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Hi Paul,
Thanks for the response.
I'll probably leave the disk alone, but I don't think think the specks
I see are due to holes in the chrome. As I bring a sample into focus
(while the disk is stopped), I see the pinholes get brighter as the
sample comes into the focal plane. For the specks, the brightness
doesn't change at all with focus. This leads me to believe that the
light I'm seeing is scattered from the surface of the disk, not light
from the sample through holes in the disk.
I also can't think of what would cause this type of damage if there are
in fact holes in the chrome. If it's damaged caused while spinning,
I'd expect the pattern to look more like long thin scratches. Another
possibility would be that something's corroding the surface...but such
a large amount of corrosion over a short amount of time seems very
unusual (I've seen this get worse since moving my setup from one lab to
another, over a period of just a couple of months). So, these factors
together make me think that it's some sort of dust...but I'd rather do
nothing than risk damaging the disk until I know for sure :)
Thanks again for the comments.
Best,
Joe
Quoting Maddox Paul <[log in to unmask]>:
> Search the CONFOCAL archive at
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
> Hi Joe,
>
> Based on your picture, I would bet that, while dust may in fact be
> building up on the disk, the "scattered light" you see is due to
> small holes forming in the chrome masking. The reason I come to that
> conclusion is because of the image you provided (very handy, thanks).
> To make that type of image, you shine light through the stopped
> disk. The pinholes are in focus nicely, if there were scattered
> light, it would reveal itself as "blurring" of the pinholes and not
> as sharply in focus features.
>
> I could of course be wrong, but nonetheless, I would resist cleaning
> this out of fear of increasing the size of those holes.
>
> Best of luck,
>
> Paul
>
> Paul S. Maddox, PhD
> Assistant Professor
> Institute for Research in Immunology and Cancer
> Dept of Pathology and Cell Biol, U. de Montreal
> P.O. Box 6128, Station Centre-Ville
> Montréal QC H3C 3J7
> CANADA
>
> Courier:
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> CANADA
>
> [log in to unmask]
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> Fax: 514-343-6843
>
> -----Original Message-----
> From: Confocal Microscopy List [mailto:[log in to unmask]]
> On Behalf Of Joseph Summers
> Sent: Saturday, July 05, 2008 7:40 PM
> To: [log in to unmask]
> Subject: Cleaning a Nipkow Disk
>
> Search the CONFOCAL archive at
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
> Hi Folks,
>
> I've been using an old Technical Instruments K2-IND Nipkow disk
> confocal and have been noticing some buildup of dust between the
> pinholes on top of the chrome-plated glass disk. This dust is
> scattering light and is clearly visible between the pinholes when the
> disk isn't spinning. I've posted a pic here:
>
> http://www.mtholyoke.edu/~jsummers/dust_pinholes.png
>
> (*note: I'm fairly certain that this is scattered light from dust on
> top of the disk, and not due to light transmitted through
> damage/scratches in the chrome because 1) the brightness of the "dust"
> doesn't change with focus, 2) I would expect scratches to look like
> streaks, 3) I can see what appears to be dust on the disk with the
> naked eye when opening up the K2-IND unit)
>
> Though this isn't much of a problem now, I imagine the attainable
> contrast of the scope will degrade over time as more dust collects.
> I'm not using the microscope in a cleanroom environment, so I suppose
> this type of thing would be expected. However, I'm curious to know if
> anyone has any suggestions for cleaning the disk. I've tried using an
> air-gun, but this doesn't really help. I'm tempted to use some lens
> cleaning paper and isopropyl alcohol, but since the problem isn't bad
> yet (and the scope isn't all that cheap), I wanted to see if there was
> any expert advice out there.
>
> I'd appreciate any input.
>
> Thanks and best,
> Joe
>
> ------------------------------------
> Postdoc, Physics Dept.
> Optoelectronics Group
> Mt. Holyoke College
> ph: (413) 538-2263
> http://www.mtholyoke.edu/~jsummers/
>
>
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