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PostPosted: Wed Jul 17, 2019 3:12 pm 
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Location: Oregon, USA
This may be a 'captain obvious' question, but is it straight forward to add phase contrast to a microscope by using a phase contrast ring of correct specs in the filter holder and adding a phase objective to the turret? Is it difficult to match ring size to objective if the two are semi-randomly plucked off of eBay? I was thinking 10-20x magnification.

My microscope hasn't been very cooperative in yielding good results via dark field patches and Rheinberg filters, so perhaps this wouldn't work well. Which leads me to wonder - if one were to buy a used modular scope from the big 4, what are some good choices?


Heather


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PostPosted: Wed Jul 17, 2019 3:50 pm 
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Heather, you face two challenges in this approach.

First, you want the phase ring as close to the iris in the condenser (usually just under) as possible. A filter ring is often placed further below this. There ARE phase condensers for several makes that accept a single ring or a slider, including from A.O./Reichert, Nikon, Leica, and surely others.

Second, the chances of different brand and model phase rings and phase-equipped matching is hit or miss. I've found several cases that work OK, but you'd like end up spending more buying "cheap" rings that don't match then just finding a full set of used. It's also possible to make your own phase rings, but it's fairly exacting work. Various approaches - some not successful -- can be found with a 'net search.


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PostPosted: Wed Jul 17, 2019 4:53 pm 
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Hi Heather,
I have done this successfully with my Biolamini, essentially a Lomo Biolam which is a simplyfied copy of the Zeiss Jena LG. But as Pete mentioned this is something like an undocumented feature and the results can vary widely. First you would need a phase objective that is compatible to the rest of you objectives, or a new set that is compatible to the stand. Then you could make test-phase rings by simply printing them with a laser printer on over head projector film.
When you have the right size you can make a phase plate from thin sheet metal, a disc with a hole and a small disc in the middle, and connect them by guing on a wire, then spray paint flat black.

If you want to enter into a modular microscope system it would be important to consider your local market. This differs a lot from e.g. Germany, Russia, USA, Japan.

Bob


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PostPosted: Wed Jul 17, 2019 5:24 pm 
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Location: Oregon, USA
Thank you PeteM and MicroBob.

Good things to consider. I will keep my eye out for a phase condenser since it seems unlikely my particular scope would work well with rings in the filter tray. Something cool and unwanted by the bidding masses might pop up on eBay. No hurry. It's just for fun and the challenge of having the occasional success amid a sea of not-so-excellent results.


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PostPosted: Wed Jul 17, 2019 7:35 pm 
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Sauerkraut wrote:
... I will keep my eye out for a phase condenser since it seems unlikely my particular scope would work well with rings in the filter tray. Something cool and unwanted by the bidding masses might pop up on eBay. No hurry. It's just for fun and the challenge of having the occasional success amid a sea of not-so-excellent results.
There is a journal article called "Condenser-less phase contrast" or something like that. From the present decade, and available (can find the exact location if of interest). It is based on using an under-stage LED-ring illumination, and phase contrast objectives. It is sort of DIY, not easy to do (I did not), but (I think) not limited to a specific microscope model.

Otherwise, to really enjoy the full power of phase contrast, the practical and time-saving approach is to find a used phase contrast microscope. They are much more abundant, and much less expensive than DIC scopes. Or maybe there is a commercial phase contrast kit (condenser+objectives) for your current microscope ?

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PostPosted: Wed Jul 17, 2019 8:48 pm 
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Hobbyst46 wrote:
There is a journal article called "Condenser-less phase contrast" or something like that. From the present decade, and available (can find the exact location if of interest). It is based on using an under-stage LED-ring illumination, and phase contrast objectives. It is sort of DIY, not easy to do (I did not), but (I think) not limited to a specific microscope model.

Is this the one ?
https://www.researchgate.net/publication/265734017_Condenser-free_contrast_methods_for_transmitted-light_microscopy
... it looks promising !

MichaelG.

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PostPosted: Wed Jul 17, 2019 9:03 pm 
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MichaelG. wrote:
Yes, this is the article. It has been mentioned on this forum and the photomacrography, in the past; but not an easy DIY task I am afraid.

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PostPosted: Thu Jul 18, 2019 4:11 pm 
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Location: Oregon, USA
Thank you for this link. I will investigate. :)


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PostPosted: Thu Jul 18, 2019 10:02 pm 
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The thing about phase contrast is that it hasn't really been developed to it's full potential yet. DIC came a long and then a whole array of focused beam, interference beam and digital contrast methods and phase kind of became stagnated as this inexpensive workhorse system for those with no dough. There is a lot to be done with the system yet.
There are these printed annuli like this that one could play with. They come in various sizes.
https://www.ebay.com/itm/Microscope-Pha ... SwmOBcB1Zf

and this block. I don't know what it is for, probably some vertical illumination phase system but if a guide was made for it, it might have enough depth to allow for vertical movement of the annuli; something probably necessary, if a good diy system were to be attempted. O.E.M. phase annuli are not cheap. There are few in this.
https://www.ebay.com/itm/Olympus-4-slid ... SwbsBXlZaK


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PostPosted: Fri Jul 19, 2019 12:36 am 
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Location: Santa Cruz, CA
apochronaut wrote:
The thing about phase contrast . . .


Just to add to Phil's points, I've purchased some of the linked phase annuli. They're laser cut plastic, a bit fuzzy from the cut edges, but workable. A buyer will want to determine what sizes are needed ahead of time - which can be done by imaging a scale and the objective phase rings with a phase telescope.

The block looking Olympus part is a set of phase rings for an old Olympus inverted IMT microscope.


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PostPosted: Fri Jul 19, 2019 3:35 pm 
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Location: Oregon, USA
apochronaut wrote:
The thing about phase contrast is that it hasn't really been developed to it's full potential yet.


That's a very interesting point. I'm about half way through that condenser-free phase contrast paper and it gives one the feeling that microscopes could be quite different in the future, in some ways. Maybe there's a future where the more advanced techniques like DIC could be accomplished with inexpensive tricks of oblique lighting as technologies advance. It seems plausible from the standpoint that, as posters have noted in other threads, that DIC and other methods produce images that may not be entirely true to their form.

If a person can fly with jet engines strapped to their feet, just maybe...Well it's fun to dream anyway.


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PostPosted: Fri Jul 19, 2019 3:56 pm 
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Sauerkraut wrote:
...I'm about half way through that condenser-free phase contrast paper and it gives one the feeling that microscopes could be quite different in the future, in some ways. Maybe there's a future where the more advanced techniques like DIC could be accomplished with inexpensive tricks of oblique lighting as technologies advance. It seems plausible from the standpoint that, as posters have noted in other threads, that DIC and other methods produce images that may not be entirely true to their form...
Actually, in the past, I think more than a decade ago, researchers have shown that by using nanometer size holes in plates, an imaging system could be built without objectives, and still achieve resolution. I do not remember the details, but it appeared to be a lens-less microscope. Fortunately, "normal" optical microscopes survived that front-end technology wave and are still being sold... :lol:

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PostPosted: Mon Jul 22, 2019 1:19 pm 
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The theory and benefit of pin hole optics is alive and well but also the conceptualization of the perfect lens, a long sought after goal going back to Diocles and more recently known as the Wasserman-Wolf Problem.
The problem has been solved , at least theoretically, by a couple of Mexican physicists, creating the framework for the mfg. of a single perfectly corrected lens. I guess, the question of whether that will be built upon in any meaningful way, remains to be seen. It may end up being of more value to cameraists, than microscopists, in the long run.


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