Darkfield stop sizing

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
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LouiseScot
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Re: Darkfield stop sizing

#61 Post by LouiseScot » Wed Mar 03, 2021 3:31 pm

Does anyone have any info on typical light sources (brightness/wattage) for dark field photomicrography? It seems a little complicated since only a fraction of the initial light actually strikes the subject(s) of interest and is reflected up through the objective. So although a LED may be blindingly bright the illuminated part of a dark field view isn't necessarily so. Any info or recommendations gratefully received :)
Thanks

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

farnsy
Posts: 209
Joined: Mon Jun 17, 2019 9:03 pm
Location: Fort Worth, Texas

Re: Darkfield stop sizing

#62 Post by farnsy » Fri May 14, 2021 7:19 pm

Louise, that is a really outstanding condenser holder you have created. I wish my 3D printing projects came out as well! I hope you share the file as yours is a very common microscope and many people will be running into this limitation.

I noticed that you mentioned that you might not need both screws to hold it up. Actually, having two screws is extremely valuable. If you were to put a small spring opposite those screws, then you will have fabricated a centerable condenser, similar to what high-end scopes have. This is a very worthwhile feature. In many cases, the reason people have difficulties with brightfield patch stops is because the condenser is not centered properly. Actually having a condenser that is not perfectly centered can be the reason lots of things don't work out well (Rheinberg, I'm looking at you!). If I were you, I would modify my condenser mount to make provision for a little spring (and maybe make the hole a bit bigger). I wouldn't be surprised if you could get improved patch stop results with the regular condenser by making it centerable, although getting good darkfield at 40X using a patch stop is a questionable proposition on any level of microscope. I think it's 100% worth it to get your brightfield condenser working well with patch stops, especially if you have a 3D printer. There are lots of oblique illumination, circulular illumination, and Rheingberg illumination possibilities if you get it working well. I have created a bunch of parameterized patch stop files in openscad I'd be happy to share with anyone who wants them.

With your tinkering skills, you could probably get phase contrast working on a scope like this. That would be humorous since those phase kits generally cost a lot more than your scope did, but you never know. There are lots of 160mm phase objectives on ebay and in other places, and with appropriate tinkering, you could probably rig a phase condenser or at least some matching annuli.

There has been some discussion about high and low end microscopes here. These days you can get pretty good images from an entry-level scope, it seems. Where they often suffer is their expandability and the capabilities for which they are designed. If you are able to create or cheaply add the parts needed to improve and add functionality, you can add some real value to your scope. This is, in spirit, similar to what is done by people who fix up, improve, and combine top shelf microscopes that are older and perhaps not initially functional. Apochronaut is an expert at the latter.

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: Darkfield stop sizing

#63 Post by LouiseScot » Fri May 14, 2021 8:24 pm

farnsy wrote:
Fri May 14, 2021 7:19 pm
Louise, that is a really outstanding condenser holder you have created. I wish my 3D printing projects came out as well! I hope you share the file as yours is a very common microscope and many people will be running into this limitation.

I noticed that you mentioned that you might not need both screws to hold it up. Actually, having two screws is extremely valuable. If you were to put a small spring opposite those screws, then you will have fabricated a centerable condenser, similar to what high-end scopes have. This is a very worthwhile feature. In many cases, the reason people have difficulties with brightfield patch stops is because the condenser is not centered properly. Actually having a condenser that is not perfectly centered can be the reason lots of things don't work out well (Rheinberg, I'm looking at you!). If I were you, I would modify my condenser mount to make provision for a little spring (and maybe make the hole a bit bigger). I wouldn't be surprised if you could get improved patch stop results with the regular condenser by making it centerable, although getting good darkfield at 40X using a patch stop is a questionable proposition on any level of microscope. I think it's 100% worth it to get your brightfield condenser working well with patch stops, especially if you have a 3D printer. There are lots of oblique illumination, circulular illumination, and Rheingberg illumination possibilities if you get it working well. I have created a bunch of parameterized patch stop files in openscad I'd be happy to share with anyone who wants them.

With your tinkering skills, you could probably get phase contrast working on a scope like this. That would be humorous since those phase kits generally cost a lot more than your scope did, but you never know. There are lots of 160mm phase objectives on ebay and in other places, and with appropriate tinkering, you could probably rig a phase condenser or at least some matching annuli.

