Polarizing filters

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
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DonSchaeffer
Posts: 733
Joined: Sun Mar 22, 2020 10:06 am
Location: Winnipeg, Manitoba, Canada

Polarizing filters

#1 Post by DonSchaeffer » Thu Jul 09, 2020 8:36 pm

Where can you get polarizing filters to set up a polarizing microscope?

Zuul
Posts: 212
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Location: California

Re: Polarizing filters

#2 Post by Zuul » Fri Jul 10, 2020 12:28 am

You buy polarizer sheets on Amazon or use camera filters. (Circular polarizers need to be oriented correctly to work. Linear can have either side up.)

DonSchaeffer
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Joined: Sun Mar 22, 2020 10:06 am
Location: Winnipeg, Manitoba, Canada

Re: Polarizing filters

#3 Post by DonSchaeffer » Fri Jul 10, 2020 2:32 am

Thanks. I'll lok for sheets. Those filters are expensive and too big.

Zuul
Posts: 212
Joined: Fri May 01, 2020 9:01 pm
Location: California

Re: Polarizing filters

#4 Post by Zuul » Fri Jul 10, 2020 3:12 am

DonSchaeffer wrote:
Fri Jul 10, 2020 2:32 am
Thanks. I'll lok for sheets. Those filters are expensive and too big.
You can get them for peanuts used, though. Just have to keep your eyes open. If you have a local camera shop they probably have a drawer full of old used ones. The small ones aren’t any good for modern lenses.

Mraster2
Posts: 84
Joined: Sat May 02, 2020 7:29 pm

Re: Polarizing filters

#5 Post by Mraster2 » Fri Jul 10, 2020 2:37 pm

It is something I have been meaning to try but didnt get the rountuit! till I saw your post and I have just ordered (on ebay) a cheap replacement iphone polarizing film to try.
I have no idea if it is linear or circular even* !

Did you fix the heat problem from your lamp? because one film should go below the stage and might melt ?

* edit : I am assuming that linear is needed ???

BramHuntingNematodes
Posts: 511
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: Polarizing filters

#6 Post by BramHuntingNematodes » Fri Jul 10, 2020 3:52 pm

All the sheets I have seen are linear. Quarter wave plate film is significantly more expensive for the area.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

PeteM
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Location: N. California

Re: Polarizing filters

#7 Post by PeteM » Fri Jul 10, 2020 4:11 pm

DonSchaeffer wrote:
Fri Jul 10, 2020 2:32 am
Thanks. I'll lok for sheets. Those filters are expensive and too big.

The camera filters come in a myriad of sizes - I've bought them as small as 14mm for phones and in dozens of sizes to fit microscope heads and field (illumination) lenses. Prices are typically under $10 for the imports. They can be left in their mounts for easy handling or (usually) removed with a small spanner to replace something that may be faded, broken, or delaminated. They're measured by thread size - the actual filter area is usually a couple mm smaller.

These come sandwiched between glass. They're flat, scratch resistant, and cut perfectly round. The film is fine for casual work, but the glass polarizers hold up better for the long term.

The main deficit of both the cheaper camera types and the film is that it often won't achieve quite as dark an extinction (when crossed) as OEM microscope polarizers and filters. Still good for most purposes. If you want utmost extinction for something like a DIC system, a better Japanese or US made camera polarizer will often do better than one of the cheapest Chinese ones (those sometimes under $3 shipped, still nicely mounted in threaded holder).

Zuul
Posts: 212
Joined: Fri May 01, 2020 9:01 pm
Location: California

Re: Polarizing filters

#8 Post by Zuul » Fri Jul 10, 2020 5:01 pm

I have one Tiffen and one Hoya that together offer excellent extinction. Those are good mid-priced brands. The cheap ones that I got bundled with lenses aren't nearly as good. The Amazon film I got falls somewhere in between.

NinetySix
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Joined: Sun Sep 08, 2019 1:35 pm

Re: Polarizing filters

#9 Post by NinetySix » Thu Aug 20, 2020 2:54 pm

I've had great results using the cheapest polarising film I could find on eBay locally, about AU$3 to suit an iPhone 6 I think it was.

Cutting the film into filter sized pieces gave unimpressive results, a little better than a film I carefully peeled from an LCD salvaged from a printer left on the side of the road.

However, once applied (self adhesive, peel 'n stick) to glass the filters became very effective, holding them crossed up to a lightbulb only the tiniest hint of an led die was visible in an otherwise pitch black background. I cut a standard microscope slide into a square (25x25mm) and then cut a tiny piece from each corner till it was a perfect fit in the recess underneath the trinoc dovetail. I used a larger piece of quite thin glass from a picture frame cut about 60x60mm and sit that on to of the field lens. The filters have to be placed with the filter sides facing away from each other (as in the glass sides facing towards each other) for maximum extinction.


Sample photos here:

https://photos.app.goo.gl/wGiciW1yfQfd2JpX6
https://photos.app.goo.gl/HsvcHDtoxqwbheet5

MicroBob
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Joined: Sun Dec 25, 2016 9:11 am
Location: Northern Germany

Re: Polarizing filters

#10 Post by MicroBob » Thu Aug 20, 2020 5:51 pm

Probably the cheapest option: The film from some 3D cinema glasses. They sre circular polarizers do have to be used the right way round. On a binocular microscope s good place for the analyser is below the bino inside the tube head. This gives better results than on top of one of the eyepieces

Element 56
Posts: 271
Joined: Thu Oct 13, 2016 3:48 pm
Location: Lancaster County, PA

Re: Polarizing filters

#11 Post by Element 56 » Thu Aug 20, 2020 7:27 pm

Might not be within your budget but I use these folks,

https://www.apioptics.com/

Their film is very good quality and easy to work with. Also it doesn't stink! I bought a used sheet once and the smell wasn't worth the price savings!

Kirby

Bemoc
Posts: 55
Joined: Wed Sep 16, 2020 4:23 am

Re: Polarizing filters

#12 Post by Bemoc » Sat Oct 10, 2020 7:53 pm

There is a guy who makes them into the right sizes, and he gives out good advice and has a bunch of sets. His cover letter says: "Please consider purchasing our complete Rheinberg filter set - or even a subset. It is such a giant step up in viewing and photographing subjects. We offer both in our Ebay store as well as other items - Affordable Microscope Filters." . His name is David, AffordableFiltersGuy. I got the DIY polarization set which came with two eyepiece rounds, two condenser filter holder rounds, one green round condenser-sized, and one sheet of the stuff about 1.5" x 2.5". Also two pages of clear and friendly instructions. Main thing is that his filters have plastic on both sides, which must be removed.

Greg Howald
Posts: 58
Joined: Tue Oct 20, 2020 6:44 am

Re: Polarizing filters

#13 Post by Greg Howald » Sat Oct 24, 2020 3:24 pm

I took a chunk of pvc pipe of the right diameter to fit over my illuminator and glued the polarizer to that. That way I can rotate the polarizer to adjust the degree of polarization.
Greg

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