1/4 wave filter source

[JWW]

Looking for an inexpensive source for (3) 60mm (actual filter diameter) 1/4 wave filters. I tried some Edmund Optics 1/4 film, but it's a bit too 'thin' for my intended purpose.

[PeteM]

If you want a 1/4 wave plate purely for visual effects - and not an exact wavelength determination - there are a number of DIY alternatives. Several have been mentioned in past posts: layers of clear packing tape, CD covers, a circular polarizer oriented with the wave plate in the direction you need it, and so on. It might be worth trying large welding hood protector plates (polycarbonate) to see if they are linear and near the right wavelength - usually the plastic has to be stretched as in most tapes and films but those might have been molded from one side. Ebay seller Techno occasionally has something, though usually not that large a diameter. The Edmund filters could be glued to a frame or sandwiched between glass. Circular camera polarizers (a linear polarizer plus a wave plate) can be quite cheap, up to around 72mm, if you can work around having a polarizer in the path.

If you need something more exact, sandwiched in glass, the only sure method I know is to stack a few Federal Reserve Notes together, and hand them over for the real thing - even, usually, on eBay.

[JWW]

I have acquired a few Wild Heerbrugg POL rotary stages over the years. Two of which are missing the the rotating slider which holds a 1/4 wave filter and the swing-out holder which holds a linear polarizer. Both filters are 60mm in diameter. I've designed a new slider and swing-out linear polarizer holder and each needs the proper filters. The 3D-printed slider operates as well as the original, including the gears. I had no problem finding 60mm linear polarizers but now need the 1/4 wave filters. I am going to experiment with some Emund 1/4 film but haven't received it yet. It's pretty thin as I have used it in the past but prefer to use something thicker.

I don't know if camera rotating polarizers are made up of two filters, or if they're glued together. If they're two separate filters and have retaining rings, then I suppose that would work if I found something close to 60mm in diameter. I have a B+W 77mm camera C-POL filter, which rotates but I only see one retaining ring, so I assume those filters are glued together, not that it would work in my application.

Of course, I can always modify my design to accommodate a little smaller filter for the slider.

-JW:

[PeteM]

Beautiful stages and nice work on those sliders.

It might be possible to make up a sort of 60 mm OD blackened washer with about a 55 mm ID. Stretch the Edmund material flat with tape along the edges at room temperature, put a coat of plastic-metal adhering adhesive on one side of the washer (2.5mm or so adhering area), place the washer on the flattened film, add a weight, let it cure - and maybe have a rigid-enough assembly.

You could also try above-room-temperature assembly to get it even more taut, though it might induce unwanted strain in the film.

[macnmotion]

I've bought 1/4 lambda wave plate filters from the following seller on ebay. I don't see 60mm listed but maybe you can contact them and ask if that's something they can get for you.

https://www.ebay.com/str/techno2020?mkc ... media=COPY

[JWW]

Pete,

That's who I purchased the 60mm linear filters from. BTW, I did ask the eBay seller if they make the 1/4 wave filter but haven't heard back. I did find what I wanted but I'd still like to know if that seller makes them.

[PeteM]

Hi did have a 50mm or so wave filter, a while back. Techno is a good and reliable seller IMO, but in this case the wave filter had a significant defect - a sort of square (machine-made) defect that showed up when imaged between polars.

[JWW]

I made a short video on the progress of my slider and swing-out polarizer for the Wild rotating polarizing stage. Sorry for the OOF slider closeup in the beginning of the video.

https://www.youtube.com/watch?v=sEIb4wlDayw

In case anyone wants to know, I purchased the 1/4 wave retarder here;

https://www.apioptics.com/

-JW:

[PeteM]

JWWW -- nicely done and illlustrated - thanks for the post.

Which of the quarter wave plates did you choose (glass high performance?) and are you happy with it? Also curious if you went larger than 50mm and the cost?

[JWW]

Bummer. The slider came out perfect, so I thought. I tried installing it in one of the rotating POL stages, but it doesn't fit. It seems hair is too thick, and I do mean hair. It's hard to describe the installation. The stage has to be disassembled, and the slider has to be placed inside. Once closed and screwed back together, if it's too thick, it compresses the slider a touch too much and won't let the gears move. The tolerances are already pretty tight, but I'm sure I can eventually fix it. I have a machinist granite surface plate, so I'll put some wet/dry paper on it and sand one side. I'm pretty burnt out at the moment, so I'm pulling off this project for a while. Here's a link to the filters I purchased. I bought the 50mm ones. I'm sure they'll work fine, but I have not tested it to verify.

Just something to note. One of the (3) centering screws is a total bear to fix. Every stage has had to be repaired so far. I have only one left to do. So far, I've been super lucky. The circled screw is made out of brass and hollowed/bored out. It has a brass tube inside that has a spring inside it. It, too, was all gummed up. It took me a week on each stage to get the screw out. I've soaked it in 99% alcohol and Sea Foam Deep Creep. Even then, it was extremely difficult to turn. I had to file a deeper and slightly broader slot in the screw head so I could use a huge screwdriver. It took everything I had to turn that puppy, but I got them all out. I was quite surprised the thread wasn't damaged. The ones I've repaired all work fine now.

https://www.apioptics.com/product/apqw9 ... .100%22%29

-JW:

[Macro_Cosmos]

A circular polariser consists of a 1/4 λ plate and a linear polariser. If you have one lying around, take it apart and you have your waveplate with an additional linear polariser.

[JWW]

A circular polariser consists of a 1/4 λ plate and a linear polariser. If you have one lying around, take it apart and you have your waveplate with an additional linear polariser.

Thanks, all the ones I've ever seen are glued together.

-JW:?

[Phill Brown]

I've only seen bonded to make a single element filter.

[Macro_Cosmos]

The one I pulled apart must be very cheap or very old then, unfortunate. I have seen film type waveplates for less than $20 for a 50x50mm square. Supposedly they are used for screens.