MicrobeHunter.com Microscopy Forum

Used on eBay would probably be cheapest if you can find the right pair.

Scarodactyl wrote: ↑

Wed Aug 04, 2021 6:30 pm

Used on eBay would probably be cheapest if you can find the right pair.

Yeah, but I'm not keen on that and there's nothing for sale in the UK at the moment anyway. I'd rather get new if I can.
Louise

LouiseScot wrote: ↑

Wed Aug 04, 2021 6:03 pm

Thorlabs sell DIC prisms but, of course, everything from them is expensive! A Nikon N2 Condenser prism is about £908 with tax and a 20x prism slider is the same. So starter Nomarski DIC parts for £1800.... Tempting. If anyone knows of another source for less, I'd obviously be interested Maybe there's a cheap Chinese source?

Louise

I think Thorlabs only sells Wollastan prisms (https://www.thorlabs.com/newgrouppage9. ... oup_id=917). I haven't seen Nomarski mentioned there.

This thread seems to cover an Olympus formfactor compatible looking set-up: viewtopic.php?f=24&t=13375

microb wrote: ↑

Thu Aug 05, 2021 9:41 pm

LouiseScot wrote: ↑

Wed Aug 04, 2021 6:03 pm

Thorlabs sell DIC prisms but, of course, everything from them is expensive! A Nikon N2 Condenser prism is about £908 with tax and a 20x prism slider is the same. So starter Nomarski DIC parts for £1800.... Tempting. If anyone knows of another source for less, I'd obviously be interested Maybe there's a cheap Chinese source?

Louise

I think Thorlabs only sells Wollastan prisms (https://www.thorlabs.com/newgrouppage9. ... oup_id=917). I haven't seen Nomarski mentioned there.

This thread seems to cover an Olympus formfactor compatible looking set-up: viewtopic.php?f=24&t=13375

They do sell Nikon/Nomarski prisms for their DIY Cerna systems:

https://www.thorlabs.com/newgrouppage9. ... up_id=8569

Having since seen the prices for Olympus UIS2 U-DIC equivalents, maybe Thorlabs prices aren't so bad after all!

Louise

Some olynpus prisms just went up on UK eBay, including condenser prisms and a nosepiece slider, not cheap but cheaper than thorlabs. The condenser prisms are mostly for specialized water immersion objectives though.

Scarodactyl wrote: ↑

Fri Aug 06, 2021 3:29 pm

Some olynpus prisms just went up on UK eBay, including condenser prisms and a nosepiece slider, not cheap but cheaper than thorlabs. The condenser prisms are mostly for specialized water immersion objectives though.

Yeah I've seen them. I want to avoid anything 'non-standard', if possible, and I want to get matching condenser/slider prisms . At the moment, the Thorlabs/Nikon seem to be the best bet. At the same time, I'm trying to keep an open mind

Louise

Looking again the slider is a normal doc slider, and a couple of the objective prisms aren't marked for water immersion. But of course that all requires more research.

Scarodactyl wrote: ↑

Fri Aug 06, 2021 6:09 pm

Looking again the slider is a normal doc slider, and a couple of the objective prisms aren't marked for water immersion. But of course that all requires more research.

I don't have any data/info on them and they are a bit more expensive than the Thorlabs/Nikon sliders anyway.

Louise

Yeah, it looks to me like the nikon nosepiece prisms are 1k or 1.6k usd depending on n1 or n2, and the condenser prisms are 1k and up, while the olympus ones on eBay are 1.2k for the slider and 250ish for the objective prisms. Not a huge savings for sure unless you want to make a full dic setup with more than one objective prism, but then you have to take all the other hardware into account which sounds like a headache anyway, and that's assuming ones not marked wi are good for nonspecialized objectives.
Hmmmmm.... thinking about it I do have an objective based on olympus's water immersion series. I wonder if it is also dic compatible with these less typical prisms....no, stop, I must resist.

Scarodactyl wrote: ↑

Fri Aug 06, 2021 6:44 pm

Yeah, it looks to me like the nikon nosepiece prisms are 1k or 1.6k usd depending on n1 or n2, and the condenser prisms are 1k and up, while the olympus ones on eBay are 1.2k for the slider and 250ish for the objective prisms. Not a huge savings for sure unless you want to make a full dic setup with more than one objective prism, but then you have to take all the other hardware into account which sounds like a headache anyway.
Hmmmmm.... thinking about it I do have an objective based on olympus's water immersion series. I wonder if it is also dic compatible with these less typical prisms....no, stop, I must resist.

