Dear Aryeh,
You don't mention what microscope you are using and it could matter based on the
optical system and what is in focus, for example, between eyepieces and
objectives. I have had problems with dirt on the glass at the bottom of the
eyepiece tubes. If the eyepieces are ever removed when setting the condenser
diaphragm for Kohler illumination, dirt might get in. Have you investigated
internal, "exposed" surfaces? Cheers, John.
"Aryeh M. Weiss" wrote:
> I have a problem with some artifacts in my brightfield images which I cannot
> track down.
>
> When the condensor is set to a low NA, there are a lot of dark spots in
> the observed image. However, these spots do not originate in the condensor
> (verified by tilting the condensor -- they dont move).
> When the NA of the condensor matches the NA of the objective, they
> almost disappear. Problem is, in this setup, we often have to work with
> very low NA illumination (for example, with the condensor well removed its
> correct focus setting). Under these conditions, the spots are quite prominent.
>
> Their location does not change when the objectives are changed.
> They do not appear to be in any of the image planes.
> We have cleaned all of the exposed surfaces.
> They appear both in visual observations and with two different cameras,
> so they are not detector artifacts.
>
> We can acquire them as a background image and subtract, but it is certainly
> better to get rid of them in the optics, before processing.
>
> Any ideas will be much appreciated.
>
> Thanks in advance,
> --aryeh
> Aryeh Weiss | email: [log in to unmask]
> Department of Electronics | URL: http://optics.jct.ac.il/~aryeh
> Jerusalem College of Technology | phone: 972-2-6751146
> POB 16031 | FAX: 972-2-6751275
> Jerusalem, Israel | ham radio: 4X1PB/KA1PB
--
C. John Runions, Ph. D.
Department of Plant Sciences
University of Cambridge
Downing St.
Cambridge
UK CB2 3EA
email [log in to unmask]
phone (01223) 766 545
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