Question about darkfield inmersion condenser

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clipi
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Question about darkfield inmersion condenser

#1 Post by clipi » Mon May 21, 2018 10:39 pm

Hello...
I just got a Leitz laborlux 12 microscope and I was wondering about darkfield condenser
for inmersion objectives 1.25-136
I did not find any on ebay, so would it be posible to use a conderser from other brands?
such as Amscope? Or condenser as brand/objective specific?

Thanks so much

apochronaut
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Re: Question about darkfield inmersion condenser

#2 Post by apochronaut » Tue May 22, 2018 12:22 pm

Any DF immersion condenser will work on any microscope providing the following conditions are met.

1) it can be made to fit in a firm enough mount that allows it to be accurately and precisely centered. If the microscope has a sleeve type condenser mount, finding or adapting a sleeve type condenser, isn't that difficult but with dovetail types, it takes a little more adaption.
2) When mounted, it can be raised enough, so that it can maintain oil contact with the bottom of the slide. Some condensers have threaded bodies and the entire condenser can be raised or lowered independent of it's mount.
3) Objectives must be available that have an N.A. below that of the minimum N.A. of the condenser, which is usually around 1.1-1.2. To obtain good contrasty DF, the N.A. should be not just below but between .80 and 1.0. You mentioned immersion objectives 1.25-136. Is that an adjustable objective, with an iris that controls the N.A. between those two extremes, or a range of possibilities, of the objective N.A.s, you could use?

clipi
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Re: Question about darkfield inmersion condenser

#3 Post by clipi » Tue May 22, 2018 5:08 pm

Hello thanks for your reply
Unfortunately the 100x objective I have has no adjustable NA.
I was thinking in getting a condenser from other manufacturer with 1.25 to 1.36 but I was not sure
if the optic would be compatible.
Thanks again

apochronaut
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Re: Question about darkfield inmersion condenser

#4 Post by apochronaut » Tue May 22, 2018 8:04 pm

Most older 100x oil immersion objectives have the possibility to replace the rear diaphragm of the objective with a funnel stop. Leitz, I think did not, opting rather to swap out the rear lensless part of the barrel with a section containing an iris diaphragm. Once plan objectives came along, the barrels tended to get pretty stuffed with glass, so funnel stops became old school. Objectives with a full barrel of glass, sometimes have the possibility of restricting the N.A. by replacing the rear diaphragm with one a little smaller in diameter. I was able to do this with a Reichert 63X N.A. 1.0 glycerin immersion, by replacing the rear diaphragm with one from the 100X oil immersion, from the same series.Generally, the higher the magnification, the smaller the diameter of the rear diaphragm, so swapping one from an objective of a higher magnification and therefore fitted with a smaller diaphragm, to one of lower magnification isn't often an option with a 100X objective. However, some mfg. made such a device, specifically for some objectives, kind of like a flat funnel stop. The rear diaphragm must be free standing , though. Some of them are integrated into the back lens. There is also the possibility of putting a small restrictor over the back of the objective.

I would imagine that 160mm Leitz objectives with an iris are not that common and also not terribly cheap. I don't think I have ever had a 100x , 160mm Leitz objective in my hands. Is it possible to put a restrictor at the rear of the objective? Even a doughnut of black paper or thin cardboard will do the trick but there has to be a way of centering it accurately and you will likely have to play around with diameters a little.

einman
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Re: Question about darkfield inmersion condenser

#5 Post by einman » Wed May 23, 2018 1:03 am

Apochronaut- I have Leitz 100X objectives with and without an iris. Would it help you to have a picture to recommend a fix? If so let me know what you want to see.

clipi
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Re: Question about darkfield inmersion condenser

#6 Post by clipi » Wed May 23, 2018 10:06 am

So if I undertood it correctly.... if I contrain the rear diafragm of the objective I would be able to use a 0.9NA condenser? right
or I could use other manufacturer condenser that I can fit in the moving platform.

I guess the size of the new ring is a trial an error thing right?