DIC impulses can be hard to resist! Um, the sliders are the objective prisms and the round prisms are for the condenser. Normally, though, sliders are objective specific though the Olympus ones don't seem to be? I just don't have the info. At least I can be sure the Thorlabs sliders will work with the specified condenser prisms - hopefully!

Louise

Oh yeah, mixed up my terms there. Typically these are set up with one prism being objective specific and the other being more general (or with epi dic either one per objective or one slider for all). With the olympus system the slider goes above the objectives and is the nonspecific one, while the condenser prisms are the more specific ones. Iirc Nikon might do it in reverse with the condenser being less specific and the nosepiece taking one per objective. Or maybe they've swit hed between models, for epi nikon used to be one objective per prism but switched to a single slider.
Of course that breaks down a bit with more specific applications anyway. Olympus has the upper sliders in a few variations but also a specific prism for some water immersion objectives.

LouiseScot wrote: At least I can be sure the Thorlabs sliders will work with the specified condenser prisms - hopefully!

Louise

Well, you can only really be sure that the Thorlabs prisms will work properly IF you use them with one of the compatible Cerna condensers AND the exact same objective for which the objective prism was designed. Different condensers have different focal lengths, and objectives differ in the location of their back focal plane.

So you are using a different condenser, or a different objective - even of the same magnification - then you really can't be sure that it'll work. There really isn't such a thing as a "20x prism". It is only a prism designed to be used with one specific 20x objective, one specific condenser, and one specific condenser prism. They all need to match.

I wouldn't spend any serious money on a set of Thorlab prisms unless I wanted to use them as designed in a Cerna setup.

I think you are better off looking for a used DIC microscope, or picking up some cheaper nomarski prisms from an epi DIC setup and play with them.

viktor j nilsson wrote: ↑

Fri Aug 06, 2021 7:39 pm

LouiseScot wrote: At least I can be sure the Thorlabs sliders will work with the specified condenser prisms - hopefully!

Louise

Well, you can only really be sure that the Thorlabs prisms will work properly IF you use them with one of the compatible Cerna condensers AND the exact same objective for which the objective prism was designed. Different condensers have different focal lengths, and objectives differ in the location of their back focal plane.

So you are using a different condenser, or a different objective - even of the same magnification - then you really can't be sure that it'll work. There really isn't such a thing as a "20x prism". It is only a prism designed to be used with one specific 20x objective, one specific condenser, and one specific condenser prism. They all need to match.

I wouldn't spend any serious money on a set of Thorlab prisms unless I wanted to use them as designed in a Cerna setup.

I think you are better off looking for a used DIC microscope, or picking up some cheaper nomarski prisms from an epi DIC setup and play with them.

It's to be used with my diy system so I can vary the prism positions as needed. They are Nikon prisms so not specific for the Cerna system. I emailed Thorlabs earlier to try and get more info on the prisms they sell.
Louise

https://www.ebay.com/itm/224515344198?h ... Sw5F5g23fB

This is the set I've been using in my DIY DIC setup. Four prisms, two are the same (10x/40x/100x). Having two of the same it's great, as it enable you to create a symmetrical setup where you use two identical objectives (one as condenser and one as objective) and two identical prisms. That automatically fulfill the DIC criteria, you just need to place the prisms at the BFP.

They show up from time to time for good prices. I paid $180 for mine.

LouiseScot wrote: ↑

Fri Aug 06, 2021 7:45 pm

viktor j nilsson wrote: ↑

Fri Aug 06, 2021 7:39 pm

LouiseScot wrote: At least I can be sure the Thorlabs sliders will work with the specified condenser prisms - hopefully!

Louise

Well, you can only really be sure that the Thorlabs prisms will work properly IF you use them with one of the compatible Cerna condensers AND the exact same objective for which the objective prism was designed. Different condensers have different focal lengths, and objectives differ in the location of their back focal plane.

So you are using a different condenser, or a different objective - even of the same magnification - then you really can't be sure that it'll work. There really isn't such a thing as a "20x prism". It is only a prism designed to be used with one specific 20x objective, one specific condenser, and one specific condenser prism. They all need to match.

