Confocal Microscopy List - Re: Guidance wanted on illumination stability

Re: Guidance wanted on illumination stability

Posted by Gordon Scott on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Guidance-wanted-on-illumination-stability-tp5784748p5787611.html

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Hi Guy,

No the copy strategy didn't work. Of course one only finds that out
after the event. Ho Hum. :-(

My original thoughts on video were as yours, however I _think_ most
cameras take a full image and then the lines are downloaded
sequentially, but I'm also very aware that that may not be the whole, or
even the correct story. If the line rate _is_ important, and I guess if
the data is downloaded from the camera `live' line-by-line, rather than
as a complete image, then 100kHz will definitely show artefacts and the
case is closed .. I need to keep the linear control.

The main aim is actually to avoid unnecessary waste heat, though saving
money is always nice. I'm not sure it would make a particularly
significant effect on price, but it may. Any waste heat I have I then
have to get rid of. LEDs must not get as hot as bulbs and indeed we
actively cool them to get the best out of them, so getting the excess
heat out of the boxes needs heat sinks and fans or similar. At present
that waste heat puts a frustrating limit on what's feasible with the
units, and I'd like to remove that frustration.

Thanks for your comments.

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

> -----Original Message-----
> From: Guy Cox [mailto:[hidden email]]
> Sent: 29 November 2010 23:15
> To: Confocal Microscopy List
> Cc: Gordon Scott
> Subject: RE: Guidance wanted on illumination stability
>
> 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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> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
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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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