(5nm) and the pinhole equivalent to 1 airy disc ( physical problem) . .
However,  when opening the airy disks  to 3 more light comes in which
may eliminate this diffraction pattern that may be widening the spectra.
.

I have observed problems while taking normal spectra from a Chroma red
slide or when I observed narrow spectral peaks from the MIDL lamp. Are
they any other test substrates that can be used to detect optical issues
in a spectrometer based confocal microscope. Some of the manufactures of
confocal microscopes have not accepted this lamp as a standard to QA
their machines.
Thanks for your comments
Bob

Robert M. Zucker, PhD
U.S. Environmental Protection Agency
Office of Research and Development
National Health and Environmental Effects Research Laboratory
Reproductive Toxicology Division, MD 72
Research Triangle Park, North Carolina, 27711
Tel: 919-541-1585; fax 919-541-4017
e-mail: [log in to unmask]



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  |      To:       [log in to unmask]                                                                |
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  |      Subject:  Re: Pinhole and resolution                                                                   |
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Dear Bob

I'd speculate that this is a mechanical problem.
As we all know- in a Leica system the same pinhole is used for all the
PMT-s. I could imagine that your PMT3 (or actually it is probably the
"filter" slider in the front of it it) is not in its correct position. I
suppose that for optimal performance the position of the pinhole and
that of the slider  is critical.  A wrongly positioned slider could
explain both the reduced spectral performance (compared to the other two
PMT-s)  and the fact that with opening  the pinhole the performance gets
better  (probably with  an opened pinhole the slider position is less
critical).

Cheers     Gabor


--
Gabor Csucs PhD
Light Microscopy Centre ETH Zürich
Inst. of Biochemistry
ETH Hönggerberg HPM D 8.1
http://www.lmc.ethz.ch

Tel:41-1-633-6221
e-mail: [log in to unmask]