Posted by
Zdenek Svindrych-2 on
URL: http://confocal-microscopy-list.275.s1.nabble.com/confocal-detectors-and-deconvolution-tp7588223p7588240.html
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Hi Steffen,
the electron multiplication process is stochastic both in HyDs and regular
PMTs. The difference is that HyDs are always used in photon counting mode
(afaik), whereas PMTs (GaAsP or other) may or may not, depending on the
instrument. HyDs should be able to handle higher photon rates than photon
counting PMTs (at least that's what Leica used to say), while they have much
bigger active area than SPADs, so they are easier to align. That being said,
I'd like to see more SPADs on regular confocals...
Best, zdenek
---------- Původní e-mail ----------
Od: Steffen Dietzel <
[hidden email]>
Komu:
[hidden email]
Datum: 11. 5. 2018 11:01:03
Předmět: Re: confocal detectors and deconvolution
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Am 10.05.2018 um 17:19 schrieb Vitaly Boyko:
> there is no big difference between HyDs and GaAsP detectors.
I disagree on this. In my view, the major difference is that the HyD
always operates in photon counting mode whether, as far as I know, the
PMTs (with or without GaAsP) create an electron cloud of which the size
is determined by the number of photoelectrons AND statistics, and the
cloud size is then digitized. So the output created by one photon may
vary substantially depending on the number of electrons created on the
first dynodes (which in turn is a statistical process). My information
may be outdated and newer PMTs might have extra tricks, if so please
correct me.
Another difference is apparently the size of the photcathode. If memory
serves me right, the larger cathode of the GaAsP PMTs (compared to HyDs)
creates more dark noise. I like our HyDs a lot, I appreciate having a
gray value of "21 photons" instead of some random number. But having
said this, at the end of the day what counts is the sensitivity of the
whole system, and not of the detector alone. So to do this right there
is no substitute for testing your own samples on different machines with
your applications in mind.
As for deconvolution, yes, it can create artefacts. But so does confocal
microscopy (a point becomes an Airy pattern, not a point). And if you do
it right the deconvolved image will be closer to the truth than the
original image. Should you have the third edition of the handbook
around, have a look at the preface, last paragraph.
Steffen
--
------------------------------------------------------------
Steffen Dietzel, PD Dr. rer. nat
Ludwig-Maximilians-Universität München
Biomedical Center (BMC)
Head of the Core Facility Bioimaging
Großhaderner Straße 9
D-82152 Planegg-Martinsried
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