I could no find Leitz 100x objective with iris. Can I uses lenses from other manufacturer provided that they have 160mm length?
Thanks so much!!
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apochronaut
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Re: Question about darkfield inmersion condenser

#7 Post by apochronaut » Wed May 23, 2018 12:33 pm

According to the Leitz information that they made available around the time that they changed their system from 170mm to 160mm, the difference between the two systems is most pronounced with low magnification objectives and therefore long focal lengths. As the focal length of the objective decreases, the deleterious effects of the extra 10mm, makes little difference. So, it seems that either a 170mm Leitz objective , or a 160mm Leitz objective would be suitable but only the 170mm versions( beta optics) that were D.I.N. ( 45mm parfocal) would be directly useable. The alpha optics, which were also corrected for 170mm but were 37mm parfocal would also work but Leitz mfg'd. plezy adapters for those to increase their length and make slight optical corrections. So, any Leitz objective would work but not Leica because they were evolutions of the American Optical/Reichert infinity corrected system(delta optics). Further it seems that the eyepieces designed for the 160mm 45mm parfocal objectives(gamma optics), should work for the 170mm systems but not the other way around.

Other 160mm, 45mm parfocal objectives will work too. I am assuming you are interested in having plan objectives, so that complicates things a bit because always with older objectives, the plan feature is rarer.
It is also a bit of a crap shoot, as to whether the Leitz eyepieces would provide the right corrections for other objectives. It's better to have no plan than plan that is riddled with lateral chromatic aberration. I trialled a group of Leitz periplan 10x eyepieces a while ago, with the intent of utilizing their field flattening characteristics in a compact field microscope. As it turned out anyway, non of the fields I have taken it into are any flatter but here is what I found out about the eyepieces, nontheless. The objectives were all 37mm parfocal and the brands were all German and made by 3 companies : Hertel & Reuss branded Hacker, Conrad Beck & Sons branded CBS and E. Leitz. The only Leitz eyepieces that were corrected properly for those objectives were older Leitz periplans, from the 170mm system and I think even a 37mm parfocal system.

Other objectives you might consider would be these: PZO, Vickers or Baker, Jena. Jena would probably need compatible eyepieces in addition but often Jena objectives are priced absurdly low, so adding in a pair of w.f. eyepieces probably won't set you back too much. Only the newer ones are D.I.N., so you have to watch for that. The same situation exists for Zeiss West except for the price, which is usually high.

There are D.I.N. objectives from India and China but they are priced higher than you can land a used one from one of the above brands for. Bausch & Lomb had a small lab line of microscopes with 160mm tubes and D.I.N. objectives. The objectives were planachro; made in China but I have heard , quite good. The objectives are black and clearly marked with 160mm. I saw a new 100x 1.25 one with an iris sell, in the last 6 months for under 100.00. They might be worth keeping an eye out for.
Chinese and Indian ones are available at the click of a button , others will require some patience but one or more options will come along eventually.

apochronaut
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Re: Question about darkfield inmersion condenser

#8 Post by apochronaut » Wed May 23, 2018 12:42 pm

einman wrote:Apochronaut- I have Leitz 100X objectives with and without an iris. Would it help you to have a picture to recommend a fix? If so let me know what you want to see.

Pictures of the back element of the non-iris version. I have had 170mm Leitz planapos here and I seem to recall that they had an integrated rear diaphragm and lens pack, so the diaphragm could not be replaced with a smaller diameter one. It helps if there is a slight relief below the rear edge of the thread, so that a small doughnut can be made and just dropped in.

einman
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Re: Question about darkfield inmersion condenser

#9 Post by einman » Wed May 23, 2018 1:58 pm

Image
Image
Image

clipi
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Re: Question about darkfield inmersion condenser

#10 Post by clipi » Wed May 23, 2018 2:28 pm

Thanks so much for you indeph explanation!.
I found this objective on aliexpress, Is this one of the Chinese objective that you mentioned?

What about using a 60x lens with 20x ocular? such as this from LeeTurn
60X Achromatic DIN Objective for Biological Microscope Bio-microscope Bottom Lens 160/0.17 60X/0.65 Conjugate Distance 195 mm

Thanks again.
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apochronaut
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Re: Question about darkfield inmersion condenser

