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Yes - that would be lock-in detection. And also yes: background is a big problem for us since we image during visual stimulation of animals. But shouldn't a good Ti:Sa pulse lock-in of our DAQ board also improve signal itself? If we sample at the beginning of the lifetime decay of our fluorophores this should be better than random sampling at 125MHz, or not? I have no experience in doing this so I might be on the wrong track here... especially since I don't know if our slow amplified PMT signal would smear out these timing issues anyways...

Tobias

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Von: Confocal Microscopy List [[log in to unmask]]" im Auftrag von "Mark Cannell [[log in to unmask]]
Gesendet: Donnerstag, 17. November 2011 12:42
Bis: [log in to unmask]
Betreff: Re: Fast two-photon imaging: Constant fraction discriminator and variable delay for Laser pulse-synch

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Sounds like you want to implement lock-in detection. Is background a problem -or why else are you trying to do this? Nanosecond delay devices exist, google nanosecond digital delay.

Mark


On 17/11/2011, at 11:04 AM, Tobias Rose wrote:

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>
> Dear all,
>
> I am trying to sync the sample-clock of our 125Ms FPGA Daq-board to the pulse rate of our 80Mhz Ti:Sa MaiTai for fast (resonant scanning) 2p imaging. To be independent of the small, jittery, and wavelength-dependent sync output of the MaitTai I thought to use a constant fraction discriminator (CFD) and combine the latter with a variable delay. The idea would be to maximize fluoerescence readout during the peak emission time of our fluorophores by tuning the delay to a detection sweet spot during acquisition.
>
> Does this even make sense for analog integration (not photon counting) - or am I trying to solve a problem that I don't even have?
>
> What equipment would you suggest? For the CFD this looks promising on paper:
> http://www.phillipsscientific.com/preview/6915pre.htm
>
> I could not find any of-the-shelf variable delay that would span ~20ns... I know that the STED people usually build their own but this is beyond my expertise. Can anyone suggest a vendor and device?
>
> Thanks!
>
> Best,T