Zeiss IM with hoffman modulation

What equipment do you use? Post pictures and descriptions of your microscope(s) here!
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Scarodactyl
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Zeiss IM with hoffman modulation

#1 Post by Scarodactyl » Sat Oct 22, 2022 10:32 pm

I picked this up a few months back at a university surplus sale but business has been busy and I only managed to track down the proper power supply and replacement bulb. It's a real big Zeiss inverted scope with a hoffman condenser and, oddly, Nikon hoffman objectives.
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For the most part it seems to be in good shape, though there is some delam in the head and eyepieces and the condenser rack and centering screws are stuck. (I really need some tips on the screws and rack in particular, not sure if I should try oil or?)
Unfortunately I really don't have a strong idea of how to use hoffman modulation, or an inverted scope in general. I'm sure I'll resell it eventually (though I'm not looking forward to moving or packing it up, it's heavy!) but I wanted to at least get a taste of this technique and see how it compares. I am able to get some images which seem fairly similar in effect to Leica's Rotterman contrast or other tuned oblique illumination with a bit DIC flavor to them. It has three hoffman objectives and some phase as well, but I only seem to get good results with two of the hoffman filters (it has three hoffman filters and one open slot).
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The condenser pillar has two pencil lines, one higher up marked 'phase' and one lower down labeled 'hoffman' so presumably it once had another condenser.
I'll be honest I really don't have a great idea of how to use this scope but I do like what I'm seeing of Hoffman so far. I assume it will work better when I can get kohler set up.

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ImperatorRex
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Re: Zeiss IM with hoffman modulation

#2 Post by ImperatorRex » Sun Oct 23, 2022 8:40 am

Congrats Scarodactyl to the IM35. It is a great scope!
Obviously new kind of micro and lots of stuff to get into.
Did you check already the HMC manual here:
https://vdocuments.mx/hoffman-modulatio ... tml?page=7

Setting up the Köhler Illumination should be possible - I can see that your scope includes the iris aperture diaphragma.
Pls sent me a PM and I can share you an english operating manual, it describes the process of setting the koehler illumination.
For the most part it seems to be in good shape, though there is some delam in the head and eyepieces and the condenser rack and centering screws are stuck. (I really need some tips on the screws and rack in particular, not sure if I should try oil or?)
Maybe first to fix the the mechanical issues, then later conclude to get after the delaminated stuff. My proposal really here to completely dismantle and clean the parts from the hardened grease (e.g. with petrol ether etc). Relubricate and reassemble. Just dropping oil to soften the grease may not be a permanent solution, maybe just to temporarily makes thing a bit better.

If you consider to make great use of the Nikon HMC objectives you may conclude to get Nikon eyepieces, so their optical correction also may better match to the objectives. But I have no experience how these optics overall perform with the optical dimensions of the Zeiss setup. Tubus length of Zeiss and Nikon are 160mm and Objective distance is also 45mm.
But maybe other Zeiss standard users have made some experience using Nikon objectives and eyepieces on a Zeiss stand?

Personally I have just used HMC over a short period of time, then I concluded to prefer Phase Contrast and DIC. But I also know someone that commented that HMC is best for his application. So depends.
If you have questions, just let me know. Happy if I can help.

PS: I can see some dust on the scope. So cleaning and careful cleaning of the optical surfaces probabely is required to get a good performance finally. Dust also can sit and rest withing and below the objective turret. There is lense sitting dirctly below the objective turret housing, so to cleanse you will need to unscrew the complete objective turret block, a bit cumbersome because the screws on the rack are bit difficult to reach and un-screw. So the whole action takes a bit more time.

Scarodactyl
Posts: 2775
Joined: Sat Mar 03, 2018 9:09 pm

Re: Zeiss IM with hoffman modulation

#3 Post by Scarodactyl » Mon Oct 24, 2022 5:33 pm

ImperatorRex wrote:
Sun Oct 23, 2022 8:40 am
https://vdocuments.mx/hoffman-modulatio ... tml?page=7
I hadn't, thanks! I will need to spend some time with it.
ImperatorRex wrote:
Sun Oct 23, 2022 8:40 am
Pls sent me a PM and I can share you an english operating manual, it describes the process of setting the koehler illumination.
Thanks, I will send a PM. Kohler does seem like it shouldnt be an issue as long as I can unstick the centerig screws and rack.
ImperatorRex wrote:
Sun Oct 23, 2022 8:40 am
Maybe first to fix the the mechanical issues, then later conclude to get after the delaminated stuff. My proposal really here to completely dismantle and clean the parts from the hardened grease (e.g. with petrol ether etc).
It does need some care, though it's fortunately only a few elements gummed up. I'm honestly not sure how to disassemble it, especially when the screws are stuck, but I will have a go. The delamination isn't a huge issue really, at least compared to others ahead of it.

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