Posted by
Guy Cox-2 on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Guidance-wanted-on-illumination-stability-tp5784748p5786388.html
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Gordon,
Your strategy of copying to the list didn't seem to work.
Anyway, I think that lots of list members, having seen the question,
like to see the answers.
If someone is taking conventional images with a 1 second
exposure 100kHz ripple will not be noticeable. But if you are taking
video at 25 fps 525 line (international video) your line rate is about
13 kHz (US video about 14kHz) so I'd imagine there would be rather
unwelcome diagonal stripes on the image and you'd be getting angry phone
calls from your customers.
You haven't told us the other side of the trade-off. Do
you want to eliminate the linear stage to save money - if so, how much
cheaper would it make a CooLED illuminator? Or is it to save power?
How much would that save? Given that an LED source already uses hugely
less power that an HBO 100 mercury lamp, would anyone care?
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:
[hidden email]]
On Behalf Of Gordon Scott
Sent: Tuesday, 30 November 2010 2:34 AM
To:
[hidden email]
Subject: Guidance wanted on illumination stability
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Hi Guys,
I'm looking at ways to further improve the performance and efficiency of
our light sources.
There are always tradeoffs when doing this and I'd like to better
understand what tradeoffs are acceptable for real microscopy users.
Our present illumination sources all use a switched-mode pre-regulation
and a linear final regulation for the LED power, so ripple is very low,
but at a cost for us of some power wasted in the linear stages.
I can improve that efficiency and reduce the waste by foregoing the
linear stage and regulating directly with the switching mode, but the
tradeoffs are a longer On/Off switching time than is feasible with
linear, and a high-frequency ripple.
My simulations suggest switch-on and switch-off times of around 50us and
a ripple of around 25% at 100kHz, which would be reasonable from an
electrical/energy point of view.
The question is, of course, would any of the people likely to use it
find that performance difficult or unacceptable?
I've copied to the list rather than posting direct, so hopefully the
replies will come to me rather than cluttering the list.
Thanks for considering the question, even if you need not, or choose
not, to answer.
Kind regards,
Gordon.
--
Gordon Scott Design Engineering
Custom Interconnect Ltd.
http://www.cil-uk.co.uk CoolLED
http://www.coolled.com CoolLED is a division of Custom Interconnect Ltd.
Phone +44-1264-321321
CIL House, Charlton Road, Andover SP10 3JL, UK
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