Re: Objective phosphorescence

Posted by Martin Wessendorf-2 on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Objective-phosphorescence-tp7587588p7587604.html

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Interesting.  I was using the widefield 'scope in my lab today and saw
something that I've seen a thousand times before, but never thought
about: Near-UV excitation causes the optics in my sub-stage condenser to
fluoresce yellow.  However, as others have said, I don't know whether
the source is the glue, the glass, or the housing.

Martin Wessendorf




On 11/20/2017 9:33 PM, Benjamin E Smith wrote:

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> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Hey microscopists,
>     We observed an odd phenomenon today on a microscope and was wondering if
> anyone else has ever seen it.  We were using a DMD do a full field flash
> with 420nm light during the flyback of the scanning mirror on a 2P imaging
> rig.  We noticed that after the light was turned off, there was a
> millisecond long slewing of the signal that looked a lot like
> phosphorescence.  In the following image, you can see that the LED is on
> for the first portion of the scan, then turns off and the apparent
> afterglow: https://goo.gl/2ENHwL
>
> This afterglow was also apparent with an oscilloscope looking at the PMT
> and fast mirror signals: https://goo.gl/2AMsvB
>
>     We then systematically removed components from the optical path, and
> cleaned everything, and we were eventually able to determine that the glass
> in the objective itself was glowing, where if the objective was removed and
> the DMD image was shined onto a piece of lens paper or metal, the afterglow
> went away:
> https://goo.gl/arXYF5
> https://goo.gl/cVo2Ev
>
>      The final nail in the coffin to our suspicions was when we then mounted
> a plano-convex N-BK7 lens onto the microscope and the effect came back, and
> the thicker the lens, the stronger the effect. Also, the effect went away
> when we used 540nm light.
>
> With a bit of internet searching I also came across this paper that
> confirms there is some visible fluorescence in glass due to trace elements:
> http://www.schott.com/d/advanced_optics/87330898-4e56-4d70-965a-3f03c7bc0c80/1.1/schott_tie-36_fluorescence_of_optical_glass_us.pdf
>
> Even when I saw the slew, and the first thing that came to mind was
> phosphorescence, the last thing that came to mind was that the glass in the
> objective itself was the offender, so I wanted to post this to both give
> other people a heads-up, and also to see if anyone else has run into this
> phenomenon.
>
> Cheers,
>     Ben Smith
>

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