*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
*****

Dear Aryeh, 
    I've experienced three causes of horizontal bands on a Leica SP5.

1.) Issues of initialization of the electronics resulting in horizontal bands. This 
is very simple do diagnose and it is not what you see. 
2.) 50-100Hz banding caused by light in the room (monitors or light bulbs). 
Again, this is not what you see.
3.) Horizontal lines that are photobleached into the sample. This has been an 
issue on our system and seen with both a Ti:Sapphire laser and a Ar:ion. What 
really puzzled me is that I see the bands on screen only when I change pixel 
resolution or  field of view rotation. For nice fixed and mounted samples, it is 
possible to see the lines also through the eyepiece. The issue can be 
characterized using fluorescent plastic and high power settings of the laser. It 
is a while I am not checking the issue, but in the past I had the impression 
that happened only with one objective. Furthermore, the photobleached 
regions were much darker than what was actually imaged by the confocal, 
giving the impression that the problem was during the re-tracing of the laser, 
perhaps happening when the pixel resolution was much lower of the diffraction 
limit with the blanking of the laser not working at all. I got this from another 
reply to this post. However, I must say we tested the blanking of the lasers 
and was working. We changed both AOM and EOM controllers. If I will find the 
time I will re-check the issue and post a follow-up. 

Cheers, 

Alessandro