Filters for Olympus CX41 (phase, polarization and darkfield)

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Dreamspy
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Joined: Fri Feb 08, 2019 4:49 pm

Filters for Olympus CX41 (phase, polarization and darkfield)

Post by Dreamspy »

I'm looking for contrast enhancing filters for my Olympus CX41. Polarization filters especially, but phase contrast and darkfield as well.

I see that these filters have been sold with the microscope before:

https://www.spachoptics.com/CX41-PHASE- ... se-pol.htm

...but I haven't been able to locate them anywhere online for sale.

I assume that I can retro-fit some polarizers and create a darkfield filter myself, but would be great just to find the original ones or something that works fine Out-of-the-box.

So my question is, anyone know where to buy these filters?

Here are some images of the filter holders if anyone is interested:

Image

Image

Alan Wood
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Post by Alan Wood »

Here are links for the U-ANT analyser and the U-POT polariser:

https://spectraservices.com/U-P115.html

https://www.spachoptics.com/OLYMPUS-U-P ... -u-pot.htm

I suspect you will want to find cheaper alternatives!

Here is a cheap source for the CH2-DS darkfield central stop:

https://www.optics-pro.com/dark-field/o ... h-/p,54014

And here are 2 of the phase contrast attachments:

https://www.optics-pro.com/microscopy/m ... /m,Olympus

Alan Wood

Dreamspy
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Post by Dreamspy »

Alan Wood wrote:Here are links for the U-ANT analyser and the U-POT polariser:

https://spectraservices.com/U-P115.html

https://www.spachoptics.com/OLYMPUS-U-P ... -u-pot.htm

I suspect you will want to find cheaper alternatives!

Here is a cheap source for the CH2-DS darkfield central stop:

https://www.optics-pro.com/dark-field/o ... h-/p,54014

And here are 2 of the phase contrast attachments:

https://www.optics-pro.com/microscopy/m ... /m,Olympus

Alan Wood
Those are expensive! So some alternatives would be great :) But I'm a bit clueless on where to get those. Edmunds optics is the only online optics source that I know. Would that be a good source? Or some other source you recommend?

Dreamspy
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Post by Dreamspy »

I'm also curious about how to use birefringent filters to enhance polarization filtering.

From the following youtube video:

https://youtu.be/q5lBC2hyoZE?t=43

there seems to be a good method to introduce a birefringent retardation filter somewhere in the optical pathway above the sample. Possibly layering my stuff like this (from top down):


Polarizer
Birefringent filter
Sample
Polarizer (at 90 deg wrt above pol filter)

Does this look coorect?

I'm mainly interested in knowing if this is something that could be done on my CX41? I assume that I'd have to do some custom fitting since the CX41 doesn't have 3 slots for filters.

Alan Wood
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Post by Alan Wood »

The awkward bit will be making an analyser to replace the U-ANT. It is in the imaging light path so it needs to be good quality film, and cut to the right size.

You can use a linear polarising filter for a camera to replace the U-POT. Just put it on top of the black piece where the light comes out of the base, where it is easy to rotate.

You can put a retarder on top of the polarising filter. It is below the objective so quality is not too important. You can try all sorts of plastic films, CD wraps, greeting card wraps, cake box windows, anything you can find. Rotate it to find the best position.

This report of this Quekett Microscopical Club meeting may give you some ideas:
http://www.quekett.org/about/reports/20 ... sed-public

Alan Wood

Pau
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Post by Pau »

Edmund polarizers are very good. I use one of them* as analyzer in my DIC setup and it works great, while setting it up I compared the Edmund's with a Nikon and an Olympus analyzers and the results were the same
For the substage polarizer you can use a plastic polarizer** or a plastic sheet***
Camera polarizers do work but they are not designed to work crossed. I've tested several ones and most of them induce blue color cast and not high extinction, only one (B+W) didn't make color cast although its extinction ratio was not as high as dedicated microscope pols, so they are useful to make nice observations and pictures but in principle not so convenient for exigent work.