#11 Post by apochronaut » Wed May 23, 2018 3:30 pm

You could only use a 60x with 20X eyepieces , if the N.A. of the objective was 1.15 or higher, otherwise the image would be degraded due to empty magnification. The other outcome of using 20X oculars is that typically, unless they are of a superior and fairly complex design, the f.o.v. is fairly restricted and the eye relief quite short. Inexpensive 20X would almost definitely suffer from those two shortcomings. Most companies do not offer good 20X anymore and in the past, some of the better examples were specifically designed as compensating eyepieces for certain objective families. They usually also had short eye relief.
You could use a good 15X or even 16X but again they would have to be good. Not all eyepieces are created equal and excellent W.F. 15s are more expensive to make than 10X, so they are unlikely to be cheap either. Good W.F. 15X can have a larger apparent field than the 10X in the same series and can approach the actual field covered by a 10X, fairly closely. If a 10X eyepiece has an actual field covering 334 um with a 60X objective( a normal situation for a 10X 20mm f.n.eyepiece), in order to cover the same actual field , a 15X would have to have an f.n. of 30mm). I only know of one that achieves this( I'm sure there are others available for relatively recent systems at high cost) but some relatively inexpensive eyepieces can get close, around 25 or 26mm to cover an actual field of around 280 um at 900X. Various of the major microscope companies made them. It would be best to use them with as high an N.A. 60X as possible and preferably immersion. One of the secrets in the design of such eyepieces is in maintaining planarity, so in that it would be necessary to make sure that the objective and eyepieces are well matched.


Yes. the objective you are showing is a S.E. asian D.I.N. 100x with iris. Probably, Chinese. Maybe someone who has used one, could offer up a review?

apochronaut
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Re: Question about darkfield inmersion condenser

#12 Post by apochronaut » Wed May 23, 2018 3:50 pm

einman wrote:Image
Image
Image
It looks like with a nicely cut diaphragm, you could drop one right in there. I would start by measuring the existing i.d. of the diaphragm accurately, then measure the inside of the back of the barrel itself. Ideally, a diaphragm that would thread right in on those existing threads would be great but cutting a disc of stiff black paper to the i.d. of the barrel and then a hole to 75% of the i.d. of the existing diaphragm in the exact center would be where I would start. If it is dark, then you could open it up bit by bit until you start to lose DF, then take your prototype and make a measured piece. If it is not quite dark, then make a slightly smaller one and refine it. Fair amount of fiddling but then , if the objective comes pretty cheap and you can't find one with an iris, the results will work.

apochronaut
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Re: Question about darkfield inmersion condenser

#13 Post by apochronaut » Wed May 23, 2018 3:55 pm

Here are a couple used options.
https://www.ebay.ca/itm/183216616154?ul_noapp=true
https://www.ebay.ca/itm/232748650882?ul_noapp=true

Both are D.I.N. and would likely require matching oculars. Anyone know for sure?

einman
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Re: Question about darkfield inmersion condenser

#14 Post by einman » Wed May 23, 2018 7:36 pm

apochronaut wrote:Here are a couple used options.
https://www.ebay.ca/itm/183216616154?ul_noapp=true
https://www.ebay.ca/itm/232748650882?ul_noapp=true

Both are D.I.N. and would likely require matching oculars. Anyone know for sure?
My recollection, in regards to objectives and matching oculars, is that Zeiss was the most dependent in the proper pairing in general.

apochronaut
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Re: Question about darkfield inmersion condenser

#15 Post by apochronaut » Wed May 23, 2018 8:21 pm

Based on a kind of reverse engineering principle; using Zeiss oculars with other objectives, since I sold all of my Zeiss West objectives to someone who wanted only Zeiss quite a while ago but ended up with some eyepieces; I would agree. I can't get the Zeiss eyepieces to correct well for anything. They are KPL . I also think the Jena is eyepiece sensitive.......However both are well priced and it would be worth matching some eyepieces, if someone really wanted DF.

clipi
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Re: Question about darkfield inmersion condenser

#16 Post by clipi » Thu May 24, 2018 11:09 am

So the the issue is either finding a compatible objective with iris ring (seem less likely)
or finding a dark field condenser for objective with large NA values (might require mounting modifications)

Does anyone knows what is the size of the hole on the remobable condenser holder where the condenser is attached?
Also I have seen other manufacturers condenser caps.... with 1.25 N.A. not sure it they would fit or be even compatible

Thanks again!
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apochronaut
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Re: Question about darkfield inmersion condenser

#17 Post by apochronaut » Thu May 24, 2018 1:43 pm

Einman would know more about that condenser than I. Your condenser looks to be only a .55 N.A., so it is designed for lower power objectives and a wider field coverage. For 40X and up, I guess you rotate that .55 aux. lens out of the way, and it is a 1.25?

einman
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Re: Question about darkfield inmersion condenser

#18 Post by einman » Thu May 24, 2018 2:13 pm

I have not been able to find a cap from another manufacturer that fits. Although I recently had some adapters made to fit a 1.4 NA cap from Zeiss I plan on testing in more depth.

