http://confocal-microscopy-list.275.s1.nabble.com/Guidance-wanted-on-illumination-stability-tp5784748p5787547.html
our illumination products.
may not be acceptable to end users. My suspicion and also your 120Hz
to keep the linear control. 100kHz/25% ripple at 120fps would appear to
to, say, 16% (640 lines), which is very likely intolerable. I'm also
Custom Interconnect Ltd.
> -----Original Message-----
> From: Confocal Microscopy List
> [mailto:
[hidden email]] On Behalf Of Craig Brideau
> Sent: 29 November 2010 17:56
> To:
[hidden email]
> Subject: Re: Guidance wanted on illumination stability
>
> *****
> 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.
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