Hello Aryeh and Listers,
I've seen this several times with argon lasers and there are at least 2 reasons I found which can cause this issue. First, repeated fast live scans, where the live scans are at 1/2 or 1/4 of the horizontal spatial resolution and perhaps too much laser power or the preview is going on for too long. Going to the final scan at full spatial resolution reveals the stripes which are likely just bleach lines. Move to a new field and if there are no stripes, I think this explanation may hold up. Second, if the argon laser is slightly older, and has a rheostat on it for tuning power, I have found adjusting this can alleviate the banding you see. I do not know the exact explanation for why the banding results when this power tuning is off, but I do know that I have been able to alleviate the issue by tuning the rheostat. There may be other reasons like Guy's suggestion, these are just what I have experience with. Good luck. Cheers 
Farid. 
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-----Original Message-----
From: Aryeh Weiss <[log in to unmask]>
Sender: Confocal Microscopy List <[log in to unmask]>
Date:         Fri, 31 Aug 2012 15:35:44 
To: <[log in to unmask]>
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Subject: horizontal dark lines appearing

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We see (apparently) periodic horizontal dark lines with our Leica SP5, 
when using the argon ion laser. Images that show these lines can be seen 
at the following link:
http://cl.ly/2m2h0R1u1J2w

There were some some posts on the list about this, with the suggestion 
that the laser is dying. However, when last I checked (a few weeks ago), 
that laser was putting out plenty of power (although the 488nm line was 
relatively weak compared to the 514nm line). Also, the lines have some 
periodicity (50Hz?). Faster scan rates increase the line spacing, but it 
does not appear to be linear with scan speed.
Frame averaging will average it out, so it is not correlated with the 
scanning system. So the lines are annoying, but average signal seems fine.

None of the other lasers do this, and it is independent of detector. 
Therefore, we assume that the problem is upstream of the vis laser 
combiner/AOTF. That leaves the fiber, laser head, and power supply.

We suspect the laser, but it would be more satisfying to understand what 
causes this behavior. Understanding the cause may lead to knowing how to 
fix it without replacing the laser, but even if not, I like to know why 
things work (or dont work) the way they do.

Has anyone has seen something similar?

Thanks in advance
--aryeh
-- 
Aryeh Weiss
Faculty of Engineering
Bar Ilan University
Ramat Gan 52900 Israel

Ph:  972-3-5317638
FAX: 972-3-7384051