Re: Guidance wanted on illumination stability

Posted by Craig Brideau on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Guidance-wanted-on-illumination-stability-tp5784748p5785309.html

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
*****

It really depends on your acquisition and what you are trying to see.  For
instance if you are using a camera with long exposure time then the ripples
will average out in the image and you won't have a problem.  On the other
hand if you are sampling at say ~120 Hz you will have alternating dim and
slightly brighter images.  This may be a problem your users can live with,
depending on what they are looking for.
Finally, if you are aware of the noise and its frequency AND it is
consistent then you can probably subtract it out post-processing.

Craig


On Mon, Nov 29, 2010 at 8:33 AM, Gordon Scott <[hidden email]>wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> *****
>
> 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 [phone]
>            CIL House, Charlton Road, Andover SP10 3JL, UK
>
>
> This message has been scanned by MailController -
> www.MailController.altohiway.com
>
> This message and any attachments are strictly confidential and intended
> solely for the addressee. Any unauthorized use or disclosure, in whole or in
> part, is prohibited. E-mails are subject to possible alteration. Custom
> Interconnect Ltd and the sender decline any liability if this message and/or
> any attachments have been altered, changed or falsified. If you are not the
> intended recipient of this message, please delete it and notify the sender
> immediately.
>
> Custom Interconnect Limited is a limited company registered in England and
> Wales. Registered number: 2026753. Registered office: CIL House 48 Charlton
> road Andover, Hampshire United Kingdom SP103JL.
>