Identification of microscope objectives

[Amoeba]

I have been looking at a list of microscope objectives and since I am a relative newbie to microscope optics I have been trying to decipher the meaning of various markings. Thanks to some useful information on this site and elsewhere I think I have identified most of them as follows:

A, ACHRO - achromatic
APO - apochromatic
DIC - Differential Interference Contrast
DLL [Nikon] - dark low phase contrast
EF - extended (wide) field, requiring appropriate eyepieces
EF [Leitz] - semi-plannar (flat-field)
FL - fluorite
LWD/ULWD - ultra/long working distance
NC/NCG - no cover glass
NFl - achromat?
NFL [Olympus] - ?
NH - negative high (specimen darker than background)
NIC - Nomarski Interference Contrast
Nil - ?
Oel [Leitz, Zeiss] - oil immersion
OIL - oil immersion
Ph - Phase contrast
Ph1, Ph2, Ph3 [Zeiss] - Phase contrast
Phaco - Phase contrast
Phv [Zeiss] - phase contrast variable
Pl [Leitz] - plannar
PL - positive low (specimen brighter than background)
PL [Leitz] - plannar to a certain image diameter (18mm?)
PLAN - planar (photographic work)
PLANFL - Planar fluorite
PLL - ?
P/POL - optimised for a polariosation microscope
WI - water immersion

I suppose 'NFL' should be obvious since it seems to be very common, but I couldn't find a definition so I would be obliged if someone could tell me what it means?

Also, what does 'Oel' mean in the description of some objectives?

While I am here, I might as well ask whether objectives for 160mm tubes can be used on a microscope with 170mm tubes, for example a Leitz SM-LUX? I have seen information stating that objectives of the correct tube length must be used, but this seems to be contradicted by it being stated elsewhere that 160/170 are interchangeable. Are there any drawbacks to using a 160 on a 170 tube and is an adapter required?

I am aware that some objectives require a parafocal PLEZY adapter, but how do I identify them from their description?

EDIT (30/11/2017): List updated following comments

[MicroBob]

About mixing components I could only give you some sources in german - are you interested?
Oel is Öl when your typewriter has no "Ö"-key. It means Oil immersion objective.

Mixing components is in some cases possible. But you need considerable knowledge to get it right without a long and costly trial and error process. Usually mixing of microscope parts doesn't make much sense.
I would recommend to buy a complete and working microscope that is dependably in serviceable condition. The typical ebay-buy has a couple of problems. Solving them keeps you away from getting ahead with using you scope.

[MicroBob]

PL on a leitz objective means planar to a certain image diameter (18mm?) It's not quite the same as Pl. on a Leitz objective though
EF on a leitz objective means "semi-planar" up to 18mm image diameter, probably as planar as an older plan objective
Pol doesn't mean polarised: It means its optimised for use on a polarisation mic. The optics are selected for low level of mechanical stresses
Phaco, ph, ph1, ph2, ph3... means phase contrast
phv on a Zeiss Jena objective means variable phase contrast +/-

You can see: These components are maker - specific and standardistion was never a topic.
The typical buyer, university, institute, company just bought what the sales representative from the company that's name was engraved on their microscope stands recommended.

[zzffnn]

I remember seeing "NFL" on some Olympus projection eyepiece (for camera / trinocular tube of microscope).

Leitz said their correct eyepiece/objective combination, when used correctly, can be moved between 160/170 tube system with a tube length error of about 3mm, if I remember correctly. But don't do it, unless you know exactly what combo to use.

I have seen DLL (dark low low phase contrast) from Nikon. And PLL as well.

[Amoeba]

About mixing components I could only give you some sources in german - are you interested?

I have some understanding of German and can read it to a degree but only with difficulty. If you have one or two references then I will try to read them but this might be difficult with technical documents.

Oel is Öl when your typewriter has no "Ö"-key. It means Oil immersion objective.

I thought that was the case but wasn't sure. Since I saw this in both Leitz and Zeiss objective descriptions and both are German in origin, this makes sense. Not all were 100x though. Some were 50x. I don't think I saw it on a 40x though. Thanks for confirming this.

Mixing components is in some cases possible. But you need considerable knowledge to get it right without a long and costly trial and error process. Usually mixing of microscope parts doesn't make much sense.
I would recommend to buy a complete and working microscope that is dependably in serviceable condition. The typical ebay-buy has a couple of problems. Solving them keeps you away from getting ahead with using you scope.

It sounds like I should stick to 170/x objectives. I have been offered a microscope complete with 4 objectives, but there is a selection of objectives to choose from. The standard compliment with most high power microscopes seems to be 4x, 10x, 40x and maybe also a 100x. However, I have also read that it is good to have intermediate magnifications such as 20x or 50x. I'm not sure whether a 2.5x would also be useful? Then there is the choice between NPl, EF and Phaco.

