Objective has defect

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
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coominya
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Objective has defect

#1 Post by coominya » Fri Apr 06, 2018 1:21 pm

I bought an old Nikon lk-e with phase contrast on the cheap off ebay and the 10x obj has this defect. I guess it's a bin job right? All else on the scope is good.



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Last edited by coominya on Sat Apr 21, 2018 6:58 am, edited 1 time in total.

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ImperatorRex
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Re: Objective has defect

#2 Post by ImperatorRex » Fri Apr 06, 2018 4:34 pm

Probabely some Immersion Oil inside? Before throwing away you can try to clean. I did dismantle and clean an Zeiss achromat 40 completely up to the front lense :-)
Between the front lense and the following lense there was the oil. Actually I did not believe that I get all those lenses and stuff correctly centered and mounted. But surprisingly it worked quite well and I could not spot any issue afterwards.

So if you are patient give it a try, nothing to loose...except some of your spare time.

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Crater Eddie
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Re: Objective has defect

#3 Post by Crater Eddie » Fri Apr 06, 2018 4:36 pm

Odd that it is green, or is that a trick of the lighting?
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ImperatorRex
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Re: Objective has defect

#4 Post by ImperatorRex » Fri Apr 06, 2018 4:50 pm

The green color might come from the brass metall, some copper iones due to some corrosion etc.?

Hobbyst46
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Re: Objective has defect

#5 Post by Hobbyst46 » Fri Apr 06, 2018 5:55 pm

The green coloration is so uniform, strange that corrosion should appear like this. Besides, typical corrosion copper compounds are either blue or turqouise, not green. Is old Canada Balsam green?
An insane idea - did someone try to insert a green filter WITHIN the phase objective???
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MichaelG.
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Re: Objective has defect

#6 Post by MichaelG. » Fri Apr 06, 2018 6:50 pm

Hobbyst46 wrote:Besides, typical corrosion copper compounds are either blue or turqouise, not green.
Green is quite a common colouration when Oil or Grease oxidises in the presence of Brass.
... Sorry, I don't know the chemistry.

MichaelG.
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MicroBob
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Re: Objective has defect

#7 Post by MicroBob » Fri Apr 06, 2018 6:52 pm

Grease in contact with brass often turns green. Copper roofs also turn green.

Economically the lens is probably a write off but if you like repairing things it is very well possible to rectify this lens.

Hobbyst46
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Re: Objective has defect

#8 Post by Hobbyst46 » Fri Apr 06, 2018 7:36 pm

@MicroBob
@MichaelG
Actually the hue of that strange looking half-moon coloration is affected by the lighting and photography as well...
I hope that coominya will take the trouble and discover what it really is, just to satisfy (my) curiosity... :roll:
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MicroBob
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Re: Objective has defect

#9 Post by MicroBob » Fri Apr 06, 2018 7:51 pm

The green area has a black border. This would be typical for a fluid medium between two surfaces.
Is there a forum here for bets? :lol:

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coominya
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Re: Objective has defect

#10 Post by coominya » Sat Apr 07, 2018 1:25 am

Thanks for all the input guys, I decided to strip it down and as it turned out it was immersion oil caught between the bottom 2 elements. I cleaned them up with isopropyl alcohol and the empty objective barrel with petrol then isopropyl. I assembled it all by the numbers (But I think) the second bottom most lens may have flipped during insertion because the view doesn't focus crisply and the par-focal is out by a reasonable amount. Still, a good first foray into such a repair and I'll pull it apart again sometime soon and correct whatever is wrong.


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Last edited by coominya on Sat Apr 21, 2018 7:07 am, edited 2 times in total.

MichaelG.
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Re: Objective has defect

#11 Post by MichaelG. » Sat Apr 07, 2018 5:43 am

Good progress there ... Looks like you might salvage it.

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MicroBob
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Re: Objective has defect

#12 Post by MicroBob » Sat Apr 07, 2018 5:52 am

If you haven't changed the order of the lenses it is no big problem to get it together again:
Five lenses, each two sides=2 ^5 =32 oportunities to get it right :lol:

Hobbyst46
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Re: Objective has defect

#13 Post by Hobbyst46 » Sat Apr 07, 2018 8:16 am

Nicely done. Thanks for posting and revealing the problem source.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

billbillt
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Re: Objective has defect

#14 Post by billbillt » Sat Apr 07, 2018 4:21 pm

Hi,
Thanks for sharing this interesting disassembly... Could you tell how the phase ring is put on the element.. Is it painted on?..

