Homemade phase annuli

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BramHuntingNematodes
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Homemade phase annuli

#1 Post by BramHuntingNematodes » Fri Mar 20, 2020 2:30 am

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So these were made from watch glass from Esslinger. They offer pretty fine gradations of precise sizes for watch crystals; cheap, so i bought a dozen 32.5mm. These will fit exactly into the filter holder of a Wild M11 condenser, and after some trial and error, the third one from the left matches pretty well the Wild 20x Ph objective the mad atomic scientist that owned my scope before me had attached. The process is simple enough, although getting the spray enamel to adhere to the glass took some doing. I scrubbed them with acetone and rubbed them with polyester fleece with the vague hopes of giving them a static charge. Drying in hotter temperatures leads to a more matte finish. Then I hot glue them to a 1/2 inch wood dowel and center it in the lathe within 3-4 thousandths of an inch with a dial indicator. I can't get much more accurate than that with my wooden headstock and cheap chuck. I use hot glue because it adheres pretty solidly but snaps off easily with the application of a sharp chisel (bevel side to the glass although I don't know that it makes a difference). Also sticking the whole fixture in the freezer for ten minutes usually makes the glue give up. With the steady application of a razor blade and some vernier calipers I can quite effectively control not only the outside diameter of the ring, but also the width of the ring. You make two concentric cuts, and a little doughnut of enamel lifts up easily off the glass (if performed a day or two after apply the enamel). I would perform this operation under stereomicroscope, naturally.
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Kimwipes for scale. Here you can plainly see the finish variations in the outside two (gloss) and the inner two (matte). Matte is more desirable, although I haven't noticed much in the way of reflected glare off any of them. Now I got to rig up a centering filter holder since the condenser is very slightly off center! I would make the condenser centering, but that seems beyond my art at this moment.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

PeteM
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Re: Homemade phase annuli

#2 Post by PeteM » Fri Mar 20, 2020 4:49 am

Glad that worked out.

There is also an Ebay seller who makes and sells a wide variety of phase contrast annuli to fit various condensers; laser cut from Delrin (I believe). Many "makers" and "maker-spaces" will have the cheap 2D CAD and simple laser cutters needed.

MicroBob
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Re: Homemade phase annuli

#3 Post by MicroBob » Fri Mar 20, 2020 8:10 am

Nice work!
how did you determine the size of the rings?

Bob

BramHuntingNematodes
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Re: Homemade phase annuli

#4 Post by BramHuntingNematodes » Fri Mar 20, 2020 12:07 pm

This represents a trial and error refinement process to match an objective. I hope that in the future the matching will take less time, and perhaps I can even use some of the wrong sized annuli for some different objective. Eventually I will attempt to make phase plates as well, but I assume that will take extensive experimentation.

Thanks petem, but I kind of already built a lathe to make microscope parts with and am now firmly entrenched in the sink cost fallacy.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

viktor j nilsson
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Re: Homemade phase annuli

#5 Post by viktor j nilsson » Fri Mar 20, 2020 12:22 pm

If you print concentric circles on a sheet of acetate and put it in the filter tray you can use a phase telescope to look at it at the back focal plane (with the correct objective in place) and see how large the rings need to be.

MicroBob
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Re: Homemade phase annuli

#6 Post by MicroBob » Fri Mar 20, 2020 1:17 pm

You can even make so-so phase annulli by printing a set onto overhaed projector film. When you do the design with a CAD program (can be the simplest freeware 2D) and print to scale you already have the dimensions. They won't be great for permanent use but allow to get the sizing right.

There is a website from an Italian who painted objective phase rings with a sharpie.

You habe built yourself a lathe? Could you post a picture?

Bob

BramHuntingNematodes
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Re: Homemade phase annuli

#7 Post by BramHuntingNematodes » Fri Mar 20, 2020 1:38 pm

That's not a bad idea about the circles. I have a clear plastic ruler around here I could use even. So far I have been eyeballing the proportion, which interestingly works OK. I am hoping that I will be able to detect coatings and materials that induce the desired phase change with the current matched pair of objective and annulus. At 20x, it might be a little close to be useful, though. It's an experiment after all!

The lathe is described here:
https://imgur.com/gallery/kUucEIi

and I finished the cross slide eventually:
https://imgur.com/gallery/vLwbrKc

So far I have used it to modify a condenser to fit a slightly smaller sleeve, made some funnel stops that work pretty well, and these annuli. I haven't turned any wood on it yet despite the possibility.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

MicroBob
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Re: Homemade phase annuli

#8 Post by MicroBob » Fri Mar 20, 2020 4:07 pm

Nice lathe, congratulations!
My chinese lathe is among my most used tools of all.

