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Continuously variable darkfield / COL mask

 
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zzffnn



Joined: 22 May 2014
Posts: 1815
Location: Texas USA

PostPosted: Fri Mar 31, 2017 12:36 pm    Post subject: Continuously variable darkfield / COL mask Reply with quote

Does any microscopist here have for sale or know of (an eBay search term of) a continuously variable darkfield / COL mechanical mask?

I like my Leitz Heine zoom condenser very much, and like to have a cheaper mechanical mask that does a similar thing for a regular condenser.

Something like the rosette part of this condenser:
http://www.ebay.com/itm/WATSON-amp-SONS-THE-UNIVERSAL-039-MICROSCOPE-BRASS-CONDENSER-DARK-FIELD-APERTURE-/151938429441?redirect=mobile&nma=true&si=waUm1xbv7UyuW4W9Ke6IvoM6qz4%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

I know it exists, but is rare.

I know of Zeiss pancratic condenser and Reichert Polyphos condenser but do not want those. I just want a universal mechanical rosette to put onto the focal plane of a regular condenser.

Thank you very much.
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GaryB



Joined: 29 Jul 2016
Posts: 521

PostPosted: Fri Mar 31, 2017 2:15 pm    Post subject: Reply with quote

I did a search on those a while back after seeing these on Molecular Expressions site https://micro.magnet.fsu.edu/primer/techniques/darkfield.html to no avail. It may be possible to make a version of it using a small blacked cocktail umbrella as a pattern. Mounted on a spider, it could provide what's needed.

If I had a cocktail umbrella I'd try myself. It'd work if small enough. Hmm, where do I find one around here.... *rubs chin*
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Cactusdave



Joined: 09 Jun 2009
Posts: 1631
Location: Bromley, Kent, UK

PostPosted: Fri Mar 31, 2017 2:19 pm    Post subject: Reply with quote

Usually called a leaf stop or variable leaf stop. They are quite rare but do occasionally turn up on Ebay. More useful information here http://www.olympus-lifescience.com/de/microscope-resource/primer/techniques/darkfield/ Leaf stops are mentioned about half way down this informative page.
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Ichthyophthirius



Joined: 07 Mar 2013
Posts: 873

PostPosted: Fri Mar 31, 2017 3:32 pm    Post subject: Reply with quote

Hi,

I've got one of these. From what I can see (I haven't dismantled it), they are not that complicated.

I'm waiting for someone to come up with a DIY version. You can build regular apertures with parts made by 3D printing or water jet cutting; shouldn't it be possible to build a reverse iris?

Someone needs to do the drawings Wink
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zzffnn



Joined: 22 May 2014
Posts: 1815
Location: Texas USA

PostPosted: Fri Mar 31, 2017 4:05 pm    Post subject: Reply with quote

Gary and Dave,

Yes, that was where I saw such a variable leaf mask initially.

Ichty,

I would be interested in such a 3D printing/DIY of reverse iris, if someone makes it. Use it with an aplanatic achromat condenser, results should be pretty good, even though there is no internal reflection mechanism (like that of Leitz Heine) to provide good light efficiency.
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