How to make a lambda wave plate?

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Wes
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How to make a lambda wave plate?

#1 Post by Wes » Sun Jul 14, 2019 11:42 am

Hello everyone

Does anyone have experience with making DIY wave retarder plates for polarized light studies? I tried making one out of cellophane but it was not optically clear and deteriorates the image quality when placed between the specimen and analyzer; when placed between the polarizer and specimen it produces interesting interference effects but I don't think thats technically the same thing (effects of this device together with polarizer rotation attached below). Perhaps someone knows of a cheap and optically clear material that I can use (the cellophane I used was the kind that comes with microscopes slides).

Thanks
Wes
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Re: How to make a lambda wave plate?

#2 Post by zzffnn » Sun Jul 14, 2019 2:36 pm

Wes,

I don't think optically clear "lamda plate" material that you can place above obejctives can be found cheaply. Unless you found a surplus eBay seller who knows nothing about his stuffs. I would jump on it before you, if there is one :twisted:

I used cheap cellophane "lamda plate" the cheap way, below sample and above polarizer, and like the esthetics. But that is only good for hobby use.

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Re: How to make a lambda wave plate?

#3 Post by Wes » Sun Jul 14, 2019 3:13 pm

Yes I missed a new full lambda plate from Zeiss for $85.00, it was mislabeled in terms of its manufacturer (probably explaining the nice price) but I forgot the bidding deadline and I really regret it.
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Re: How to make a lambda wave plate?

#4 Post by abednego1995 » Mon Jul 15, 2019 2:23 am

Try mica. It used to be the material of choice :-)

Cheers,
John

Microworldofgems
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Re: How to make a lambda wave plate?

#5 Post by Microworldofgems » Mon Jul 15, 2019 4:58 am

Edmund optical has lambda plate plastic sheet available for about 15 bucks for a 2 inch square.

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Wes
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Re: How to make a lambda wave plate?

#6 Post by Wes » Mon Jul 15, 2019 6:59 am

abednego1995 wrote:Try mica. It used to be the material of choice :-)

Cheers,
John
Microworldofgems wrote:Edmund optical has lambda plate plastic sheet available for about 15 bucks for a 2 inch square.
Thank you John and Microworldofgems. These are great ideas!
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Re: How to make a lambda wave plate?

#7 Post by MicroBob » Mon Jul 15, 2019 2:50 pm

Hi Wes,
not tried for microscopy, but might be an idea: The plastic foil to wrap flowers in is optically very nice.
Another source may be screen protectors for cameras and smart phones and display windows of cameras and objective covers of smartphones.

It also is a big question whether you want a retarder of unspecified properties or something precise to use on a polarizing microscope = measuring device with added image option.
I'm sure that the original lambda plates have the right amount of retardation but I wouldn't bet on them supporting perfect image quality as this is not necessary for pol work.

Bob

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Re: How to make a lambda wave plate?

#8 Post by Hobbyst46 » Mon Jul 15, 2019 8:18 pm

MicroBob wrote:...not tried for microscopy, but might be an idea: The plastic foil to wrap flowers in is optically very nice.
Hi Bob, actually, the popular transparent foil for flower wraps is cellophane.
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Re: How to make a lambda wave plate?

#9 Post by Wes » Tue Jul 16, 2019 11:28 am

If its really clear the flower shop cellophane might be just what I need. Neat suggestion!
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Re: How to make a lambda wave plate?

#10 Post by MicroBob » Tue Jul 16, 2019 11:47 am

Our house is very old, built began in the last months of WW2. When we bought it in 2000 there were still some single pane windows and we used this flower foil to get a bit better isolation without much effort. So I have looked a lot through this material! :lol:

Bob

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Re: How to make a lambda wave plate?

#11 Post by Hobbyst46 » Tue Jul 16, 2019 1:23 pm

Microworldofgems wrote:Edmund optical has lambda plate plastic sheet available for about 15 bucks for a 2 inch square.
What I found םn their site at these prices are pieces of flexible modified polycarbonate film. Thickness is not specified. They also sell "polymer" retarders, which are sandwitched film between two glass plates. But for 10X the price.
In fact, flat hard transparent CD/DVD plastic packages are made of polycarbonate (guess); I wonder if they can serve as retarders (what with the tiny scratches...).
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Re: How to make a lambda wave plate?