BillT

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coominya
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Re: Objective has defect

#15 Post by coominya » Sat Apr 07, 2018 7:12 pm

billbillt wrote:Hi,
Thanks for sharing this interesting disassembly... Could you tell how the phase ring is put on the element.. Is it painted on?..

BillT
I didn't notice to be honest, I lost my loupe a while ago and used only eye glasses so could not see any great detail. I have a few ordered so when one arrives I'll rebuild it and then see if I can ascertain the method used. I also suspect I have somehow left a smear of oil on those two bottom elements so what would be the best way to ensure they are totally clean? I was thinking of a quick rinse in engine degreaser, then mild soapy water, then fresh water and finally isopropyl alcohol or white spirit.

I am just relieved the lenses are all separate with no compounds to deal with.

billbillt
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Re: Objective has defect

#16 Post by billbillt » Sat Apr 07, 2018 7:41 pm

Hi,

I think I would stay away from the engine degreaser... It may be too harsh... I think the Isopropyl alcohol would be fine .... Someone used cleaned plastic tweezers to handle cleaned elements once and had no complaints... Keep us informed on your progress...

The Best
BillT

billbillt
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Re: Objective has defect

#17 Post by billbillt » Sat Apr 07, 2018 8:11 pm

Coominya,

Here is a link to web page about cleaning most anything optical... It may give you more info..

https://www.photonics.com/a32199/Cleani ... est_Method

BillT

apochronaut
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Re: Objective has defect

#18 Post by apochronaut » Sun Apr 08, 2018 8:12 pm

You are doing well so far. Make sure to check any doublets near the bottom very carefully for oil invasion. To have turned green, the oil has been there for a while and the cement, could be starting to be compromised without it being yet noticeable.

I have done dozens of these and it is amazing how much dirt or film can cling to those lenses, quite unperceived by good eyesight or even a small hand lens, even after scrupulous cleaning.

My standard routine is to clean all non lens items in a weak detergent solution , usually with a small soft brush. Air dry them under cover. When dry blow them off with a compressor, then put away under cover.The unmounted lenses I cleran as well as I can with quite conventional surfactants. I use a tiny amount of very plain, clear unscented dish detergent to remove the oil and rinse completely with isopropyl and water, drying and polishing with fine absorbant paper. Then lightly brush each surface with a fine very clean artists brush under some blower pressure, or use a very clean blower brush. Mounted lenses, I clean with cotton swaps and a very small amount of lens cleaner that has some surfactant in it, and then isopropyl. Isopropyl itself, is not good at removing deposited film, especially if it has an oily base.

All lenses need to be inspected individually under a stereo microscope. There can be contaminants on those lenses, that you cannot see otherwise. Once each surface has been certified film and fleck free, I put each one in a covered spotlessly clean petri dish. At reassembly, I again inspect each surface under a stereo microscope. There is almost always something more to remove. I pick up tiny debris with a very fine very clean artists brush.

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coominya
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Re: Objective has defect

#19 Post by coominya » Mon Apr 09, 2018 6:16 am

apochronaut wrote: Make sure to check any doublets near the bottom very carefully for oil invasion....
There are none, it's an old scope and all lenses thankfully are single elements.
I have done dozens of these and it is amazing how much dirt or film can cling to those lenses, quite unperceived by good eyesight or even a small hand lens, even after scrupulous cleaning.
Sounds like sound advise.

All lenses need to be inspected individually under a stereo microscope....
I knew I should have bought that stereo inspection microscope the other day, I just didn't want to be greedy. I already have 3 and it's only been a month and a half back into the hobby.

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coominya
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Re: Objective has defect

#20 Post by coominya » Mon Apr 09, 2018 6:18 am

billbillt wrote:Coominya,

Here is a link to web page about cleaning most anything optical... It may give you more info..

https://www.photonics.com/a32199/Cleani ... est_Method

BillT
Thanks bill. I'll study it before I proceed.

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