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 Post subject: Polarising filters for microscope
PostPosted: Sun Mar 21, 2021 3:55 pm 
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My microscope plan objective has a thread to take a filter, so I was planning on purchasing polarisers so I can also use it as a polariscope when needed by screwing one into the objective and covering the transmitted light with another.

Most photography polarising filters are listed as 'circular' in order to work with autofocus systems on cameras. Will these work in the required manner for a polariscope, or do I need to track down the older linear types? I can't seem to find any information by searching the net.

Many thanks for any advice.


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 Post subject: Re: Polarising filters for microscope
PostPosted: Tue Mar 23, 2021 8:43 pm 
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A circular polarizer is just a linear polarizer with a quarter wave plate stuck to it. As long as the linear side is facing down it will still work as an analyzer--this is easy to test since only with the two filters flipped the right way will they give extinction.

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 Post subject: Re: Polarising filters for microscope
PostPosted: Wed Mar 24, 2021 3:10 pm 
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Many thanks, I was concerned the wave plate may have made a difference, that makes getting them easier.


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 Post subject: Re: Polarising filters for microscope
PostPosted: Wed Mar 24, 2021 7:19 pm 
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It's actually a bit beneficial, since plane polarized light can interact oddly with flat reflective surfaces (like prisms and mirrors). Official microscope analyzers will usually have one as well.
The main potential issue with using photographic filters like this is that they are sometimes a bit thicker than the official ones which may introduce aberrations depending on how high your microscope's numerical aperture goes. I'm a bit curious which one you have, sounds like a CMO unit.

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