I wouldn't spend any serious money on a set of Thorlab prisms unless I wanted to use them as designed in a Cerna setup.

I think you are better off looking for a used DIC microscope, or picking up some cheaper nomarski prisms from an epi DIC setup and play with them.

It's to be used with my diy system so I can vary the prism positions as needed. They are Nikon prisms so not specific for the Cerna system. I emailed Thorlabs earlier to try and get more info on the prisms they sell.
Louise

No, not specific for the Cerna system, but specific to that specific Nikon objective, and a condenser with a specific focal length, which Cerna must have chosen to match the other components.

viktor j nilsson wrote: ↑

Fri Aug 06, 2021 7:49 pm

LouiseScot wrote: ↑

Fri Aug 06, 2021 7:45 pm

viktor j nilsson wrote: ↑

Fri Aug 06, 2021 7:39 pm

Well, you can only really be sure that the Thorlabs prisms will work properly IF you use them with one of the compatible Cerna condensers AND the exact same objective for which the objective prism was designed. Different condensers have different focal lengths, and objectives differ in the location of their back focal plane.

So you are using a different condenser, or a different objective - even of the same magnification - then you really can't be sure that it'll work. There really isn't such a thing as a "20x prism". It is only a prism designed to be used with one specific 20x objective, one specific condenser, and one specific condenser prism. They all need to match.

I wouldn't spend any serious money on a set of Thorlab prisms unless I wanted to use them as designed in a Cerna setup.

I think you are better off looking for a used DIC microscope, or picking up some cheaper nomarski prisms from an epi DIC setup and play with them.

It's to be used with my diy system so I can vary the prism positions as needed. They are Nikon prisms so not specific for the Cerna system. I emailed Thorlabs earlier to try and get more info on the prisms they sell.
Louise

No, not specific for the Cerna system, but specific to that specific Nikon objective, and a condenser with a specific focal length, which Cerna must have chosen to match the other components.

I've asked them about compatibility and interchangeability in my email. I suspect the prisms are maybe Nikon oem components. The N2 condenser prism should work with a range of objectives. There's a 20x and 40x slider. I have a 20x Nikon apo objective which is specified for dic and N2. I hope I get a reply from them sometime next week. I'll post what they say, if it's of interest.

Louise

Hi All
Hope everyone is well. I'm pretty much back on the (DIC) case! Not quite full time, but almost.
Firstly, I didn't get much out of Thorlabs re their Nikon prisms. They just repeated what's in their online catalogue, so not very helpful. However, I did find some Nikon Eclipse tables. I gather one can use almost any objective >10x with their N2 prism. Obviously, pan fluors and apos specified for DIC are best. The N2 condenser prism should work with 20x, 25x, 40x and 60x objectives together with matching objective prism sliders. I'm a bit puzzled as to why their objective prisms are angled at 5 deg to the horizontal. There must be a good reason - anyone know? I thought it could be to prevent reflections but that's a guess.
Anyway, I had a bit of an epiphany re the Sanderson prism fringes which I spent ages struggling with before. The answer is buried in Rathi's paper though they never explained it. I found it by serendipity really. All that is needed is to place a piece of correctly oriented, unstrained polycarbonate in front of the condenser prism (between the condenser prism and the condenser lens) and the fringe patterns are shifted to allow proper adjustment. Such a simple answer to what seemed an intractable problem before! It's amazing how helpful a break from a problem can be.
So now, using a 60x objective I can adjust the fringe patterns to pretty much match Rathi's and other published images of prism fringes for a 60x setup. What I need to do though is build a setup/holder that will easily let me make fine adjustments to the prism positions and fringe spacing. However, first I'll have to see whether I can now actually achieve DIC - or not!
Here are pics of the condenser and objective fringes as seen by a camera at the normal viewing position with adjustments to pick up the corresponding focal planes:


Condenser prism:

Objective Prism:

Not great photos but good enough to show the fringe patterns with zeroth order approximately in the centre.

I'll be very pleased if I can get this thing to work! If I can, I'll endeavour to physically shorten the setup which I think should be possible. As it is, even if it does work, it's a bit impractical.

The game's afoot! More to follow!

Louise

Wow, that looks great! I'll look forward to seeing how it progresses from.here.

