Pol Sliders ... Advice needed please

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MichaelG.
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Pol Sliders ... Advice needed please

#1 Post by MichaelG. » Thu Mar 04, 2021 2:24 pm

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I have three sliders for my CTS M72 Polarizing Microscope, but I am struggling to understand how they are used.

All three are marked with the word ‘Slow’ and a directional arrow, but only the Quartz Wedge seems to vary in its behaviour when inserted to differing extent. ... So what does the word ‘Slow’ imply ?

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CTS Pol sliders
CTS Pol sliders
03AB3789-020A-48FD-B53D-BA903CEE66FC.jpeg (174.44 KiB) Viewed 3161 times
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To my very limited understanding:
The Mica plate provides 1/4 wavelength retardation, and
The Sensitive Tint plate provides one wavelength retardation

The Olympus Java tutorial seems singularly unhelpful:
Insertion of a first-order retardation plate or compensator between the specimen and the analyzer changes the optical path difference of light passing through the specimen. Compensator plates providing a retardation of one entire wavelength (550 nanometers) are termed sensitive tint or first-order red plates. These quartz plates can be utilized to determine the sign of birefringence exhibited by the specimen.
Ref. https://www.olympus-lifescience.com/en/ ... drotation/
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... because it doesn’t explain how !!

I am obviously missing some small snippet of assumed knowledge; so could someone kindly advise me ?

I can produce pretty colours, but I really want to learn how to use this microscope.

Thanks
MichaelG.
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apochronaut
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Re: Pol Sliders ... Advice needed please

#2 Post by apochronaut » Thu Mar 04, 2021 3:48 pm

Maybe it's just a caution of how to insert the sliders due to their delicacy. Ramming a mica or quartz slider up to it's stop with some force probably could cleave the mica or fracture the quartz.

Tom Jones
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Re: Pol Sliders ... Advice needed please

#3 Post by Tom Jones » Thu Mar 04, 2021 4:24 pm

MichaelG,

That's indicating the "slow wave" axis for the waveplate. Slow waves and fast waves are properties of polarized light. You're going to find those interesting to play with. The sensitive tint should be a full wave (AKA first order) retarder, the quarter wave (lambda) retarder is just that, and the quartz wedge slider varies the retardation depending on the plate thickness you are looking through.

If you really want to jump into a deep rabbit hole :shock: , start learning about polarization in general, and polarization microscopy.

https://www.microscopyu.com/techniques/ ... ized-light

https://www.edmundoptics.com/knowledge- ... aveplates/

https://www.newport.com/n/introduction-to-waveplates

https://www.olympus-lifescience.com/en/ ... rderplate/

And since you really want to learn, here's the polarized light microscopy bible: https://www.mccrone.com/mm/book-review-essentials-plm/ It's pricey (~$225) but a very thorough text. And boy, do you have a lot of reading to do!! :roll: 8-) :lol:

Oh, yeah. I'm NOT an expert by any means! :?

Tom

MichaelG.
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Re: Pol Sliders ... Advice needed please

#4 Post by MichaelG. » Thu Mar 04, 2021 5:02 pm

Tom Jones wrote:
Thu Mar 04, 2021 4:24 pm

[...]

And since you really want to learn, here's the polarized light microscopy bible: https://www.mccrone.com/mm/book-review-essentials-plm/ It's pricey (~$225) but a very thorough text. And boy, do you have a lot of reading to do!! :roll: 8-) :lol:
Thanks for the links, Tom

I actually purchased that one on behalf of our Microscopical Society in 2019 ... but was rather disappointed to find that it’s basically a collation of course notes for the College, not a newly-written book.

I have been trying to work my way through ‘The Polarizing Microscope’ by A.F. Hallimond [of Vickers], but am finding it heavy going.

We shall persevere !!

MichaelG
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MichaelG.
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Re: Pol Sliders ... Advice needed please

#5 Post by MichaelG. » Fri Mar 05, 2021 3:13 pm

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For anyone else treading the same treacherous path :
Here are two useful links

https://faculty.uml.edu/Nelson_Eby/89.5 ... oscopy.pdf

https://babel.hathitrust.org/cgi/pt?id= ... =1up&seq=9

and my recommendation of ‘Introduction to Crystal Optics’ by C.E. Marshall
... Published by Cooke Troughton & Simms, in 1953

MichaelG.
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Wes
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Re: Pol Sliders ... Advice needed please

#6 Post by Wes » Fri Mar 05, 2021 3:20 pm

Hi Michael,

I once attempted to write a post about the nature and use of wave plates. You can find it here: https://www.microbehunter.com/microscop ... 875#p71875

In short the retardation plate is a piece of optically anisotropic material that exhibits direction-dependent variation in its refractive
index resulting from its molecularly ordered nature. The wave plate's slow axis is the direction in which light experiences the highest refractive index.

Wes
Zeiss Photomicroscope III BF/DF/Pol/Ph/DIC/FL/Jamin-Lebedeff
Youtube channel

MichaelG.
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Re: Pol Sliders ... Advice needed please

#7 Post by MichaelG. » Fri Mar 05, 2021 7:11 pm

Thanks for the reminder, Wes ... Much appreciated.

MichaelG.
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hans
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Re: Pol Sliders ... Advice needed please

#8 Post by hans » Mon Mar 08, 2021 7:58 pm

No theory, but if a concrete example would be useful, this AO manual gives a procedure for checking gout crystals:
https://user.xmission.com/~psneeley/Per ... Manual.pdf

MichaelG.
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Re: Pol Sliders ... Advice needed please

#9 Post by MichaelG. » Mon Mar 08, 2021 11:22 pm

Interesting ... Thanks, Hans

MichaelG.
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