There has been some discussion about high and low end microscopes here. These days you can get pretty good images from an entry-level scope, it seems. Where they often suffer is their expandability and the capabilities for which they are designed. If you are able to create or cheaply add the parts needed to improve and add functionality, you can add some real value to your scope. This is, in spirit, similar to what is done by people who fix up, improve, and combine top shelf microscopes that are older and perhaps not initially functional. Apochronaut is an expert at the latter.
Hi

Thanks for your input! The V2 holder is ok and does the job though it's not particularly good for easily adjusting the height of the condenser (although the darkfield condenser is used pretty much as high as it will go). It might benefit from being a bit deeper/thicker but I haven't done any more with it. It's a simple enough shape to make :)
I don't know how to attach an .stl file - I tried but the forum wouldn't let me :( You can get the hole spacing from the original plastic helical part. I made the V2 holder 13mm thick. As I say, it might benefit from being a bit thicker but I'd have to check what the useable limits might be for each condenser. I think the hole was 37mm diameter (but just big enough to allow the condensers to easily move through it). The other dimensions aren't critical as far as I can remember. The main thing is to have the hole centred in respect of where the objective centre would be. The screw holes should allow for some adjustment. Obviously, once fitted and adjusted/centred, the holder can be left alone. The one I made is still in place though is being used with the brightfield condenser at the moment :)
I'm currently beavering away trying to put together a DIY DIC but not for the Swift... There is a thread called 'DIY DIC' with a published paper about how to put together a DIC system based on polycarbonate prisms aka Sanderson Prisms. I don't know whether I'll be able to get it working but I'm having a go! It's fairly simple but a bit unwieldy using the quoted lenses - it's based on a 4f optical correlator with 200mm lenses plus a final 160mm lens so that's 560mm without all the bits you need to make it work! If I can get it working, I'll certainly post about it! I should have some results (for good or ill!) within the next week or so.

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

farnsy
Posts: 209
Joined: Mon Jun 17, 2019 9:03 pm
Location: Fort Worth, Texas

Re: Darkfield stop sizing

#64 Post by farnsy » Fri May 14, 2021 9:20 pm

LouiseScot wrote:
Fri May 14, 2021 8:24 pm
I don't know how to attach an .stl file - I tried but the forum wouldn't let me :( You can get the hole spacing from the original plastic helical part.
I think the right thing to do is post it on thingiverse. Most people won't come to this forum for information on this. Make sure you have really clear tags so people can find it. Way to contribute! I posted an initial pass at darkfield patches. Since then I've made a ton more designs and greatly improved it, but I haven't posted them yet.
LouiseScot wrote:
Fri May 14, 2021 8:24 pm
I'm currently beavering away trying to put together a DIY DIC but not for the Swift... There is a thread called 'DIY DIC' with a published paper about how to put together a DIC system based on polycarbonate prisms aka Sanderson Prisms. I don't know whether I'll be able to get it working but I'm having a go! It's fairly simple but a bit unwieldy using the quoted lenses - it's based on a 4f optical correlator with 200mm lenses plus a final 160mm lens so that's 560mm without all the bits you need to make it work! If I can get it working, I'll certainly post about it! I should have some results (for good or ill!) within the next week or so.
I really hope you have success. There is a lot of DIY skill (and interest) represented by the folks in this forum. I hope we are efficient at sharing it. Probably what we need is a wiki.

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: Darkfield stop sizing

#65 Post by LouiseScot » Fri May 14, 2021 9:34 pm

farnsy wrote:
Fri May 14, 2021 9:20 pm
LouiseScot wrote:
Fri May 14, 2021 8:24 pm
I don't know how to attach an .stl file - I tried but the forum wouldn't let me :( You can get the hole spacing from the original plastic helical part.
I think the right thing to do is post it on thingiverse. Most people won't come to this forum for information on this. Make sure you have really clear tags so people can find it. Way to contribute! I posted an initial pass at darkfield patches. Since then I've made a ton more designs and greatly improved it, but I haven't posted them yet.