Scarodactyl wrote: ↑

Sun Aug 22, 2021 4:44 pm

Wow, that looks great! I'll look forward to seeing how it progresses from.here.

Hiya - thanks for the encouragement! I've had a quick go at trying to image a mounted diatom strew but the results were a bit blurry... My cheap, Chinese 60x plan achro isn't great and some of the other optics need improving. It's not a proper microscope - it's components and bits put together on some v-section. There isn't a proper stage - just a 3d printed slide holder with micrometer adjustment so focusing is tricky. I think I'll spend some time improving the 'condenser' and better aligning the optics. Will keep me busy!

Here is a crop of part of the strew
At least I can see some things through my contraption


Louise

Thought it worth a mention that a Nikon Optiphot DIC system showed up on the Ebay US site today. It's in Japan. With shipping and tax might it might end up around $3200 US for a buyer in the US or Europe? I can't vouch for the seller or the scope, but a quick glance suggests it's more or less complete. One would have to check that the DIC prisms are present - it could be there is just an upper slider and a phase contrast rather than universal condenser?

Recent comparable asking prices seem to be two to three thousand dollars more. And that's not including what looks like a complete and fairly pricey polarization setup.

This is the first Optiphot version and not quite as desirable as the Optiphot 2 with it's brighter lamp (100 watts vs. 50 watts) and the DIC slider set at a 45 degree angle. Some of the objectives are also an earlier Nikon plan achromat version to the later "CFN" versions with the three chromed knurls on the body. However, they're still pretty good. Both the first and second Optiphot models produce very good DIC in my experience.

I mention it because the cost of a new DIC slider and three condenser prisms might well be about as much.

PeteM wrote: ↑

Sun Aug 22, 2021 6:50 pm

Thought it worth a mention that a Nikon Optiphot DIC system showed up on the Ebay US site today. It's in Japan. With shipping and tax might it might end up around $3200 US for a buyer in the US or Europe? I can't vouch for the seller or the scope, but a quick glance suggests it's more or less complete. Recent comparable asking prices seem to be two to three thousand dollars more.

This is the first Optiphot version and not quite as desirable as the Optiphot 2 with it's brighter lamp (100 watts vs. 50 watts) and the DIC slider set at a 45 degree angle. Some of the objectives are also an earlier Nikon plan achromat version to the later "CFN" versions with the three chromed knurls on the body. However, they're still pretty good.

I mention it because the cost of a new DIC slider and three condenser prisms might well be about as much.

Thanks but the point of this (now very long) thread is to build my own! I've looked at buying a Nikon N2 prism but really only if I need to, and in order to help me get the Sanderson prisms working.

Louise

LouiseScot wrote: ↑

Sun Aug 22, 2021 12:21 pm

All that is needed is to place a piece of correctly oriented, unstrained polycarbonate in front of the condenser prism (between the condenser prism and the condenser lens) and the fringe patterns are shifted to allow proper adjustment. Such a simple answer to what seemed an intractable problem before! It's amazing how helpful a break from a problem can be.
So now, using a 60x objective I can adjust the fringe patterns to pretty much match Rathi's and other published images of prism fringes for a 60x setup. What I need to do though is build a setup/holder that will easily let me make fine adjustments to the prism positions and fringe spacing. However, first I'll have to see whether I can now actually achieve DIC - or not!

Hi Louise, glad to hear that you've been able to solve this problem. That too is how I was able to replicate the symmetric interference patterns from Rathi's paper: I stacked 2 prisms between the polarizers, small adjustments of the bending force on one of them led to noticeable changes in the fringe pattern (here and here). I was not able to obtain a symmetric fringe pattern with a dark band in the middle using a single prism because significantly more bending force led to small shifts of the pattern towards the center. Hans also showed the same trend here, an asymmetric fringe pattern from a single prism, and a symmetric pattern from stacked prisms under a lower bending force.

