Converting an oil immersion objective to a water immersion objective.

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apochronaut
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Converting an oil immersion objective to a water immersion objective.

#1 Post by apochronaut » Thu Jul 07, 2022 1:04 am

Multi- immersion objectives function by moving a group of optical elements internally in order to adjust the correction for spherical aberration caused by the N.A. differential between the immersion medium and the glass of the front lens. Front lenses are usually crown glass and of around 1.52 N.A.
The method of adjustment is essentially a duplicate function of a correction collar in a dry objective.

Non adjustable objectives are finely tuned in the factory in order to reduce the spherical aberration to as low a level as is possible for the objective's application. Normally, this is accomplished by hand shimming the lens cells relative to each other with thin measured washers that are the same dimensions as the walls of the lens cells. Due to variables in manufacturing, primarily in the glass batches, each objective has shimming unique to it. Changing the shimming will change the correction for spherical aberration, just like adjusting the collar will change the correction for s.a. in an adjustable objective.

The following images describe the breakdown of an AO cat.# 1026 50X .85 oil achromat w./iris and it's conversion to a water immersion objective by changing the shims between the front lens group and the second lens group. All other original shim sets were retained. A second #1026 objective was used as a control and it's performance as a water immersion objective unaltered and as well as with oil were used to measure the success of the reshimming of the first objective. At the beginning, the first objective had a poorer image with oil than the control, as well as with water. The shims were increased in as small increments as possible until the altered objective achieved just a shade poorer performance with water than the control objective with oil but a superior performance with water than the control objective. I stopped thickening the shim once the performance began to deteriorate.The shims were obtained from damaged AO objecctives and sized with a vernier to obtain a range of thicknesses.
The test slide was a prepared mount.
1) Complete objective
2) Lens housing threaded off and iris adjustment collar removed
3) Front collar and bezel unthreaded, iris removed.
4) The front lens housing pushed out of the barrel. You can see the shimset just at the end of the barrel surrounding the second lens group.
5) An alternate set of shims waiting to be installed.
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apochronaut
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Re: Converting an oil immersion objective to a water immersion objective.

#2 Post by apochronaut » Thu Jul 07, 2022 1:19 am

A few more.

6) New shims installed.
7) Front lens ready to press into barrel
8) Lower section of shroud( front lens cap and bezel) threaded on, tightening the lens cells against their backstop under the iris shelf.
9) Objective reassembled.

The re-shimmed objective provides an image with a noticeable improvement in the definition of cellular inclusions, and borders with better contrast when compared to the same objective in it's original state when both are water immersed.
Attachments
1657149502483.jpg
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1657149573818.jpg (149.87 KiB) Viewed 3898 times
1657149275310.jpg
1657149275310.jpg (145.44 KiB) Viewed 3898 times

deBult
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Re: Converting an oil immersion objective to a water immersion objective.

#3 Post by deBult » Thu Jul 07, 2022 1:45 am

Wow, “car”-tuning at its best :D

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woyjwjl
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Re: Converting an oil immersion objective to a water immersion objective.

#4 Post by woyjwjl » Thu Jul 07, 2022 1:48 am

Expect comparison images to be displayed
Micrographers from China, thanks to the forum for providing a platform for exchange

apochronaut
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Re: Converting an oil immersion objective to a water immersion objective.

#5 Post by apochronaut » Thu Jul 07, 2022 1:59 am

I will have to use a tablet camera afocal. My mirrorless on a trinocular isn't available at the moment but the tablet will give a comparison at least.
ideally, the sample should be a live water sample, since the reason for this conversion was for a forum member who wants it as an objective to view live protists.

Scarodactyl
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Re: Converting an oil immersion objective to a water immersion objective.

#6 Post by Scarodactyl » Thu Jul 07, 2022 2:46 am

I'm impressed! What a cool project. I would not have expected that to be possible without ruining the objective.

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Re: Converting an oil immersion objective to a water immersion objective.

#7 Post by woyjwjl » Thu Jul 07, 2022 3:02 am

apochronaut wrote:
Thu Jul 07, 2022 1:59 am
I will have to use a tablet camera afocal. My mirrorless on a trinocular isn't available at the moment but the tablet will give a comparison at least.
ideally, the sample should be a live water sample, since the reason for this conversion was for a forum member who wants it as an objective to view live protists.
Smartphone cameras should be better than "tablet camera afocal"
Micrographers from China, thanks to the forum for providing a platform for exchange

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Re: Converting an oil immersion objective to a water immersion objective.

