*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
*****
Prior to Dr. Hell's excellent 2007 paper cited below using laser light pulses in the ns range, Dr. Nishigaki et al, in 2006 used the LED approach successfully, though with more modest gains. They custom built a pulsed diode with broader duty cycle (0.5 to 2ms) that reduced bleaching of organic dyes and associated cell toxicity. Apparently driving diodes much faster than this raises heating concerns.
Or is this no longer true?
Stroboscopic illumination using light-emitting diodes reduces phototoxicity in fluorescence cell imaging. Nishigaki T, Wood CD, Shiba K, Baba SA, Darszon A. Biotechniques. 2006 Aug;41(2):191-7.
Mike Ignatius
Molecular Probes, Life Technologies
-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]] On Behalf Of Jeremy Adler
Sent: Tuesday, November 30, 2010 7:27 AM
To: [log in to unmask]
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 might also be useful to have pulsatile LEDs operating in the
nanosecond range - there was a Stefan Hell paper that showed very
significant reductions in photobleaching when the gap between pulses
was longer than the fluorescent lifetime. Is this possible with LEDs ?
Quoting Gordon Scott <[log in to unmask]>:
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> *****
>
> 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:[log in to unmask]]
>> 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:[log in to unmask]]
>> On Behalf Of Gordon Scott
>> Sent: Tuesday, 30 November 2010 2:34 AM
>> To: [log in to unmask]
>> Subject: 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
>> *****
>>
>> 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
>>
>>
>> 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.
>>
>
Jeremy Adler
Genetics & Pathology
Rudbeckslaboratoriet
Daghammersköljdsväg 20
751 85 Uppsala
Sweden
0046 (0)18 471 4607
|
