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Hi Peter,
I tell you 80 MHz is a *high* frequency. What are you aiming at? 1024 x 1024
pixels at 80 fps? That sounds cool. But how many photons do you think you'll
get in a pixel? I bet mostly zero. Maybe one, from time to time... So you
may end up with heavy smoothing anyway. If you get whopping 10^9 photons per
second in the bright parts of your image, that translates to a SNR of 3.5 :-
).
I don't want to put you off, just go ahead and try it (and keep us posted).
Just remember that every piece of cable needs proper impedance matching
(termination), also the 'speed of light' is somewhat lower in a cable (20 cm
/ ns), also add some 1 to 5 ns per each comparator or amplifier stage and
you may end up not knowing which pulse came from which pixel (and of course
another 3 ns delay due to the lifetime of your fluorescent protein).
Detectors with integrated amplifiers are also available, but it's either low
speed 'intensity based', with some 6 MHz bandwidth, or fast photon counting
(and these are currently not able to do 10^9 counts per second). I haven't
seen anything in between that would be suitable for your project. So
combining fast detector, fast mplifier and fast digitizer is challenging,
even if you use commercially available building blocks...
I know I didn't help much, but, good luck!
zdenek
--
Zdenek Svindrych, Ph.D.
W.M. Keck Center for Cellular Imaging (PLSB 003)
University of Virginia, Charlottesville, USA
http://www.kcci.virginia.edu/workshop/index.php
---------- Původní zpráva ----------
Od: Peter Rupprecht <[log in to unmask]>
Komu: [log in to unmask]
Datum: 27. 1. 2015 4:41:25
Předmět: Preamplifier for fast point-scanning
"*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****
Dear list,
I'm looking for preamplifiers for use in a resonant scanning 2P microscope,
using fluorophors like GCaMP or OGB in vivo. Acquisition will be time-locked
to the 80 MHz laser pulses, so the bandwidth of the PMT preamplifier should
be at least 80 MHz in order not to smooth adjacent pixels too much.
Right now, I'm using this model, which seems to be used by many others in
the field (as far as I can see):
http://www.femto.de/en/products/current-amplifiers/variable-gain-up-to-200-
mhz-dhpca.html
Is there another option which might be better than this standard solution
for some applications? I'd be glad to hear some opinions on that.
Best regards,
Peter"
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