#8 Post by zzffnn » Thu Jul 07, 2022 4:09 am

Apochronaut has very sharp eyes (that are more critical than most microscopists that I know of), when judging objective image quality. He has convinced me with many examples that I was able to later on verify myself. I personally will blindly trust him on image quality in the future, without needing to see comparison photos.

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Re: Converting an oil immersion objective to a water immersion objective.

#9 Post by woyjwjl » Thu Jul 07, 2022 6:07 am

zzffnn wrote:
Thu Jul 07, 2022 4:09 am
Apochronaut has very sharp eyes (that are more critical than most microscopists that I know of), when judging objective image quality. He has convinced me with many examples that I was able to later on verify myself. I personally will blindly trust him on image quality in the future, without needing to see comparison photos.
Your statement in effect puts more pressure on Mr Apochronaut :mrgreen:
Micrographers from China, thanks to the forum for providing a platform for exchange

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Re: Converting an oil immersion objective to a water immersion objective.

#10 Post by zzffnn » Thu Jul 07, 2022 7:23 am

:mrgreen: In this case, there isn’t / wasn’t any pressure.

I sent apochronaut that oil -invaded objective, because we both want to gamble on it and see if we can modify it for water immersion. If it doesn’t turn out right, we would still learn something and have fun.

That partially damaged objective was sold to me for low price by a very kind microscopist friend, who also admires apochronaut’s skills and wants to witness his magic. We both know that apochronaut is one of the very few who can pull off such a feat. It requires a rare combination of sharp eyes, optical knowledge, skillful hands and collection of tools / parts.

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Re: Converting an oil immersion objective to a water immersion objective.

#11 Post by apochronaut » Thu Jul 07, 2022 11:18 am

woyjwjl wrote:
Thu Jul 07, 2022 3:02 am
apochronaut wrote:
Thu Jul 07, 2022 1:59 am
I will have to use a tablet camera afocal. My mirrorless on a trinocular isn't available at the moment but the tablet will give a comparison at least.
ideally, the sample should be a live water sample, since the reason for this conversion was for a forum member who wants it as an objective to view live protists.
Smartphone cameras should be better than "tablet camera afocal"
Unfortunately, I only have a dumbphone. My tablet has a 5 mp camera. It is good enough for comparison photos. Since I intend to send it to Fan in as good a state as possible for his application, the shim thickness is yet to be optimized for aqueous samples and a .17 cover slip but I will make some comparison pictures at this point with a mounted subject with well known characteristics.
The control objective by the way was n.o.s. when it came to me, so I have no reason to doubt it's performance. At .85 N.A. , it compares well with other similar objectives I have that have similar specifications, some dry, some immersion. They include a 40X .85 advanced achromat , two different 50X .80 oil planachros, a 40X .70 planfluor and a 40X .80 planapo, all infinity corrected. I do also have similar specced objectives from 160mm systems, 40X .70 water, 43X .85 dry, 45X .85 dry , 44X .85 fluorite, as well as all of water, oil and dry objectives in 40 to 50X magnifications at .95 or 1.0 N.A. as achro, fluorite or apochromat designs. Lots of comparators but those of a similar N.A. are the most useful. There really isn't much point in comparing it to a 47.5X .95 apochromat with a correction collar for instance.

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Re: Converting an oil immersion objective to a water immersion objective.

#12 Post by Hobbyst46 » Thu Jul 07, 2022 2:42 pm

zzffnn wrote:
Thu Jul 07, 2022 7:23 am
I sent apochronaut that oil -invaded objective...
A creative and interesting conversion !
Gentlemen, I think I had already asked that in the past, but: is the objective, before and after the conversion, impervious to the immersion liquid ? there are no special seals, are there ?

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Re: Converting an oil immersion objective to a water immersion objective.

#13 Post by apochronaut » Thu Jul 07, 2022 3:58 pm

No, just tight machining. The leaks don't occur around the front lens with this type of objective. When I received it, the second lens cell, third lens cell and iris diaphragm were invaded with oil, plus the third doublet had lost it's mooring and was hanging it's head in abject shame. Whatever cement AO was using was oil soluble but in their defense, I guess they figured that oil shouldn't be in there..The rear of the front lens wasn't coated in oil.
The oil entered between the front bezel and the front lens housing. The microscopist that was using it likely used an excess of oil and each dip into the oil was like a tiny hydraulic pump, pushing a little more into the seam. Likely it was being used for DF and the action of turning the iris control ring probably at some point loosened the front part of the barrel , opening up a leaky joint.
As the oil was pumped in bit by bit it seeped between the shims into the interior and through the iris lever channel onto the iris blades.

