Posted by
Michael Giacomelli on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Resonant-scanning-preamplifer-bandwidth-tp7584591p7584593.html
*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopyPost images on
http://www.imgur.com and include the link in your posting.
*****
Hi Heping.
The idea is to sample synchronously with the excitation so that you
don't get beating between the sample and excitation clocks (imagine a
situation where one sample gets two pulses, then next zero pulses, the
next 2 pulses, ...) not necessarily to Nyquist sample the excitation
itself.
As for analog bandwidth, it should be set high enough to sample the
motion of the excitation spot across the sample. Since most systems
use a resonant scanner with a bidirectional line rate of no more than
16kHz and a laser with an 80 MHz rate, that's 5000 pulses per line,
but probably no more than 1024 pixels. Even accounting for the fact
that the scanner is moving faster in the center of the scan than the
edges, there is typically still at least 2 excitation pulses per
pixel, which means the analog bandwidth of the image will be around
half that of the excitation (~40Mhz) at the center and less on the
edges. Therefore you'll be ok with an amp with at least that much
bandwidth and an 80 MHz sampling rate, at least for many systems.
Keep in mind though that you don't want too much bandwidth either,
there is no advantage to amplifying frequencies that are not in your
signal, and you'll quickly start to pick up FM radio stations if you
go above 80MHz.
Mike
On Mon, Jan 4, 2016 at 11:53 PM, Heping Yuan <
[hidden email]> wrote:
> *****
> 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.
> *****
>
> Hello list users. I had a question about analog to digital conversion in resonant scanning two
> photon microscopes. I have seen older discussions involving some users of the open source
> ScanBox and ScanImage programs and they advocate for using sampling rates that match
> with the Ti-Sapphire laser repetition rate (80 MHz). However, they also suggest using
> preamplifiers with cutoffs that match this sampling rate (80 MHz). Should the preamplifier
> not be at most half of the sampling rate to avoid aliasing? I believe there may be more
> subtle details I am not aware of.
>
> Thank you for your time.
>
> Heping