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Hello again:
I forgot to ask: can you check your external path with a visible light laser as
well? This might tell you if it is an optical filter issue only.
Good luck!
Sophie
____________________________________________________
Sophie M. K. Brunet, Ph. D.
Research Officer
Optical Spectroscopy, Laser Systems and Applications
Chemistry 112 sessional lecturer
[log in to unmask]
306-966-1719 (office) 306-966-1702 (fax)
____________________________________________________
Saskatchewan Structural Sciences Centre
University of Saskatchewan
Thorvaldson Bldg.
110 Science Place
Saskatoon, Sk S7N 5C9
____________________________________________________
Quoting "S. Brunet" <[log in to unmask]>:
> Search the CONFOCAL archive at
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
> Hello:
>
> The best troubleshooting I can recommend is to put a mirror at the focus of
> the
> objective. Track the reflected beam using an IR card or IR viewer. Our
> system
> has a dichroic which is intended to block the IR beam when I use the Mira and
> the internal PMTs. Extra filters are used in the non-descanned path. Check
> your default settings and your external detector path. Maybe something is
> not
> transmitting or not reflecting 750nm. Are you sure that you external PMT can
> detect 750nm?
>
> By the way, many bandpass filters will transmit IR light (usually 800 -
> 100nm).
>
> Good luck!
> Sophie
> ____________________________________________________
> Sophie M. K. Brunet, Ph. D.
> Research Officer
> Optical Spectroscopy, Laser Systems and Applications
> Chemistry 112 sessional lecturer
> [log in to unmask]
> 306-966-1719 (office) 306-966-1702 (fax)
> ____________________________________________________
> Saskatchewan Structural Sciences Centre
> University of Saskatchewan
> Thorvaldson Bldg.
> 110 Science Place
> Saskatoon, Sk S7N 5C9
> ____________________________________________________
>
>
> Quoting Jerry Sedgewick <[log in to unmask]>:
>
> > Search the CONFOCAL archive at
> > http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
> >
> > I know this had been discussed in the past, but I didn't follow the thread.
> > I
> > seem to be getting more engineer types wanting to use our confocal.
> Because
> > they often have ancillary equipment they need to set up to replace the
> > stage, I
> > am cornered into providing a spot for them on a custom-built
> > multiphoton. They
> > are forever wanting to see surfaces or reflection from particles: if my
> > memory
> > serves me well, reflection cannot be had unless the illumination wavelength
> > matches the reflected wavelength. But I'm starting to wonder whether
> another
> > phenomenon I am not aware of creeps in, for, on this custom
> > multiphoton, I have
> > replaced a cube with a 50/50 beamsplitter so that the reflected wavelength
> is
> > the same as the illumination wavelength, and removed filters from in front
> of
> > the PMT detector (sensitive out to 800nm or so), set the pulsed laser
> > at 750nm,
> > and even placed a 1/2 waveplate and glan polarizer in the laser path with
> > another polarizer in front of the PMT to play with these (I believe the
> > polarizer in front of the PMT, however, is a circular polarizer as the
> > reflected light never quite extinguished with cross-polarization).
> > Inexplicably, I got no reflection off surfaces.
> >
> > The custom multiphoton has two paths, one for the external detectors
> > (where the
> > 50/50 beamsplitter sent the reflected light) and internal PMTs in a
> Fluoview
> > 300 confocal unit. Strangely, if I sent the reflected light to the
> internal
> > PMTs, I was able to get a reflection, if I was willing to live with a
> bright
> > spot in the middle of the field. This wasn't supposed to happen because
> the
> > reflected light was (supposedly) blocked by bandpass filters, but, after
> > placing another 650sp filter in the reflected light path, the reflection
> went
> > away. (Clearly, a portion of the laser light bled through).
> >
> > In any event, it is confounding to get the reflection in one instance, and
> to
> > not get it in the other even when optimized. Any ideas?
> >
> > Jerry Sedgewick
> > University of Minnesota
> >
> >
> >
> >
> >
> > --- http://USFamily.Net/dialup.html - $8.25/mo! --
> > http://www.usfamily.net/dsl.html - $19.99/mo! ---
> >
>
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