Polarizing objectives on an ordinary bright field microscope

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papaki72
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Polarizing objectives on an ordinary bright field microscope

Post by papaki72 »

Is it possible to use such objectives under an ordinary biological microscope? If not is it possible to adapt a bright field microscope to act as a polarizing microscope?

Pau
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Post by Pau »

Yes it is for sure if the specifications (tube correction, parfocal distance and thread) match your microscope.

For most amateur pol work you don't need dedicated pol objectives, in my experience almost any good objective (and most not so good ones) work very well for pol. In most cases pol objectives are just normal objectives certified to be strain free.

You can adapt almost any BF microscope for pol, you just need to place a polarizer under the condenser (at the filter try or over the light source and and another one, called analyzer, over the objective, usually into the microscope head. You need at least one of them to be rotatable to regulate polarization.
A circular rotating stage is convenient to orientate the specimen but not absolutely required.
You want linear polarizers, although if you already have circular ones putting them with the "front side" facing to the specimen they just work as linear.

For the substage polarizer you can use even film sheets of good quality, as analyzer you need a good flat glass filter. Camera polarizers can do but often do not full extinct light providing a nice but in principle undesirable blue cast and background although some good expensive ones like the B+W usually work well.
Pau

papaki72
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Post by papaki72 »

Would the insertion of a filter in the microscope head affect the tube length and hence deteriorate the quality of the image?

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Post by Pau »

With an infinite corrected microscope it will not (in fact inserting optical elements between the objective and the head with no image degradation is in the origin of the infinite design).

With finite corrected microscopes in principle it will do although in practical terms it will be irrelevant except for critical work with high NA objectives. I've done it for many years for low magnification petrography with no issues.

Many finite corrected microscopes place that intermediate optics between two lenses (telan lenses) that create an infinite space between them in an intermediate piece between the microscope nose and head.

What is your intended application? What magnification and equipment do you plan to use?
Pau

papaki72
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Post by papaki72 »

I am a hobbyist and I am using a Biolam R5 microscope that uses compensating eyepieces. I have a pair of 10x infinity corrected and I am looking for objectives of 20x and 10x.
In no case can it be said that I am doing critical work.

Olympusman
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Hybrid polarizing microscopes

Post by Olympusman »

Here is an article I wrote on hybrid pooarizing microscopes:

http://www.microscopy-uk.org.uk/mag/ind ... polar.html

Mike
Michael Reese Much FRMS EMS Bethlehem, Pennsylvania, USA

Pau
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Post by Pau »

After a quick search I can't find info about "R5" but AFAIK the Biolam is a finite (160mm) corrected microscope, so infinite objectives will not work well.
Infinite corrected microscopes do have an adequate tube lens generally placed at the base of the head to converge the parallel rays exiting from the objective to focus them inside the eyepieces/camera. In many cases you can focus a finite scope with infinite objectives but this will degrade the image, especially with high NA objectives, and you will lose parfocality

As I formerly proposed, just dropping a good polarizer inside the microscope over the objective and another one rotatable over the light source will work well and it's very simple.
Pau

johan
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Post by johan »

I've done what you'd like to do on a different brand of microscope. I bought an item like this but for my brand (Nikon labophot): http://www.ebay.co.uk/itm/Polarizing-As ... 2394519036

My scope is also a finite so it works on finites. This comes with 2 components, one part that you open up the scope for to drop into the space between the eyepiece and the nosepiece, and another part that just sits on top of the bottom illumination source. Dropping the part in means you're not adding any distance. It all works very well together indeed.

My advice would be to contact the seller who makes these things and see if they can make or have such a set for your brand and model of scope. The seller goes by the name of optitec2020 - http://www.ebay.co.uk/usr/optitec2020?_ ... 7675.l2559 - I am not affiliated in any way.

Good luck
My extreme-macro.co.uk site, a learning site. Your comments and input there would be gratefully appreciated.

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