PL on a leitz objective means planar to a certain image diameter (18mm?) It's not quite the same as Pl. on a Leitz objective though
EF on a leitz objective means "semi-planar" up to 18mm image diameter, probably as planar as an older plan objective
Pol doesn't mean polarised: It means its optimised for use on a polarisation mic. The optics are selected for low level of mechanical stresses
Phaco, ph, ph1, ph2, ph3... means phase contrast
phv on a Zeiss Jena objective means variable phase contrast +/-

Thanks for these clarifications. I stand corrected on Pol. I correct/add to my reference table. What does Pl on a Leitz objective mean? Does that also mean that NPl is not the same as NPL? I capitalized the 'L' not realising it might make a difference but I have indeed seen it predominantly in lower case on Leitz objective descriptions. Also it was Fl rather than FL. I also missed on: Nil?

I remember seeing "NFL" on some Olympus projection eyepiece (for camera / trinocular tube of microscope).
...
I have seen DLL (dark low low phase contrast) from Nikon. And PLL as well.

I have added these to my list. Are you able to tell me what NFL and PLL mean please?

Leitz said their correct eyepiece/objective combination, when used correctly, can be moved between 160/170 tube system with a tube length error of about 3mm, if I remember correctly. But don't do it, unless you know exactly what combo to use.

Indeed 'when used correctly'. Which again suggests i should perhaps stick with the 170 for now. I don't want to go into the additional cost and nuances of shims and adapters just yet. Thanks.

[mrsonchus]

Hi, I can offer you a little info re Leitz objectives as I have a Leitz Orthoplan and a Leitz SM-LUX....

The Orthoplan is the 'extra widefield' model if you like, and to achieve planarity fully with it's large up to 28mm field you will need objectives (Leitz) marked 'Pl' - meaning of course planar (i.e. flat-field) but specifically to the widest-field in the range -- that of the Orthoplan.
For the smaller field of the SM-LUZ a fully planar objective would be 'NPL' which is Leitz for 'normal plan' objectives. Of course the 'Pl' may be used on the SM-LUX and the 'NPL' used on the Orthoplan - the degree of planarity is all that will be different - I know this because I have both types and have actually used these combinations.

So, if you have a Leitz SM-LUX (a superb 'scope that has an image quality every bit as good as the mighty Orthoplan) you may only need 'NPL' for planarity but always snap-up a 'PL' if you have the choice I'd say.

Tube lengths - both SM-LUX and Orthoplan are as you know 170mm TL and according to a Leitz memorandum of the time when the transition was made from the 170mm to the to-become-std 160mm the 160mm may be used on the 170mm with no discernible loss of image quality, optimally true for objectives of x16 or higher.
The technical reason for this is that the actual 'optical tube length' that determines the position of the intermediate image that is 'picked-up' by the eyepieces only differs by 2mm not the 10mm by which the 'mechanical' (i.e. the actual metal bits) tube lengths differ.

I can also vouch for this as I use a superb 160mm x63 (dry) objective as my 'biggest dry one' objective on my Orthoplan and it outperforms the 170mm x70 easily - definitely no image compromise.

Hope this helps, sorry I'm short of time - If you would like more details re the Leitz 'scope just let me know.

John B.

[apochronaut]

Npl means neoplan or normal plan, which is the same as what was once called semi-plan.
Plan is a variable concept and simply means that the field is flat. However, each optical system has only so much possibility in this regard and while the field might be flat, it is only flat up to a certain f.o.v. "Normal" could probably be taken to be 18mm but then, I have come across eyepieces that are marked pk( plan kompensating) that are only 17mm f.o.v. The AO objective # 1303, a 63X .80 spl achromat is flat to about 18mm. It is a semi-plan achromat. AO engineered the system it was to be used in as a 20mm f.o.v. system but in fact, there were also student models they made at the time that had a narrower f.o.v. and that objective could be used in them as well. In such a system the # 1303 gives a pretty flat image.

Everybody liked to put their stamp on their optics. It was a small way of keeping customers in the fold, when the Japanese entered the ring seriously in the 80's, and undercut the big western manufacturers. Gray's Encyclopaedia of Microscopy and Microtechnique , doesn't list most of the codes noted in your post above. Most of them are proprietary. Lately, there have been some attempts at a more standardized approach.
https://www.microscopyu.com/microscopy- ... ifications

[Amoeba]

John B, thank you for your insights on the tube length differences on the Leitz microscope. I found that information very helpful.

