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John,

 

            Here are a few thoughts. First, try mounting a moving
polarizer above your condenser and use your condenser in the transmitted
light position. You would be able to use your fixed analyzer and then
spin the polarizer to parallel or crossed position. This would be the
simplest answer. Fashion some type of a holder for the polarizer and
simply sit it on top of the condenser, knowing which direction the
polarizer is oriented, you could quickly manually orient the filter for
either position. Some microscopes come with empty, spare filter holders
that fit between the light source and the condenser. Check to see if you
have one, and then adapt your filter to the holder.

If you need to mount analyzers in your filter cubes, try the following:
Do you have access to a light box? If so, put a polarizing filter on top
of the box. Adhere it to the box with some tape by the edges so it will
not shift. Put your filter cube with polarizer in it above the first
polarizer, and orient it either to parallel or crossed position. Use a
small drop of nail polish on a toothpick at an edge of the polarizer to
"glue" it in place in the filter cube, then carefully screw the
retaining ring into place once the glue has hardened. This is a trick
I've seen with some older optics when someone needed to orient a filter
or lens in an exact position. I don't know how reasonable it is to
expect 1 degree accuracy, but I'm willing to bet that if the filters
stay put when you screw in the retaining rings, you'll have your
solution. The key, obviously, is to be careful with the glue so it
doesn't ruin the filters. Superglue would be too low in viscosity, and
hot melt glue from a glue gun might not hold securely, and is flexible.
If you have glass polarizers, the nail polish can be removed from the
filters with acetone or non-toxic polish remover if necessary for
repositioning. The nail polish dries slowly enough that you would have
time to turn the polarizer in the holder if you don't align it perfectly
to start with. 

Another possibility would be to go to a camera store and to purchase a
polarizing filter mounted to fit on a 35mm camera lens. These can't be
too expensive. You could use this lens above your condenser in place of
a rotatable analyzer. Whether these suggestions solve your problem or
not, please post your answer so the rest of us can benefit. Thank you,
John.

 

Ed Haller

 

Edward Haller, Lab Manager

Microscopy Core Labs

University of South Florida

College of Medicine

Tampa, FL 33612

813-974-0569

 

________________________________

From: Confocal Microscopy List [mailto:[log in to unmask]] On
Behalf Of John Oreopoulos
Sent: Thursday, June 05, 2008 2:51 PM
To: [log in to unmask]
Subject: How to align polarization filters in two filter cubes

 

Hello confocal listserver,

 

I have an unusual situation that I'm hoping someone out there might be
able to advise me on. I would like to modify my lab's inverted Olympus
IX70 microscope to have the ability to look at polarized light when
illuminated in the transmission pathway. I want to polarize the white
light that illuminates the sample, and then analyze the polarization of
the image by examining the light that comes through the sample with
another polarizer that can be oriented parallel and perpendicular to the
direction of the polarizer in front of the light source. 

We have DIC optics for the microscope - this means that I have a
polarizer that can be fitted on top of the light source condenser, and I
also have a fixed position analyzer that can slide in below the
fluorescence filter cube turret. My problem is that the polarizer in the
analyzer slider is fixed in a direction that is crossed to the polarizer
in front of the light source. What I really want to do is to be able to
rotate the the polarizer in the slider to the parallel direction as
well. I know that Olympus and Leeds sells rotating analyzers that can
slot into these positions on the microscope, but my supervisor does not
have the funds to afford these right now. So I've come up with a
slightly cheaper alternative solution.

We bought two 1" round film polarizers from Edmund optics (~20$ each).
These are the exact same size as interference filters that normally get
fitted into the fluorescence filter cubes which go in the rotating
turret below the objective nosepiece on the inverted microscope. My plan
was to take two empty fluorescence filter cubes and insert a polarizer
in each - one oriented in the parallel direction and one in the
perpendicular direction. Here is my problem: how can I orient and lock
the position of the the two polarizers in the filter cubes such that
they are aligned with their polarization axis directions correctly?
Ideally, since I'm trying to be quantitative with the imaging, I'd like
their alignment from their relative crossed position to be within 1
degree or less. When I screw them down with the retaining ring of the
filter cube, they rotate slightly in the cube before they become locked.
Also, I can't tell if I'm dropping them into the filter holder in the
right position since their reference axis position is marked on the edge
of the filters. Can anyone out there suggest a good method to overcome
this problem? How do the microscope manufacturers align their polarizers
in the sliders they sell for DIC imaging, etc?

 

Thank you in advance for any help!

 

John Oreopoulos, BSc,

PhD Candidate

University of Toronto

Institute For Biomaterials and Biomedical Engineering

Centre For Studies in Molecular Imaging

 

Tel: W:416-946-5022