I have been using the Leitz series 56 condenser which allows the use of darkfield stops which are readily available on E-bay. Though not on par with a dedicated darkfield condenser it is nevertheless satisfactory for me.

These condensers pop up regularly on E-bay either as a part or mounted on a scope.
I recently sold one.

I acquired on as a part and the other mounted on a stand which I summarily sold.

apochronaut
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Re: Question about darkfield inmersion condenser

#19 Post by apochronaut » Thu May 24, 2018 3:54 pm

einman wrote:I have not been able to find a cap from another manufacturer that fits. Although I recently had some adapters made to fit a 1.4 NA cap from Zeiss I plan on testing in more depth.

I have been using the Leitz series 56 condenser which allows the use of darkfield stops which are readily available on E-bay. Though not on par with a dedicated darkfield condenser it is nevertheless satisfactory for me.

These condensers pop up regularly on E-bay either as a part or mounted on a scope.
I recently sold one.

I acquired on as a part and the other mounted on a stand which I summarily sold.
So, in order to increase the N.A., you need to change the cap to a higher one. Do you know what the thread diameter is?

einman
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Re: Question about darkfield inmersion condenser

#20 Post by einman » Thu May 24, 2018 6:39 pm

Thread diameter varies with the model condenser. I do not have this model condenser.

apochronaut
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Re: Question about darkfield inmersion condenser

#21 Post by apochronaut » Thu May 24, 2018 11:12 pm

I was just thinking that if it was R.M.S., one of those Baker oil immersion cardioid DF condensers with the R.M.S. thread could be fitted in, as long as the lens pack underneath threads off. Baker and I think one other company made those, to thread into a condenser body so designed. The older Spencer/AO 1.3 N.A. achromat aplanat was built that way too but in that case the intention was for the user of apochromats to fit an identical apochromat objective into the condenser housing, as a critically matched condenser.

clipi
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Re: Question about darkfield inmersion condenser

#22 Post by clipi » Fri May 25, 2018 8:29 am

I am also looking for some of this phase and dark field sliders and cups.
The Slider is for condenser 56 and the the cup for condenser LK.
If you have them and could share the picture with dimensions I might create a 3D printed version
and share the stl file.
I know that the slider are being sold on ebay, but the seller don´t ship to Europe.
Thanks
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1 LK S 1.1 513 555.JPG
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einman
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Re: Question about darkfield inmersion condenser

#23 Post by einman » Fri May 25, 2018 2:15 pm

Image


I have several styles but they are all essentially the same. Here are two. Measurements are the same. This type allows you to insert the darkfield or phase stops separate from the holder.

clipi
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Re: Question about darkfield inmersion condenser

#24 Post by clipi » Sat May 26, 2018 12:13 am

Thanks..

I belive the top hole is 27mm and the bottom 24.5 mm which should be diameter of the actual ring rigth?

I made a first attemp.. if you can print it out and check out how close I got to the actual slider.
Once I get it right I can make other rings, give it thickness and 3d print. I might also make a version for laser cutters.
Thanks.
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einman
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Re: Question about darkfield inmersion condenser

#25 Post by einman » Sat May 26, 2018 3:37 am

Image
Image
Image

clipi
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Re: Question about darkfield inmersion condenser

#26 Post by clipi » Sat May 26, 2018 3:27 pm

Seem I am a little bit off scale.
What is diammeter of the annuli that you insert in the hole? 27mm I presume right?
Thanks!

einman
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Re: Question about darkfield inmersion condenser

#27 Post by einman » Sat May 26, 2018 9:52 pm

clipi wrote:Seem I am a little bit off scale.
What is diammeter of the annuli that you insert in the hole? 27mm I presume right?
Thanks!
It is very close. A little short in overall length. Yes the diameter of the annuli is ~27 mm (26.90 mm by my measurements).

clipi
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Re: Question about darkfield inmersion condenser

#28 Post by clipi » Sat May 26, 2018 11:24 pm

Do you mind taking aditional measurement?
I like to know the distances marked in red
Thanks a lot!!
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einman
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Re: Question about darkfield inmersion condenser

#29 Post by einman » Wed May 30, 2018 2:07 pm

ok. will try and get this later today.

clipi
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Re: Question about darkfield inmersion condenser

#30 Post by clipi » Wed May 30, 2018 3:47 pm

Thanks so much!!!

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