#12 Post by Tom Jones » Tue Jul 16, 2019 2:51 pm

Look at the 50mm x x50mm. Full, 1/2 and 1/4 wave. $18 each for the full wave, $12 each for the 1/2 and 1/4. Click on "Specifications and Documents" below each description to get the full data, including thickness. Put them below the condenser as they are not optically clear enough to go between the specimen and the eyepiece.

https://www.edmundoptics.com/search/?cr ... 3AMTQ4Mjc1

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Re: How to make a lambda wave plate?

#13 Post by MicroBob » Tue Jul 16, 2019 4:00 pm

Hobbyst46 wrote:In fact, flat hard transparent CD/DVD plastic packages are made of polycarbonate (guess);
Hi Doron, I think they are Polystyrene, cheap and transparent.

Bob

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Re: How to make a lambda wave plate?

#14 Post by Seb28 » Tue Jul 16, 2019 6:05 pm

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Re: How to make a lambda wave plate?

#15 Post by Hobbyst46 » Wed Jul 17, 2019 8:53 pm

MicroBob wrote:
Hobbyst46 wrote:In fact, flat hard transparent CD/DVD plastic packages are made of polycarbonate (guess);
Hi Doron, I think they are Polystyrene, cheap and transparent.

Bob
Bob, thanks for the correction; yes it is polystyrene.

Just for fun, I performed a small experiment with cellophane and a CD package plate. Such experiments have been done and posted by other folks in the past.

1) Sandwiched A 2cm x 2cm piece of thin flower-wrap cellophane between twp slides, placed the sandwich-slide on top of the polarizer (which in turn is laid on the field aperture). The other polarizer in inside the head, above the objectives. Rotation of the sandwich-slide creates a partial spectrum of background colors. Adding a second layer of cellophane creates a full spectrum and fairly strong coloration.

2) Cut a 2cm X 2cm piece of solid transparent polystyrene from the front plate of a DVD package. Placed the piece on the polarizer on top of the field aperture, and repeated the experiment. The same rainbow effect was obtained. I was not sure about the birefringence of PS, but there it is and it works.
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Re: How to make a lambda wave plate?

#16 Post by Hobbyst46 » Thu Jul 18, 2019 2:58 pm

MICA is one of the materials for making retarders. I just noticed that small MICA plates are being sold, very cheaply (a few $$ apiece) as replacement parts for microwave ovens. Various dimensions. No idea about their optical properties - transparency, etc - maybe someone will try those.
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Re: How to make a lambda wave plate?

#17 Post by Wes » Fri Jul 19, 2019 7:16 pm

Tom Jones wrote:Look at the 50mm x x50mm. Full, 1/2 and 1/4 wave. $18 each for the full wave, $12 each for the 1/2 and 1/4. Click on "Specifications and Documents" below each description to get the full data, including thickness. Put them below the condenser as they are not optically clear enough to go between the specimen and the eyepiece.

https://www.edmundoptics.com/search/?cr ... 3AMTQ4Mjc1
Thats kind of what I'm doing now. A piece of polystyrene or cellophane goes above the polarizer but below the condenser (thats how I get the images in the OP). But technically speaking that's not the same as a dedicated phase plate that's going above the specimen, is it?
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Re: How to make a lambda wave plate?

#18 Post by patta » Sun Oct 24, 2021 5:23 pm

Sunday project: Mica
I am in a similar situation, vintage scope without wave plate. I'm missing the psychedelic fun of polarization.
This summer I've found some crystals of Mica in a gravel road. Let's make a Lambda wave plate! Like the pioneers!
Unfortunately those crystals turned out too dirty and wicked, they made some color effect but also awful image quality. Then, remember, when I was a kid I had mineral-period and went once to a local abandoned mica mine (risking life of course). Dig in the old boxes, and some better, large and clean crystals were there, waiting for me!.