Water does not have the same ability to be pumped against gravity, plus it readily evaporates, so I don't fear a repeat of that kind of creeping seepage with water. Nervertheless , once I am done poking and prodding at this 1026, I will seal that metal to metal seam with water resistant cyanoacrylate, to inhibit the lower shroud from loosening.

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Re: Converting an oil immersion objective to a water immersion objective.

#14 Post by apochronaut » Thu Jul 07, 2022 10:53 pm

I made some tablet pictures to give a rough comparison. The last picture is through a 40X .66 planachro for a reference.
The diatom is a Striatella, I think . Difficult to image with BF and it is a 5X crop , so blurry and clear at the same time.
The only objectives that image the edge striae well are the modified #1026 with water immersion and the NOS #1026 with oil immersion.
Attachments
NOS 1026 50X 85  NA objective Water Immersion.jpg
NOS 1026 50X 85 NA objective Water Immersion.jpg (47.89 KiB) Viewed 3716 times
Modified 1026  50X  85 NA objective Water Immersion.jpg
Modified 1026 50X 85 NA objective Water Immersion.jpg (52.9 KiB) Viewed 3716 times
Modified 1026 50X 85 NA objective Oil Immersion.jpg
Modified 1026 50X 85 NA objective Oil Immersion.jpg (48.82 KiB) Viewed 3716 times
NOS 1026 50X 85 NA objective  Oil Immersion.jpg
NOS 1026 50X 85 NA objective Oil Immersion.jpg (70.97 KiB) Viewed 3716 times
1023 40X  66 NA  dry objective.jpg
1023 40X 66 NA dry objective.jpg (44.04 KiB) Viewed 3716 times

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Re: Converting an oil immersion objective to a water immersion objective.

#15 Post by zzffnn » Fri Jul 08, 2022 4:42 am

:shock: Very well done, thank you, apochronaut!

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Re: Converting an oil immersion objective to a water immersion objective.

#16 Post by apochronaut » Fri Jul 08, 2022 2:10 pm

Well, I'm happy you're happy so far. I went back at that this morning with the aim to see what an AO 40X .80 planapo would do and discovered that I had left the 40X phase diaphragm dialled in when I did those photos. What that does is increase contrast at the expense of resolution when used in BF, something like closing the condenser iris down too far.
So using the clear aperture and the 1242 achromat condenser, I did another test with the modified 50X .85 #1026 oil achromat used with water immersion , the 40X .80 #1323 planapo and a 40X .66 #1128 planachro. This time I picked another diatom out of that strew, probably a Synedra. It has very fine striae about of about a micron spacing. In most BF situations with ordinary achromat objectives, you can't really see them on this hundred year old slide.
So, the 1128 and 1026 are both compromised somewhat by the refraction that diatoms typically exhibit. the 1323 much less.
With the dry .66 1128, the striae can just barely be partially seen with the condenser output optimized. Definitely , no punctae.
With the water immersed 50X .85 1026, most striae are visible through depth focusing but just barely. No punctae or maybe just a few along the edge.Punctae on that diatom might be .5 micron?
The 40X .80 1323 objective resolved striae and just barely punctae but the punctae not really clearly. The slide thickness is not optimized for that objective , so it might do better with a thinner cover slip.

Bear in mind ; that is a mounted sample and the 1026 , although working reasonably well with water immersion, still needs a subtle adjustment probably, for aqueous samples. Hopefully, as good or better than oil with those.
I will try to do some better highly cropped pictures of the Synedra striae a.s.a.p. .

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Re: Converting an oil immersion objective to a water immersion objective.

#17 Post by Microscopy_is_fun » Fri Jul 08, 2022 6:45 pm

apochronaut wrote:
Thu Jul 07, 2022 1:04 am
5) An alternate set of shims waiting to be installed.
Great work! How do you decide, which shim thickness you need for converting from oil to water immersion?

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Re: Converting an oil immersion objective to a water immersion objective.

#18 Post by apochronaut » Fri Jul 08, 2022 9:35 pm

I know it can be done mathematically but not having the patent handy , I would only be guessing at the dimensions and n of the glasses used. The front lens is a likely accurate guess but batch differences get in the way, so I lack data.

In this particular case, I just have about 6 objectives from the same series that are Euchered and I took all of the shims from them and graded them according to thickness, then made a list of all possible combinations of spacings.
From there it was just a matter of time and patience.

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