You now have 2 prisms before the condenser in order to have a symmetric interference pattern. From the fringe patterns of the Nomarski prisms in objective sliders shown here I assume that 2 prisms would be needed at the back focal plane (again, for a symmetric interference pattern). Am I right in assuming that a total of 4 prisms would be needed for a Sanderson-DIC setup: two at the condenser level and two at the back focal plane of the objective?

jmp wrote: ↑

Mon Aug 23, 2021 2:55 pm

LouiseScot wrote: ↑

Sun Aug 22, 2021 12:21 pm

All that is needed is to place a piece of correctly oriented, unstrained polycarbonate in front of the condenser prism (between the condenser prism and the condenser lens) and the fringe patterns are shifted to allow proper adjustment. Such a simple answer to what seemed an intractable problem before! It's amazing how helpful a break from a problem can be.
So now, using a 60x objective I can adjust the fringe patterns to pretty much match Rathi's and other published images of prism fringes for a 60x setup. What I need to do though is build a setup/holder that will easily let me make fine adjustments to the prism positions and fringe spacing. However, first I'll have to see whether I can now actually achieve DIC - or not!

Hi Louise, glad to hear that you've been able to solve this problem. That too is how I was able to replicate the symmetric interference patterns from Rathi's paper: I stacked 2 prisms between the polarizers, small adjustments of the bending force on one of them led to noticeable changes in the fringe pattern (here and here). I was not able to obtain a symmetric fringe pattern with a dark band in the middle using a single prism because significantly more bending force led to small shifts of the pattern towards the center. Hans also showed the same trend here, an asymmetric fringe pattern from a single prism, and a symmetric pattern from stacked prisms under a lower bending force.

You now have 2 prisms before the condenser in order to have a symmetric interference pattern. From the fringe patterns of the Nomarski prisms in objective sliders shown here I assume that 2 prisms would be needed at the back focal plane (again, for a symmetric interference pattern). Am I right in assuming that a total of 4 prisms would be needed for a Sanderson-DIC setup: two at the condenser level and two at the back focal plane of the objective?

Hi Jmp

I wish I'd known before... I've actually changed it a bit now. I just have one piece of polycarbonate before the objective prism. It's just a spare piece of polycarbonate. It has to be oriented correctly. When in place, it allows me to look down the tube and adjust both the condenser and objective prism fringes (at different focal planes). With the condenser prism removed I can see the objective prism fringes using the dslr+lens. I think I just used a mirror and lens to see the condenser fringes. Aligning the two sets of fringes can be a bit tricky. I think that when in situ the fringes are not exactly the same as when looking at each prism with cross polarisers and extra polycarbonete piece outside of the optical train. Anyway, I'm actually working on the other optics now - I need to fit a proper condenser! Hopefully, that will give me better images. I'm still not certain if I've actually achieved DIC but I think I'm getting there... There are still a number of things I'm not sure about.

Louise

I'd like to try a set-up like this. If either of you have models for frames with I guess two layers of polycarbonate. Let me know. I'm setting up a CNC for aluminum and can use this as a test case for parts.

Thanks,
Ted

microb wrote: ↑

Mon Aug 23, 2021 4:46 pm

I'd like to try a set-up like this. If either of you have models for frames with I guess two layers of polycarbonate. Let me know. I'm setting up a CNC for aluminum and can use this as a test case for parts.

Thanks,
Ted

I'm currently just using the open frames as per Rathi. It might be worth waiting a bit until someone definitely has it working...
Louise

LouiseScot wrote: ↑

Mon Aug 23, 2021 5:00 pm

microb wrote: ↑

Mon Aug 23, 2021 4:46 pm

I'd like to try a set-up like this. If either of you have models for frames with I guess two layers of polycarbonate. Let me know. I'm setting up a CNC for aluminum and can use this as a test case for parts.

Thanks,
Ted

I'm currently just using the open frames as per Rathi. It might be worth waiting a bit until someone definitely has it working...
Louise

Here is a link to the Rathi paper:
https://www.quekett.org/wp-content/uplo ... prisms.pdf

LouiseScot wrote: ↑

Mon Aug 23, 2021 5:10 pm

LouiseScot wrote: ↑

Mon Aug 23, 2021 5:00 pm

microb wrote: ↑

Mon Aug 23, 2021 4:46 pm

I'd like to try a set-up like this. If either of you have models for frames with I guess two layers of polycarbonate. Let me know. I'm setting up a CNC for aluminum and can use this as a test case for parts.

