Questions and recommendations on DIY filters for Nikon inverted phase contrast diaphot

[macnmotion]

Hi. I've got a Nikon inverted diaphot with phase contrast condensor addition. I've watched Microbe Hunter's videos on DIY dark field filters and other filters. Will any of these filter techniques work with the setup I have? The microscope has a filter holder after the light box and before the condensor. If I make a dark field filter and use it there, will it work? If yes, has anyone figured out the dimensions required for the black circle?

In general, can anyone familiar with this microscope suggest any DIY modifications that might allow alternative views? Thanks.

[ldflan]

Your cheapest approach would probably be to make a set of patch stops and replace one of your phase contrast annuli with them (one at a time, perhaps). I have not tried it.

Probably the best thing you can do if you are willing to invest some money is lay hands on a set of Nikon TMD - sized condenser dovetails (either from parts or perhaps 3D printed - the dovetails don't have to be very strong). I have glued dovetails to a LOMO OI-13 oil immersion darkfield condenser (which is superb).

For lower powers, I use an unmodified Omax/Amscope NA 0.7-0.9 dry darkfield condenser - the dovetail is just a little too small for the Diaphot, but it can be made to work with some frustration, and does OK. Someday I will improve it.

Another useful condenser for the Diaphot is the low power achromatic condenser for the Optiphot, which fits the Diaphot just fine.
e.g. --
https://www.ebay.com/itm/154575960515?m ... media=COPY

Last, Diaphot 300 condensers can be modified to fit the TMD by removing the orienting pin behind the dovetail.

DIC is of course a bit difficult and expensive to come by for the Dipahot, but it's a good system.

Hoffman Modulation Contrast gear was very frequently used on the Diaphot (IVF work in plastic dishes, I suppose) and there seems to be a lot on eBay right now. I personally think HMC images are very good, quite close to DIC.

[macnmotion]

Your cheapest approach would probably be to make a set of patch stops and replace one of your phase contrast annuli with them (one at a time, perhaps). I have not tried it.

Probably the best thing you can do if you are willing to invest some money is lay hands on a set of Nikon TMD - sized condenser dovetails (either from parts or perhaps 3D printed - the dovetails don't have to be very strong). I have glued dovetails to a LOMO OI-13 oil immersion darkfield condenser (which is superb).

For lower powers, I use an unmodified Omax/Amscope NA 0.7-0.9 dry darkfield condenser - the dovetail is just a little too small for the Diaphot, but it can be made to work with some frustration, and does OK. Someday I will improve it.

Another useful condenser for the Diaphot is the low power achromatic condenser for the Optiphot, which fits the Diaphot just fine.
e.g. --
https://www.ebay.com/itm/154575960515?m ... media=COPY

Last, Diaphot 300 condensers can be modified to fit the TMD by removing the orienting pin behind the dovetail.

DIC is of course a bit difficult and expensive to come by for the Dipahot, but it's a good system.

Hoffman Modulation Contrast gear was very frequently used on the Diaphot (IVF work in plastic dishes, I suppose) and there seems to be a lot on eBay right now. I personally think HMC images are very good, quite close to DIC.

Wow, you know much more about my microscope than I do. I have lots of questions about your post, but let me start with simple ones concerning the phase contrast turret. The turret has 4 positions. The primary position contains a removable annular diaphragm. I assume your suggestion is to try placing a patch stop filter there, in place of that diaphragm? That would be better than placing the patch stop filter in one of the filter slots up near the light box? I hadn't thought of placing it in the turret, it wouldn't be difficult to try.

If I try that, other than trial and error is there any way to determine the correct size of the blocking circle in the patch stop filter?

Finally, the removable annular diaphragm has such a small aperture that the contrast using it with my 10x objective is way too strong, and it's unusable with my 40x because it let's almost no light through. For these reasons I don't use it at all. What's it's purpose? I'm not understanding a use case that would result in a decent image using it.

Thanks.

[ldflan]

I am not sure what you mean by the "primary position." There were two types of phase contrast turrets for the Diaphot - an ELWD NA 0.30 version, and a LWD NA 0.52 version. Which do you have? If the first, there should be a PhL, Ph1, Ph2 and Ph3 annuli. All of them are removable / replaceable.

I suspect the one that is "too strong" for you 10x is the PhL annulus. It's for low power phase objectives like the 4x. The other annuli are for objectives as marked. If I were to make a darkfield patch for the turret, I would remove the one I use least.

As for the size of the patch(es), I know you can calculate it or project it, and that there are articles on the web explaining how to do it, but you'd have to search them out. I haven't tried to do it myself.

Oh and I double-checked my Amscope dry darkfield condenser and see that I in fact glued a dovetail to it, but I think it's something I had lying around and is just a tad too small, so my comment that it almost fits out of the box is probably wrong. Memory fails...

[macnmotion]

Ok thanks. Yes I mean position PhL. The others appeared to me to be permanent, and as such I never looked harder to see of they came out. But since I only have 10x and 40x objectives, the phL is the one I leave empty so that's the one I would use to try the patch filter. I'll see if I can find info on calculating the size, otherwise I'll print out a range of sizes.

Thanks also for the correction about the dovetail. Ultimately if I wanted I could print precisely matching dovetail plates. I haven't researched yet alternative condensers, and since I'm in Thailand I likely wouldn't until next year when I next visit the USA.

[ldflan]

Well, I'd be concerned about whether it's possible to get any darkfield effect using the long or extra-long working distance condensers. The DF condenser usually must be pretty close to the slide for the light to enter at the correct angle... So I kind of doubt you will be able to get it to work with the ELWD condenser, but I am not positive about that.