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Dan--I can only help on the front end of the 
calculation--with our FV1000, we typically run a 
pixel dwell of 4µs; on the new Zeiss 710 (same 
specimens), it was more like 1µs, so 10µs seems 
high.
Julian

>Search the CONFOCAL archive at
>http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
>Dear all,
>
>Recently I was calculating the maximum permissible exposure (MPE) power
>level for confocal or multiphoton microscopy for tissue imaging. It seems to
>me that currently the optical power used by most confocal or multiphoton
>studies in tissue imaging far exceeds the MPE limit. Here is how I
>calculated it and please tell me if I am doing something wrong. The
>literature I have found so far do not talk about tight focusing.
>
>According to the ANSI-Z136.1 standard, in the NIR range with an exposure
>time of 10^-7 to 10 second, the MPE level is 0.56*t^0.25, t being the pixel
>dwelling time. Considering a typical pixel dwelling time at 10 microsecond,
>the MPE level is 31 mJ/cm-2. Assume we have a focal spot size of 1 micron,
>the average power should be 0.31 nJ or 0.031 mW. That seems like an awfully
>small number considering a few mW (even tens of mW) is routinely used in
>human skin imaging.
>
>If some one has worked on this before, please advise me what is wrong here.
>Thank you very much for your input.
>
>Dan Fu


-- 
Julian P.S. Smith III
Director, Winthrop Microscopy Facility
Dept. of Biology
Winthrop University
520 Cherry Rd.
Rock Hill, SC  29733

803-323-2111 x6427 (vox)
803-323-3448 (fax)
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