Thanks,
Ted

I'm currently just using the open frames as per Rathi. It might be worth waiting a bit until someone definitely has it working...
Louise

Here is a link to the Rathi paper:
https://www.quekett.org/wp-content/uplo ... prisms.pdf

I had seen the paper. But it seemed that some extra work was needed to get it working.

microb wrote: ↑

Mon Aug 23, 2021 7:27 pm

LouiseScot wrote: ↑

Mon Aug 23, 2021 5:10 pm

LouiseScot wrote: ↑

Mon Aug 23, 2021 5:00 pm

I'm currently just using the open frames as per Rathi. It might be worth waiting a bit until someone definitely has it working...
Louise

Here is a link to the Rathi paper:
https://www.quekett.org/wp-content/uplo ... prisms.pdf

I had seen the paper. But it seemed that some extra work was needed to get it working.

I'm still working on it! But, as I say, I'm using the Rathi open frame design. I'm kindof doing it all on an optical prototyping system based on aluminium extrusion. You have to be able to place the prism holders in the right places i.e. within/very close to the condenser, and at the extended objective position as if it was a Wollaston-type prism. It's fairly clear from Rathi's paper.

Louise

LouiseScot wrote: ↑

Mon Aug 23, 2021 4:19 pm

jmp wrote: ↑

Mon Aug 23, 2021 2:55 pm

LouiseScot wrote: ↑

Sun Aug 22, 2021 12:21 pm

All that is needed is to place a piece of correctly oriented, unstrained polycarbonate in front of the condenser prism (between the condenser prism and the condenser lens) and the fringe patterns are shifted to allow proper adjustment. Such a simple answer to what seemed an intractable problem before! It's amazing how helpful a break from a problem can be.
So now, using a 60x objective I can adjust the fringe patterns to pretty much match Rathi's and other published images of prism fringes for a 60x setup. What I need to do though is build a setup/holder that will easily let me make fine adjustments to the prism positions and fringe spacing. However, first I'll have to see whether I can now actually achieve DIC - or not!

Hi Louise, glad to hear that you've been able to solve this problem. That too is how I was able to replicate the symmetric interference patterns from Rathi's paper: I stacked 2 prisms between the polarizers, small adjustments of the bending force on one of them led to noticeable changes in the fringe pattern (here and here). I was not able to obtain a symmetric fringe pattern with a dark band in the middle using a single prism because significantly more bending force led to small shifts of the pattern towards the center. Hans also showed the same trend here, an asymmetric fringe pattern from a single prism, and a symmetric pattern from stacked prisms under a lower bending force.

You now have 2 prisms before the condenser in order to have a symmetric interference pattern. From the fringe patterns of the Nomarski prisms in objective sliders shown here I assume that 2 prisms would be needed at the back focal plane (again, for a symmetric interference pattern). Am I right in assuming that a total of 4 prisms would be needed for a Sanderson-DIC setup: two at the condenser level and two at the back focal plane of the objective?

Hi Jmp

I wish I'd known before... I've actually changed it a bit now. I just have one piece of polycarbonate before the objective prism. It's just a spare piece of polycarbonate. It has to be oriented correctly. When in place, it allows me to look down the tube and adjust both the condenser and objective prism fringes (at different focal planes). With the condenser prism removed I can see the objective prism fringes using the dslr+lens. I think I just used a mirror and lens to see the condenser fringes. Aligning the two sets of fringes can be a bit tricky. I think that when in situ the fringes are not exactly the same as when looking at each prism with cross polarisers and extra polycarbonete piece outside of the optical train. Anyway, I'm actually working on the other optics now - I need to fit a proper condenser! Hopefully, that will give me better images. I'm still not certain if I've actually achieved DIC but I think I'm getting there... There are still a number of things I'm not sure about.

Louise

Actually, thinking about it again, and more logically, then it must need the extra polycarbonate piece with the condenser prism as there's no point in only shifting the fringes after the specimen... I'll check it out later and confirm

Louise

Yes, it be good to know if that's the case. I've postponed work on this project for several reasons, one being that I need to re-design the prism sliders. My current 3D printed sliders did work for some tests, but they deform even when a small bending force is applied to the prism... and then don't 'slide' into the microscope. I might need to try a different filament (perhaps one of the carbon reinforced ones) or be creative with the use metal to craft a frame, without a milling machine (which shouldn't be as hard as it might sound). Of course, it would be good to know if I should re-design each slider to hold one or two prisms before going any further.