* https://www.edmundoptics.com/f/high-con ... ers/12725/ not inexpensive!
** https://www.edmundoptics.com/f/High-Con ... ers/14383/
*** https://www.edmundoptics.com/f/High-Con ... ilm/14385/
Pau

Dreamspy
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Post by Dreamspy »

Pau wrote:Edmund polarizers are very good. I use one of them* as analyzer in my DIC setup and it works great, while setting it up I compared the Edmund's with a Nikon and an Olympus analyzers and the results were the same
For the substage polarizer you can use a plastic polarizer** or a plastic sheet***
Camera polarizers do work but they are not designed to work crossed. I've tested several ones and most of them induce blue color cast and not high extinction, only one (B+W) didn't make color cast although its extinction ratio was not as high as dedicated microscope pols, so they are useful to make nice observations and pictures but in principle not so convenient for exigent work.

* https://www.edmundoptics.com/f/high-con ... ers/12725/ not inexpensive!
** https://www.edmundoptics.com/f/High-Con ... ers/14383/
*** https://www.edmundoptics.com/f/High-Con ... ilm/14385/
Thanks for the hints. But it seems that the price of a homebuilt analyzer is approaching the price of the original Olympus. I'll look into this. :)

Alan Wood
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Post by Alan Wood »

The analyser and polariser are both the same sort of material, the analyser goes above the subject, the polariser goes below the subject.

You can buy a square of polarising film material, cut it to the size needed for your analyser, and see how you get on. £5 plus postage for a 2-inch square:

http://www.quekett.org/about/shop

Be careful with the film for your analyser, don't crease it, don't get fingerprints on it.

Alan Wood

Dreamspy
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Post by Dreamspy »

Alan Wood wrote:The analyser and polariser are both the same sort of material, the analyser goes above the subject, the polariser goes below the subject.

You can buy a square of polarising film material, cut it to the size needed for your analyser, and see how you get on. £5 plus postage for a 2-inch square:

http://www.quekett.org/about/shop

Be careful with the film for your analyser, don't crease it, don't get fingerprints on it.

Alan Wood
Ok that's a steal. I thought I had to go for the more expensive options for the required optical quality.

JohnyM
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Post by JohnyM »

While it's fine for polarizer, you'll notice the difference between dedicated quality microscope analyzer and sheet.

Dreamspy
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Post by Dreamspy »

JohnyM wrote:While it's fine for polarizer, you'll notice the difference between dedicated quality microscope analyzer and sheet.
So if I understand this correctly, I should be safe with using the cheap film polarizer below the sample, but it's advised to use a quality polarizer in the optical path (above the objective) ?

JohnyM
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Post by JohnyM »

That's correct.

Dreamspy
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Post by Dreamspy »

Alan Wood wrote:And here are 2 of the phase contrast attachments:

https://www.optics-pro.com/microscopy/m ... /m,Olympus

Alan Wood
Say which of those items would I need?

I assume I need the Olympus CKX3-SLPIC ring diaphragm for inversion contrast (IVC) to put on my light source, but regarding the other items, I'm not so sure. Any hints on that?

Saul
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Re: Filters for Olympus CX41 (phase, polarization and darkfi

Post by Saul »

Dreamspy wrote:I'm looking for ... darkfield as well...
Are they 28mm in diameter and 3mm thick ?

Dreamspy
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Re: Filters for Olympus CX41 (phase, polarization and darkfi

Post by Dreamspy »

Saul wrote:
Dreamspy wrote:I'm looking for ... darkfield as well...
Are they 28mm in diameter and 3mm thick ?
Not so sure... can I measure these lengths somewhere on the microscope?

If I understand correctly then darkfield is a mask you put on the light, right? In that case the diameter is much more than 28mm (of the light), and the thickness can be anything really, since there is a lot of empty space between the light and the collimator lens before the sample. Or am I misunderstanding something here?

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