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
813-974-0569
From: Confocal
Microscopy List [mailto:[hidden email]] On Behalf Of John Oreopoulos
Sent: Thursday, June 05, 2008 2:51
PM
To: [hidden email]
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
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
Institute
For Biomaterials and Biomedical Engineering
Centre
For Studies in Molecular Imaging
Tel:
W:416-946-5022
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