AO objectives and cover slip thickness

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
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photomicro
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AO objectives and cover slip thickness

#1 Post by photomicro » Sat Sep 30, 2017 10:28 am

None of my AO objectives for my Series 10 have a figure for cover slip thickness on them. I realise there is no need for the first number of the usual '160/0.17', being infinity, but why no cover thickness?

Moreover, looking through some literature, it isn't mentioned what thickness the correction is for.

I am sure someone on here will know, as there seems much expertise in this line of stands.

Mike

apatientspider
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Re: AO objectives and cover slip thickness

#2 Post by apatientspider » Sat Sep 30, 2017 12:26 pm

Spencer and American Optical objectives were corrected for a 0.18 cover slip thickness at least up until they switched from a 160 mm tube length to infinity correction - according to their literature anyway. Not sure what thickness later objectives were corrected for.

Jim

apochronaut
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Re: AO objectives and cover slip thickness

#3 Post by apochronaut » Sun Oct 01, 2017 5:30 pm

There must have been a master list somewhere, that AO published, giving the specifications and applications of various AO catalogue #'s. I have never heard of such a thing but it makes sense that there must have been some reference, to go back to, when confronted with a cat.#. Not every dealer or service tech. would know everything about everything. Presumably, that piece of data would be in such a reference but clues are out there.

With the development of the infinity system, you are correct, Jim. It changed to .17. I'm sure I read that but do not remember where. It is however printed on the one objective that was directly engineered and made out of Austria for the early infinity system, cat.# 1303 ; 63x .80. It says oo/0.17 right on the barrel. Those, never carried the brand AO on the barrel; just Reichert Austria , engraved and later Reichert-Jung.

apatientspider
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Re: AO objectives and cover slip thickness

#4 Post by apatientspider » Sun Oct 01, 2017 7:03 pm

I don't own any of the infinity corrected microscopes, but....

Out of curiosity I skimmed through the manuals for the AO #10 and AO #20 - both of which used infinity corrected optics. Even as late as that their objectives were still being corrected for 0.18 mm thick coverglasses. Look on page 5, just underneath the table of characteristics for their lenses.

Looking through the manual for the #110 - on page 6 there is a table #1 of characteristics for their infinity corrected objectives and eyepieces. At the bottom of said table there is a note which says all working distances are in air above a 0.18 mm coverglass. Ditto for the #120 manual.

However, at the beginning of the #110 manual, on page 2, there is a picture of an objective - cat.# 1303 - that is clearly marked 0.17 - just as you say, Phil. Pictures of others on that page are not marked for coverglass thickness.

I'm gonna make a wild guess here: unless marked otherwise all of their objectives are corrected for a coverglass thickness of 0.18 mm - just as they had always been way back when it was just Spencer Lens Co. and everything was 160 mm tube length. Anything later than the #120, I couldn't say without searching out the manuals.

Just my two dollars worth.


Jim

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Re: AO objectives and cover slip thickness

#5 Post by apochronaut » Sun Oct 01, 2017 9:30 pm

Not so wild a guess. It seems to be the case. Odd that they would include the Austrian derived # 1303 in their stable, unmodified from it's original design, unless it was because everything they made with a higher magnification was oil and therefore the cover slip thickness was fairly irrelevant, or only much relevant with objectives of an extremely small w.d. such as # 1311, where a thicker coverslip, might impact focus.
and
With objectives of a lower magnification, all dry ones except four that I can identify are .66 N.A. or lower, where a .01 difference in cover slip isn't going to be noticeable. It is obviously not practical to adjust the cover slip thickness during observation, so where the 63x objective is in the nosepiece, it seems best to err towards a thinner cover, rather than thicker. For a long time now, I have been using between .14 and .16 and including the sample itself, it comes out about right.

There are 3 objectives, I can think of, aside from the # 1303, where a small deviation in cover slip thickness might be a problem.All are pretty uncommon.

cat. #CB1053(?) ..not exactly sure of the cat.# on this one, since my only contact with it is physical. C , was code for coated, B, I'm not sure. That could be a serial # but the 1053, looks suspiciously like an AO cat. #. This is an infinity corrected apo, 43x .80. Has a correction collar, with a .14 minimum, a .22 maximum and a .18 center. The rest are just hatchmarks. Looks like .18 is the nominal measurement.


cat. # 1323. This is 40x .80 planapo, with no correction collar. Presumably, it is corrected for .18 . Very little literature is around on these. I have used it with fairly thick samples ( .22) and it is unusually forgiving. Some higher N.A. objectives are less affected by spherical aberration due to sample thickness variation than others, due to the internal spacing of the elements. An example of that is the 50x .85 oil immersion cat.# 1026. Although, it is fully at home with oil, it provides a very good image with water or dry.

cat. # 1891 This is a 40x .80 or .85 advanced achromat, which was intended for use in vertical fluorescence. So was, the cat. # 1303. Again, there is very little info. about this objective. It existed as a strain free version which was compatible with the strain free versions of # 1017, 1019, # 1029, so presumably it is corrected for .18, although it's compatible use with # 1303 seems odd.

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