MicrobeHunter.com Microscopy Forum

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

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.)

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

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.

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 ???

All the sheets I have seen are linear. Quarter wave plate film is significantly more expensive for the area.

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).

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.

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

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

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

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.

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