I think that as it's specific to the Swift it's probably not worth putting on Thingi. Anyone can easy copy it from what I've posted and someone with more CAD skill than I have could probable make a more sophisticated version with proper height adjustment. I really only did it to prove that it was possible to add a df condenser to the Swift :)

LouiseScot wrote:
Fri May 14, 2021 8:24 pm
I'm currently beavering away trying to put together a DIY DIC but not for the Swift... There is a thread called 'DIY DIC' with a published paper about how to put together a DIC system based on polycarbonate prisms aka Sanderson Prisms. I don't know whether I'll be able to get it working but I'm having a go! It's fairly simple but a bit unwieldy using the quoted lenses - it's based on a 4f optical correlator with 200mm lenses plus a final 160mm lens so that's 560mm without all the bits you need to make it work! If I can get it working, I'll certainly post about it! I should have some results (for good or ill!) within the next week or so.
I really hope you have success. There is a lot of DIY skill (and interest) represented by the folks in this forum. I hope we are efficient at sharing it. Probably what we need is a wiki.

Thanks! I'll just see what I can do. The paper isn't explicit about exactly how to construct it. I've effectively built another microscope on some T-section, together with all the lenses, prisms, slide holder, polarizers and LED light source. It's currently a metre long! I think I'm going to need another section... A mirror or two might be a good idea haha
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

farnsy
Posts: 209
Joined: Mon Jun 17, 2019 9:03 pm
Location: Fort Worth, Texas

Re: Darkfield stop sizing

#66 Post by farnsy » Fri May 14, 2021 9:45 pm

LouiseScot wrote:
Fri May 14, 2021 9:34 pm
I think that as it's specific to the Swift it's probably not worth putting on Thingi. Anyone can easy copy it from what I've posted and someone with more CAD skill than I have could probable make a more sophisticated version with proper height adjustment. I really only did it to prove that it was possible to add a df condenser to the Swift :)
Up to you, of course, but I wouldn't sell myself short if I were you. I would guess your Swift is one of the three most popular microscope sold to hobbyists, along with the AmScope 490 series and Omax scopes. Folks who buy the AmScope or Omax have access to a fitting darkfield condenser, but the Swift buyers do not, AFAIK. Plenty of folks in the same boat you were in before you fabricated it who would like to have that capability. Not sure how many of them have a 3D printer, but some will for sure. Doesn't cost anything to post a design.

Dubious
Posts: 426
Joined: Sun May 09, 2021 7:55 pm

Re: Darkfield stop sizing

#67 Post by Dubious » Mon Jun 07, 2021 4:56 am

LouiseScot wrote:
Tue Feb 16, 2021 2:42 am
apochronaut wrote:
Tue Feb 16, 2021 2:28 am
This forum gets a steady stream of threads started by people trying to make a silk purse out of a sow's ear. It's mostly that they blew 300 or 350 bucks on a cheap Chinese microscope and then want to save a few pennies by diy'ing DF stops for the cheap condenser, rather than buying a proper DF condenser. The guy who runs this forum apparently posted a video praising the Swift 380T. Am I correct in that? I have only watched a few minutes of a couple of his videos and they seemed way off base. I couldn't take any more. Is there some sort of run on these Chinese hobby grade microscopes because of some internet recommendations?
It is a bit of a tragedy, if so.
I really like my Swift 380T - it's excellent value for money! There's no option to fit a DF condenser - it's a basic finite microscope without upgrades. It's not meant to compete with anything more professional or sophisticated - it is what it is. As I said, if one really needs a DF condenser then one should get another microscope. But there's no harm fiddling with what you have and trying to get the best out of it! For me, fiddling about is half the fun! Maybe more than half :)

Louise

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: Darkfield stop sizing

#68 Post by LouiseScot » Mon Jun 07, 2021 9:12 am

Of course, I did actually manage to fit an AmScope Darkfield Condenser - with a bit of 3D printing!

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

Dubious
Posts: 426
Joined: Sun May 09, 2021 7:55 pm

Re: Darkfield stop sizing

#69 Post by Dubious » Tue Jun 08, 2021 6:58 pm

Kudos on the df condenser holder, which looks quite nice. The Swift 380T seems like a capable performer at the price. Experimentation is good. Took some fiddling, but I got darkfield to work quite well on my vintage Leitz by poking an appropriate stop up the hollow core of the brightfield condenser assembly to near the iris (this particular condenser has no filter holder--filters are instead placed in a holder on the base Kohler lens). BTW, if anyone likes halogen lighting and wants to see a slightly more capable alternative to the 380T, check out the Amscope T530B. Amscope has dropped the price to $353 (Ebay USA). It has Kohler illumination and a more conventional condenser arrangement--drop down, rack-and-pinion, and screws to adjust laterally.

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