Posted by
Zdenek Svindrych-2 on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Laser-stability-over-time-tp7587681p7587684.html
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Hi Milan,
I did some quick measurement to determine short-term fluctuations of the
lasers on our LSM880, basically just transmitted light detector at fairly
low gain (but the PMT response should still be linear), a quick series of
about 100 images, 'stdev' stack projection in ImageJ.
The 633 HeNe and the 561 DPSS lasers were very stable (0.5 % RMS noise, I
did not checked how big contribution comes from the detector noise), but the
Ar-ion laser fluctuates much more, around 1 % RMS at 488 nm, around 1.5 %
RMS at 458 nm. The 514 line was the least stable, with RMS of 2 % at full
power and 3 % at standby. You can compare it with your numbers. A 3 % RMS
noise would become visible when you get 1000 (or more) photons per pixel...
I did not look at the spectral properties of the noise, but it looks like
most of it is within microsecond to millisecond range.
If you are interested in long-term fluctuations (hours, days), you first
need to make sure you have very stable detector (maybe a photodiode, or a
PMT in photon-counting mode?), or very stable light source to compare with.
You can also compare two different lasers to see where the fluctuations are
coming from.
The way you did your measurements (with a mirror in focus, confocal
detection) the main contribution will be the mechanical stability (z drift)
and a bunch of other things...
Good luck!
Best, zdenek
--
Zdenek Svindrych, Ph.D.
Research Associate - Imaging Specialist
Department of Biochemistry and Cell Biology
Geisel School of Medicine at Dartmouth
email:
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Od: Milan Esner <
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Komu:
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Datum: 15. 12. 2017 10:46:16
Předmět: Laser stability over time
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Dear colleagues,
we have new Zeiss LSM880 confocal microscope in our facility and performing
measurements of laser stability over time.
I am using slide with mirror and measuring reflection on internal detectors.
However the results shows quite high fluctuation for all lasers.
I would like to ask you if you are measuring the stability in time of lasers
on your microscopes and what is the correct method for this measurement and
also how big fluctuation you observe on your system?
Thanks a lot for sharing your experience. Best regards,
Milan
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