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Also, to add to all the info on the Zeiss META, it should be noted that
those "blocking pins" can be adjusted as to their position, so that they cut
out the most laser light and the least amount of signal. These pins, of
course, make it impossible to do any reflected light imaging with the META.
It's worth knowing if those are in the right place.
-Holly
__________________
Holly L. Aaron
CRL Molecular Imaging Center
http://imaging.berkeley.edu
-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]] On
Behalf Of Jeremy Lerner
Sent: Wednesday, August 17, 2005 2:44 PM
To: [log in to unmask]
Subject: Re: Reflected light
Search the CONFOCAL archive at
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As I understand it the Meta detector is a classic Czerny Turner (CT) in
which case an image of the pinhole is imaged onto the detector at each
wavelength present in the source. If the source is monochromatic, such as a
laser, then a 100 micron pinhole will be imaged at the laser wavelength in
the focal plane of the spectrometer coincident with the IMPT. The image of
the laser illuminated pinhole will be observed as an oval, due to either
inherent anamorphism, or this plus astigmatism (most likely).
I think it is safe to assume that the spectrometer is correctly oriented;
however it is not safe to assume that the detector is in the right place.
If the IPMT is correctly positioned then the laser wavelength will hit a pin
and be blocked. If the IPMT is translated, or rotated, then the image of
the pinhole could conceivably hit the side of a pin and bounce onto detector
elements that should normally see no light. In the worst case the image of
the pinhole will strike the space between detector elements and be unequally
split with at least some energy bouncing onto adjacent detector elements.
This is the way all wavelength dispersive spectrometers work prism or
grating; so even if the spectrometer is not a CT, it would make no
difference to the comments above.
If anybody is interested in copy of "The Optics of Spectroscopy - a
Tutorial", in which all these issues are described, let me know and I will
send you a pdf. I have presented this tutorial at many SPIE workshops.
Jeremy
LightForm, Inc.,
Tel: (908) 281-9098
Cell: (908) 963-4262
eMail: [log in to unmask]
Web: www.lightforminc.com
"There is nothing worse than a sharp image of a fuzzy concept."
Ansel Adams
----- Original Message -----
From: "Ian Dobbie" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, August 17, 2005 4:04 PM
Subject: Re: Reflected light
> Search the CONFOCAL archive at
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
> "Miller, Jason" <[log in to unmask]> writes:
>
> [snip]
>
>> However, Zeiss actually has laser line "blocker pins" that sit directly
>
>> over the part of the META prism element that corresponds to the laser
>
>> lines you have on your system. So as long as your pinhole is small
>
>> enough (1 Airy unit), all reflected laser light will be blocked by the
>
>> pin and you can operate the META detector in a emission bandwidth that
>
>> includes some of your excitation laser lines. As far as I know, these
>
>> "blocker pins" don't exist on the filter channels and may explain why
>
>> you see scattered light with the same pinhole diameter in the filter
>
>> channels, but not in the META detector.
>
>
> Just a slight side point. As far as I understand it, the META uses a
> bent diffraction grating, to refocus the light on the detector and to
> produce the spectrum in one dimension. The blocking pins are then
> mounted on the front of the detector. This arrangement has some
> advantages, eg the ease of blocking the excitation lines, and only
> requires one optical component. However, even a coated grating doesn't
> have great transmission into one side peak, hence the relatively low
> sensitivity of the meta detector compared to the standard
> detector. The other two (or three) detectors are entirely
> conventional, with barrier filters in a filter wheel, then a PMT.
>
> Ian
>
>
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