Making the plates:
Cleaving the crystals is easy; cutting them properly and without scratching, more difficult.
A neat trick I've read somewhere, use scotch tape to "peel off" the mica layers; it works.
To make quarter-wave, the plate should be about 30 micron. Very thin, but feasible: mica cleaves very thin by itself..
I've just made many random attempts and chosen the plates that worked best on the microscope. Anyway the plates are so thin and delicate that measuring the thickness invariably meant scratching and ruining it. They are super-soft and crack like nothing.
Also tried much thicker plates (like 100-200 um) they seem to work ok, probably as n + 1/4 retard.
Some of the plates, worked pretty nice, colorful image and not too much loss of sharpness/contrast. Even if the plate weren't perfectly flat and with visible defects.

I've then tried to sandwich the plate between two coverslips, so it gets protected and may last long. But no success here, bad images, I think because the coverslips are not parallel and warp, so degrading the image.
I'll keep the best "naked" mica slices, mounted on slider, and be very delicate with them. I got 4-5 good ones with different color effects.


Disclaimer:
Laborious Indians (Radical?) sell customized-to-your-size wave plate sliders for like 40$ (incl shipping, warranty and greetings) so this DIY quarrying mica and slicing it makes sense only as fun/didactical activity.

Mica plate thickness:
https://sci-hub.se/https://doi.org/10.1 ... 98)00074-7
Mica quarter wave photos.jpg
Mica quarter wave photos.jpg (219.07 KiB) Viewed 591 times
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Mica quarter wave.jpg
Mica quarter wave.jpg (63.5 KiB) Viewed 591 times
Last edited by patta on Mon Oct 25, 2021 4:56 am, edited 5 times in total.

Alexander
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Re: How to make a lambda wave plate?

#19 Post by Alexander » Sun Oct 24, 2021 5:35 pm

Just replace your linear pol filter with a circular one. The difference is nothing but a 1/4 lambda wave plate.

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Re: How to make a lambda wave plate?

#20 Post by patta » Sun Oct 24, 2021 5:58 pm

Alexander wrote:
Sun Oct 24, 2021 5:35 pm
Just replace your linear pol filter with a circular one. The difference is nothing but a 1/4 lambda wave plate.
I'll go back to the gravel road, hunting for circular polarization crystals!

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Re: How to make a lambda wave plate?

#21 Post by MikeBradley » Mon Oct 25, 2021 12:08 am

The Quekett microscopy club in the UK has supplies available from their shop:
"Wave retarders – £9.20 plus postage
Available as ¼, ½ or full wave retarders in 2-inch squares."

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

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Re: How to make a lambda wave plate?

#22 Post by microcosmos » Mon Oct 25, 2021 1:25 am

I thought it might be worth mentioning this home-made Berek compensator made from a mica plate, which rotates to give variable retardation.

Patta - thanks for the story and images - I enjoyed them!

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Re: How to make a lambda wave plate?

#23 Post by Wes » Tue Oct 26, 2021 6:59 pm

patta wrote:
Sun Oct 24, 2021 5:23 pm
What a cool project! I don't think I've ever seen mica in the wild but most likely I haven't been paying attention. As you pointed out the success of this project depends on a high quality source of mica so my question would be where do you find the finest mica?
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Re: How to make a lambda wave plate?

#24 Post by patta » Thu Oct 28, 2021 7:04 am

Wes wrote:
Tue Oct 26, 2021 6:59 pm
Thanks!
Sure you've had mica under your eyes, it is widespread; in most granite rocks, when there is something shiny, it's small mica crystals usually.
To check, just rub your finger against it: if some glitter attaches to the finger, that's our waveplate material.

Large clean cristals, a bit more rare... mine came from a dedicared mine in Piona, Italy, near to where I grew up.
The other crystals I've found on the "gravel road" come from some generic crushed granite; not so good but with some patience, I think was possible to find something clear enough, 6mm size, for optical use.

I've read that the best crystals today come from a mine in India... let's take a trip there!

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