BramHuntingNematodes
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Re: Homemade phase rings

#9 Post by BramHuntingNematodes » Sun Nov 15, 2020 7:12 am

So I am following along with great interest the paper mentioned previously by Apo, Bennett, Jupnik, Osterberg and Richards "Phase Microscopy"(1946), as well as some of the previous and later citing work. I can produce the annuli pretty readily now, so on to the phase rings. Were going to put them close to the back focal plane and hope for the best. A question of how these could be fashioned was posed, I think I have settled on sandwiching thin film phase retarding rings and some kind of wet applying amplitude dampening layer between circular cover slips. In the paper, many different tantalizing configurations were assessed; however, I possess only quarter-wave thin film, so positive and negative contrast can be fashioned with rings of this and varying degrees of shading. Looking back to Burch (1934), some in the past have whipped thin strands of molten resin into miniscule toroids and flattened them between glass, so there's always something else to experiment with in future trials. Here is my setup if anyone else would like to give it a go:

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Essentially a turntable, a micromanipulator, an Xacto knife. Attempts were made with hole punches, leather-working punches, knives, a lathe and sharpened awls before this current iteration. None of these produced anything even close to acceptable.

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Little shaded pole motor hooked up to a footpedal.

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I used a spare bit of the thicker polarizing film as a test. I find here the trick is to lower the blade suddenly rather than creep up on it. There is also a knack acquired in lining up the blade exactly tangent with the path of rotation. The results, I think, are very good. In fact, this most recent experiment was so promising I found I had to post it.

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Our tolerances are tightening and our rings are shrinkening. 5mm OD is about OK for some lower power phase setups-- the 1mm width of the band is too wide by at least half. I believe this can be readily achieved with the existing method.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

MichaelG.
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Re: Homemade phase annuli

#10 Post by MichaelG. » Sun Nov 15, 2020 8:12 am

Great work, Bram

You might find these useful:
1mm Radial Increments.pdf
(23.25 KiB) Downloaded 275 times
MichaelG.
Too many 'projects'

apochronaut
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Re: Homemade phase annuli

#11 Post by apochronaut » Sun Nov 15, 2020 7:55 pm

That's all really great stuff, Bram. Here are some ideas from some experiments I pursued. Perhaps there is something here for you. I haven't time right now to further much in the way of phase experiments.

The phase diaphragms and matching phase retardation plates don't necessarily need to be circular. They can be other shapes, as long as they match but obviously if utilizing almost all phase objectives generated out of factories, the diaphragms must be circular.

With infinity corrected objectives, the desired ring does not have to necessarily be at the rear focal plane. It can be forward in the objective ( front focal plane?), or above the objective entirely. Examples exist. Why would this not also be true with finite objectives?

Many phase coatings are layed down in an evaporative process, probably somewhat similar to the way some lens coatings are deposited. I put some time into depositing rings using a liquid evaporative process, after depositing them somewhat akin to block printing. I couldn't afford the time to do a more refined job of it but the process has some merit.
I used tiny O rings as the print block and various substances as the material. Soy sauce, fine soot, graphite, black iron residue from heating acidic substances in an unseasoned cast iron cooking utensil, similar from unoxidized aluminum, silver tarnish obtained by heating tarnished silver in salt water in the presence of aluminum foil, black dye obtained from boiling old swiss chard leaves or white beets, several vegetable dyes fixed with a mordant. Boiled onion skin fixed with alum made a really permanent clear mustard yellow, which dries quite clear but dense. The O ring printing blocks can be adjusted in size somewhat by buffing them on fine emery paper.
The beet (beta vulgaris) dye is curious. Beets occur in various colours. Deep red we all know but boiling yellow beets produces a vivid yellow dye as intense as that from a red beet, only yellow. There are white beets, which I grow. Boiling white beets has the peculiar effect of yielding a black dye in the water, something similar to the darkening of the water that occurs when green swiss chard, especially older swiss chard leaves are boiled. Swiss chard is actually the same plant as the beet, just a version bred for the leaves, rather than the root, so green swiss chard is actually the leaf of a white beet. The dye is slate grey and when reduced and layed down was pretty interesting. It probably would need a mordant to be permanent and might eventually bleach. The dye intensifies when the utensil is iron, so is most likey an iron compound, .
My main point is that solutions of various metal complexes, extracted from either a heating utensil , a heated substance, or combination of, with water, acid, alcohol or other liquid as a solvent, could hold promise , block printed and evaporated as a source for various phase rings and buttons.

hans
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Re: Homemade phase annuli

#12 Post by hans » Sun Nov 15, 2020 9:35 pm

Nice work, I am following with interest, having recently bough a pair (10x and 40x) of "for parts or not working" phase objectives for my Microstar IV to mess with.

BramHuntingNematodes
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Re: Homemade phase annuli

#13 Post by BramHuntingNematodes » Sun Nov 15, 2020 9:40 pm

I have a broken AO finite phase objective, but I can't bring myself to break it open to try to salvage the phase plate as it is so beautiful. Let me know if you find success.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

microb
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Re: Homemade phase annuli

#14 Post by microb » Mon Nov 16, 2020 8:34 pm

This is something I would like to try out, so if someone else has done so please let me know.

If you double tap glass to the build plate of a resin 3D printer, then zero it to include the extra thickness of the glass and tape; a black resin print of a phase contrast annuli could be layered onto the glass.

The problem there is that the resin might still let too much light through.

So alternatively, a print of just one layer would be enough if applied to an aluminum coated glass so the resin would act as a mask for etching. I haven't tried it yet, and it's possible the surface area might be too much and peal off. So maybe the default settings for the exposure time would have to be increased or the aluminum roughed up with an abrasive.

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