In light of that, the interesting thing here is that I may have a choice between the following two objectives:

Leitz Fl Oel 54/0.95 170/0.17
Leitz NPL FLUOTAR 50/1.00 OEL 160/-

The Microscope has Periplan eyepieces. So which one should I go for? The dry one of the Oil immersion? Obviously the drawback is that the 160 will not be parafocal with the remaining 'standard' objectives but are they both likely to work? Which one is optically better?

apochronaut, thank you for that reference to the eyepice information. Brilliant and just what I was looking for!

[apochronaut]

When Leitz converted from a 170mm tube to a 160mm tube, it was more than a recognition that despite the quality of the microscopes they were making, they needed to become more standardized. It was a recognition that Wild Heerbrugg , who obtained a large share in the company in 1972 and obtained complete ownership in 1986 held the purse strings. Leitz teetered on bankruptcy, more than once. It would be incredibly costly to develop an entirely new optical system. Fortunately, Leitz had Wild as an owner and from Wild's point of view, they had to go 160mm to catch up and they might as well use the Wild pattern. All Wild needed from Leitz was the name. The company carried a big cachet with that name, something Wild had not really been able to do, so with the adoption of the 160mm tube in the mid-70's , Leitz and Wild kind of merged the optical superiority of the Wild objectives, with Leitz's increased factory capacity and bigger market access. Leitz, essentially began to make Wild optics. Here is an example of a Wild Fluotar 50x 1.0 HI objective. Wild used the older term homogenous immersion instead of oel.
https://www.ebay.com/itm/WILD-HEERBRUGG ... Swxu1Z2VuC

Later, in 1990, when the grand merger of the 8 companies took place, under the label Leica, they made yet another change and began to make American Optical and Reichert infinity corrected optics, the so-called Delta optics, and subsequently refined that system beginning in 1995 with the HC and the current HCX infinity corrected systems.

Here also is a 1975 document from Leitz covering the 170/160 compatibility issue.
http://www.science-info.net/docs/leitz/ ... m-Memo.pdf

[MicroBob]

In this thread you find an image describing the possible Leitz combinations:
http://www.mikroskopie-forum.de/index.php?topic=16145.0

With the Periplan eyepieces, the ones marked 10x 18 are for 160mm and pick up the image 10mm down the tube. A Periplan 10x is for 170mm and picks up the image 18mm down the tube.

Oil immersion objectives: Oil immersion is unavoidable when an n.A over 0,95 is needed. Oil immersion is an advantage too between n.A of 0,7 and 0,95.
Ernst Abbe found that the maximal sensible enlargement is 500 to 1000 x the n.A.. So a 100x n.A 1.3 offers twice the useful linear enlargement compared to a basic 40x n.A 0,65. There is not enough difference between these objectives to make a 50x or 70x really necessary.
Depending on what you do you will use the 10x and 40x most. These are the objectives where I would spend my money. Lower than 10 is mostly for searching, and the 100 oil is not used that often for most applications. A 20x is nice if you have a hole free on the nosepiece. A 50x oil is less usefull. Additional objectives are nice if you get them used for a good price. In the end you probably will use your preferred set, and the rest gathers dust.

Leitz Fl Oel 54/0.95 170/0.17 Older objective, probably offers a nice crisp image, but you need to oil it
Leitz NPL FLUOTAR 50/1.00 OEL 160/- Newer Model, probably offers a nice crisp image, but you need to oil it, not compatible with 170mm tube

Here is something about the Leitz objective markings: It is really complicated with Leitz!! Forget Soudoku!
http://www.mikroskopie-forum.de/index.php?topic=17312.0

[MicroBob]

For phase contrast you also need a phase contrast condensor. Phase contrast shows certain details very well, but the image is not especially nice to look at. It shows details that are transparent but have a different refractive index from the surrounding medium.

[Amoeba]

Thank you for all of the additional info. I have read both of the linked German threads. The situation with Leitz does indeed seem confusing. In the meantime, I have also been advised that the condenser on this microscope is N.A. up to 0.90 so may be unsuitable for oil immersion anyway. I am told however that it is possible to change the lens on the condenser to enable a higher N.A. but obviously this will would mean additional cost. It is beginning to look like I might as well ignore the oil immersion lenses for now. The eyepices have been confirmed as "“LEITZ WETZLAR GERMANY PERIPLAN 10x O" which would seem to indicate that they are for 170. All this confusion with objective standards has made me wonder whether I would be better of with the Zeiss which is a standard 160mm tube.....

Time to step back and have a think.

UPDATE: I just found in the manual (see attached graphic) which suggests that using oil immersion with the standard condenser would be 'adequate', however it does recommend the No.610 condenser with an NA of 1.25. Incidentally there is a caution not to use alcohol. Does this preclude the use of IPA?

