Best way to assess condition of microscope objective optics?

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
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Rorschach
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Best way to assess condition of microscope objective optics?

#1 Post by Rorschach » Tue May 19, 2020 11:10 am

What technique do you guys use when inspecting microscope objectives for fungus, haze, delamination or scratch damage? Would a stereo microscope with brightfield transmitted light be the best tool & technique?

On the other hand, I've read that some people use a phaco telescope lens but how is that done and what else is needed?

I also happen to have the Leitz Orthoplan Vario Tube, which apparently has a Bertrand lens in it. Some people have mentioned using that when they inspect lenses. How is that done?

I'd like to check some objectives before I put then for sale.

Hobbyst46
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Re: Best way to assess condition of microscope objective optics?

#2 Post by Hobbyst46 » Tue May 19, 2020 11:45 am

Rorschach wrote:
Tue May 19, 2020 11:10 am
What technique do you guys use when inspecting microscope objectives for fungus, haze, delamination or scratch damage? Would a stereo microscope with brightfield transmitted light be the best tool & technique?
It works well according to my limited experience. Focus on each element of the lens (objective/eyepiece) in turn. Under transmitted light from a self-made LED under-stage illuminator. I was able to discover delamination in a purchased used objective, that the seller had described as "optically clear". Clear indeed was the view through that objective, but it lacked contrast. When later I started to own the stereo, and re-inspected that objective, the fault was revealed.

apochronaut
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Re: Best way to assess condition of microscope objective optics?

#3 Post by apochronaut » Tue May 19, 2020 1:02 pm

I use a stereo with a transilluminator but offset somewhat, so the illumination is a bit oblique. Focus down through the elements one by one, as suggested.
If the light is direct , very slight de-lamination or more correctly cement haze, can be missed.

Rorschach
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Re: Best way to assess condition of microscope objective optics?

#4 Post by Rorschach » Tue May 19, 2020 1:13 pm

Thanks guys for the info. Also, those tips were music to my ears as as I happen to have very good stereos at my disposal.

Based on apochronauts tip, I will try both BF and DF on the Wild stereo base as it has both options. Lovely base in general, the only drawback being the current draw of the 100W halogen (yes, I'm a bit of a treehugger).

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Wes
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Re: Best way to assess condition of microscope objective optics?

#5 Post by Wes » Tue May 19, 2020 4:59 pm

Delamination is very easy to spot with a phase telescope in polarized light. Its stained in interference colors on a dark background.
Zeiss Photomicroscope III BF/DF/Pol/Ph/DIC/FL/Jamin-Lebedeff
Youtube channel

JGardner
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Re: Best way to assess condition of microscope objective optics?

#6 Post by JGardner » Tue May 19, 2020 5:23 pm

If one doesn't have a stereo microscope or a phase telescope, are there any techniques that can be used to evaluate objectives?

Leitzcycler
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Re: Best way to assess condition of microscope objective optics?

#7 Post by Leitzcycler » Tue May 19, 2020 5:24 pm

I also happen to have the Leitz Orthoplan Vario Tube
About Variotube: is it really usefull or is it empty magnification? Any experiences?

Rorschach
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Re: Best way to assess condition of microscope objective optics?

#8 Post by Rorschach » Tue May 19, 2020 5:55 pm

Leitzcycler wrote:
Tue May 19, 2020 5:24 pm
I also happen to have the Leitz Orthoplan Vario Tube
About Variotube: is it really usefull or is it empty magnification? Any experiences?
Well, my Orthoplan system is still missing one major component so I am not yet very close to having an informed opinion on pretty much anything Orthoplan related. However, I'd think that it might be very useful for those occasions where one likes to use the 6.3x or 8x eyepieces but wants to get extra magnification for photos. If the objectives are top quality, then maybe the magnification is not empty mag? But I'll let more experienced people take the lead here :D

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wporter
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Re: Best way to assess condition of microscope objective optics?

#9 Post by wporter » Tue May 19, 2020 6:42 pm

If one doesn't have a stereo microscope or a phase telescope, are there any techniques that can be used to evaluate objectives?
A 10x hand lens is probably the best next choice. Hold the hand lens in one place close to your eye and move the objective towards and away from you to focus on different areas in the objective lens stack. You won't be able to focus on every element, but will be able to examine most of the important ones. This only works well on low mag objectives; 100x not so well.

If you don't have a 10x hand lens, get a good one. Looking backwards through an eyepiece is a poor substitute.

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