Immersion objectives

Do you have any microscopy questions, which you are afraid to ask? This is your place.
Post Reply
Message
Author
User avatar
Rossf
Posts: 163
Joined: Mon Jan 20, 2020 12:39 am
Location: Victoria Australia

Immersion objectives

#1 Post by Rossf » Wed Feb 19, 2020 12:41 am

Probably a stupid question so will ask it in beginners corner-I look at soil microbes mostly-hate oil immersion but don’t mind water immersion-will using an oil immersion in water wreck the objective or just not be corrected as well cos of difference in refractive index of water (or compost tea) to oil?
Regards ross

MicroBob
Posts: 2265
Joined: Sun Dec 25, 2016 9:11 am
Location: Northern Germany

Re: Immersion objectives

#2 Post by MicroBob » Wed Feb 19, 2020 8:21 am

Hi Ross,
the oil is part of the calculation of the objective so the objective will not work as intended. Immersion objectives are mostly used for stronger magnifications where the depth of field is only shallow. So working without a cover slip might be difficult in practice. There are water immersion objectives available. But even these are usually not meant to be placed in direct contact with whatever specimen you have as the sealant around th front lens might suffer.
If you have an objective that is not valuable and easy to replace you might just try this out. Few people will actually have tried it so realy experience is not widely available. Also the expectations are very differnt.

Bob

User avatar
Rossf
Posts: 163
Joined: Mon Jan 20, 2020 12:39 am
Location: Victoria Australia

Re: Immersion objectives

#3 Post by Rossf » Wed Feb 19, 2020 9:39 am

Thanks Bob-got an old Nikon 100x I could use and abuse and see what happens and when it happens...
Regards ross

apochronaut
Posts: 3650
Joined: Fri May 15, 2015 12:15 am

Re: Immersion objectives

#4 Post by apochronaut » Wed Feb 19, 2020 1:53 pm

I have done a fair amount of testing of oil and water immersion lenses in both mediums, as well as glycerin . Not all objectives are the same.
Although, they always work best when used with the intended medium , some perform within a hair's breadth when used with the other. In one case, a 50X .85 oil immersion achromat worked just about as well with water, probably in the range of a .75 N.A. performance and in fact , worked about at the level of a .65 objective when dry; better than some .65 objectives in fact. This makes it particularly useful, since it can be used dry and provides an image as good as most average dry objectives. If you need more detail and want to mess with oil, then so be it.
Curiously, the compatible planachro to that objective, a 50X .80 oil planachro designed about 4 years later, while slightly outperforming it's older achromat cousin as an oil immersion objective, was a dismal failure with water or dry.

I have come across others as well.
Some objectives, even though they are oil immersion have correction collars. These can sometimes be used to compensate for the difference between immersion mediums; if not oil and water, oil and glycerin at least, which is about as easy to use as water. I've also used what I call glwater or glycerthin.

User avatar
Rossf
Posts: 163
Joined: Mon Jan 20, 2020 12:39 am
Location: Victoria Australia

Re: Immersion objectives

#5 Post by Rossf » Fri Feb 21, 2020 9:45 am

Thanks for the insights Apochronaut-just remembered I’ve got a lomo water immersion 30x with iris and it performs very well dry (go figure-it is flourite so that’s probably a clue..) so there seems to be so many factors influencing success or not (possible damage to the objective notwithstanding!) have you had many objectives fail abusing them this way?
Regards ross

User avatar
daruosha
Posts: 273
Joined: Wed Oct 23, 2019 7:10 am
Location: Tehran, Iran

Re: Immersion objectives

#6 Post by daruosha » Fri Feb 21, 2020 3:50 pm

I have also used water instead of oil on oil immersion objectives and in my case the results were very poor, pretty much as same as using the objective without oil (but a few dozen of microns longer working distance than when no immersion medium is used).
Last edited by daruosha on Sat Feb 22, 2020 11:46 pm, edited 3 times in total.
Daruosh.

PeteM
Posts: 1315
Joined: Tue Dec 06, 2016 6:22 am
Location: N. California

Re: Immersion objectives

#7 Post by PeteM » Fri Feb 21, 2020 4:49 pm

I've noticed that some 100x oil objectives give a somewhat usable image without oil and others are nothing but a blur. Add immersion oil and both versions become sharp.

My guess is that an objective gives some facsimile of an image in air, then the addition refractive index of water would move it into be pretty good. And also that if there isn't an image in air, the objective will want the full benefit of the higher-than-water index of immersion oil? Be interesting to know if anyone will be trying out some oil objectives in water.

User avatar
Rossf
Posts: 163
Joined: Mon Jan 20, 2020 12:39 am
Location: Victoria Australia

Re: Immersion objectives

#8 Post by Rossf » Sat Feb 22, 2020 2:22 am

I will be! I’m waiting on an Olympus MTV-3 c-mount adapter to arrive and will do some tests and post the resulting images-also waiting on a Leitz flourite 100x with iris-who knows being flourite it may have acceptable dry image as long as the slide is oiled to condenser-that would be good-they should all arrive next week to start experimenting...I’ve noticed some 100x have a tiny front element and others about the same as the average 40x-maybe a bit smalller-I’ve even wondered about using a single brush hair to paint nail polish just around the very edge of the front element to protect the cement from water-obviously only on objectives with the larger front elements...

User avatar
ImperatorRex
Posts: 348
Joined: Fri Mar 30, 2018 4:12 pm
Location: Germany
Contact:

Re: Immersion objectives

#9 Post by ImperatorRex » Sat Feb 22, 2020 7:51 am

Found a comparision dry, water and oil immersionare here:
https://www.mikroskopie-forum.de/index. ... 7#msg28437

Comparison with Pleurosigma angulatum and Nitschia sigma (on the left photos immersion with water, on the right with oil:
https://www.mikroskopie-forum.de/index. ... 5#msg28465

apochronaut
Posts: 3650
Joined: Fri May 15, 2015 12:15 am

Re: Immersion objectives

#10 Post by apochronaut » Sat Feb 22, 2020 6:10 pm

Rossf wrote:
Fri Feb 21, 2020 9:45 am
Thanks for the insights Apochronaut-just remembered I’ve got a lomo water immersion 30x with iris and it performs very well dry (go figure-it is flourite so that’s probably a clue..) so there seems to be so many factors influencing success or not (possible damage to the objective notwithstanding!) have you had many objectives fail abusing them this way?
Regards ross
I always wonder whether an oil seal would be that much different than a water seal. Presumably. Oil has a tendency to creep, because it's evaporation rate is so slow, whereas water can breach a smaller gap. ...And some seals are metal to metal.
I haven't noticed any failures but I don't do this extensively. I use that one objective so far some, and have trialled others. I definitely don't immerse dry objectives.

I'm not sure that fluorite lenses have any more chance of being immersion flexible. The best one I have found is a high N.A. achromat but that in itself would imply the inclusion of likely some fluorite elements. It also doesn't seem to be N.A. dependent, although any small N.A. reduction of a higher N.A. objective would not be as noticeable. Currently , I think of it as a phenomenon related to where the lens is corrected for longitudinal spherical aberration, so it is strictly a function of lens design and unlikely to have been a consideration in the design.

Post Reply