[apochronaut]

IPA doesn't seem to affect the lens cement like ethanol does, so if you are worried about lens separation in balsam cemented lenses, it isn't a threat. It isn't that great a solvent of Cargille oil either. It will do the job mostly but I often find the lens surface to be a bit streaky, upon careful examination. I always seem to end up polishing the lens with a small dab of either ethanol or n-heptane to get it pristine, so I don't use it very often to remove Cargille oil, especially if the lens won't be used for a while. If the lens is going to be re-immersed very shortly after, it is o.k., because any residual oil streaks will get re-absorbed. Cargille is a synthetic. I haven't used cedar wood oil for a while, nor Crown oil. I have never used Resolve. They all probably have differing solubilities with various substances but the safest solvent , all around , and one that works is n-heptane.

I use IPA , blended with a tiny amount of scentless clear detergent and distilled water as a general lens cleaner.

[Micro-Bob]

With Zeiss microscopes everything is easy and straightforward!
You just have to keep Zeiss Oberkochen and Zeiss Jena apart, each with several different series of stands and optics.

There is no cheating, it stays difficult.
On the other hand side you can today get great used Microscopes of the big makers for comparatively little money.

The n.A 0,9 condenser is right for 95% of all situations. The immergated oil condenser might be used when scraping along the limit of the resolution of the light microscope. When you buy into one of the more common systems, you can add parts later on when you feel the need.

[Amoeba]

They all probably have differing solubilities with various substances but the safest solvent , all around , and one that works is n-heptane.

Ok, thanks. I have noted that for future reference.

There is no cheating, it stays difficult.

Ah well! I can but try! There was a Zeiss (West germany) on eBay over the weekend. It was rather dirty and looking a somewhat corroded in places so not ideal but a possible restoration project. It was up at just over 30GPB until the last couple of hours and in the end sold for over 120GBP in the last couple of minutes. Given the amount of clean up work that appeared to be required, I didn't think it was worth quite that much.

The n.A 0,9 condenser is right for 95% of all situations. The immergated oil condenser might be used when scraping along the limit of the resolution of the light microscope. When you buy into one of the more common systems, you can add parts later on when you feel the need.

One of my subjects of interest is diatoms and I understand that this is one of the areas where a x100 oil immersion objective might be useful to see the fine details. I just wondered whether I could get by without the condenser or not. To be fair, as a newbie, I am aware that I first need to master the technique of using air spaced objectives before going into the intricacies of oil immersion, but I might have an opportunity to pick up both the condenser and a couple of oil immersion objectives (x54, x100) as part of a bundle at reasonable cost which is why I am considering this very carefully.

[MicroBob]

For diatoms an oil immersion objective is really useful. In many cases a 0.9 dry condenser would be good enough for diatoms with an 1.3 oil immersion objective. But in some cases you would need all the resolution that is offered by the objective. So an oil condenser would be a good buy for you. You might also consider to add a dark field condenser. With a well decentered dark field condensor you get some kind of high power oblique lighting that takes resolution to the limit.

Oil immersion lenses are a bit cumbersome to use, but you can quickly get used to them. Make shure that:
- your objectives are parfocal, so you are already quite close when switching from the 40 dry
- you're not in a hurry
- you don't have Möllers most expensive arranged diatom slide on your stage

[Amoeba]

- you don't have Möllers most expensive arranged diatom slide on your stage

Yes, one false newbie move could be unfortunate. Point taken!
BTW, how do they arrange diatoms on a slide like that?

BTW2: what does it mean when an objective is 'infinity'?
For example: NPL FLUOTAR infinity/0 50X/0.85

[MichaelG.]

BTW2: what does it mean when an objective is 'infinity'?
For example: NPL FLUOTAR infinity/0 50X/0.85

This is a pretty good explanation: https://www.microscopyu.com/microscopy- ... al-systems

MichaelG.

[MicroBob]

BTW, how do they arrange diatoms on a slide like that?

Here: http://www.mikrohamburg.de/Programm/Pro ... 170218.pdf
you can find a beginners tutorial on arranging diatoms in german language and a link to a french video on the topic.
I have to admit though that I'm no expert on this topic by any means. But it works this way and is a good starting point for further improvements.

[Amoeba]

BTW2: what does it mean when an objective is 'infinity'?
For example: NPL FLUOTAR infinity/0 50X/0.85

This is a pretty good explanation: https://www.microscopyu.com/microscopy- ... al-systems

MichaelG.

Thanks. At least I now know they are not compatible with the SM-LUX which would have a "finite optical system of fixed tube length".

[Andy-ross]

What a good thread!