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Stan
From my practical experience longer dwell times can reduce noise. The relative effects of averaging vs accumulation depend on the detector gain so averaging at high gain is slightly more noisy than accumulation at lower gain but I think the difference is small. Combining averaging and accumulation does seem to be better for spectral imaging at narrow bandwidth for example. If your sample can stand it, increasing laser power can make much more difference, likewise making your sample brighter. I have noticed some difference in noise behaviour on the 2 systems I have used suggesting there is a significant effect of all the electronics behind the microscope.
I would be interested in your results if you do some experiments.
Lloyd
Dr Lloyd Donaldson
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-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]] On Behalf Of Guy Cox
Sent: Friday, 17 June 2011 4:46 a.m.
To: [log in to unmask]
Subject: Re: averaging vs. accumulation for noise reduction - is there a difference?
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Mark,
By my reckoning it's after 4 in the morning in Auckland - what are
you doing replying at this hour? (By the way, I'm in Taiwan, not Oz).
Guy
Optical Imaging Techniques in Cell Biology
by Guy Cox CRC Press / Taylor & Francis
http://www.guycox.com/optical.htm
______________________________________________
Associate Professor Guy Cox, MA, DPhil(Oxon)
Australian Centre for Microscopy & Microanalysis,
Madsen Building F09, University of Sydney, NSW 2006
Phone +61 2 9351 3176 Fax +61 2 9351 7682
Mobile 0413 281 861
______________________________________________
http://www.guycox.net
-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]]
On Behalf Of Mark Cannell
Sent: Friday, 17 June 2011 2:41 AM
To: [log in to unmask]
Subject: Re: averaging vs. accumulation for noise reduction - is there a
difference?
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It also depends on how the readout bandwidth is controlled for
different scan speeds...
Cheers
On 16/06/2011, at 5:26 PM, Stanislav Vitha wrote:
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> *****
>
> Hallo,
> this is a very basic question, but I cannot figure this out from what
I have
> been reading, so a simple explanation for a non-physicist would be
much
> appreciated:
>
> Is there a real difference in the improvement of the signal to noise
ratio
> between frame averaging (or accumulation) and longer dwell times
(slower
> scan) for a point-scanning confocal witrh a PMT detector?
>
> For instance, using single point scanning confocal, 12-bit
acquisition.
>
> a) averaging (or accumulating) 5 frames, 4 microseconds per pixel
> b) acquiring a single frame, 20 microseconds per pixel
>
> Assumptions:
> no saturation of the detector;
> stable environmental conditions, no focus drift, etc
>
> Would it matter (for the dfference between the two scenarios) if it
was analog
> detection or photon counting detection?
>
> I will run this little test later, but I am curious what you think.
>
> I thought that at least for the photon counting mode, the two
important
> factors would be the dark counts and the total number of counts
detected, so
> whether it is acquired in one scan or in 5 scans, it should be the
same. My
> camera expert here insists that the averaging scheme will give better
noise
> suppression.
>
> Thanks!
>
>
> Stan Vitha
>
> Microscopy and Imaging Center
> Texas A&M University
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