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Hoffman Modulation

 
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grgh



Joined: 09 Mar 2013
Posts: 327
Location: Lancashire. UK

PostPosted: Tue Mar 03, 2020 3:44 am    Post subject: Hoffman Modulation Reply with quote

Can any one help with instructions for making slit mask for hoff mod.
picked up a couple of objectives, but web instructions seem to be getting very complicated.
Old Age again rearing its head.
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Zeiss Universal Phase contrast.
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Pau
Site Admin


Joined: 20 Jan 2010
Posts: 5030
Location: Valencia, Spain

PostPosted: Tue Mar 03, 2020 4:53 am    Post subject: Reply with quote

I have no experience with Hoffman.
Likely you already know it, but in case of... https://micro.magnet.fsu.edu/primer/techniques/hoffman/hoffmanintro.html

https://micro.magnet.fsu.edu/primer/techniques/hoffman/hoffmanindex.html
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viktor j nilsson



Joined: 01 Mar 2013
Posts: 171
Location: Lund, Sweden

PostPosted: Tue Mar 03, 2020 4:58 am    Post subject: Reply with quote

I've made my own HMC slit mask from an old library card. It was just the right thickness to slide into the rotatable filter slot of my Wild Achr.Apl. condenser.



The righthand image shows the slit and HMC modulator as seen in the back focal plane. I can rotate the filter tray and slide the slit card in and out to align it.

To make it, I printed a grid system (with symbols so I could orient myself) onto an acetate sheet, cut it to the right dimensions to fit in the filter slot, and placed it in the filter slot. I then inspected the modulator and grid as seen at the back focal plane of the objective with a phase telescope. I could then see exactly what grids on the acetate sheet the slit needed to cover to match the medium gray part of the modulator (which I believe is optimal?). I cut out these grids from the acetate sheet, placed it over the library card and traced the outline of the slit. I then cut it with an exacto knife.

Simple as that, works great (but I don't use it often as I find the resolution of the Nikon 40x HMC LWD 0.55 quite disappointing compared to my Fluor 40x 0.85, not to mention my 40x 1.30).
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grgh



Joined: 09 Mar 2013
Posts: 327
Location: Lancashire. UK

PostPosted: Sun Mar 08, 2020 4:21 am    Post subject: Reply with quote

Thank you all for the suggestions, also to the PM's Received.

More to do to finish two mask, but getting there.
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